Why does the pressure rise in the heating boiler?

Pressure in the heating system that is higher than normal causes the boiler equipment safety group to periodically activate and release excess liquid through a safety valve. During this operating mode, all parts of the circuit begin to experience increased load, which may cause malfunction, therefore it is urgent to find out why the pressure in the system increases.

Reasons for increased pressure

Only a professional heating engineer can identify the exact malfunction of the boiler. That is, you will not be able to identify and repair the breakdown that caused an increase in pressure in the heating system. The main reasons for the increase in pressure that occurs during external boiler breakdowns are as follows:

1. Violation of the integrity of the heat exchanger. Given the long operating time, the walls of the equipment may crack. The reasons for the appearance of cracks are manufacturing defects, insufficient strength, water hammer or equipment wear. Fluid is added to the circuit every few days. The leak cannot be visually detected - the coolant flows very weakly, and while the burner is running, the moisture present begins to evaporate. It is necessary to change the heat exchanger; it is possible to solder it in very rare cases.
2. The pressure increases due to an open make-up valve. Due to the low pressure in the boiler circuit and the increased pressure in the pipeline, “excess” liquid begins to flow through the make-up valve into the heating pipeline.The pressure increases until it is required to be released through the safety valve.
3. If the pressure in the pipeline drops, the coolant closes the liquid supply to the boiler, in which case the pressure in the system decreases. The same problem can happen if the make-up valve is broken. It is necessary to either block it or change it.
4. Increase due to three-way valve. If the valve breaks down, liquid from the expansion tank will begin to flow into the circuit. The three-way valve needs to be replaced or cleaned periodically.
5. The pressure gauge readings remain in one place. If during changes in the operating mode of the boiler equipment, when the temperature on the pressure gauge increases or decreases, the arrow does not move, the pressure gauge is broken. It needs to be replaced.

Why does pressure increase in closed boilers?

The main reasons why blood pressure rises are as follows:

• the heating circuit is filled from the top;
• quick filling with coolant during startup;
• a loose pump fan through which air passes;
• air vent failure;
• After the system was repaired, the air was not vented.

The heating circuit must be filled from the bottom, and the safety valves must be open. It is necessary to fill gradually until liquid begins to drain from the safety taps. Before you start filling the heating circuit, all air bleed parts must be treated with a soap solution, this way you can check their normal operation.

Important! If the injection pump is leaking air, then it is the cause of the increased pressure.

Cause of increased pressure in open systems

In an open system, if the slopes of the pipes are correctly calculated, the air exits into the expansion tank.Air locks can only appear when the circuit is not filled properly with liquid during startup.

When this problem occurs, the air is released through the safety valves located on the heating radiators.

Attention! When it is not possible to reduce the pressure, it will probably be necessary to completely drain the heating circuit at the next start-up.

Other reasons

Increased pressure can also occur for the following reasons:

1. Closed shut-off valve. As a result, the pressure on the coolant supply increases and the protection of the boiler equipment is activated. All valves must be opened.
2. The expansion tank is located immediately after the pumping equipment. Thus, the pressure instantly increases and is almost immediately released, while its drops are noted. This situation can lead to water hammer in the heating circuit. To get rid of this problem, the expansion tank must be installed on the return circuit - in an area with a low temperature of the coolant. The pump is installed in front of the boiler equipment, after the expansion tank.
3. If there is a coarse filter, its mesh may become dirty. As a result, the pressure in the pipeline increases. Cleaning the strainer can help reduce water pressure. The simplest carbon filter needs to be cleaned every 5 years. Wash filters are quite expensive, but this equipment cleans the coolant much better.
4. Failure of the automatic system of boiler equipment, breakdown of sensors. It is not always possible to determine why this happened.The reason is a manufacturing defect, the use of poor quality materials during the manufacture of control elements, and improper installation. You can fix the problem yourself only by knowing the error code. If the documentation for the equipment does not contain this code and troubleshooting methods, you need to contact the service department.

Correct and long-term operation of the heating system depends on high-quality installation, proper operation of the equipment, as well as maintaining normal pressure in the system.