Heating in a multi-storey building is a complex engineering system, the correct operation of which is feasible only if many parameters comply with the standards. These parameters include the pressure in the heating system of a multi-storey building, due to which safety, efficiency, and durability are achieved.
The essence of the phenomenon
So, it is the pressure in the heating system of an apartment building that determines how effective it will be. The pressure created ensures that the coolant reaches the most distant radiators and pipes, the temperature evens out in all rooms.
The optimal value of this parameter also reduces heat losses, the water is in the radiators with the same temperature that was reached in the boiler.
Water pressure in a private house or other building is divided into several groups:
- Static. The parameter determines how intensely the water “presses” on radiators and pipes at different heights.
- Dynamic. It is formed in the process of circulation of the coolant along the circuit, it is it that contributes to the wear of the elements.
- Max. A critical value, the achievement of which is likely to provoke an accident.
In most European houses, this indicator is at the level of 7 atmospheres, this is quite enough for correct functioning. However, certain phenomena change the value (critically low level — 5 atmospheres), which causes undesirable effects.
What does it depend on?
The pressure in the water heating system of a private house varies depending on several factors:
- The degree of wear of heating devices. The obsolescence of technology invariably leads to a drop in the level of efficiency. There is only one way out — the purchase of new devices (mainly for pumps).
- The degree of overgrowing of devices with hardness salts and sludge. Exit — quality control of the coolant, periodic flushing of the heating system.
- The power of the units supplying the coolant. For multi-storey buildings, these units are heat points, for cottages — circulation pumps. The farther the building is located from the heat point, the worse things are.
- Location of the apartment. Of course, under ideal conditions, the pressure in each pipe and each radiator is the same, but this is not always possible to achieve. The minimum pressure is fixed in the corner rooms — the furthest from the main risers.
- Pipe diameters. If, during the repair process, the residents replaced the pipes in the apartment with products with a larger diameter than that of the inlet pipeline, the value does not change, but the speed of water movement decreases slightly. Interestingly, plastic pipes during operation can gradually become wider than the original diameter, which practically does not affect the pressure in the system. However, it happens that the inner layer of the metal-plastic pipe exfoliates due to temperature and clogs the passage. Then the circulation pressure drops sharply, sometimes to zero (this happens extremely rarely if the building is located near the boiler room: the coolant temperature exceeds the standard for metal-plastic).
See also: causes of pressure drops in boilers.
Common Causes of Pressure Drop
If there are problems with the heating of the house, it is likely that the problem is related to pressure. In most cases, the system is aired, the circulation pressure drops, sometimes to zero. It is solved by bypassing the coolant in the opposite direction to the “discharge”, that is, they close the supply line, after the tap, open the drain valve or plug. Back pressure easily releases air into the atmosphere. The second most common reason: supply valves on risers are clogged with sludge (according to the project, valves are installed on risers to regulate pressure, not ball valves), as well as depressurization of the heating system. The most vulnerable places in this regard are connections and joints. Of course, sometimes the pipes themselves break if they have already exhausted their service life, become dilapidated, rusty, and thinned. A leak leads to a drop in static pressure, but if this parameter is normal, the problem lies elsewhere. To simplify the search process, the main sections are checked one by one, when a defective section is found, it is cut off, restored, and compacted.
If you cannot find a leak on your own, you need to involve specialists. They take a different approach: the suspicious area is drained and filled with air, the exit of which is able to detect even a microcrack.
Even if this method shows the health of the pipeline, the problem probably lies in the boiler:
- The heat exchange circuit is covered with scale. This problem is especially relevant for systems where the coolant is not of high quality (hard water). The scale itself on the heat exchanger does not affect the circulation pressure (it affects the efficiency of the boiler), but the scale particles exfoliated from the walls of the heat exchanger are dangerous: they clog filters, automatic valves, valve seats, causing a pressure drop, sometimes a complete misalignment of the heating system;
- Damage to the expansion tank (leads to airing or to a sharp increase, as a result — a rush and, accordingly, a leak);
- Destruction of the heat exchanger due to water hammer (mainly due to the installation of ball valves instead of the recommended valves for feeding the heating system);
- Microcracks on the tank of the exchange circuit, the appearance of which is provoked by the initially low quality of production or a long period of operation.
It is necessary to eliminate leaks, blockages, and only after that raise the pressure to operating pressure. Maintenance work on the heating system is carried out only after the pressure has been reduced to static pressure or, if necessary, completely emptied. Such works include:
- Filter cleaning;
- Replacement of faulty devices;
- Drainage of the water system in connection with the cessation of gas supply in winter (emergency work on the gas main) to prevent freezing;
- Flushing the heating system from deposits and scale.
In order to check the compliance of the value with the standards, some conscious utilities carry out hydraulic tests of the heating system:
- Cold testing. All main elements are filled with cold water (temperature not lower than +5 degrees Celsius), the achieved parameter is fixed. Clause 4.6 (INTERNAL SANITARY-TECHNICAL SYSTEMS-SNiP 3–05-01–85): Testing of water heating and heat supply systems should be carried out with the boilers and expansion vessels turned off by the hydrostatic method with a pressure equal to 1.5 working pressure, but not less than 0.2 MPa (2 kgf / sq. cm) at the lowest point of the system. The system is recognized as having passed the test if, within 5 minutes of being under test pressure, the pressure drop does not exceed 0.02 MPa (0.2 kgf / sq. cm) and there are no leaks in welds, pipes, threaded joints, fittings, heating appliances and equipment. If it was possible to meet these standards, launch is allowed. If the air temperature is below +5, then the test is carried out with compressed air.
- Hot testing. As a rule, it is held before the official start of the heating season. A hot coolant is pumped under pressure close to critical for a particular system. The absence of problems suggests that during the heating season there will be no excesses.
In order not to have to urgently raise or lower the pressure, mechanical filters should be regularly inspected for blockages. Also, do not forget about the expansion tank, if necessary, pump air up to the value indicated in the passport of the boiler or expansion tank. Without fail, the heating system must be equipped with a safety group (automatic air vent + automatic pressure reliever), with the help of which air is easily bled, excess coolant is drained. An example of a factory-ready security group is in the first photo of this article.