Choosing a method of heating a home in the winter, the average homeowner seeks to kill 2 birds with one stone: to mount an efficiently working scheme with the least investment. A common solution is a one-pipe water heating system, suitable for small private houses with an area of 50 ... 250 m². Under certain conditions, it will require lower costs than other, more modern types of wiring - collector, two-pipe and Tichelman loop.
The device and principle of distribution of the coolant
The system is called single-pipe, since heated water is supplied and leaves heating radiators in a single collector. The piping is common to all batteries connected to the trunk. That is, the inlet and outlet connections of each heater are connected to one pipe, as shown in the example of a heat supply scheme for a single-story building.
How does a one-pipe radiator heating system work:
- The heated coolant coming from the boiler reaches the first battery and is divided by a tee into two unequal flows. The bulk of the water continues to move directly along the highway, a smaller part flows into the radiator (about 1/3).
- Having given heat to the walls of the battery and cooled by 10-15 ° C (depending on the power and actual return of the radiator), a small stream through the outlet pipe returns to the common collector.
- Mixing with the main stream, the cooled heat carrier reduces its temperature by 0.5-1.5 degrees. Mixed water is delivered to the next heater, where the heat exchange and cooling cycle of the main stream is repeated.
- As a result, each subsequent battery receives a coolant with a lower temperature. At the end, the cooled water is sent back to the boiler along the same line.
An important point. For the heating circuit to work stably, the diameter of the distribution pipe should significantly exceed the dimensions of the radiator hoses. The rule does not apply to vertical risers with an overflow, where gravity helps to flow down the coolant (read below about the types of systems).
The lower the temperature of the circulating water, the less heat goes to the last heaters. The problem is solved in three ways:
- At the end of the line, high-power batteries are installed - the number of sections is increasing or the area of panel steel radiators is increasing;
- by increasing the diameter of the pipe and pump performance increases the flow of coolant through the main manifold;
- a combination of the two previous options.
Connecting radiators to a single distribution line is the main difference between a single-pipe wiring and other two-pipe systems, where the supply and return of the coolant is organized in two separate branches.
Single pipe systems
To heat suburban cottages and apartments of multi-storey buildings, only 2 types of one-pipe schemes are used:
- The classic Leningrad heating system with lower horizontal wiring is shown above in the first picture.
- Radiator network with vertical risers.
Leningradka provides for the connection of radiators to a common ring highway laid horizontally above the floor. A classic of the genre is the lower lateral connection of both eyeliners. With a more modern approach, the pipes are connected diagonally to the battery, and installation technicians practice both methods.
The second scheme is used in multi-unit and two-story private houses. Through the ceilings are vertical single risers, batteries are attached to each circuit on each floor. The supply of water to the risers is provided from the lower or upper horizontal collector.
Note. Please note: the general line of the “Leningrad” with the horizontal lower wiring is a solid pipe that does not change the diameter throughout. On one-pipe risers, jumpers are provided - bypasss that pass part of the coolant past the batteries.
Both types of wiring can function with forced and natural circulation of water (by gravity). Schemes vary depending on operating conditions:
- For the Leningradka to work in gravity mode, it will be necessary to increase the internal section of the annular collector to 40-50 mm, make slopes and raise the vertical accelerating section from the boiler, otherwise there will be no flow through the radiators. An open expansion tank is connected to the highest point, as shown in the heating circuit diagram of a single-story house.
- It is better to implement the gravity principle in a two-story building according to the scheme with risers passing through the necessary rooms. A supply pipe Ø40-50 mm rises directly to the expansion tank installed in the attic. To the sides of it, horizontal branches with slopes diverge, supplying water from above to the risers and radiators. On the rise, a bypass unit with a circulation pump can be mounted.
- Closed single-circuit wiring with pressure circulation is presented at the beginning of this section. In a two-story house, the “Leningradka” must be made double-circuit - provide for a separate horizontal loop with the flow of coolant through the ceiling, as shown in the axonometric diagram.
Initially, the Leningrad system was conceived as a cheap option for supplying heat to convection heating devices. But if you wish, you can connect a small contour of a water heated floor to the highway. You will need a second circulation pump, a check valve and a three-way valve that controls the temperature of the water.
Important. The floor heating circuit can be connected at the end of the line, behind the last radiator. One condition: it is necessary to ensure the required coolant flow rate in the collector - increase the diameter and increase the performance of the main pump. Otherwise, a warm floor will take away some of the heat from the batteries.
Installation Price Comparison
Adherents of single-pipe heating networks like to remind about the cheapness of this type of wiring. The reduction in costs compared to the two-pipe scheme is justified by half the number of pipes. We affirm the following: “Leningradka” will be cheaper than a dead-end system in one case - if you solder the heating from polypropylene.
We prove our statement by calculations - take as an example a one-story dwelling with dimensions of 10 x 10 m = 100 m² (in plan). We apply the layout of the Leningradka to the drawing, count the fittings with the pipes, then make a similar estimate of the dead-end wiring.
So, for a single-pipe heating device, you will need:
- Du20 pipe to the collector (outside Ø25 mm) - 40 m;
- tr DN25 Ø32 mm to the return - 10 m;
- tr DN10 Ø16 mm for eyeliner - 8 m;
- tee 25 x 25 x 16 (outer size) - 16 pieces;
- tee 25 x 25 x 20 - 1 pc.
Reference. The return jumper going down the corridor can be omitted. Then for 9 radiators it will be necessary to increase the cross section of the ring line to the size Du25 (outer - 32 mm).
Based on the following layout, we find out the need for pipes and fittings for a two-pipe network:
- tr DN15 Ø20 mm - 68 meters (trunk);
- tr DN10 Ø16 mm - 22 m (radiator connections);
- tee 20 x 20 x 16 mm - 16 pcs.
Now we find the current prices for plumbing fittings and pipes made of 3 materials: reinforced PP-R polypropylene, PEX – AL – PEX plastic and cross-linked PEX polyethylene from well-known manufacturers. The calculation results are listed in the table:
Note. We do not take into account the cost of batteries, radiator taps and the installation of a single-tube “Leningrad” - suppose that you assemble the system yourself. The cost is determined in Russian rubles, but this fact does not play a special role, the price ratio will remain for any country.
As you can see, the costs of polypropylene tees and pipes are almost the same for both schemes - the shoulder was more expensive by only 330 rubles. For other materials, the two-pipe wiring clearly wins. The reason lies in the diameters - the prices of pipes of a larger cross section sharply increase compared with the "running" sizes of 16 and 20 mm.
Pros and cons of single pipe wiring
We will try to give an objective assessment and highlight the real advantages of single-tube water systems:
- Closed circuit with a membrane expansion tank is easier to install. One pipe is laid faster than two.
- A single trunk or riser is easier to hide in the walls than two-pipe branches (example below in the photo). Fly in the ointment: an annular manifold crosses doorways that make it difficult to lay.
- The heating network with risers is indispensable when it is necessary to organize gravity in the building on 2-3 floors. It makes no sense to go through the overlap with two pipelines, one vertical line is enough.
- Installation is cheap in one case: when a gravity flow diagram of a heating system is used in a one-story private house. Savings are achieved by laying one trunk instead of two (remember, for gravity a priori pipes of large diameters of Ø48-57 mm are needed).
- The closed type system can be automatically controlled by radiator thermostatic valves. Disclaimer: it is necessary to take into account the specifics of the operation of heating appliances and to choose the right fittings. Below we will return to this issue.
Note. Direct connection of the underfloor heating section cannot be attributed to the advantages of this scheme. The heating circuit is just as easily connected to the two-pipe wiring.
The main problem of Leningrad is cooling of the coolant as it moves toward distant batteries. It is impossible to increase the sections of radiators and the cross section of the trunk to infinity, the optimal number of devices is 4-5. on one circuit.
We list other shortcomings:
- Hydraulic instability - the influence of one battery on the work of the rest. If you block the first radiator valve, subsequent appliances will get hotter water and will overheat the room.
- In order for the coolant to flow well into the radiators with the closed Leningrad scheme, it is necessary to use full bore fittings on the branches. An increase in the hydraulic resistance of the inlet causes the water to flow further in a straight line, the flow rate of the coolant through the battery decreases.
- “Leningradka” and vertical wiring are more expensive than a two-pipe shoulder scheme. If we add the costs of additional radiator sections, then the cost of installation made of cross-linked polyethylene is compared with the radiation system, where the fittings are not used, but there is a distribution comb.
- The scheme is difficult to calculate and configure (balance). The power and heat transfer surface area of the batteries must be determined as accurately as possible.
An additional minus of gravity distributions is the large diameters of pipes laid with a slope of 3-5 mm per linear meter. The risers emerging from the ceilings stick out in plain sight and spoil the interior of the premises. Piping pipelines into walls is not always possible, you have to refine yourself and make decorative boxes.
Tips for choosing pipe diameters and connection
One-pipe heating option can be designed and mounted independently, without resorting to complex hydraulics calculations. Simplify the task and give useful recommendations on the design of single-circuit systems:
- The maximum number of heating devices on one loop of a closed "Leningrad" is 5 pcs. To deliver the required volume of coolant to the batteries, a Ø25 mm pipe (DN20) is enough. We make connections from nozzles of Ø16 mm.
- If, for objective reasons, the number of radiators on 1 ring of a closed system needs to be increased, the cross-section of the line is increased to a diameter of 32 mm (DN25), and the lead-in to 20 mm.Putting more than 7 batteries on one pipeline is not economically feasible, it is cheaper to lay 2 smaller lines.
- The minimum diameter of the horizontal collector in natural circulation is DN40, the outer is Ø48 mm. In a two-story house, the riser and the start of distributing branches are made of a Du50 pipe (Ø57 mm), remote areas are reduced to the size of Du32. Vertical lines to radiators - DN20-25 depending on the heat output of the heaters.
- For automatic heat transfer control, select full bore valves with thermal heads. In standard radiator valves, the opening is too small.
- Connection to a wall or floor gas boiler is carried out according to the standard scheme shown in the picture below. In a similar way, the strapping of the electric water heater is done.
- It is better to connect the Leningradka solid fuel boiler through a three-way mixing valve and a buffer tank. Since there is too little coolant in the system, there is a risk of overheating and boiling. A gravity wiring that holds more than 200 liters of water can be connected directly to the TT boiler.
Important clarification. When assembling a home heating network, PN 22-28 polypropylene pipes reinforced with fiberglass, aluminum foil or basalt fiber are often used. In the assortment of STABI PPR pipes, there is no standard size 16 mm, the minimum outer diameter is 20 mm. Accordingly, radiator hoses are made with a cross section of 20 x 2.8 mm.
Finally on the scope
To avoid problems during operation, use single-pipe heating networks in suitable conditions:
- “Leningradka” works well in single-storey dachas and small houses with an area of up to 150 m². If the quadrature does not exceed 70 m², one common ring for all the batteries is sufficient, otherwise the system is divided into 2 circuits or a larger pipeline is laid.
- In a 2-story building, you can assemble an open-type gravitational one-pipe scheme or a closed version with a lower wiring - to choose from. In the event of a power outage, it is preferable to organize a gravity flow and put the circulation pump on the bypass.
- A gravity drain with an overclocking collector, used in single-story buildings, is characterized by inertia. Radiators warm up slowly, the water cools down significantly due to the low flow rate, the boiler operates in extreme mode. This scheme is better not to use at all, it is outdated and will not work normally without a pump.
- Feel free to divide the “Leningradka” into 2-3 separate floor loops with the optimal number of batteries on each. Do not combine radiators of all floors in a single circulation circuit - the latest appliances will remain cold.
- The one-pipe Leningrad system is a suitable option for an autonomous heating device of a 2-3-room apartment.
Tip. It is not necessary to install single-pipe wiring in residential buildings of large area and complex configuration with a versatile and multi-level arrangement of rooms.
Masters who prove the indispensability of one-pipe heating systems often refer to multi-storey buildings of Soviet construction, they say, there are 20 batteries working in a riser. But they forget to mention the pressure and performance of centralized network pumps, unattainable in private homes. Do not listen to the unfortunate specialists and apply the optimal system options - two-pipe, collector or associated.