Closed and open systems of hot water supply: device and main differences

Having a dependable hot water supply system is crucial for maintaining the coziness and comfort of our homes. However, did you know that this can be accomplished by a variety of systems? This essay will examine the key differences and differences between closed and open hot water supply systems, highlighting their various components.

Let’s begin with the fundamentals: What precisely are open and closed hot water supply systems? In essence, their shared function is to supply hot water for different domestic uses, including heating, cooking, and bathing. Their workings and mechanisms, however, are different.

Let’s start by discussing closed hot water systems. These systems function in a closed loop, as the name implies, which means that the water used for heating moves through a closed circuit. In this setup, the water is heated by a boiler or water heater and then circulated through pipes to different fixtures and back to the heating source.

Open hot water systems, on the other hand, function very differently. Open systems have a direct connection to the main water supply, in contrast to closed systems. The system takes water from the mains, heats it, and then distributes it to the appropriate fixtures when hot water is required. The water then goes back into the drainage system after being used.

Let’s now examine some of the most significant distinctions between these two systems. One important difference is that they are more easily contaminated. Compared to open systems, which allow water to enter directly from the mains, closed systems are less vulnerable to contamination from outside sources because they are isolated from the main water supply.

Their energy consumption and efficiency represent yet another significant distinction. Since they can constantly circulate and reheat the same water, closed systems are typically more energy-efficient than open systems, which might need more energy to heat the water because it is drawn straight from the mains each time it is needed.

It is essential for homeowners to comprehend the distinctions between closed and open hot water supply systems in order to make well-informed decisions regarding their heating infrastructure. People can select the system that best fits their needs, budget, and environmental concerns by weighing the benefits and drawbacks of each one.

Closed System	Open System
A closed system of hot water supply operates in a loop, where water circulates through pipes.	An open system allows fresh water to flow directly into the heating system and then out through taps.
In a closed system, water is continuously reheated and reused.	In an open system, water is used once and then drained away.
Pressure is maintained in a closed system, often with the help of a pressure vessel.	Open systems operate at atmospheric pressure.

Types of heat supply systems

Systems for supplying heat are categorized by:

• temperature regime (high potential, medium potential and low potential);
• type of heat carrier (steam and water);
• Number of pipelines (single-pipe, multi-pipe);
• method of connection (single-stage and multi-stage);
• method of water supply for DHW (open and closed).

Not DHW, but the concept of open and closed systems governs how heat supply systems are organized.

Two categories of hot water supply schemes can be distinguished based on where the heat source is located:

1. Decentralized. Serves one object.
2. Centralized (CSHW). Water heating is provided by CHP or boiler houses. Closed or open water supply systems can be used.

In industrial plants, secondary steam is frequently utilized. Water that has been highly superheated is used for both populations and organizations.

Open system

What is an open hot water supply system? A practical solution for low-rise homes with short risers is the dead-end network. It is intended for use in residential and commercial water supply systems where a continuous hot water flow is necessary. Apart from residential structures, it can also include bathing establishments, catering businesses, and leisure associations.

The metal capacity of the open system makes it more advantageous, but because of the quick cooling, you have to empty the cooled water and wait for a while before using the hot water from the tap.

Because of the irrational use of the water resource, multi-story buildings do not use this system.

Structure of an open circuit

How does an open system operate? It is made up of a supply and return tube that are connected in an elevator or heating station where the water is heated to 60 degrees Celsius. It is then fed into the house’s internal plumbing system.

A dead-end network operates on a very basic principle. The circuit consists of a pipeline that goes to the distribution points, a heating device, and a transportation circulation pump.

What makes up an open system is:

• pipes of various cross-sections (with a diameter of 20 – 200 mm);
• thermometers;
• thermal insulation;
• check valves;
• pressure gauges;
• ball valves;
• gate valves;
• temperature regulators (with or without a controller).

There are various installation options, which include:

1. Upstream. It is realized on the under-roof technical floors in buildings with the possibility of installing water heating tanks.
2. With bottom connection. The equipment is installed in the basement, which provides easier maintenance. However, with this method, the pressure for all floors is not the same, so to maintain it is usually installed booster pumps.

The following factors affect the water’s flow rate:

• the height to which the water is delivered;
• dynamic pressure;
• unavoidable losses.

As a result, float sensors are installed in the tanks and pressure switches are mounted on the pipes. The pipeline’s branches are fitted with shut-off valves, which allow the section to be temporarily disconnected from the network, saving the need to empty the entire system for maintenance.

Pros and cons

In an open system, head stability is preserved hydraulically—that is, by forcing hot water out of the cooling water. Maximum heat energy delivery is achieved without exorbitant heat transfer medium costs.

It is inexpensive to operate because it requires little equipment and is easy to install. An open network can be sustained with just one plumber.

• water quality is not potable;
• The presence of harmful chemical impurities that can cause irritation and dry the skin;
• The presence of an orange color due to rust;
• unpleasant odor from hot water;
• in centralized conditions water has a high cost;
• it requires payment for more expensive desalinated water;
• due to improper operation of the system, it is possible to have water over 100°C, which leads to burns.

The quick cooling of hot water is the primary drawback of an open network. When they turn on the tap in the morning, many locals have to wait a while for the hot water to start flowing and the cold water to drain. The most affected apartments are those with meters installed.

Rapidly cooling water causes the temperature in heating radiators to become unstable, which is a drawback. The expense of treating the water also eliminates the benefit.

Water is supplied to the majority of the older buildings via a dead-end system. A new closed system with specially installed water-heating equipment is utilized in newly constructed buildings. Federal Law No. 190 mandates that all construction projects must transition to closed schemes by 2022.

Closed system

A closed hot water system: what is it? Heat exchange occurs in the closed or ring scheme because, in contrast to the open scheme, water from the heating network is heated without interacting with the heat transfer medium. In other words, the user uses network water to heat potable cold water that is taken from the water supply through an extra heat exchanger.

Along with the devices utilized in the dead-end circuit, the following are installed:

• controllers;
• pumps;
• plate heat exchangers for DHW;
• control panels.

Differently qualified staff members work in a complex to maintain the open network. Therefore, thermal insulation, pipes with different cross sections, gate valves, thermometers, manometers, temperature regulator taps, and valves are maintained by a team of fitters or plumbers.

The electrical units require the attention of an electrician, and the thermal automatics and controllers are the responsibility of workers from a specialized company.

Benefits of the closed system include:

• good quality hot water, close to drinking water;
• absence of unpleasant odor;
• constant temperature starting at +60°C but not above 100°C as in the open scheme;
• easier control of the system;
• Lower cost of water preparation, no need to overpay for chemically desalinated water.

Disadvantages of the system

One of the main drawbacks of a looped system is that its indisputable benefits come at a higher network cost. Higher costs result from a more technically complex scheme because individual water heaters with a vast communications arsenal are introduced. As a result, the system’s drawbacks include the need for pricey equipment, which raises capital expenses and increases maintenance costs.

Since polymer tubes cannot withstand intense heating, cheap brass tubes are used to connect this network. However, brass doesn’t corrode, so compensators are unnecessary, and the design is made simpler.

You can also include the difficulty of controlling the water flow rate here. Technically speaking, it’s not always feasible to put a storage tank close to every boiler. Due to the fact that the equipment is powered by electricity, electricity costs also rise.

Even with proper operation, closed circuit heating systems lose 0.5% of their water, so a booster pump must be used on a regular basis to replenish the water. Vacuum deaerators that are installed in the central heating plant guarantee the quality of the water.

Thus, there are benefits and drawbacks, as well as distinctions between open and closed systems. Although an open scheme is less complicated and more affordable than a closed one, the hot water quality is not as good. Although a looped network costs more and needs more maintenance, the water it contains is of higher quality.

Installing a ring scheme is advised by experts when the water supply is centralized. Installing a dead-end network is less expensive and simpler for people who use subterranean water intake, which can result in significant cost savings. Remember that you can still use it in 2021, but only for a limited time—until 2022.

Purpose and application

Pumps used for hot water recirculation serve a vital purpose. These devices guarantee that the closed pipelines used to transport the hot water operate in the necessary manner. Recirculating electric pumps raise the pressure of the liquid medium they pump and, in turn, the velocity of the liquid’s movement by forcing it into the pipeline through the rotation of special elements.

Recirculation pumps are frequently fitted with heating systems, which enhances both the economy and efficiency of the latter. As you are aware, the majority of these systems operate at the expense of the coolant, which transfers heat into the room through the pipeline. A boiler, water heater, or boiler provides the heating of the heating medium (in this case, prior to it being fed into the pipeline). The water needs to return to the heating apparatus and be again heated to the proper temperature after going through the full heating circuit.

The pipeline elements will dampen the pressure of the coolant flow, which is not further increased in any way, causing water circulation in the heating system to be slow or possibly nonexistent without the use of specialized pumping equipment. The end effect is uneven heating of the heating pipes, which leads to uncomfortable temperatures in the house’s rooms.

The hot liquid flowing through a closed pipe loop experiences an increase in head and pressure when a circulation pump is used for the hot water supply. The use of hot water circulation pumps in the plumbing systems of homes larger than 200 square meters, where the boiler is located in a separate room or the basement, and there are multiple water intake points, is particularly pertinent. If these pipelines don’t have a recirculation system with a special pump, the water in them quickly cools down. These pipelines are typically quite long. As a result, when the tap is opened, there is a lengthy wait for the heated liquid to come out.

Furthermore, when multiple taps at the water intake points are opened simultaneously, the water pressure decreases because there is nothing more to support the pressure of the liquid flowing through the pipeline due to gravity. In order to address the specific issues that owners of private and apartment buildings encounter, the DHW pump is engineered to deliver stable head and pressure as well as forced water movement within the hot water supply system.

Because the heat from tanks and water heaters can affect the thermostat, the recirculation pump should not be placed close to these items.

In addition to the aforementioned benefits, using a circulation pump in a private residence for hot water delivery and heating also saves energy. The temperature of the boiler water barely drops during transportation because in recirculating systems, the water is forced through pipes to reach all water intake points and heating radiators much faster. If the pipeline the boiler serves has forced water recirculation, it takes less time for the boiler to heat the water, which lowers the energy required to run the heating equipment.

Hot water circulation pumps are widely used in "warm floor" systems, the design of which depends on the existence of a lengthy pipeline circuit with a complex configuration made up of small-diameter pipes. The circulation pump makes sure that the heating medium flows through the pipes continuously in these situations.

What elements include the scheme of water supply of an apartment building?

A cold and hot water supply can be found in nearly every apartment building. Water is a valuable natural resource that can be used for drinking, cooking, and other domestic purposes. A contemporary system is comprised of multiple components:

1. Water meter.
2. Elevator unit.
3. Dispensers.
4. Standpipes.
5. Lines.

An apartment building’s hot water supply plan should only be created by an expert who specializes in doing such work.

Elevator unit

The system includes an elevator unit to heat the medium. This kind of node controls the water’s temperature. The following are additional features:

1. Full and continuous operation of the entire heating system is ensured.
2. The heat carrier in the system is supplied to the apartment building directly from the central supply pipeline.
3. The heating unit can switch the hot water supply between the supply and return paths. This function is often used when the ambient temperature drops to low levels.

A great deal of different components are combined in the elevator unit’s design. There are various methods for connecting; the adapter is cut in at both the heating point and the route’s inlet. Here, the quantity of taps varies greatly depending on the system’s intended use.

By using a dead-end tapping scheme with two connections for the water metering unit, HTW for DHW is produced. It ascertains that the water will only flow in response to an opened faucet or tap. The following are the connection’s drawbacks:

1. If there is no water intake from the installed riser, the water will be cold at all times.
2. Installed towel rails will be warm only in case of water intake from the required riser of the apartment. If the air temperature in the bathroom will not be heated to the required temperature, there is a probability of mold and other growths.

The four-connection scheme ensures that there is continuous water circulation throughout the system, keeping the pipes warm at all times.

Depending on the type of installed elevator unit, the heating and hot water supply can operate in three different ways:

1. The medium flows from the outlet pipe into the inlet pipe. This scheme is considered to be more efficient when the heating system is switched off during the warm season.
2. From the supply pipe to the return pipe. This option of connection is considered the most effective when applied in the fall or spring period.
3. From the return pipe to the return pipe. This scheme is suitable when the ambient temperature is low.

A dedicated room has an elevator installed. The medium can be heated with fuel or electricity.

Outlets

Outlets are made possible by the DHW system. The following characteristics of this system component are present:

1. They are laid in the basement of the building, located horizontally.
2. The outlet is created in 2 copies, which ensures high efficiency of the system.
3. The diameter of the pipe, which is used in the creation of the filling, is 32-100 mm. The rate is selected depending on how many consumers are connected.

The hot water supply is provided by pipes made of modern materials or stainless steel. The various parts of the system are connected using various fittings. They are required to ensure a high level of reliability.

risers

Installing pipes vertically creates a centralized hot water supply system. We refer to this component as a riser pipe. Hot and cold water come from different pipes.

Multiple groups that pass through a single apartment can be formed using the first riser arrangement. It supplies water to users who are spread out over large geographic areas.

In an effort to use less materials, a group of risers was made that passes through one apartment and supplies the medium to multiple nearby ones. Pipe jumpers, which come with a Maevsky tap, can be used to organize the system.

The pipes that are used to create risers have a diameter ranging from 25-40 mm. The 20 mm diameter version is used at low pressure.

General information about open and closed systems

Closed and open systems operate according to distinct principles. In a centrally closed system, the target liquid is heated via a heat exchanger to provide hot water. Water travels through a special heater rather than coming into direct contact with the heat carrier.

In a central open system, hot water supply requires blending the initial coolant with cold water. A shared main line is used to deliver the finished product to the customer.

Legislation N 416-FZ (as of December 25, 2018) "About wastewater disposal and water supply"

Differences between open and closed water supply systems

By using a closed system, it is implied that cold water from the centralized water mains will be heated using the heating medium provided by the heating network.

The heating network is the source of hot water in an open district heating and cooling system. It can only be used for household tasks like dishwashing and drying clothes. The temperature of such water can reach up to 75 degrees. It should be mentioned that water quality is the primary benefit of a closed DHW system. Water generally satisfies GOST R 51232-98 requirements if all design specifications are satisfied and no installation-related infractions occur.

Advantages of an open heating system

• easy maintenance of the system;
• The absence of a pump ensures quiet operation;
• uniform heating of the heated room;
• quick start-up and shutdown of the system;
• independence from power supply, if there is no electricity in the house, the system will be operable;
• high reliability;
• no special skills are required to install the system, the boiler is installed first, the boiler capacity will depend on the heated area.

SNiP requirements for outdoor water supply networks

When planning and building outdoor water supply networks, there are several requirements set forth by Construction Norms and Regulations (SNiP). The following is a list of these rules’ principal points:

• projects of water supply systems should be developed in parallel with sewerage projects;
• for drinking water supply systems, a sanitary protection zone must be provided for all plumbing structures and the source of water supply;
• the quality of supplied drinking water must meet state quality standards (SanPiN 4-01);
• the quality of water used for industrial purposes must meet the technological norms and requirements of the enterprise;
• the quality of water used for irrigation must meet sanitary and agrotechnical requirements;
• Cold water temperature in the systems of external water supply networks should not go beyond +2…+25°C, hot water temperature +50…+75°C
• the permissible operating pressure in the water supply system must be not higher than 0.6 MPa, not lower than 0.05 MPa;
• water supply systems should not violate the composition of architecture;
• The water supply system must comply with all electrical and fire safety standards, as well as labor safety;
• It is not allowed to get into the system contaminants from the environment, which can reduce its quality;
• Noise generated during the operation of the system and its assemblies must comply with the requirements of SNiP "Protection from noise";
• The choice of main technological solutions should be based on comparison of several possible variants.

It is possible that new water supply networks and construction technologies will emerge in the future as a result of civilization’s rapid development and the introduction of new technologies. As a result, certain changes to building codes and laws pertaining to water supply systems will be required. But only a portion of the numbers will be updated. Furthermore, the primary goal of giving humanity access to safe drinking and industrial water sources will never change.

Temperature requirements

Sanitary hygiene standards and GOST 2874-82 requirements govern the hot water parameters in residential buildings.

Resource organizations supply these specifications. The ideal water temperature is between 60 and 75 degrees Celsius.

It is illegal to try to use plumbing system water from the heating system.

DHW calculation and recirculation

Numerous factors influence the choice of equipment, including the number of bathrooms, the sanitary appliances located in them and how they operate, the number of users, the volume of liquid used, and the average water temperature that is needed. You can calculate the daily volume of liquid needed for a comfortable life by adding up all of these indicators.

For example, the water heater must heat 190 liters of water to the required temperature in 10 minutes if a family uses a shower cabin that uses about 40 liters of water for 10 minutes and draws a 150-liter bathtub at the same time.

The plumbing system’s recirculation mechanism makes sure that the water from the far end of the water intake is recycled. When distant points are more than three meters away from the heater, it is required. Recirculation can be done directly through the boiler or through a boiler.

Basic principles of operation of a closed hot water supply system

The type of water heating—open or closed—depends on the method used. A closed system is one in which the user has access to hot water. The following tenets form the foundation of the closed DHW system:

• Water supplied from the water mains enters an additional heater where it receives heat energy and is then supplied to consumers. In this case water and heat carrier are separated from each other. This system implies that the hot water supplied to the consumer has the same parameters as that which flows from the cold water tap.
  It should be noted that when using a closed DHW system, the pipes that supply hot water are more susceptible to corrosion.
• The closed DHW system consists of two pipelines – supply and return pipes. Through them water circulates in the system. This allows the use of hot water simultaneously to several consumers without a drop in water head. In addition, the closed DHW system is characterized by the ease of setting the temperature regime.
• Such a system allows you to save money, the whole point is that it maintains a constant temperature in it. This is especially relevant if the building is connected to the central water supply system. By the way, the use of a closed system of DHW allows you to connect towel rails. But, those who have installed a towel dryer face the following problem – in the summer it will be constantly hot, and this will lead to an increase in the temperature in the room. But this problem can be solved by installing shut-off valves to regulate the supply of heated water.

The quantity of hot water needed must be calculated for any water supply system. Certain factors affect their results. The quantity of tenants residing in the home is the main determinant of them. When performing calculations, the following considerations must be made:

• predictable water temperature;
• the number of occupants;
• parameters of the sanitary equipment used and a number of others.

What are the types of heaters

Commonly, there are two basic options. Let’s talk about specific kinds of water heating apparatus.

Flow-through devices

A typical gas heater is an illustration of this kind. The goal of the operating principle is to instantly heat the water as it passes through the heater. Working with a device like this is inconvenient because it needs to be turned on each time you need hot water. By now, the faucet has got to be running. Contemporary columns are automatically lit, but the gas wick needs to burn continuously.

Heating devices

Storage tanks are turning into a more cost-effective option. A device of that kind is bigger than a column. It has a tank where water volumes are gathered and heated progressively to the desired temperature. In the meantime, minimal energy is used to maintain the tank’s heating. The equipment’s drawback is that it takes a long time for the temperature to drop to a comfortable level. Electricity is typically used to power boilers.

The equipment necessary for the operation of the network

A closed DHW system is a fairly complicated engineering system that needs a specific set of tools to operate smoothly and, most importantly, safely.

Water metering unit

The water supply system in the home receives its water supply from this tank. It is equipped with a water consumption meter. Furthermore, the unit’s design allows for the potential to cut off the water supply in the event that urgent or planned pipe fitting repairs are necessary. Installed alongside the water metering unit is:

• magnetic or mesh filter of coarse purification;
• cocks and valves through which cold water is supplied;
• measuring devices – pressure gauges, thermometers;
• bypass – a bypass pipe, which is used for the time of maintenance of the water-metering unit.

Of course, a system of pipes is needed to guarantee the DHW system operates. These pipes can be categorized into three groups:

Through the outlets in the building’s basement, the water is delivered to the risers. They handle the direct supply of sanitary supplies, home appliances, towel rails, and other items to the apartments, and then the feeders deliver them to the final customers. There are numerous plans for where each group’s pipes should be located. For instance, a neighboring apartment’s water supply can be established via risers installed in one of the apartments.

Although pipe diameters are chosen during the building design process, the following measurements should generally be followed:

• Spigots from 32 to 125 mm;
• Standpipes between 25 and 40 mm;
• Lines between 15 and 20 mm.

The following components are established when creating a closed DHW system:

• metal plastic;
• pipes made of food-grade stainless steel;
• galvanized pipes.

It is important to keep in mind that metal-plastic pipes can have varying operating temperatures and pressures when placing an order for pipes. It should be noted that dishonest contractors often install pipes and pipe fittings during major repairs that do not adhere to the specifications listed in the working documentation.

Main faults of a closed DHW system

An unstable or malfunctioning hot water supply is not uncommon. Numerous objective and subjective factors influence this. In particular:

• errors made during the design and installation of the system;
• Leaks and noises occurring in the pipe fittings. As a rule, this is caused either by the exhaustion in the valve gate or by the installation of defective products;
• No heating of the towel dryer, most likely all of it is caused by air plugs.

The water supply system is generally recognized by the act, and the business that installed the HTW system ought to be involved in network warranty maintenance for a number of years after the network is turned over to the management company. That is to say, experts from the management company or the contractor company must be called in order to remove flaws from the DHW network.

Valve leakage

Leakage on screw valve stems is described.

A typical leakage location is indicated by an arrow.

• Cause: partial wear of the gland or wear of the rubber sealing ring.
• The solution: open the valve thumbscrew as far as it will go. In this case, the threads on the stem will press the gland from below, and the leakage will stop.

Noise of taps

Description: A loud noise and vibrations are audible when the hot or (rarely) cold water faucet is opened. Alternatively, one of your neighbors’ faucets may be the source of the noise.

Many unpleasant feelings can arise from the neighbor’s noisy faucet.

Cause: a continuous sequence of hydrostrokes is brought on by a deformed and crushed gasket on the screw faucet when it is half-open. Its valve, with a split-second interval, closes the seat in the mixer body. The effect is more noticeable on hot water because the pressure is typically noticeably higher.

1. Shut off the water to the apartment;
2. Unscrew the problematic faucet;
3. Replace a gasket on a new one;
4. Remove with scissors a chamfer at a new gasket. The removed chamfer will prevent the valve from beating in the turbulent water stream later on.

Changing the screw faucet’s gasket

It should be noted that ceramic faucets do not have the aforementioned issue and are completely compatible with screw threaded ones.

The image depicts a ceramic tap.

Cold towel rails

• Description: the towel warmer in your bathroom is cold and won"t heat up.
• Reason: If the water supply system of a residential apartment building uses continuous hot water circulation, the culprit is air left in the jumper between the risers after the water has been discharged (e.g. for inspection and repair of shut-off valves).
• Solution: go to the top floor and ask your neighbors to bleed the air from the jumper between the DHW risers and towel rails.

If this isn’t possible for some reason, the basement can provide the solution:

1. Shut off the DHW riser that runs through your apartment and to which your supply lines are connected;
2. Go up to the apartment and open the hot water taps all the way;
3. After all the air is out of the riser through them, close the taps and open the tap on the riser.

One way to avoid it is to install a pressure relief valve on the riser and bypass it directly from the basement.

Nuance: There might not be any pressure difference between the heating mains’ strings right after the heating season ends. In this instance, even without air gaps in the risers, towel dryers will be cold.

The difference between the route’s strings can be zero right after the heating season ends.

Estimated norms of hot water consumption

It should be highlighted that while there are numerous guidelines for estimating resource consumption, there are no guidelines for water use per person in the housing sector without the use of water meters. This is because there are significant differences in population density among the various regions of our nation. To put it another way, every region has unique norms. A settlement receives a specific volume of water in compliance with the regulations. The quantity of water used by the occupants of the apartments with water meters installed is also considered at the same time.

The volume that went through the meters is computed from the total volume of water supplied. The difference that results is divided by the total number of residents in the specified area. These folks are the ones who pay for the water that is used. Unauthorized water consumption is widespread, and unlike in developed nations, not all areas have water meters installed, which is a major contributing factor to the current state of affairs. An increasing coefficient is utilized in the computation of consumption rates. The presence of installed water heaters and the state of the sanitary appliances must be considered during the computations.

Due to the fact that every neighborhood uses a different amount of water, the consumption rate varies. The weather and the cost of fuel must be considered when heating water.

A person’s average water consumption rate has been determined. This amounts to 200 liters of cold water and 100 liters of hot water during the day. If the resident does not take a daily bath, it makes sense for him to consider installing water meters as an ordinary bathtub can hold 250 liters of water.

Significant water bill savings are possible with an installed meter. The truth is that unapproved water withdrawals, leaks, water usage for the Ministry of Emergency Situations’ requirements, and many other things are included in water bills in one way or another.

Ideal pipes for closed DHW system

Water supply pipes composed of German-manufactured Fusiolen raw materials.

• Coefficient of linear expansion is 0.035 mm/m
• Low coefficient of thermal conductivity – only 0.15 W/m*K
• Operating temperature 95 degrees, pressure 10 bar
• Warranty 10 years and 20 million Euros
• Service life up to 100 years (DVS certificate)

Water supply pipes composed of German-manufactured Fusiolen raw materials.

• Coefficient of linear expansion is 0.035 mm/m
• Low coefficient of thermal conductivity – only 0.15 W/m*K
• Oxygen permeability according to SNiP 41-01-200 and DIN 4726
• Operating temperature 95 degrees, pressure 10 bar
• Guarantee 10 years and 20 million Euros
• Service life up to 100 years (DVS certificate)

Formula for calculating consumption in a closed DHW system

Formula for determining maximum hourly flow rate and make-up:

Where:

Gm is a constant that can be agreed upon with sufficient justification or is determined by the pipeline diameter (as stated in SP 124.13330.2012);:

Vtc stands for the heating system’s total volume.

It is recommended to install tanks containing treated and prepared water for emergency make-up in large heating plants (capacity greater than 100 MW).

Additionally, using a booster pumping unit to increase water consumption is permitted. This unit can be used on the DHW system independently as well as on the HTW with the HTW’s subsequent make-up. Nominal and working pressure calculations are performed using SP 30.13330.2016.

Features of the use of a closed system on different pipelines

• Steel – rarely used in low-rise construction, more often – in large heating stations due to the peculiarities of the closed system (increased corrosion of metals). Withstand emergency temperature rise, but according to European norms are considered less efficient due to large displacement and high heat losses.
• PPR – perfectly suited for installation in closed DHW systems, because: 1) reduced system operating temperature (not below 60 ° C, not above 75 ° C), 2) increased resistance to corrosion, 3) virtually no deposits on the inner surface of the pipes, 4) all sanitary requirements are provided, 5) no sanitary treatment of pipes during their operation is required.
• Copper – a more expensive option, requiring large capital investments, high qualification of installers, and the pipeline consists of many joints. At the same time, due to the small length of the small heat supply circuit, a large diameter copper pipeline is often installed up to the boiler, and from the water heater, heat exchanger already starts the pipeline from PPP.

Therefore, if money is not an issue, the best plan for low-hot-water-consumption properties would be to combine copper pipe, boiler, and hot water piping RRP. The capital costs associated with installing utilities are greatly decreased when PDP is the only protocol used.

Federal Law "On Heat Supply"

According to Federal Law N 190 "On Heat Supply" of July 27, 2010, there are specificities in the organization and tariffication of HTW because the open system absorbs the heat carrier directly.

• The quality and safety of DHW is regulated by SanPiN 2.1.4.2496-09;
• Water should be used as a heat carrier in open systems;
• Tariffication is made in the form of two-component formulas describing heat and hot water consumption;
• Hot water suppliers are obliged to bring it into compliance with SanPiN norms;
• When concluding a contract with a consumer, tariffs for heat and for consumed hot water should be simultaneously agreed upon;
• As of January 1, 2013, a ban on connection to heating systems of capital construction facilities of hot water supply consumers who perform withdrawal directly from the system has been introduced.

In addition, the regulatory structure found in other documents:

• Water for the open DHW system shall comply with GOST 2874-82;
• Connection to the heating circuit must be made to the supply and return, in closed systems through a separate heat exchanger or water heater (SNiP 2.04.07-86);
• Central supply of hot water stipulates its minimum temperature – from 60 ° C and above (for a closed system not less than 70 ° C);
• Water intake regimes for heating and non-heating periods must be calculated;
• To ensure a reserve of make-up water should take the average flow rate of DHW with a reserve factor equal to 20% + 0.75% of the actual volume in hot water supply systems (heating) with all nodes;
• Emergency make-up is possible with chemically untreated water directly into the DHW system, and only from the HTW or domestic water supply system.

Circulating water supply system

Circulation systems are used when it is preferable to have hot water available to consumption points continuously and it is not desirable for water to drain. In a system like this, the water in the pipelines never stops or cools down; instead, it is constantly pumped through the water heater, allowing the temperature of the water to be kept constant at each point of consumption.

Water only circulates in the distribution pipes of buildings up to four stories high, and in the riser pipes of buildings higher than four stories. In addition, the water temperature at the points where the local system and centralized heating system are connected must not fall below 60 degrees (in the case of open water supply systems) or 50 degrees (in the case of closed water supply systems). The water’s temperature must be between 75 and 80 degrees Celsius in both situations.

Connection scheme for open DHW

• The heating station burns fuel, transfers energy to the heat carrier (treated water);
• Water moves through the main pipe, part of which goes through the heating circuit (to radiators, batteries, heat curtains and other appliances), and part of which is supplied to DHW consumers;
• Heating circuit and DHW circuit – circulates, water from the heating and hot water supply circuit is returned to the heating station via the return flow;
• The used hot water is drained into the sewer, and to compensate for this loss, the system is continuously and automatically recharged with prepared water.

Temperature control units (SNiP 2) are used in the heating units because the temperature in the open DHW should not be lower than 60 °C nor higher than 75 °C."Internal water supply and sewerage of buildings" (04.01, 1985). It is permissible to use dead-end and circulating wiring, i.e., with tap drainage and the supply of hot water at a consistent temperature and heat carrier circulation.

Peculiarities of working with different types of pipes

• Steel pipes – tend to accumulate rust, scale inside on the walls, can absorb traces of petroleum products and other chemically active substances. The vast majority of buildings of the old housing stock work on steel pipes with an open system. Advantage: durability, reliability, ability to tolerate emergency failures of thermal regulators. Disadvantages: corrosion, high hydraulic resistance, high production cost, large diameters lead to large displacement, which reduces the efficiency of DHW supply.
• PPR pipes – smooth, not subject to corrosion, but sensitive to the temperature of the circulating liquid. Advantages: simple and inexpensive installation, long service life, full compliance with hygienic norms, maintenance-free, high level of maintainability. Disadvantages: sensitive to high temperatures, high linear expansion (compared to steel).
• Copper pipes are not used for open systems due to their high cost, complexity of installation, high requirements to the qualification of installers.
• Metal-plastic – practically not used due to the limited range and the disadvantages of the system (low reliability of connections, delamination of the material at high temperatures, the risk of patching, constrictions, cracks).
• PEX-pipe – not used, due to small diameters and limited characteristics.

Hence, the open system can be mounted from steel piping or PPR pipes in compliance with SNiP 2.04.07-86 and GOST 2874-82, as well as taking into consideration the feasibility and feasibility study.

In the world of heating and insulating homes, understanding the difference between closed and open systems of hot water supply is crucial. A closed system operates under pressure, meaning it"s sealed and doesn"t interact with the atmosphere, while an open system is open to the atmosphere and relies on gravity to circulate water. In a closed system, water circulates through pipes and radiators, heated by a boiler, and returns to be reheated. On the other hand, in an open system, water is heated in a tank and flows by gravity to taps and showers. The key difference lies in their operation, with closed systems offering more control and efficiency, while open systems are simpler but may be less efficient. Understanding these distinctions helps homeowners make informed decisions about their hot water systems, ensuring comfort and efficiency in their homes.

Dependence of the system on the heat source

When examining hot water supply schemes on a large scale, two groups can be identified:

1. Centralized, when water heating is provided by boilers or CHP plants.
2. Local, which serves only one facility.

It is possible to use both closed and open hot water supply systems in centralized systems, also known as CSHW. The same water, but much hotter, is used as a coolant to supply warm water to civilian populations and organizations.

Water heating is provided by a district boiler house.

Discharge (secondary) steam is frequently used as a coolant in industrial settings. However, we won’t delve into this maze; instead, let’s discuss the most prevalent variation.

The difference between the two schemes and their applicability

Now let’s examine the differences between an open and closed water supply system.

1. In open, or as they are also called, dead-end schemes, in the process of water treatment, boiling water is diluted to the required temperature with cold water, and supplied to the consumer. That is, the water that needs to be heated is directly in contact with the heat transfer medium.
2. This is not the case in closed schemes – in these schemes, heating occurs by heat exchange. This is the main difference between an open and a closed hot water supply system.

Please be aware that while using an open method to get hot water is simpler, the water cools down more quickly and loses quality. The system needs to be looped in order to maintain the high temperature for an extended period of time. The characteristic of closed schemes is the circular movement of water.

Features of the organization of the water supply system in a multi-storey house

It can be difficult to maintain a high-quality hot and cold water supply in an apartment building. Every apartment is its own water supply, with the potential for multiple independent water intake points. In this sense, a multi-story residential building’s water supply system incorporates a number of pipes with various cross-sections that may be composed of various materials. These pipes ought to be connected into a single pipe system so that, in compliance with the specifications of the regulatory documentation, there is enough pressure for both hot and cold water at every water intake point.

A residential apartment building’s water supply system consists of a number of pieces of equipment. The primary equipment consists of various kinds and capacities of pumps that are further furnished with filters. Water meters, pipes inside the apartment building, and shut-off and regulating valves are also part of the system. Regulators for water pressure are an additional requirement.

Composition of the central water supply system

Water intake structures, treatment plants, and distribution networks make up centralized water supply systems in multi-story buildings. The water travels a considerable distance from the pumping station to the reservoir before entering the apartment. The water is not sent to the distribution network until it has undergone treatment and disinfection. The latter is used to supply water to equipment and appliances. Steel, copper, or metal can be used as the pipe material for multi-story buildings’ centralized hot water supply system.

Types of water supply schemes

There are three types of water supply systems:

• collector;
• serial;
• combined (mixed).

Use the collector wiring scheme as apartments with lots of plumbing equipment are becoming more and more common. It is the ideal choice to ensure that all appliances operate normally. A collector-style hot water supply system does away with pressure drops at various points of connection. This system’s primary benefit is this.

A closer look at the plan leads us to the conclusion that using sanitary equipment for its intended purpose concurrently won’t present any issues. The fundamental aspect of the connection is that every single water user is linked to the riser isolated collectors of the cold and hot water supplies. Because pipes have few branches, there is very little chance that there will be a leak. Although the equipment for these water supply schemes in multi-story homes is relatively expensive, they are simple to maintain.

Experts say that installing sanitary appliances in a collector scheme for hot water supply is more complicated. These drawbacks, however, are not as significant when you consider the collector scheme’s many benefits, which include hidden pipe installation and consideration of the unique qualities of each piece of equipment.

The simplest wiring method for a multi-story house is a sequential hot water supply scheme. A system like this has been around for a long time—it was implemented during the Soviet era. The cold and hot water supply pipelines are run in parallel, which is the fundamental feature of this device. Use of this system is recommended for apartments with one bathroom and minimal sanitary supplies, according to engineers.

A multi-story building’s hot water supply system is commonly referred to as a "tee system." In other words, branching lines that are connected to one another by tees branch off of the main trunk lines. Although this scheme is easy to install and uses less consumable material, it has a few significant drawbacks:

1. In case of leakage it is difficult to search for damaged areas.
2. Impossibility to supply water to a separate sanitary appliance.
3. Difficulty of access to the pipes in case of breakage.

Nuances

It is important to consider the following peculiarities when performing open DHW calculations:

1. An open system can have forced or natural circulation. In the first case, the movement of liquid and pressure build-up is carried out with the help of a pump. Natural circulation is carried out due to hydrostatic pressure of the liquid.
2. If the open hot water system will not be used in the private sector, you should know that it is impossible to legally carry out the intake of warm water from the heating circuit in apartment buildings commissioned after January 2013.
3. When installing an open DHW system in a private house, high operational efficiency can only be achieved if the length of the pipelines is short and the water is drawn quite frequently. Otherwise, the consumer will always receive a strongly cooled liquid when the tap is opened.

Making the choice between an open and closed hot water supply system affects your home’s efficiency and comfort. Both systems have benefits and drawbacks, so it’s important to know how they differ.

Open systems have a more straightforward design and use convection to move water through the pipes naturally. Their lower installation and maintenance costs make them an affordable option for smaller households with less hot water consumption. Open systems, however, can be less effective and are more likely to lose heat, particularly in colder regions.

Closed systems, on the other hand, provide greater control over water temperature and flow by using a network of pipes and a pump to circulate water. Closed systems are more energy-efficient and more appropriate for larger homes or regions with severe winters, even though they might need a higher initial investment. Furthermore, closed systems have a longer lifespan due to their reduced susceptibility to scaling and contamination.

It’s important to weigh factors like your household’s hot water usage, budget, and climate when choosing between the two systems. You can evaluate your needs and select the system that best suits your needs by speaking with a qualified HVAC technician.

In summary, both closed and open hot water supply systems have advantages, and the decision ultimately comes down to your unique situation. By comparing the benefits and drawbacks of each system, you can make an informed choice that will guarantee the longevity, comfort, and efficiency of the hot water supply in your house.

Video on the topic

Installation of a closed hot water supply system. Morning with Gubernia. 25/10/2024. GuberniaTV

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