How to make a heating system with natural circulation

It’s crucial for your comfort and wellbeing to keep your house warm and comfortable during the winter. While there are many different kinds of heating systems available, designing a system with natural circulation is a cost-effective and environmentally responsible choice. Rather than using pumps or other mechanical devices, this method uses the natural movement of heated air to distribute warmth throughout your home.

A natural circulation system makes use of the idea that hot air rises and cold air sinks, in contrast to forced-air heating systems that rely on fans or pumps to move warm air. You can achieve effective and efficient heating in your home without using external energy sources by placing heating elements strategically and letting natural convection currents do their job.

Appropriate insulation is one of the most important parts of a natural circulation heating system. By properly insulating your home, you can reduce heat loss and guarantee that the warmth produced by your heating system remains inside where it is most needed. You can create a barrier that keeps heat from escaping and keep your home warmer for longer periods of time while using less energy by caulking gaps and insulating walls, floors, and ceilings.

The size and layout of your house, as well as the positioning of heating components like radiators or heating panels, should all be taken into account when designing a natural circulation heating system. By placing the heaters strategically, you and your family can be as comfortable as possible because there won’t be any cold spots and the heat will be distributed throughout the entire space.

Theoretical horseshoe – how it works by a gap

Gravity is the reason behind natural water circulation in heating systems. How does this take place?

1. We take an open vessel, fill it with water and begin to heat. The most primitive option is a pan on a gas stove.
2. The temperature of the lower layer of the liquid grows, the density decreases. Water becomes easier.
3. Under the influence of attraction, the upper heavier layer drops to the bottom, displacing less dense hot water. Natural circulation of fluid, called convection begins.

Reference: The density of water does not depend linearly on temperature. The graph makes it evident that the liquid’s density drops more quickly the stronger the warming.

As an illustration, heating 1 m³ of water from 50 to 70 degrees will make it easier by 10.26 kg (we can see the temperature-dependent density table below). The liquid cube will lose 12.47 kg if the heating is continued to 90 °C, even though the temperature delta will only change by 20 °C. In conclusion, circulation is more active the closer the water is to boiling.

Similar to this, on the home heat supply network, coolant circulates due to gravity. Coolant that has returned from the radiators pushes up the water that has been heated by the boiler, causing it to lose weight. At a temperature differential of 20–25 °C, the flow rate is only 0.1–0.25 m/s, as opposed to 0.7–1 m/s in contemporary pumping systems.

The following effects result from the fluid’s slow passage through the heating devices and highways:

1. The batteries manage to give more heat, and the coolant – cool by 20-30 ° C. In a conventional heating network with a pump and a membrane expansion tank, the temperature drops by 10-15 degrees.
2. Accordingly, the boiler should produce more thermal energy after the burner launches. Hold the generator at a temperature of 40 ° C is pointless – the current will slow down to the limit, the batteries will become cold.
3. To deliver the required amount of heat to the radiators, you need to increase the passage section of the pipes.
4. Fitings and reinforcement with high hydraulic resistance are able to worsen or completely stop the very. This includes reverse and three -way valves, sharp turns of 90 ° and narrowing of the pipes.
5. The roughness of the internal walls of the pipelines does not play a big role (within reasonable limits). Small fluid speed – low friction resistance.
6. Solid fuel boiler + Summarian heating system can safely work without a heat accumulator and mixing unit. Due to the slow flow of water, condensate in the fuel is not formed.

As you can see, the coolant’s convection movement has both positive and negative points. It is best to use the former and minimize the latter.

Constructive features

For the gravity system to function as intended, you must adhere to the following specifications:

• The source of heat is any energy -dependent heat generator with output pipes with a diameter of 40-50 mm;
• At the output of a boiler or stove with a water circuit, an accelerated riser is immediately mounted – a vertical pipe along which a heated coolant rises;
• The riser ends with an open -type expansion tank installed in the attic or under the ceiling of the upper floor (depending on the type of wiring and the design of a private house);
• The capacity of the tank is 10% of the volume of the coolant;
• It is advisable to choose heating devices with large sizes of internal channels – cast -iron, aluminum, bimetallic devices;
• For better heat transfer, heating radiators are connected by a different way – the lower or diagonal;
• On radiator eyeliners, special full -pass valves with thermal heads (feed) and balancing valves (return) are placed;
• It is better to equip batteries with manual air troops – Maevsky cranes;
• The feeding of the heating network is organized at the lowest point – near the boiler;
• All horizontal sections of the pipes are laid with slopes, minimal – 2 mm per meter, medium – 5 mm/1 m.

It should be noted that the slopes serve two purposes: they direct the flow of coolant in the proper direction and allow air to pass through an open expansion capacity and climb through pipelines. A word of caution about the radiators: steel panels can get warm too, provided the system is constructed correctly.

Systems for gravity heating are turned on and run at atmospheric pressure. Will it, however, function with a membrane tank in a closed diagram? In response, we say that although natural circulation will still exist, coolant speed and efficiency will decline.

Just mentioning how liquids’ physical characteristics change under high pressure can suffice to support the response. The density of water will rise along with the shift in boiling point to 110 °C that occurs when the system pressure reaches 1.5 Bar. Because there is little difference in the masses of the cooled and heated streams, the circulation will slow down.

4 gravitational heating schemes

Four types of circuits with the coolant’s natural course are utilized to organize the energy-dependent heating of private homes:

• horizontal two -pipe with upper outlet;
• combined with horizontal collectors and single -pipe vertical risers;
• one -pipe with lower wiring – the classic "Leningrad";
• Vertical wiring with individual water supply to each radiator – the so -called "spider".

Furthermore. It is also important to note that some artisans are able to outfit their floors with gravity warmth. It is much simpler to install traditional floor heating, a pump, and a continuous power supply instead of this idea, which does not justify the forces and means invested.

We would like to suggest using the first two systems right away: combined and two-pipe. Spider installation is too complex, and Leningrad wiring is not well suited to a dump. Learn more about these schemes’ advantages and disadvantages.

Two -pipe and combined wiring

Since these two schemes are nearly identical, we combined them. Since the turn of the century, the first has been utilized in single-story homes with wood stoves; at that time, heating without a pump was known as steam. A tank placed in the firebox served as the heat source until gas boilers were added later.

The mechanism of two gravitational heating

• An accelerated manifold rises from the heat generator, which goes out into the attic or under the ceiling of the boiler room, and there is an open expansion tank;
• The feed pipeline, which goes under the slope through all the rooms (under the ceiling), is horizontally into the riser;
• Another option – the insulated pipe is laid horizontally in the attic;
• Vertical icages to batteries are made from the distributing highway;
• Radiator outputs are cut into a reverse manifold, laid with a slope above the floor;
• Heating devices are equipped with locking reinforcement – cranes or thermal heads at the feed, with balance valves – at the “Return”.

Note: As they get closer to the last batteries, they decrease to conserve materials and improve the coolant distribution of the horizontal branches. A calculation is used to determine the precise diameter.

The two-story country homes are intended to use the combined gravity system. The distinction from the two-pipe wiring mentioned above is that each riser provides heat to two to four radiators spread across various floors. Devices are connected using a single pupil method, with a bypass available on the upper batteries. The differences have vanished.

The primary benefit of both turns is a dependable samothek scheme that has been successfully implemented for many years. The natural convection circulation will function even if you create very slight slopes that can clearly withstand the diameters of the highways (or, better yet, allow for a margin).

• pipes are laid openly in rooms;
• The heating network cannot be filled with antifreeze, since the non -freezing liquid evaporates from an open expansion capacity;
• The system needs to be replenished several times during the season, the interval between the recharge depends on the mode of operation of the heating;
• Pipes Ø40 … 50 mm of the road, to reduce the cost of installation, you have to take black steel or polypropylene.

The following drawbacks apply to all heating networks that have natural circulation. One way to "defeat" an open gasket is to remove the feed to the attic, install collectors and risers in the walls, or build ornamental boxes. Given how challenging it is to weld steel and plastic pipes into the wall’s indentations, we advise choosing the last option.

Suggestions. For a summer kitchen, garage, or small cottage, a two-pipe option is appropriate. These buildings’ interiors don’t have any strict specifications, and pipes cannot be hidden.

"Leningrad" with natural circulation

The scheme is a perfect replica of the original Leningrad wiring. Every radiator in the house is connected to a single collector that is installed along the exterior wall. Variations in the "Leningradka" gravity:

• increased size and slope of the main line;
• the presence of an accelerated manifold in the form of a loop, thanks to it, the coolant occurs in the batteries;
• A small number of heating devices – a maximum of 4 pcs.

The Leningrad system has the advantage of a simpler installation; one pipe will suffice for wiring instead of two. It is true that there is no way to decrease the collector’s cross section, so the savings are quite small.

The primary flaw is the "lazy" water flow into radiators, which results in the reduction in efficiency. The ring collector is where the majority of the coolant circulates. The batteries are getting scarcer because the ones farther away are warming up considerably more.

It is advised to add to the circulation pump that is mounted on the bypass, "Leningradka." The plan will undoubtedly function more enjoyablely with forced motivation; you can even add a few radiators. When the light stops, turn on the flashlight and adjust the brightness on the screen.

Scheme "Spider" – device and principle of operation

This system’s architecture looks like this:

• The insulated expansion reservoir is located in the attic, exactly in the center of the building;
• risers of the corresponding diameter from batteries and heat generator are suitable for the tank;
• The collection of cooled coolant from radiators is organized in a traditional way – in the horizontal highway.

The way it works is as follows: water heated by gravity in a boiler rises into a container, from which the consumers split off through smaller cross-sectional pipes. Buildings with one or two stories can use this wiring.

The true benefits of the "spider" lie in the coolant’s effective hydraulic distribution and the elimination of the upper horizontal wiring that runs through the rooms. On the presentation, there is a single, sizable riser that connects the boiler to the tank, where the ore measuring Ø15–25 mm is obtained. For branches, you can use stitched polyethylene and metal-plastic.

Drawbacks of the "Spider" gravitational scheme:

• complexity of installation, many pipes and joints in the attic;
• There is no saving of materials, instead of 1 distribution line, a dozen smaller pipes are used, which must be insulated;
• Spider cannot be mounted in a house without an attic.

In the video below, a do-it-yourself builder demonstrates the assembly of a similar system—albeit a closed one—even in a three-story structure. It is simple to identify similarities between the upper manifold of the combined circuit with natural circulation and the attic reservoir, which serves as the distributor.

One of the most important things we cover in our guide to insulating and heating your home is setting up a heating system with natural circulation. Using the force of physics, this technique distributes warm water throughout your house without the use of pumps or other mechanical equipment by taking advantage of temperature variations. You can efficiently warm every corner of your home by optimizing the natural flow of heated water through the strategic placement of radiators and the careful sizing and arrangement of pipes. This method not only provides efficient heating but also lowers energy usage and upkeep expenses, improving the comfort and environmental friendliness of your house.

Calculation of the gravity system

Follow these steps in order to calculate and design heating with natural circulation:

1. Find out the amount of heat necessary for heating each room. Take advantage of our instructions for this.
2. Select a power -dependent boiler – gas or solid fuel.
3. Develop a scheme by taking as a basis one of the options proposed here. Divide wiring by 2 shoulders – then the highways will not cross the front door of the house.
4. Determine the flow rate of the coolant for each room and calculate the diameters of the pipes.

Note: Use the standard value of 0.5 cm per meter length to calculate slopes instead of doing the math. Variations within the range of 0.7… 0.2 cm/1 m are permitted, either in a greater or lesser direction.

Notify everyone right away that Leningradka cannot split into two branches. This indicates that the ring pipe will undoubtedly cross the front door’s threshold. The boiler will need to be positioned in the pit in order to withstand all of the slopes.

The gravitational two-pipe system’s pipe diameters are calculated in each of the following ways:

1. We take the heat loss of the entire building (Q, W) and determine the massive flow rate of the coolant (G, kg/h) in the main line according to the formula below. The temperature difference between the supply and the “return” Δt is taken equal to 25 ° C. Then we transfer kg/h to other units – tons in an hour.
2. According to the following formula, we find the cross -sectional area (f, m²) of the main riser, substituting the value of the speed of natural circulation ʋ = 0.1 m/s. Counting the area of the circle into diameter, we get the size of the main pipe suitable for the boiler.
3. We count the thermal load on each branch, repeat the calculations and find out the diameters of these highways.
4. We move to the following rooms, again determine the diameters of the sites in thermal costs.
5. Choose the standard dimensions of the pipes, rounding the obtained numbers up.

Let’s calculate the gravity system in a 100 m³ single-story house as an example. Heat loss radiators have already been indicated, and the planning for heating radiators has already been applied. Moving on to the final rooms, we begin at the boiler’s main collector:

1. The size of the heat loss of the house is Q = 10.2 kW = 10200 watts. The flow rate of the coolant in the main riser is g = 0.86 x 10200 W / 25 ° C = 350.88 kg/h or 0.351 t/h.
2. The area of the transverse supply pipe f = 0.351 t / h / 3600 x 0.1 m/s = 0.00098 m², diameter d = 35 mm.
3. The load on the right and left branch is 5480 and 4730 W, respectively. The number of coolant: g1 = 0.86 x 5480 /25 = 188.5 kg/h or 0.189 t/h, g2 = 0.86 x 4730 /25 = 162.7 kg/h or 0.163 t/h.
4. Right branch section F1 = 0.189 /3600 x 0.1 = 0.00053 m², the diameter will be 26 mm. Left branch: F2 = 0.163 /3600 x 0.1 = 0.00045 m², D2 = 24 mm.
5. The DN32 and DN25 mm lines will come to the nursery and the kitchen (rounded up). Now we count the dimensions of the collectors for the bedroom and the living room + corridor with heat loss 2.2 and 2.95 kW, respectively. We get both DN20 mm diameters.

Take note! The diameters produced by the computations show how big the pipelines’ internal passages are (designation – DN or DU).

The pipes still need to be picked up. The boiler riser will receive Ø48 x 3 if you cook heating from steel. Five branches: 32 x 2.8 mm and Ø42 x 3 mm. A 26 x 2 pipeline makes up the remaining wiring, which connects the batteries to the eyeliner. 5 mm. The external diameter is indicated by the first size number, and the wall thickness (the range of water and gas pipes) is indicated by the second.

Do -it -yourself installation recommendations

Steel or polypropylene pipes work better for laying the primary natural circulation lines. The cause is the large diameter (Ø40 mm) and excessive cost of the polyethylene. Radiator eyeliners can be made from any practical material.

Advice: Avoid using compression fittings when building a gravity network of metal-plastic heating since they significantly narrow the internal passage.

How to create wiring that can withstand any incline:

1. Start by marking. Designate the installation points of the batteries, the points of connection of the carts and the highways of the highways.
2. Set the tracks on the walls with a pencil starting from distant batteries. Adjust the size of the inclination with a long building level.
3. Move from extreme radiators to the boiler room. When you draw all the tracks, you will understand what level to put a heat generator. The input pipe of the unit (for cooled coolant) should be located at the same level or below the back line.
4. If the floor level is too high, try to shift all the heaters up. Horizontal pipelines will rise. In extreme cases, make a recess under the boiler.

Once the markup has been applied, samp the partition holes and cut the furrows beneath the hidden gasket. After that, double-check the tracks, make any necessary corrections, and start the installation. In the same sequence, replace the batteries first, then the pipes leading to the furnace. Install a drain pipe for an expansion tank.

There are no issues with the gravity network of pipelines, so Maevsky’s taps don’t need to be touched. All of the air will enter an open tank if you simply roll water slowly through the tap tile at the bottom. Use the manual air tower if any radiator stays cold even after warming up.

Conclusion

Lastly, we’ll make an effort to talk you out of installing a gravitational system with natural circulation. This is the most costly and time-consuming way to heat a private residence. Additionally, aesthetics – it’s not always feasible to sew up with plasterboard boxes or waln up healthy pipes into the walls. Compare the price of an electric generator and a closed two-pipe wiring system versus a dump. Presumably, the cost will remain unchanged.

Installing a natural circulation heating system has many advantages for homeowners who want to increase the comfort and energy efficiency of their homes. These systems function without the need for pumps or other mechanical components by utilizing gravity and convection, which lowers installation and maintenance costs.

The simplicity of a natural circulation heating system is one of its main benefits. The system becomes intrinsically more resilient and less vulnerable to mechanical failures when it is not dependent on pumps. Over the system’s lifetime, this may result in less downtime and maintenance costs, giving homeowners long-term savings and peace of mind.

In addition, compared to their pumped counterparts, natural circulation systems may be more environmentally friendly. These systems contribute to a greener, more sustainable future by reducing energy consumption and carbon emissions by doing away with the need for electricity to power pumps.

The capacity of natural circulation heating systems to deliver even warmth throughout the house is another important benefit. The uniform distribution of heat produced by the naturally occurring flow of heated water or air eliminates cold spots and maximizes occupant comfort.

All things considered, installing a natural circulation heating system can be an economical and environmentally responsible decision for homeowners. Utilizing the laws of physics, these systems provide ease of use, dependability, and effective heat distribution, which makes them an appealing choice for homeowners seeking to enhance the insulation and heating of their homes.

Video on the topic

Summary heating system in an old house – shock!

Natural circulation in the heating system