Most Common Problems And Breakdowns In Boilers

Technician repairing combi Gas Boiler

How to detect the boiler error?

There are different types of breakdowns or failures in gas boilers and, although they are not very frequent, they can be a real headache. This is why most boilers have an electronic display on the front to notify the user of the type of fault.

Normally, an error code appears on that screen indicating what fault it is. This code is specific to each boiler and brand. To find out what error the boiler has, the user must look for the error in the boiler instruction manual or search the internet for the error code.

The boilers have multiple sensors to detect breakdowns or faults. Thanks to these sensors, the boilers stop when they encounter a problem, which makes them very safe devices. Among the sensors that we can find are:

  • Air pressure sensor
  • Smoke sensor
  • Water pressure sensor
  • Heating temperature sensor (flow and return)
  • DHW temperature sensor (flow and return)
  • Next, we show the most common breakdowns in boilers and their possible solutions.

Boiler pressure rises with heating

There is no reason to be alarmed if the water pressure in the Boiler Repair when the heating is turned on. This is normal, because the volume of water increases at higher temperatures.

The problem comes when the pressure increase is considerable. Normally, gas boilers work at 1.5 bars, increasing to 1.8 or 2 bars of pressure when in operation. If the pressure exceeds 3 bars, the safety valve is activated, which empties the circuit of excess water until the appropriate pressure is recovered.

If this happens, it is an indication that the boiler’s expansion vessel is not working properly, since it is responsible for absorbing excess pressure.

Possible causes:

  • The expansion vessel loses air: when this happens and we fill the water circuit up to 1.5 bars (normal pressure) we would be facing a problem since there would be more water than it should (so the pressure would increase) and also no that excess pressure would be absorbed. If we are faced with a problem of lack of air, we can introduce it ourselves into the expansion vessel through the howitzer if we have an air pump.
  • The membrane of the expansion vessel is punctured: the water filters to the side where the air has to go, causing there to be less pressure in the boiler. If we see that there is less pressure and we fill the boiler with more water, when it starts up the pressure will increase a lot since the expansion vessel will not absorb it. This failure can be checked by pressing the core of the expansion vessel air filling valve, if water comes out, the membrane is broken.

Another possible reason for an increase in pressure is the poor closure of the boiler filler valve, so that water continues to enter the circuit causing the pressure to rise. This problem has an easy solution if it is due to the fact that it is not closed properly because you only have to close it, but you have to call a technician if water continues to enter when you close it completely, as it may be a problem of wear or calcification and it is necessary replace it or disassemble it for cleaning.

The pressure increase can also be caused by air pockets in the radiators, which by occupying the space where there should be water, increases the pressure of the circuit. So whenever the pressure increases, the first thing to do is bleed the radiators. You can do this yourself using a screwdriver.

Another possible reason is a fault in the heat exchanger between the heating circuit and the DHW circuit. The heating one is usually at 1.5 bars while the DHW one is found at 5 bars. If these communicate there will be an increase in pressure in the heating system. For this type of fault it is necessary to contact an authorized technician.


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