Solid fuel boiler piping: schemes with and without heat accumulator

Efficiency and dependability are the most important factors when it comes to home heating. This can be accomplished, in part, thanks to the solid fuel boiler system. It is imperative to comprehend the piping schemes when contemplating the installation of a new system or the upgrade of an existing one. We’ll look at two typical configurations in this post: one with and one without a heat accumulator.

Let’s start by going over the essentials. A solid fuel boiler is a kind of heating system that produces heat by burning solid fuels such as coal, wood, or pellets. These boilers are well-liked by many homeowners due to their dependability and capacity to deliver steady warmth.

Let’s examine the piping schemes now. Without a heat accumulator, the water in the system is heated by the boiler and then circulated through the underfloor heating system or radiators to provide warmth throughout the house. Simple and reasonably priced, this setup is ideal for smaller properties or those with lower heating requirements.

However, a system that incorporates a heat accumulator adds another element to the mix. The boiler’s excess heat can be stored for later use in the heat accumulator, which functions as a thermal store. As a result, the boiler will be able to run at maximum efficiency when required and store any excess heat for periods of lower demand.

Which plan is therefore best for you? That depends on a number of variables, including your budget, the size of your property, and your heating needs. For smaller homes or those with constant heating needs, a system without a heat accumulator might be adequate. But if you want more flexibility and efficiency, a setup using a heat accumulator might be something to think about.

In conclusion, the efficiency and performance of your solid fuel boiler can be greatly impacted by the piping scheme you select. You can choose the plan that best meets your needs and tastes by being aware of the variations between schemes with and without a heat accumulator.

Scheme Type Description
With Heat Accumulator This scheme involves connecting the solid fuel boiler to a heat accumulator, which stores excess heat for later use. It allows for more consistent heating and can increase efficiency.
Without Heat Accumulator In this setup, the solid fuel boiler is directly connected to the heating system without a heat accumulator. While simpler in design, it may result in less consistent heating and efficiency compared to the setup with a heat accumulator.
  1. Types of strapping the boiler, working on solid fuel
  2. Open system with natural circulation
  3. Disadvantages
  4. Closed system with natural circulation
  5. Closed system with forced circulation
  6. The simplest variant with forced circulation
  7. Solving the problem of condensation
  8. Collector piping with forced circulation
  9. Strapping with hydrostrelka
  10. Circumference of solid fuel boiler with heat accumulator
  11. Strapping for 2 boilers
  12. Connection of an indirect heater in the piping system
  13. Rules of boiler piping
  14. Typical schemes of piping
  15. Scheme of piping without heat accumulator
  16. Scheme of piping of solid fuel boiler with heat accumulator
  17. Scheme with buffer tank
  18. Schemes of strapping of wall-mounted boilers
  19. Combined scheme with expansion tank and circulation pump
  20. Standard (basic)
  21. With mixing unit
  22. The essence and importance of gas boiler piping
  23. Strapping with three-way valve
  24. With installation of indirect heating boiler
  25. The storage tank acts as a DHW boiler
  26. Connection of thermal storage tank and separate DHW boiler
  27. Parallel connection of two heating boilers
  28. Requirements for connection and installation of the boiler
  29. Classic solid fuel boilers
  30. Pyrolysis boilers on solid fuel
  31. Pellet heaters
  32. Necessary units and assemblies for piping of tt boiler
  33. Heat accumulator calculation
  34. Requirements for an uninterruptible power supply
  35. Ways to protect tt boiler and heating system from overheating
  36. What is better to pour into the heating system when heating with a solid fuel boiler
  37. Where the heat accumulator is used and how it is organized
  38. A little bit about the purpose and design
  39. Manufacturing of heat storages in factory conditions
  40. Budget storage tank made of cylinders
  41. How you can make a heat accumulator
  42. The basis for the design of the buffer tank is how the flows should be directed
  43. How much buffer capacity will be needed?
  44. Assembling a simple heat accumulator
  45. First step
  46. Second step
  47. Third step
  48. Fourth step
  49. Fifth step
  50. Sixth step
  51. Selection of the heat accumulator
  52. How to calculate the required volume of the heat accumulator
  53. Calculation of the heat accumulator
  54. Connection professional recommendations
  55. With liquid mixing
  56. With hydrodistribution
  57. General installation instructions
  58. Installation procedure
  59. Preparing for piping
  60. Complete set of strapping
  61. Power supply requirements
  62. Connection of the boiler to the communications
  63. How to choose a buffer tank
  64. Calculation of the minimum required volume
  65. Number of heat exchangers
  66. Maximum allowable pressure
  67. Material of the inner tank
  68. Other selection criteria
  69. Two-pipe system with top connection
  70. Advantages and disadvantages of the two-pipe system with overhead distribution
  71. Features of installation of two-pipe systems with top distribution
  72. Nuances of strapping installation
  73. Video on the topic
  74. Boiler piping without buffer.

Types of strapping the boiler, working on solid fuel

The following strapping variations are identified for various heating systems:

  • with natural circulation;
  • with forced circulation;
  • with hydrostrels;
  • with heat accumulator;
  • for 2 boilers at the same time;
  • with the connection of an indirect water heater.

Open system with natural circulation

Just a few components make up strapping (shut-off mechanisms, regulating devices, etc.). ο.) and requires no energy at all.

Fundamental guidelines to remember when installing:

  1. Radiators should be 0,5 m above the level of the boiler location.
  2. The expansion tank is selected open type and installed above all other elements of the system – a heated attic is perfect for this purpose.
  3. The pipes are placed at a slight slope.

Such piping arrangement has drawbacks of its own. There is no control over the coolant’s temperature. The interior walls of the pipeline are negatively impacted by air that enters the spigots through the open tank.


The primary benefit of the solid fuel boiler gravity scheme is its independence from the availability of electricity. There are numerous additional drawbacks:

  • Low efficiency and impossible to adjust. The speed of movement of the coolant in such systems is low. Therefore, to achieve high efficiency is not possible. It is not possible to regulate it either. So it is impossible to adjust to weather conditions.
    Pipes under the ceiling are not pleasing to the eye
  • Every time the system warms up (in the morning, for example), the return temperature is very low. Because of this, condensate forms, corroding the heat exchanger. And there is no way to fight it.
  • Unaesthetic design. To ensure circulation, the supply pipes must be located above the radiators. Strapping solid fuel boiler in a gravity system is made by a pipe 32 mm or more. Sometimes the supply is pulled above them – at the level of one meter (or a little higher) from the floor, sometimes – under the ceiling. And the pipes have a considerable diameter, so that the view is still the same.

Because of all these drawbacks, natural circulation heating systems are becoming less and less common. Individuals would rather have more convenient and controlled heating systems and create redundant power supplies (by adding batteries or a generator).

Closed system with natural circulation

Systems with natural circulation, both open and closed.

The previous connection scheme is comparable to this one. The primary distinction is that the expansion tank is installed on the return pipe and has a diaphragm. A reserve of at least 10% of the coolant’s typical volume must be present in the tank.

In the event that boiler piping made of polypropylene is chosen, metal pipes must be installed in two sections to guarantee system safety:

  • on the section from the heat generator to the safety group;
  • on the return pipe, on which the sensor and three-way valve are mounted.

This is necessary because polypropylene has a low heat conductivity, which causes the equipment to respond to temperature changes more slowly.

Closed system with forced circulation

Pumps are used in closed-type systems to facilitate coolant circulation. This makes it possible to arrange the pipes horizontally and without any slope.

Positioned in between the expansion tank and the heater are the temperature sensor and pump. The system depends on energy. Faster room heating is ensured by this type of piping.

Forced circulation piping of the closed type.

The simplest variant with forced circulation

An externally piped heat exchanger is a feature of a basic solid fuel boiler. More "advanced" models might have an automation that controls the combustion intensity (through a damper). In simpler terms, there is absolutely no automation observed, with the exception of the integrated thermometer/manometer (which isn’t always the case). Besides, they don’t have circulation pumps installed in them. As a result, when selecting the unit for your network, consider both the potential for regulation and its thermal capacity.

The simplest way to heat the house with hot water is to use an indirect boiler, as shown in the solid fuel boiler circuit diagram in the figure below.

Aid. An indirect heating boiler is a storage water heater as opposed to direct heating boilers (gas or electric), which have their own water heating element. The latter is an external device, such as a heater or system. In our case, the water inside the boiler is heated by the heated coolant that passes through the internal coil of the boiler from the heating system.

The water will heat up more quickly because the boiler is connected before the first radiator. In this version, closing the shut-off valve stops the coolant from passing through the boiler. Here, the radiators receive all of the heat. You turn on the faucet when you need to warm the water. Less heat is received by radiators, but the water warms up fast.

Solid fuel boiler strapping using a circulation pump

It is perfectly acceptable that the circulation pump is on the supply side (when purchasing, make sure the operating temperature range is 110°C and higher). Additionally, the safety group, expansion tank, and automatic air vent are located at the highest point of the system.

Additionally, be mindful of the two taps located before and after the boiler, as they require regular maintenance. By turning off the taps during the heating season, you can fix a boiler that breaks down. It is very practical and convenient that the system does not require the water to be drained. It’s a good idea, by the way, to place a tap in front of the boiler, which can be removed for maintenance or repairs without emptying the system.

The solid fuel boiler will operate more efficiently (faster coolant movement, more heat transfer) if you connect it in accordance with this plan. Another benefit is that if you choose a pump with multiple speeds, temperature regulation may be possible. A great addition would be smaller diameter pipes that could be placed beneath the radiators. If the circulation pump has enough power, the coolant will be pushed through them.

Additionally, there are drawbacks. Energy dependence comes first. Install an uninterruptible power supply with a battery or/and generator if power outages are frequent. The second drawback is that condensate formation is not resolved by strapping the solid fuel boiler in this plan.

Solving the problem of condensation

The heat exchanger experiences condensation when the temperature of the return water falls to between 50 and 60°C. A three-way mixing thermostatic valve with a remote sensor and a jumper between the supply and return are used to solve the issue. There are three connection sockets on it. Two of the inlets are opened or closed based on sensor signals, while one is always open. Because it is a mixing valve, the flow changes gradually rather than suddenly. The coolant temperature gradually starts to change as it gets closer to the boundary temperature, partially closing the second loop.

50–90 cm before the boiler inlet (two inlets are used), on the return, is where the three-way valve is installed. Make sure the valve is installed with its open side facing the boiler at all times; otherwise, the circuit won’t function. The remote sensor is run into the return pipe, and the third input is linked to the supply.

Proper solid fuel boiler plumbing

It functions as follows:

  • As long as the temperature of the coolant in the return is higher than normal, the hot water supply is closed (valve in the closed position).
  • When the temperature drops below the set limit (depends on the system parameters, but usually 40°C), the sensor signals to open the valve. Part of the hot coolant is mixed with the cooled coolant, the temperature rises.
  • When the temperature rises above the second threshold (60°C), the valve is closed.

In this manner, the temperature at which condensate does not form is supplied to the boiler. One drawback to this solid fuel boiler piping design is the potential for overheating.

Let’s take a closer look at the sub-mixture node. This is a feature found in the majority of solid fuel boiler piping schemes because there isn’t yet a better method for dealing with condensate.

Hot water node blending with the return

The circulation pump is situated in the return pipeline in the variant mentioned above. It has an oblique filter in front of it; even in closed systems, this detail is important. Occasionally, certain sororities are still "caught." The fact that there are shut-off valves on both sides is more crucial. They enable pump replacement or repair without completely draining the system.

Collector piping with forced circulation

A system like this is made up of collectors, or combs, which are large cross-section branch pipes with multiple outlet openings connecting heat consumers. Installed between the supply and return pipes is the collector.

Collector piping will give you more effective system control, but connecting it will take more time and more pipes.

Strapping with hydrostrelka

A large-diameter vertical branch pipe is called a hydrostrelka. Once such an element is incorporated into the system, heat consumers at varying heights can be connected, allowing for flexible temperature mode regulation of each device independently.

It is connected to the supply and return pipes in the same manner as the collector: right after the expansion tank and before the heating elements.

Circumference of solid fuel boiler with heat accumulator

The tank is a buffer tank that enables the heat produced by the boiler to be gathered and stored.

Fuel consumption can be decreased because of the device’s significant improvement in equipment efficiency.

Heat accumulator and solid fuel boiler strapping.

The configuration creates two circuits:

  • The boiler is a heat buffer;
  • accumulator – thermal appliances.

The coolant fills the buffer tank during circulation. The buffer tank heats up when the boiler runs in intensive mode. This enables the coolant’s temperature to be maintained for a while after the tab has burned. A three-way valve is inserted right after the buffer to control the temperature mode. The same location is where a pump is installed.

Strapping for 2 boilers

In addition to the solid fuel boiler, another one that runs on gas or electricity can be connected to improve the heating system’s dependability and safety.

In this instance, the connection scheme will remain the same regardless of the fuel type used by the additional boiler.

A heat accumulator, which serves as a substitute for a hydrostrelka, is typically installed. It gathers heat from the boilers and directs it toward the radiators, heated floors, towel dryers, and other fixtures.

Boiler strain for two units.

There’s another alternative plan. In this instance, the system’s temperature is maintained by gas or electric equipment, with the solid fuel boiler serving as the primary heat generator. You can avoid spending money on a heat accumulator by doing this.

How does it operate? The system’s temperature drops when the fuel runs out. This process is corrected by the sensor, which also initiates the additional boiler. Concurrently, the primary boiler is turned off. Once an electric or gas device is turned on, it will keep the coolant at that temperature until fresh fuel is added to the main boiler. At that point, the active device will be turned off using the same procedure.

Connection of an indirect heater in the piping system

If you connect a solid fuel boiler to a heat exchanger, you can use the boiler to heat water. In this instance, indirect heating will occur. Such a system will save electricity during the winter, and in the summer, when the air conditioning isn’t working, heating elements can be used to heat the boiler.

This kind of pipework can be linked to heating systems that use natural coolant circulation as well as systems that use electric pumps.

Rules of boiler piping

Correct TTCS tying is essential for the heating system’s overall dependable and efficient operation.

It’s important to consider a few key points:

  1. To avoid condensate formation, the temperature difference between the supply and return should be no more than 20 °C.
  2. Installation of pressure gauges will allow you to control the pressure within the limits specified in the instructions to the equipment and regulatory documents.
  3. To maximize efficiency, connections should be sealed.
  4. No combustible materials should be used in the piping elements.
  5. In order to avoid scale formation and clogging of pipelines leading to equipment failure, it is necessary to keep the coolant clean.
  6. If the building is higher than one storey, forced circulation of the heat carrier should be used.

Typical schemes of piping

Although the living room and boiler room share many features, each is unique, so in order to properly strap the heating, a separate project must be developed. These projects are built upon standard schemes that represent the fundamental positions of system installation under various conditions in a way that is common to all.

Scheme of piping without heat accumulator

One of the most important considerations when selecting a solid fuel heating boiler plumbing method is the existence of a heat accumulator. The heating system is constructed using the small and large heating system circles if the buffer tank is not available. The following guidelines are followed when installing a small circle:

  • Immediately after the boiler, on the supply of the heating system install a safety group.
  • Literally, after 1.5 m of the pipeline, a tee is installed. The pipe connects the supply and return of the heating system.
  • A wedge-shaped valve is installed on the connecting pipe to control the intensity of coolant circulation in the small circle of heating.
  • On the return is installed three-way mixing valve, connected to the pipe connecting the supply and return.

This scheme’s operating principle is as follows:

  • After switching on the boiler, the heated coolant circulates through the small heating circle. Three-way valve prevents cold, not heated water from entering the heat exchanger. Big difference in temperature between supply and return leads to the fact that the boiler starts to "cry". A large amount of condensate is formed, which negatively affects the heat exchanger.
  • The coolant is gradually warmed up and after heating over 60°C, the three-way valve is opened. From this point, begins to work a large circle of the heating system.
  • The small circle of the heating system continues to function as a make-up unit, preventing boiling of the heat carrier and reducing the gap between the supply and return temperatures.

Scheme of piping of solid fuel boiler with heat accumulator

Actually, the boiler’s piping is the same for solid fuel heating. The heat accumulator itself and a three-way valve for sub-flow are added to the scheme. In addition to the points already covered for the conventional CT scheme, it is also important to make three additional clarifications if we employ such a scheme:

  1. The main function of the three-way sub-mix unit is to monitor the temperature in the heating system and add hot water from the heat accumulator to it.
  2. In order to heat the volume of water in the thermal accumulator, a solid fuel boiler of excessive capacity must be used.
  3. The volume of the heat accumulator is selected based on the volume of the interior of the house and the degree of its insulation.

You will thus be let down if you attempt to heat the heat accumulator TT using a boiler of roughly nominal capacity. For example, a 200 square meter home could have a 2.5 ton heat accumulator and a 20 kW TT boiler, or 2,500 liters or 2.5 cubic meters of space.

A well-insulated house within the designated area can be heated with the power of a solid fuel boiler that possesses these qualities. However, not enough to heat the coolant in the heat accumulator and the house at the same time.

Note: In reality, a 20 kW TT boiler will be able to heat the TA. However, if the 60 kW boiler heats this area in a single approach, the 20 kW boiler will need to be "fried" constantly.

Scheme with buffer tank

The purpose of the heat accumulator-equipped solid fuel heating boiler scheme is to prevent the working fluid from boiling and to maintain a steady temperature within the system (the TTC is not well controlled, necessitating constant fuel and draught control).

A hermetically sealed tank placed between the boiler and the customer is called a heat accumulator. The gadget works on the principle of storing extra heat in its own volume and supplying it to the system as needed.

A mixing unit, a three-way valve equipped with a temperature sensor, controls the coolant’s temperature.

Schemes of strapping of wall-mounted boilers

Primary and secondary rings make strapping of floor gas boilers and other heating appliances easier. If you divide the heating system into multiple rings and install a separate circulation pump for each ring, you will need fewer devices overall to regulate the system’s operation. The end user is guaranteed a consistent supply of hot coolant because of these precautions.

The complexity of the strapping scheme for a two-circuit appliance is evident. Making contact with a specialized gas organization is a reasonable solution. Its employees will promptly link the apparatus to the gas supply network.

Combined scheme with expansion tank and circulation pump

This variation adds a circulation pump to the traditional open circuit. By applying pressure to the network pipelines, it stops the coolant from being circulating through the thermal circuit.

The plan bears a lot of similarities to the earlier one. Furthermore, a node equipped with a circulation pump is situated on the return bypass. Prior to the pump, a filter is included to remove mechanical impurities (rust, sand, debris) from the water. The bypass pipe has taps installed on it to make it possible to remove the pump and filter. To reverse the flow, cut a bypass valve on the main return pipe as well.

After the expansion tank is connected, a tap is also installed on the supply pipe, and an air valve is installed in the supply pipe to remove air from the system. A pressure gauge needs to be installed in order to regulate the pressure in the network at the supply.

It is very challenging to determine the working pressure at the pump outlet with such a scheme. Here, it’s important to maintain consistent circulation while also preventing an excessive water overflow through the expansion tank. This is essentially impossible in real life.

Standard (basic)

A solid fuel boiler’s connection scheme is made up of a few fundamental components that work together to heat a private home’s rooms all at once.

Firstly, take into account the safety group, which is situated near the boiler.

It consists of:

  • pressure gauge to measure the pressure in the pipeline;
  • The air vent is automatic and serves for venting;
  • safety valve, which is adjusted to 3 bar (critical pressure in the heating system).

The safety group activates in an emergency, such as when the lights go out or there is a sudden increase in temperature or pressure within the system. When the pressure gauge reaches a predetermined point, the valve opens, allowing air to escape and lowering the system’s pressure.

Caution: installing any equipment between the heating unit and the safety group that would prevent the heat carrier from flowing freely is strictly prohibited.

The circulation pump is ranked second in significance. Its job is to transfer the coolant at a specific pace throughout the system. Install it tightly on the return between the boiler and the three-way valve. Use cocks to help you cut in along the bypass route. If needed, close the cocks to allow water or antifreeze to enter directly.

Connecting the pump to the boiler water supply pipe is strictly prohibited. In the event of an emergency, boiling water in the boiler will produce steam, and if the pump is not made to handle a steam-water mixture, this will only make matters worse and may even spark an emergency.

With mixing unit

The mixing unit, which consists of a three-way mixing valve with a thermal head, a remote temperature sensor, and a jumper connecting the supply and return pipelines (bypass), is another crucial component. Its purpose is to guard against condensation and temperature swings for the boiler.

The way the system operates is as follows:

  1. Boiler is flooded, pump is running, water or antifreeze moves through the bypass in a small circle.
  2. The temperature on the return pipe has risen to 60 degrees, the sensor signals and the thermal head presses the stem of the three-way valve.
  3. It opens and starts mixing cold water with hot water.
  4. Gradually the whole heating is warmed up and the valve completely closes the bypass – all the coolant circulates through the unit.
  • The heating section from the boiler to the safety group, the bypass and the return from the bypass to the heat generator must be made of steel pipes, while the rest of the piping can be made of plastic, as it is easier to work with;
  • Propylene pipes are thick-walled and do not conduct heat well, so the overhead temperature sensor will not show the temperature correctly, because of this the valve will not work properly.

The essence and importance of gas boiler piping

Strapping is a group of engineering procedures used to unite the thermal scheme’s components and nodes into a single heat-generating complex. Its executive plan is completely customized and is based on the boiler type, number of heating circuits, safety automatics, internal house heating system wiring, and domestic hot water heater.

Every piece of primary and auxiliary gas boiler equipment is considered to be dangerous; even the tiniest piping mistakes can result in irreversible processes and put life-support systems at risk of fire or emergency.

Regarding this, it’s critical to handle the gas boiler’s plumbing responsibly and adhere to safety regulations and standards when installing and using small-capacity gas boilers. For this reason, it is advised that only qualified individuals handle all design, installation, and adjustment tasks related to gas boiler equipment. Boiler unit piping functions:

  1. Uniform distribution of heat and velocity flows through the heating and DHW system.
  2. Compensation of thermal expansion of piping systems and hot heating surfaces (boiler, boiler).
  3. Removal of air from the water coolant.
  4. Control of the medium pressure and discharge of water, in case of exceeding the maximum threshold, through the expansion tank.
  5. Creation of the set mode in the gas-air path of the boiler.
  6. Maintaining a sanitary temperature of the internal air in the heated object.

Air is removed from the water coolant by strapping the gas boiler.

Strapping with three-way valve

A circuit for the emergency supply of cold water to the heat exchanger or in a special coil installed inside the equipment is provided by the boiler to further prevent it from overheating.

The equipment inside the heat exchange unit that includes a temperature sensor and a three-way valve allows this unit to function. The sewer system receives the heated water discharge.

With installation of indirect heating boiler

Any connection scheme can be used to pipe a solid fuel boiler with an indirect heating boiler. To provide hot water, cold water is heated in a boiler.

Every appliance that uses hot water is linked to the system in parallel with the water heater. Here, it’s crucial to keep in mind that, in order to maximize operating efficiency, the unit should have a three-way valve that can be used to stop the water discharge if it hasn’t heated up yet.

The storage tank acts as a DHW boiler

Within the heat accumulator, the accumulating tank is shaped like a spiral. The hot water circuit’s flowing water is heated by the hot coolant inside. Up to two days can pass in a boiler burnout or shutdown when the heat accumulator keeps the room at a comfortable temperature. as long as the DHW function is not utilized.

An automatic thermal mixing device regulates the coolant’s temperature and flow:

In addition, the device has a built-in thermoventilator, a connector, an emergency automatic natural circulation valve, and a check valve in case of a power outage.

The following is the device’s operating principle. The thermal valve opens the water supply from the storage tank when the thermal fluid reaches a specific temperature (780C). By controlling the cross-section of the return flow from the central heating system to the bypass duct, the temperature is maintained at the predetermined level.

Diagram showing how to connect a dual-purpose heat accumulator to a solid fuel boiler: Safety group, thermal storage tank, thermomixer, diaphragm-type expansion tank, system make-up valve, heating system circulation pump, radiators, mixing three-way valve, check valve, and DHW circulation pump are the first ten items.

Connection of thermal storage tank and separate DHW boiler

The number of users and the equipment’s capacity determine the DHW system’s passive heating boiler’s volume. When plumbing pellet boilers, polypropylene constructions and materials are not advised. At peak loads, the heat exchanger’s temperature at the outlet frequently rises above the operating temperature of polymer-based pipes.

Pipework for a solid fuel boiler and a separate DHW boiler: 1. The boiler. 2. Group 3. safety system. 4. A membrane tank for expansion. 5. 6. The pump. 7. Three-way valve for mixing. 8. Make-up valve for the system. 9. The radiator. 10. Boiler with indirect DHW. 11. Tank for thermal storage.

Parallel connection of two heating boilers

Users frequently combine two distinct types of heating sources into a single heating scheme in order to increase the service life and distribute the resources used more evenly. In this instance, a solid fuel boiler provides the majority of the wintertime heat. When using the electric boiler for water heating in the summer, it is turned on in emergency mode.

Diagram of the piping for a solid fuel heating boiler connected to an electric boiler in parallel: 1. A boiler for pellets. 2. The heating system safety group. 3. An alternate boiler, either gas or electric. 4. A separator that clears the system of air. 5. The pump for circulation. 6. Three-way manual mixing valve. 7. The protection valve against dry run. 8. Tank for expansion. 9. A valve for adding water. 10. Tank for thermal storage. 11. Sink. 12. 13. The pump for DHW.

A pellet boiler-based heating system is very intricate and needs to be set up carefully. Make sure you thoroughly familiarize yourself with the instruction manual supplied by the manufacturers’ companies before beginning any installation work.

Requirements for connection and installation of the boiler

Let’s first investigate the kinds of heat sources that operate on solid fuels before answering this query.

Classic solid fuel boilers

They only come in floor, single, or double circuit varieties. The sole purpose of the single-circuit heat generator is space heating. Dual-circuit: the home’s hot water supply is maintained. Most frequently, cast iron or steel are used to make them. Longer heat retention is achieved with cast-iron ones, but their weight necessitates a reinforced base. Steel heat exchangers are less expensive and simpler to maintain, but they are more prone to scale buildup. Antifreeze is occasionally used, but water is typically used as a heat carrier.

In these units, the fuel is:

  • wood;
  • coal;
  • sawdust, chips;
  • briquettes pressed from coal;
  • peat briquettes;
  • pellets – pressed pellets made of woodworking waste: shavings, sawdust, chips.

Benefits of these units:

  • independence from electricity;
  • simplicity and ease of operation;
  • reasonable cost.
  • rapid combustion of fuel, and, as a consequence, it is necessary to constantly put it in the unit;
  • low efficiency (coefficient of performance) – a lot of fuel is burned;
  • very often it is necessary to clean the unit;
  • the combustion process must be constantly monitored.

Pyrolysis boilers on solid fuel

This is a contemporary, high-tech unit with two chambers. Firewood burns very slowly, almost smoldering, in the primary chamber, releasing combustible gases that burn in the second chamber.

  • greater fuel economy: more heat is generated at low load;
  • high efficiency of the heat generator, up to 80% – wood burns almost completely;
  • fuel control – 1-2 times a day;
  • automation and appropriate equipment control the operation of the unit.
  • dependence on electricity – all the equipment operates from the power grid;
  • high price – depends on the capacity, the larger the heated area, the more expensive the heat generator;
  • the large size of the unit requires a large boiler room.

Pellet heaters

These units are made up of an auger that feeds fuel into the heat generator, a nozzle, a hopper filled with pellets, and a boiler.

  • there is no condensate in the heat source, as the fuel is constantly fed into the unit by means of a screw and burns almost completely;
  • the unit can operate for up to 8 hours without human presence;
  • Fire- and explosion-proof: the burner extinguishes as soon as the fuel stops flowing into the unit;
  • pellets are relatively cheap;
  • high efficiency of the boiler, up to 85 %;
  • combustion waste is perfectly used as fertilizer for the garden plot.

The consumer must contend with the heat generator’s high cost.

However, in time, these expenses will be justified by the costs incurred.

While they use coal pellets, the identical kind of units have a retort-style nozzle.

The solid fuel boiler in a private home needs to be installed and connected correctly for the entire heating system to function properly. No formal authorization is needed, nor is documentation required; however, the installation must adhere to SNiP 42-01-2002 (Construction Norms and Rules), which has been authorized by Russia’s Gosgortechnadzor.

Let’s examine the key components of the installation of the heat generator:

  • heating unit and the initial fuel stock is placed in a special room – boiler room, the area of which should be at least 7 square meters. м;
  • the wall near the heat source must be insulated with a non-combustible coating 8 mm thick;
  • the distance from the unit surface to the ceiling must be at least 120 cm;
  • it is obligatory to pour a foundation under the base of the heat generator, protruding beyond the contours of the unit by at least 25 cm, 7-10 cm thick;
  • the heat source should be located at a distance of at least 0.5 m from the wall;
  • if possible, concretize the floors and lay tiles;
  • a window aperture must be designed in the boiler room to ventilate the room;
  • determine the size and type of chimney;
  • install supply ventilation.

The following should be given particular attention when connecting the heating source for optimal performance.

  • to prevent condensate formation it is necessary to ensure that the temperature difference between the coolant at the boiler inlet and at the boiler outlet is within 20 degrees;
  • install sensors to measure the pressure in the system;
  • Before starting the heating operation, check all pipe connection points for tightness;
  • in single-storey houses with a small area is better to use a scheme with natural circulation.

The pertinent documentation for the fuel unit that was purchased specifies the specific requirements for connecting and installing the heating unit.

Necessary units and assemblies for piping of tt boiler

The entire list of fittings needed to pipe the boiler into the system will vary depending on the design selected, whether a buffer tank is needed, and other equipment. It will be necessary to have the following bonds with a standard connection:

  • Thermostatic or thermo-mixing valve – it is necessary to stabilize the heating medium heating and prevent overheating and boiling of the latter.
  • Expansion tank – provided in any heating scheme. Membrane expansion tank is installed in closed systems with forced circulation of the coolant. In gravity schemes, an open tank is installed at the highest point of the water circuit.
  • Circulation pump – installed in closed and open systems with forced circulation of liquid in the water circuit. Some solutions, such as the use of a buffer tank, two parallel connected boilers, requires the installation of two modules of circulation equipment at once.
  • Check valve – coordinates the direction of the heat flow of the fluid. It is used when connecting a membrane tank. Prevents the occurrence of duplicate flow in the case of simultaneous connection of electric and solid fuel boilers.
  • Collector – used for simultaneous connection of underfloor heating and radiators. Without a manifold, it is impossible to do without a manifold when making a radiant heating system, when each heating device is led to a separate pipeline. Collector in the heating system is necessary for most modern heating schemes.
  • Air evacuator – automatic valve, included in the standard equipment of the safety group. In automatic mode, bleeds air from the heating system.
  • System make-up valve – controls the pressure and total volume of coolant in the system. When falling below the minimum value, opens and supplements the water circuit with liquid.
  • System pressure sensor – also part of the safety group. Indicates the nominal pressure in the heating system, often the first to indicate overheating of the coolant. By checking the readings of the thermometer and pressure sensor (manometer), it is convenient to set the necessary operating mode and adjust the automatic draught regulator.
  • Coarse filter – installed on the return, just before the circulation pump. It is recommended that the filter should be installed before the buffer tank, expansion tank and other sensitive elements of the heating system.
  • Hydraulic arrow – hydraulic arrow in the heating system, is necessary for boilers using the principle of long burning and modulating power settings. Practically – this device replaces a buffer tank and has a general principle of operation.
  • Mixing unit or sub-mixture unit – mixes hot and cool water from the heating cohort to prevent boiling and reduce the difference between the supply and return of the coolant.

Heat accumulator calculation

The thermal energy accumulation tank can be manufactured independently or bought prefabricated. However, the question of how big the tank should be naturally emerges. Ultimately, an excessively large tank will be very expensive, and a small tank will not provide the desired effect. The response to this query will assist in calculating the heat accumulator; however, you must first ascertain the starting calculation parameters:

  • Heat losses of the house or its square footage;
  • duration of inactivity of the main heat source.

Let’s calculate the storage tank’s capacity using the example of a typical 100 m2 home that needs 10 kW of heat for heating. Assume that the boiler’s net idle time is six hours and that the system’s heat carrier averages sixty degrees Celsius. It makes sense that the accumulator should provide the system with 10 kW per hour during the inactive period of the heating unit, for a total output of 10 x 6 = 60 kW. This is the recommended level of energy storage.

Since the tank’s temperature should be as high as possible, we’ll use 90 °C for our computations as more residential boilers still can’t reach that level. The following formula determines the needed heat accumulator capacity, given in mass of water:

  • Q is the amount of stored heat energy, in our case it is 60 kW;
  • 0.0012 kW / kg ºC is the specific heat capacity of water, in more familiar units of measurement – 4.187 kJ / kg ºC;
  • Δt – the difference between the maximum temperature of the coolant in the tank and the heating system, ºC.

So, a water accumulator must have a capacity of 60 / 0.0012 (90 – 60) = 1667 kg of water, by volume it is about 1.7 м3. But here there is one point: the calculation is made at the lowest temperature outside, which is not often, excluding northern regions. In addition, after 6 hours, the water in the tank will cool down only to 60 ºC, so, in the absence of cold weather, the battery can be "discharged" and further, until the temperature drops to 40 ºC. Hence the conclusion: for a house of 100 m2 a storage capacity of 1 will be enough.5 m3 if the boiler will be inactive for 6 hours.

Requirements for an uninterruptible power supply

You must first ascertain the requirements placed on the device in order to ascertain which uninterruptible unit will work with the gas boiler. Understanding the UPS’s primary indicators and how they represent the effectiveness of its operations will be beneficial. Several of them:

  • Active and total (taking into account the reactive component) power, defined as the product of the supply voltage by the current in the load.
  • The coefficient of harmonic distortion, indicating the quality of the output voltage – the deviation of the shape of the sinusoid from the ideal form.
  • Availability of an external battery, which allows the boiler operation not to be interrupted in the complete absence of mains power supply for several hours.
  • Duration of operation in standalone mode.
  • Limits of permissible fluctuations of input voltage in Volts.

It should be feasible to connect extra batteries when lengthy power outages are anticipated due to the boiler equipment’s operating conditions. Additionally, it would be ideal for the purchased device to be able to automatically track the grid’s condition and return to normal power supply mode.

Ways to protect tt boiler and heating system from overheating

The main drawback of using solid fuel boilers is that they cause the heating system to boil. Controlling the units’ operation is a challenging task. Modern systems use multi-level protection to prevent boiling:

  • Small heating circle – initially, the scheme prevents condensation from occurring. After a large heating circle has been started, the construction plays the role of a sub-mixture unit.
  • Safety group – includes air vent, pressure gauge and pressure sensor. In case of excessive overheating, the pressure in the system increases, which causes the valve to blow off and discharge a certain amount of water from the water circuit.
  • Diaphragm tank – pressure in the expansion tank in a closed heating system solid fuel boiler, varies, depending on the heating medium heating. The capacity is selected by taking into account the total volume of the coolant, according to special formulas. The pressure in the heating system should be no more than 2 mbar. Most of the heat exchangers of tt boilers, can not withstand large parameters and deform at overheating.
  • Buffer tank – connecting the solid fuel heating boiler to the heating system through a storage boiler makes it virtually impossible for the coolant to boil.
  • Connection of a circulation pump – in case of power failure, the movement of the coolant stops, which leads to almost instant boiling. Safety regulations require the pump to be connected via an uninterruptible power supply.

The formula 1 kW = 15 liters of water is used to determine the ideal volume of the heating system. The outcome is used to choose the expansion membrane tank or calculate how much coolant or antifreeze is needed.

What is better to pour into the heating system when heating with a solid fuel boiler

A heating system that is connected to a solid fuel boiler can run on nearly any kind of coolant. Numerous factors influence the decision:

  • Type of building – in heated rooms, it is more appropriate to use ordinary water as a fluid for the heating system.
  • If it is planned to sink the building from time to time, it is better to use a non-freezing liquid.

Heating system antifreeze has an additional characteristic besides its primary freezing point of -15°C. Large heat inputs are needed to heat the fluid. As a result, antifreeze boiling is less common than boiling regular or distilled water.

The safety and lifespan of the heating apparatus are impacted by the solid fuel boiler’s pipe selection. A licensed heating technician must be involved in the calculation of the heating system.

Where the heat accumulator is used and how it is organized

All that the heat energy accumulator consists of is an iron tank that is insulated and has spigots to connect to the main water heating system. The buffer tank serves as both a heat storage tank and a source of indoor heating during boiler shutdowns. In two situations, the heat accumulator takes the place of the heating unit:

  1. When heating the dwelling with a stove with a water circuit or a boiler that burns solid fuel. The accumulation tank works for heating at night, after burning through wood or coal. This allows the homeowner to rest easy instead of running to the boiler room. It is comfortable.
  2. When the source of heat is an electric boiler, and electricity consumption is accounted for by a multi-tariff meter. Energy at the night tariff is twice as cheap, so during the day the heating system is fully provided by the heat accumulator. It is economical.

A Kospel electric boiler with a hot water storage tank is on the right of the picture, and a 400-liter Drazice buffer tank is on the left.

Important point. The solid fuel boiler’s efficiency is increased by the tank-hot water accumulator. Ultimately, intense combustion is the heat generator’s peak efficiency, and it cannot be continuously maintained without a buffer tank to absorb excess heat. Less wood is consumed when it burns more effectively. This also holds true for gas boilers, whose low combustion modes result in decreased efficiency.

A straightforward principle governs how the coolant-filled accumulator tank functions. The water in the tank is heated to a maximum temperature of 80–90 ºC (the accumulator is being charged) while the heat generator heats the building. When the boiler is turned off, hot coolant from the storage tank begins to flow to the radiators, heating the house for a predetermined amount of time (discharging the heat battery). The tank’s capacity and the outside air temperature determine how long the operation will last.

The design of a heat accumulator manufactured in a factory

The scheme depicting the most basic factory-made accumulating tank for water consists of the following components:

  • The main tank of cylindrical shape, made of carbon or stainless steel;
  • 50-100 mm thick thermal insulation layer depending on the insulation material used;
  • outer skin – thin painted metal or polymer cover;
  • connection fittings cut into the main tank;
  • immersion sleeves for installation of thermometer and pressure gauge.

Note: More costly heat accumulator models for heating systems come with additional coils for solar collector heating and DHW. The integrated electric heating elements in the upper zone of the tank represent an additional practical option.

A little bit about the purpose and design

Let us first discuss the purpose of this crucial unit and take a quick look at its factory layout before making any recommendations regarding its production. In the event that the house needs to be heated on a periodic basis, accumulating tanks filled with water are utilized.

  • When operating an electric boiler with a multi-tariff meter, when heaters can economically function only at night. The unit, working at full capacity, heats the house and accumulates heat energy in the tank with water;
  • heat accumulation is also necessary for solid fuel boilers, which, on the contrary, stop at night or other times, if there is no one to put a new portion of wood or coal in the furnace;

Water is stored in a circular tank that is part of prefabricated units. It is submerged in several coils, which house the boiler’s coolant as well as the coolant from other heating circuits. It is possible to verify that the design is expensive due to its complexity through examination of the heat accumulator’s drawings.

If you attempt to construct a heat accumulator yourself using a similar device as a model, the final cost will not be significantly less than that of the factory one. It will cost you a lot of time and money to work on coiling coils made of copper or stainless steel tubes, sealing inlets, and installing insulation. There is an easier way, which is explained below, for homeowners who wish to put together and install a homemade heat accumulator.

Manufacturing of heat storages in factory conditions

It is a good idea to become acquainted with factory assembly technology if you are apprehensive about installing a heat accumulator and choose to build one yourself.

Cutting blanks for the bottom and lid on a plasma machine

Although you can’t replicate the technological process in your home workshop, there are some useful techniques that you can implement. The hot water storage tank in the factory is constructed as a cylinder with a hemispherical bottom and a lid in the following order:

  1. Sheet metal 3 mm thick is fed to the plasma cutting machine, where it is used to make blanks of end covers, body, hatch and stand.
  2. The lathe is used to make the main sockets with a diameter of 40 or 50 mm (thread 1.5" and 2") and dip sleeves for monitoring devices. A large flange for the inspection hatch, measuring about 20 cm, is also machined there. A socket is welded to the last one for tapping into the housing.
  3. The housing blank (the so-called shell) in the form of a sheet with holes for the fittings is sent to the rollers, bending it under a certain radius. In order to obtain a cylindrical water tank, it is only necessary to butt weld the ends of the billet.
  4. From metal flat circles hydraulic press stamps hemispherical lids.
  5. The next step is welding. The order is as follows: first the casing is welded on tack welds, then the covers are welded to it, and then all welds are welded together. At the end, fittings and an inspection hatch are connected.
  6. The finished storage tank is welded to the base, after which it undergoes 2 permeability tests – air and hydraulic. The last is made by pressure of 8 bar, the test lasts 24 hours.
  7. The tested tank is painted and insulated with basalt fiber at least 50 mm thick. From above the container is covered with thin sheet steel with polymer color coating or covered with a dense cover.

The accumulator’s body is bent using rollers to shape an iron sheet.

Citation. Various materials are used by manufacturers to insulate the tank. For instance, polyurethane foam insulates Russian-made heat accumulators known as "Prometheus."

Manufacturers frequently use a special cover (you can choose the color) in place of a liner.

The majority of factory heat accumulators are made to withstand a maximum pressure of 6 bar and a heating system temperature of 90 °C. This value twice surpasses the safety valve threshold (limit -3 bar) that is fitted on the safety group of gas and solid fuel boilers. The video displays the entire production process in detail:

Budget storage tank made of cylinders

If you have a small boiler room, we recommend building a cylindrical heat accumulator out of propane cylinders.

A DIY heat accumulator and a TT-boiler combination

Our other master-expert Vitaly Dashko created a design for a 100-liter capacity that is intended to serve three purposes:

  • unload the solid fuel boiler in case of overheating, taking excess heat;
  • to heat water for household needs;
  • to provide heating of the house for 1-2 hours in case of TT-boiler extinguishing.

Note: Due to its small volume, the heat accumulator’s autonomous operation duration is limited. It can, however, be installed in any furnace room and, because it is connected directly and does not require a pump, can remove heat from the boiler following a power outage.

This is the appearance of an unclad cylinder tank.

What you’ll need to assemble the storage tank is:

  • 2 standard propane cylinders;
  • at least 10 m of copper tubing Ø12 mm or stainless steel corrugation of the same diameter;
  • fittings and thermometer sleeves;
  • Insulation – basalt wool;
  • Painted metal for the trim.

To prevent the residue gas from exploding, you must remove the cylinders’ valves and use a bolgar to cut off the caps. Then, fill the caps with water. Gently coil the copper pipe around a pipe with an appropriate diameter. Follow these steps:

  1. Using the provided drawing, drill holes in the future heat accumulator for the thermometer sockets and thermometer sleeves.
  2. Weld a few metal brackets inside the cylinders to mount the DHW exchanger.
  3. Place the cylinders one on top of the other and weld them together.
  4. Install the coil inside the resulting tank, letting the ends of the tube through the holes. Use stuffing box packing to seal these areas.
  5. Attach the bottom and the lid.
  6. Install an air bleed fitting in the lid and a drain valve connection in the bottom.
  7. Weld the brackets for attaching the cladding. Make them of different lengths so that the finished product has a rectangular shape. It will be inconvenient to bend the lining in a semicircle, and it will not be aesthetically pleasing.
  8. Insulate the tank and screw the liner with self-tapping screws.

Linking the reservoir to a TT boiler in the absence of a circulation pump

This heat accumulator’s design is unique in that it connects to the solid fuel boiler directly—as opposed to using a circulation pump. Thus, for jointing, Ø50 mm steel pipes laid on a slope are utilized, and coolant circulates due to gravity. To supply water to radiators, a pump and three-way mixing valve are installed after the buffer tank.

How you can make a heat accumulator

The heat accumulator is typically designed in the factory as a round barrel with a circular cross section. Typically, the volume ranges from 500 to 2000 liters. Height: up to 2.5 meters, diameter: up to one meter. It has numerous welded-in fittings and is supported by legs. May include one, two, or more spiral heat exchangers to link separate circuits, such as a solar collector or a water heater that heats the water as it runs.

To prevent the air in the boiler room from becoming too hot, a layer of thermal insulation is placed inside the tank. Branded heat accumulators have an intricate internal flow distribution system. You can watch the video to see the Buderus commercial.

The basis for the design of the buffer tank is how the flows should be directed

The connection to the buffer tank is made in the following manner in order to create the proper direction of flows.

  • Supply from the boiler – in the upper part.
  • Supply from the tank to the radiators – in the upper part, at the boiler supply level
  • Return from radiators – in the lower part.
  • Return to the boiler – in the lower part, just below the return from radiators.

In this instance, the liquid in the heat accumulator needs to flow from top to bottom, from the boiler to the radiators, and along the boiler circuit ring.

Temperature sensors can be used to determine the direction of fluid flow; in general, the boiler return should be warmer than the radiator return.

It is crucial to follow this principle: the heat accumulator won’t function correctly unless the coolant flow rate in the boiler circuit is greater than the flow rate in the radiators. Usually, the consumer circuit’s higher hydraulic resistance using the same pumps provides this.

As soon as hot coolant enters the thermal accumulator, it is pumped from the upper section to the radiators. This allows for operational control of the entire heating system and responsiveness to daily temperature variations.

When installing a heat accumulator, the most crucial thing to remember is that the boiler must be protected against cold return. One way to do this is by using a three-way valve.

How much buffer capacity will be needed?

What is the critical volume of the heat accumulator that is deemed sufficient? The standard operating mode, assuming radiators function properly, involves heating to +90 degrees and cooling to +60 degrees. The energy that can be stored and used is contained within a 30-degree difference.

An average insulated 100 m³ house will require one ton of water to heat it for five hours during peak frost, according to a straightforward thermal calculation. Additionally, at daily average seasonal temperatures.

In actuality, a small, well-insulated home with a 1.2 ton capacity can be without a 30 kW wood-fired boiler for two days. It doesn’t make sense to put a buffer tank under 0.8 tons.

Assembling a simple heat accumulator

The idea behind the simplest heat accumulator is similar to that of a thermos. The water retains its warmth for a considerable amount of time due to the unit’s walls, which virtually conduct no heat.

In order to put together such a unit, the following gadgets are required:

  • tank. The volume should be selected individually, according to your needs and possibilities. The objective minimum is 150 liters;
  • material for thermal insulation. Mineral wool is excellent;
  • adhesive tape;
  • copper tubes for making the coil;
  • concrete slab or planks for formwork and mortar for pouring.

An iron barrel can serve as the foundation for the assembly of the heat accumulator. As previously stated, the volume is chosen on an individual basis; however, using a tank that is less than 150 liters makes no particular sense.

First step

Getting the barrel ready for more work. If the tank is old, make sure to completely clean it of all impurities and corrosion remnants.

View of the heat accumulator overallHeat sinks and spigots. 1. The heating system. 2. The upper coil. Bottom coil is number three. TA cooling is number four. Group 5: safety. Magnesium anode number six Spouts on one side, heat accumulator on the other. 1. Wats thermocouples. 2-Boiler with solid fuel. 3-thermal sensors for the controller of the solar system

Second step

Cover the external walls with a layer of thermal insulation. Mineral wool is a wise selection. In addition, duct tape is wrapped around the barrel in multiple layers after it has been covered with thermal insulation.

Third step

Encase the tank in foil. We also use adhesive tape to secure the material. Cover the insulated structure with sheet metal if you’d like.

Fourth step

Form a coil that will be used to move the coolant. We use a copper tube for this purpose, which has a diameter of roughly 20–30 m and a length of 8–15 m, depending on the volume of the barrel we choose. Insert the pipe into the tank after bending it into a spiral. The boiler and coil are connected. This coil will eventually be heated, and the water in the tank will receive the heat as a result.

Fifth step

We create spigots in the accumulator’s side walls. One pipe will carry cold water into the tank, while the other will carry hot water out. Install taps in the pipes so that the water flow can be quickly stopped.

Sixth step

Connect the thermal storage tank and install it.

We examine the diagram to gain a better understanding of the heat accumulator’s connection order.

Crucial! Only a concrete slab can support the drum. Purchase a pre-made item or cast the base ourselves.

The accumulator is connected to the heating system that uses a single boiler in accordance with the method under consideration. If additional heating units are used, the plan will get considerably more intricate. Safety valves, explosion protection, temperature and pressure sensors, and other components must be installed in the system. It is advised that you only attempt to assemble such a unit if you possess the necessary knowledge and expertise.

This post will go over the specifics of solid fuel boiler piping with an emphasis on two main configurations: those that use a heat accumulator and those that don’t. Selecting the appropriate system for your home’s heating and insulation is essential for both comfort and efficiency. We’ll analyze the benefits and drawbacks of each plan so you can decide which is best for your family. It is crucial to comprehend these piping configurations whether your goal is to optimize heat retention, minimize energy usage, or optimize your heating system. Let us now explore and clarify solid fuel boiler piping so that you can maintain a comfortable and economical home.

Selection of the heat accumulator

The other selection criteria for the tank are primarily about options and are not as crucial. A built-in coil that heats water for domestic use is one of them. If there are no other options for heating, it might be helpful, but this approach is undoubtedly inappropriate for high DHW network costs. Furthermore, a portion of the heat accumulator’s "charge" will be removed by the heat exchanger, shortening the amount of time that the heating system can operate independently.

An effective feature that is integrated into the top section of the TEN tank is its ability to keep the coolant’s temperature at a predetermined level. Electric heating means that in the event of an emergency, the system won’t defrost and can even continue to heat the house after the battery has "discharged" and the boiler hasn’t been started.

Only in southern regions is the second coil for connecting the solar system useful, as it allows you to load the heat accumulator with solar activity.

However, you should consider the tank’s working pressure when making your choice. Remember that the majority of solid fuel boilers are built to withstand jacket pressure of up to 3 bar, and the buffer tank should be able to safely withstand the same amount.

How to calculate the required volume of the heat accumulator

An inefficient solution is to have a tank that is either too big or too small for the heated coolant to accumulate. This means that the required volume of the tank must be determined mathematically, with difficult-to-achieve results due to approximations of the initial data, which includes heat losses in the room, the house’s foundation and walls’ insulation properties, the insulating qualities of the building materials used for the walls, floors, and partitions, and the same parameters for window and door openings. However, the heat accumulator can still be roughly calculated. This method is meant to be used in the event that the building’s precise heat losses are unknown, particularly if it has not yet been constructed.

The following factors can be used to determine the heat storage tank’s size and volume:

  1. The total area of the heated premises;
  2. Thermal capacity of the heating equipment.

The volume of TA is determined by these two factors.

Assume for the moment that the heated area of the room must be used to determine the heat accumulator’s volume for the heating system. The calculation is as simple as multiplying the area in square meters by four (Sx 4). For instance, a 200 liter tank would be needed for a house with a 50 m2 total heated area. Practice indicates that the boiler can only be loaded with solid fuel once per day with such a TA volume. Both the economy and efficiency are excellent.

Astute proprietors will advise installing a pyrolysis boiler, which functions identically. However, the functioning of this type of boiler is somewhat more intricate and inefficient, as follows:

  1. First the fuel is ignited and ignited;
  2. The air supply is then restricted;
  3. The last to be activated is fuel smoldering (pyrolysis).

When fuel is burned, the coolant’s temperature rises sharply. The pyrolysis process keeps the coolant’s temperature at a certain level, but a lot of heat energy just vanishes into the chimney pipe during the process, barely heating anything. Another drawback is that when coolant reaches its highest temperature, it may boil and overflow the expansion tank. Additionally, PVC pipes used for heating distribution may break more quickly due to elevated temperatures.

Calculation of the heat accumulator

It is best to speak with a qualified expert to determine the heat accumulator’s necessary capacity. However, there are also computation techniques that allow you to estimate the buffer device’s capacity, which can help you decide what kind of boiler to buy, where to put the thermal storage, and how big the boiler room should be.

There are two ways to compute:

  • simple, based on the practice of specialists;
  • according to the formula.

Experts have concluded that 25–50 liters of heat generator volume are required for every 1 kW of boiler output, based on years of experience. The truth lies in the midst of things. The house will be cold because the heater will only accumulate heat and the system won’t have enough of it if you put in a smaller storage tank, which will result in the boiler operating with less efficiency.

Based on the formula, the capacity is determined in this way: Where Q = mc (T2-T1)

  • Q – amount of accumulated heat,
  • m – volume of water in the tank,
  • c – specific heat capacity, equal to 4200 J/(kg-K) ,
  • T2 and T1 – water temperature values at the inlet and return flow.

Connection professional recommendations

You have multiple options for connecting the heat accumulator in order to optimize the efficiency of your solid fuel boiler-based private heating system. Professional masters use them frequently, but you can learn how to do them yourself because they don’t involve any complicated or magical concepts.

A word of caution: keep in mind that the fundamental idea behind building the boiler’s continuous fuel circulation system directly affects the cost of the work.

With liquid mixing

The plan for attaching the heat accumulator to a typical solid fuel boiler is very evident. applied simply and economically to the strapping of permanent heating systems, which rely on the boiler’s simple gravity fuel circulation system. In this case, the following takes place:

  • During the heating of a set volume of water in the heat exchanger of the device itself, it begins to circulate through the entire system of the installed pipeline, which passes through the boiler valve.
  • When the temperature set by the user is reached, the built-in valve actively starts working and accordingly maintains the pre-set value, gradually adding only cold water from the boiler itself.
  • At this moment, hot water from the installed unit is poured into the tank – this is how the heat accumulator is charged.
  • During the entire time, which can only be determined by the boiler tank, the fuel is completely burned out.
  • Begins the reverse process, which consists of supplying water to small radiators. The temperature remains stable all the time.
  • When the direct source of necessary heat can not support the stable heating of water in the tank heat accumulator, the installed valve is quickly and reliably closed, and the system immediately acquires its original state.

The boiler instantly enters a unique buffer mode that restricts system operation to the check valve in the event of a power outage or circulating pump failure.

After reaching this temperature inside the boiler, the water actively flows into the installed tank. After that, it is directed toward multiple heating radiators. This ongoing procedure guarantees a clean drop in high temperatures and a seamless heating of the water.

Advice: The heat accumulator should be positioned high enough to avoid contact with the heating radiators in order to guarantee optimal performance from the heating scheme.

With hydrodistribution

Systems of this kind are available for practically all boiler models. They make it possible for a steady and uninterrupted power source. It is important to accurately and clearly provide a source of stable and complete power supply in order to guarantee that the entire system under consideration operates correctly and efficiently.

This idea can be put into practice in the following way: the installed boiler will only act as a special tank, stabilizing the temperature of a large enough volume of water to ensure comfort in the room. This makes sense when multiple private heating circuits need to be powered simultaneously.

Today’s users and developers also frequently connect the heat accumulator to this kind of solid fuel boiler.

The specific heat accumulator connection scheme that is selected will depend only on the needs of the home’s owner and occupants. In this case, weighing all the benefits and drawbacks is essential, as is considering numerous factors that may have a big impact on the decision.

The area that will be heated by a solid fuel boiler, the components and units used throughout the installation, the anticipated number of circuits created in the strapping, and the existence of a well-planned system for the room’s hot, steady water supply all play a significant role.

Arranging the connection scheme correctly is a difficult task that calls for the appropriate approach and heightened focus. It is best to leave the process to knowledgeable and experienced professionals if you are unsure of your knowledge.

General installation instructions

Ascertaining the location of the heating unit’s installation is essential before making a purchase. The furnace room is meant to be used for this, but frequently there isn’t enough room for it because an existing gas or other heater occupy it. The installation of a solid fuel boiler in a private residence can then be done in the annex, behind the wall of the furnace room. A metal frame is assembled and sandwich panels or insulated profiled sheeting are placed on top. For those who choose to heat with coal, this is a convenient option because there won’t be any dirt inside the house.

All low-cost solid fuel boilers for low-power homes may be installed directly on the coarse floor screed. Because they lack a screw conveyor or fan for feeding pellets, they are lightweight and do not cause vibration loads on the base. Building a concrete foundation that sits on the ground and compacted crushed stone bedding is advised for units that produce more than 50 kW of power. The foundation should not be attached to the screed because it is constructed 80–100 mm above its level. A foundation is also necessary for long-burning boilers with heavy load lifting and lowering mechanisms.

Private home projects typically include a chimney shaft built into the wall’s thickness and a chimney exit through the roof. A chimney must be installed for a solid fuel boiler if the shaft is nonexistent or currently occupied by a gas heater. It is preferable to use metal double-walled chimneys with insulation for this purpose. They are easily affixed to the home wall, lightweight, and constructed from sections of the necessary length. The same double-walled tees and bends are made for turns and branches. The figure below illustrates chimney installation techniques both with and without an exhaust shaft.

There needs to be natural exhaust ventilation in the furnace room. An exhaust shaft located in the wall is used when heating boilers are installed in private homes. The shaft has a smaller cross-section and runs parallel to the chimney. It should be under the room’s ceiling if it is not placed in the overflow grate on the outer wall. The hood’s function is as follows:

  • In the furnace room, a vacuum is created, as a result of which the supply air from other rooms is sucked in and used for combustion. Boiler units with a capacity of 50 kW and above require the organization of a separate supply ventilation system.
  • Removal of combustion products that accidentally got into the room.

The figure depicts the approximate equipment layout and boiler installation diagram for solid fuel heating.

Often, country homes’ boiler rooms lack a sewerage outlet. This is not entirely accurate, as there are instances when emptying the boiler’s water jacket or the system is required. The same outlet is where the safety valve’s discharge is directed.

Installation procedure

The following guidelines are recommended for the installation of solid fuel boilers:

  1. Release the product from the factory packaging.
  2. If there is little space in the furnace room, it is better to assemble the product outdoors. Install all doors and ash pan drawer, as well as other elements supplied separately. It is not necessary to install the fan and automation devices, this is done after the boiler installation.
  3. Move the unit into the room and install it on the foundation or floor so that the gas outlet is on the same axis as the chimney pipe. At home installation of solid fuel boiler with your own hands should be done with a helper, the weight of the equipment is rarely less than 50 kg.
  4. Fix the boiler on the foundation or screed so that there is no misalignment.
  5. Connect the chimney, install the fan with control unit and safety group.
  6. Connect the boiler to the heating system according to the selected scheme.

Preparing for piping

Three tasks are solved by boiler piping:

  1. Uniform distribution of heat throughout the system.
  2. Protect the boiler from overheating, which is fraught with stopping the equipment (the best option) or explosion (the worst option).
  3. Qualitative supply of hot water, if the boiler is two-circuit.

The heating boiler’s strapping can be classified as complex or simple (conditionally) based on the complexity of the installation. Simple strapping is typically done for expensive boilers that already have the majority of the coolant distribution and protection components built in. It consists of a minimal number of devices, devices, and units. When installing the simplest boiler—which functions more like a gas burner—complex boiler piping—the same set of pipes seen in the picture—is installed.

Boiler piping for solid fuel

Note: Generally speaking, the cost of the boiler and its pipework are inversely correlated: the more expensive the boiler, the easier and less expensive its installation; conversely, the less expensive the boiler, the more intricate and costly the piping system.

However, this is not true for industrial facilities, where higher safety standards are in place and a full piping scheme—which occasionally duplicates the heating boiler’s built-in functions—must be created in order to meet acceptance standards.

Boiler pipe variation

The piping of industrial boilers placed in sizable boiler rooms that provide heat to specific neighborhoods or businesses is not taken into account in this material.

Complete set of strapping

The following components make up the piping:

  • Membrane expansion tank. It is designed to compensate for surges in the volume of the coolant during heating. Such a need arises in closed heating systems. There is an elastic diaphragm inside the vessel, which divides it in half. In one half there is air or nitrogen (in this case the tank walls are not subject to corrosion). When the volume of coolant increases, it provokes gas compression: as a result, the total pressure in the system remains practically at the same level. The standard volume of the expansion tank is 10% of the coolant volume. For a rough calculation, the ratio of 15 liters/kilowatt of heating boiler output is usually used.
  • Safety valve. Discharges excess coolant when the pressure in the circuit rises to dangerous values. As a result, pipes and radiators are saved from bursting. A drainage pipe is provided for draining the water into the sewer system. If this valve operates regularly, it indicates insufficient capacity of the expansion tank.

  • Air vent. If air plugs occur, they are automatically expelled outside. This refers to air accumulations formed in the system as a result of draining the coolant. Because of them there are hydraulic noises and additional obstacles for normal circulation in the mode of low hydraulic head.
  • Pressure gauge. Controls the operating pressure in the circuit. It is sometimes replaced by a thermomanometer, which additionally records the temperature. The scale of the device should be marked up to 4 atmospheres.
  • Open expansion tank. Replaces the expansion tank, air vent and safety valve in an open circuit. In this case the system does not face the problem of overpressure. A tap is used to connect the tank, which communicates with the atmosphere, to the DHW system: this ensures the make-up of the circuit.
  • Indirect boiler. Inside this insulated container with a heat exchanger, hot water is prepared. The heat is supplied by the coolant from the heating system flowing through the heat exchanger. This element is included in the scheme of piping of gas single-circuit heating boiler.

  • Circulation pump. Thanks to it the forced circulation of the heating medium through the heating circuit is realized. When selecting a suitable pump pay attention to the level of pressure and performance created by it. The power consumption of modern models is adjustable between 50 and 200 W. Thanks to this, the speed of the coolant flow can be changed depending on the situation.
  • Hydrostrelka. Several heating circuits can be connected to this container with spigots. Its task is to unite supply and return pipes. As a result, it is possible to bring together systems with different temperatures and fluid velocities, smoothing out their mutual influence.

  • Coarse filter. Inside the settling tank with a filter mesh, large particles in the water are delayed. Most often it is about sand and scale. This prevents clogging of the thin tubes of the heat exchanger in the gas boiler.
  • Two- and three-pass thermostatic mixers. Thanks to them, it is possible to create recirculation of the coolant, the temperature of which is an order of magnitude inferior to that of the main circuit. A thermal head is used to control the mixer valve gate. The valve changes its position in response to the temperature of the sensing element.

Power supply requirements

Due to their energy dependence, Baxi boilers require a 220V electrical voltage in order to operate. Since the unit’s electronic equipment is essentially incapable of withstanding network voltage surges, experts advise installing a voltage stabilizer prior to the boiler.

Installing a surge suppressor will also be required to shield the boiler from surge currents during thunderstorms or when nearby powerful electrical equipment is turned on.

Grounding the two-circuit boiler with a potential of 0.5 V between ground and neutral is equally important for the safety of equipment operation and maintenance. A continuous potential on the grounding bar caused by improper grounding can result in failures during ignition and frequent boiler shutdowns.

As a result, the house will become cold and the air in the rooms will cool.

An improperly grounded boiler can result in a continuous potential on the grounding bar, which can cause ignition malfunctions and frequent boiler shutdowns. As a result, the house will get colder and the indoor air will cool down.

Connection of the boiler to the communications

The Baxi boiler unit is installed in a non-residential space, like the kitchen, and has dependable supply ventilation and three hours of air exchange per hour.

According to the approved piping scheme, the heating circuit is connected to the supply/return connections on the unit’s rear panel.

Next, the boiler’s chimney system is connected:

  1. Install the flue pipe through an adapter to the flue pipe of the boiler.
  2. The chimney and the flue pipe of the unit must have the same dimensions, it is specified by the manufacturer in the technical documentation.
  3. The flue duct is selected so that the chimney section is as short as possible.
  4. The vertical section of the pipe from the connection point to the header must be at least 6 m and provide a draft in the furnace chamber in the range 0.8 mm – 3.0 mm water column.
  5. The draught is measured during the operation of the appliance.
  6. The chimney must be thoroughly attached and must not rest on the boiler unit.
  7. The places where the pipe passes through the structural elements of the wall, ceiling and roof must be well insulated.

Next, attach the internal components to the Baxi boiler’s control module:

  • connect the transformer for piezo ignition and the gas pressostat to the 6 terminal connector;
  • connect the main 2-stage valve to the 9-terminal connector;
  • connect the additional 2-stage valve to the 3-terminal connector;
  • connect the left electrode of the ignition cable and the right electrode of the ionization cable to the piezo igniter;
  • Install the primary sensors for temperature and pressure in the technical openings indicated on the piping diagram provided by the manufacturer.

How to choose a buffer tank

Calculation of the minimum required volume

The tank’s volume is the most crucial parameter, which needs to be decided upon right away. To optimize efficiency, it should be as big as possible, but only up to a certain point where the boiler output is enough to "charge" it up.

The following formula is used to determine the buffer tank volume for a solid fuel boiler:

  • where, m is the mass of the coolant, after calculation it is not difficult to convert it into liters (1 kg of water ~ 1 dm3);
  • Q – required amount of heat, calculated as: boiler output * period of its activity – heat losses of the house * period of boiler activity;
  • k – boiler efficiency;
  • c – specific heat capacity of the coolant (for water it is a known value – 4,19 kJ/kg*°C = 1,16 kW/m3*°C);
  • Δt – the temperature difference between the supply and return pipes of the boiler, readings are taken at steady-state operation of the system.

For instance, the heat loss for a typical house with two masonry bricks covering 100 m2 is about 10 kW/hour. As a result, 10 kW of heat (Q) are needed to keep the balance. A 14 kW boiler with an 88% efficiency rating heats the entire house; the boiler burns through wood in 3 hours.

First, we must determine how much heat is needed.

14*3–10*3 = 12 kW is Q.

Consequently, t = 0,336 cubic meters, or 336 liters, and m = 12 / 0,88*1,16*(85-50) = 0,336. This is the buffer tank’s minimum required capacity. At this capacity, the heat accumulator will store and distribute an additional 12 kW of heat after burning the charge (3 hours). More than an additional hour of warm batteries on a single charge is what the house in the example experiences.

Number of heat exchangers

Heat exchangers inside the storage tank made of copper.

The existence and quantity of heat exchangers should be the second thing to check after choosing the volume. The decision is based on the preferences, the CO’s requirements, and the tank connection scheme.

A basic heating system only needs an empty model without any heat exchangers.

The small boiler circuit can only operate with forced circulation, so if natural circulation is intended for the heating circuit, an additional heat exchanger is required. Compared to a heating circuit with natural circulation, there is more pressure in this situation. It will also be necessary to purchase additional heat exchangers for DHW or underfloor heating.

Maximum allowable pressure

The maximum allowable operating pressure must be considered when selecting a buffer tank with an extra heat exchanger; this pressure cannot be lower than that of any of the heating circuits. Most models without heat exchangers are made with tanks that can withstand internal pressures of up to 6 bar, which is more than sufficient for a typical CO.

Material of the inner tank

There are currently two different inner tank construction options:

  • mild carbon steel – covered with a waterproof anti-corrosion coating, has a lower production cost, used in inexpensive models;
  • stainless steel – more expensive, but more reliable and durable.

Other selection criteria

Once the primary technical requirements have been established, you can focus on other aspects that improve effectiveness and user comfort:

  • the possibility of connecting TEN for additional heating from the power grid, as well as additional control and measuring devices, which are mounted by threaded or socket (but in no case welded) connection;
  • the presence of a layer of thermal insulation – in more expensive models of heat accumulators between the inner tank and the outer shell there is a layer of insulating material that contributes to even longer heat retention (up to 4-5 days);
  • weight and dimensions – all of the above parameters affect the weight and dimensions of the buffer tank, so it is worth determining in advance how it will be brought into the boiler room.

Two-pipe system with top connection

The expansion tank is positioned highest in a two-pipe heating system with a top connection.

The only difference between this two-pipe scheme and the previous one is that the expansion tank is supposed to be installed in the uppermost portion of the system—perhaps under the ceiling or in the insulated attic. The coolant then descends to the radiators, where it transfers some of its heat before returning via the return pipe to the heating boiler.

Why is a plan like this required? It works best in buildings with several stories and lots of radiators. This results in more uniform heating and eliminates the need to install numerous air bleeders because the air will be evacuated through the expansion tank or an additional bleeder that is a part of the safety group.

Advantages and disadvantages of the two-pipe system with overhead distribution

Positive attributes abound:

  • multi-storey buildings can be heated;
  • saving on air bleeders;
  • it is possible to create a system with natural circulation of the coolant.

There are a few drawbacks as well:

The concealed heating installation will become more challenging if vertical distribution is used.

  • pipes are visible everywhere – this scheme is not suitable for interiors with expensive finishes, where the elements of heating systems are usually hidden;
  • in tall houses it is necessary to resort to forced circulation of the coolant.

The plan is still widely used and quite popular in spite of its drawbacks.

Features of installation of two-pipe systems with top distribution

It is not necessary to place the heating boiler at the lowest point thanks to this scheme. The supply pipe is redirected upwards right after the boiler, and an expansion tank is placed at the highest point. This uses a lateral or diagonal radiator connection scheme because the coolant supply to the radiators is done from above. The cooled coolant is then directed toward the return pipe.

Nuances of strapping installation

Maevsky cocks are fitted in all heating schemes, barring open ones, at the highest points in order to extract air.

Considerations for ensuring system performance include the following subtleties:

  1. The surface under the installation of the boiler must be strictly horizontal.
  2. Dimensions of the base – size of the unit + 10 %.
  3. An expansion tank should be used in any heating system with a boiler.
  4. Preferred connection of devices – threaded connection.
  5. Connection of the heating unit should only be made using steel or copper pipes.

Boiler safety strapping for solid fuel. You can read more about the private home plan that involves strapping the heating boiler at this link.

Selecting the appropriate plumbing layout for your solid fuel boiler system is essential for effective home insulation and heating. Every scheme has pros and cons, and choosing one with or without a heat accumulator is up to you.

Heat is transferred directly from the boiler to the radiators or underfloor heating system when the piping scheme does not include a heat accumulator. This configuration is easier to install and maintain because it is more basic and uncomplicated. But without a heat accumulator, the system might heat unevenly and experience temperature swings, especially when there isn’t much demand.

However, there are a number of advantages to including a heat accumulator in the plumbing design. When needed, the accumulator gradually releases the excess heat that the boiler produces. This contributes to more even and comfortable heating by helping to maintain a constant temperature throughout the house. Additionally, by minimizing fuel consumption and lowering the frequency of boiler cycling, a heat accumulator can raise the system’s overall efficiency.

Think about your heating needs, your budget, and the space you have available when choosing between the two options. For smaller properties or seasonal use, a piping scheme without a heat accumulator might be adequate; however, larger homes or those with higher heating demands might gain from the extra stability and efficiency that a heat accumulator offers.

The final decision regarding the plumbing scheme is based on your personal requirements and tastes. You can choose the best option for your house and ensure year-round comfort and efficiency by speaking with a heating and insulation specialist.

Video on the topic

Boiler piping without buffer.

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