Heating systems require precise control. They work in a high pressure, and this pressure sometimes due to unforeseen reasons could increase to critical limits. The temperature rise of the coolant due to failure of the control system of heat exchangers causes the boiling water. This forms steam, which just breaks the pipe. Expensive repair of the heating, destruction of the premises and burns of the skin – here is a list of consequences that can occur when you neglect this issue.

Devices pressure control in thermal communications are the gauge and automatic relief valve overpressure CEILING. The first helps to visually assess the system operation and in time to prevent crashing. The second responds promptly in emergency situations, and preventing destruction.

Relief valve excessive water pressure, air

Why the need for a relief valve overpressure

The name of the device it is clear that unwanted pressure in any system should be given, and this is the main task of the valve. But what is excess pressure? Elements, which are assembled from the thermal circuit, and it is basically a pipe, boiler, and pumps, are designed for a certain pressure inside them, the value of which is due to the thickness and material of manufacture. When designing concrete heating system all its components take with a margin of safety. Is the excess pressure exceeding the rated working pressure of the system, but not beyond that which can destroy any element of heating.

The relief valve overpressure is applicable not only in a heating system, but wherever there is pressure above atmospheric: hot water, steam and gas plants, air compressors.

The device and principle of operation of the valve mechanism

Installation of all types of protective valves is approximately the same. It includes the base and a movable part. The base is a hollow housing having a threaded connection by which it is attached to the system. Inside the case there is a movable rod which can move in the longitudinal direction. This rod is in a certain position holds the spring.

When the pressure in the system exceeds the nominal, the stock is fixed and covers the vent hole. If for any reason the system pressure began to rise, there comes a point when it exceeds the force of the compression spring. The latter starts to be supplied and releases the stock. Stock steps aside and opens the hole. Excess pressure is released, the mechanism returns to its original position. This process is accompanied by a sharp hiss, and must attract attention.

In what heating systems does the safety group apply

The most volatile and vulnerable to pressure are the steam heating system. This is because adjustment of combustion of solid fuel is very difficult to control, and in some boilers it is not provided. In a short time the temperature in such thermal circuits is able to increase sharply, leading to boiling water. It's not terrible for open systems with the presence of the expansion tank, but currently they are rarely used. In closed circuits installation of the valve just need.

In addition to increasing the temperature as the cause of exit under the control of the pressure level can also fail the device pumping water into the system. This is usually powerful pumps that can break the pipes or working in idle, simply to fail. In such cases it is also desirable to use a resetting device.

If the question of savings is not worth it to set the relief valve overpressure for heating will always be correct. Only electric and gas boilers on this account less demanding, as they have a reliable system of level sensors temperature heat exchangers.

Types of pressure relief and regulating valves

Professional heating system have not one, but several sensors pressure relief installed in the most sensitive areas. A full set of these systems contains:

  • Automatic relief valve excess pressure. Devices come in many different designs and are typically mounted in each branch of the heating system. There are regulated and non-regulated mechanisms of this type. In adjustable, you can set any threshold pressure.
  • Reverse bleed valve. Performs two functions: it directs water flow in one direction and relieve excess pressure.
  • Relief valve excessive water pressure ball. Serves to control the pressure manually.
  • Straightening valve. It produces unnecessary air, creating congestion in heating mains and circuits. There are automatic types and manual adjustments. The latter is installed on each radiator.
  • The valve regulating the flow. Inside has a thermostat, changing valve capacity until his ceiling. This type of mechanism installed in the main inlet to the radiator to adjust the temperature in it.

Rules for installing safety valves

That the valve reliably worked and in time reacted at the right moment, there are certain rules for its installation:

  • The device cuts into the system at the boiler outlet, so that the hot water pressure can be immediately reset.
  • Place the valve as far as possible at the top.
  • To reset the inlet valve is connected outlet pipe that is directed down the drain.
  • The diameter of the valve inlet should not be narrowed in the threaded connection, so as not to reduce the capacity of the mechanism.
  • In the connection of the valve is strictly forbidden to put additional valves.
  • Mounting position the valve must be accessible for possible replacement and maintenance.
  • It is better to fasten the valve to the quick-release connection.

Selection of the valve according to the pressure rating in the system

Each heating system has its working pressure. It is determined by the parameters of the boiler. All safety valves must be designed for operation in the range of this pressure. Depending on the capacity of the system choose the valve appropriate bandwidth. For standard types of boilers suitable are the following:

  • Boilers gas wall mounted, operating at a system pressure of 1.5 to 2 bar - a 3 bar valve.
  • Gas floor boilers, rated for 1 to 1.5 bar, are a 3 bar valve.
  • Boilers and furnace heat exchangers for pressures up to 1 bar – valve at 1.5 bar.
  • System hot water with pressure up to 4 bar relief valve excess pressure of the heater 6 bar.

For your reference: 1 bar equals 0.987 atmosphere.

Overpressure relief valve

This safety valve is mainly put on the high-pressure compressor. They protect from breaking the capacity of pumping and is often combined with a switch of the power piston mechanism. The working principle of these devices is similar to previously discussed drop mechanisms. Only instead of liquid or steam pressure on the stock having just air. Another feature of the air valve of the compressor in that, since the bleed part of the air valve is not returned to its original position. His return and the inclusion of electricity occur only when the pressure drops below a certain level. That is, the valve operates in a certain pressure range.


Ideal for the safekeeping of any heating system is the inclusion of a protective group, which includes the relief valve overpressure, pressure gauge and razvodovsky valve. In addition to it makes sense to put the temperature sensors that will disable the heating equipment or additional cooling system when the temperature of the coolant above a predetermined level.