Central heating water pressure problem.

[bramfield]

I have a Vokera Mynute 28e system boiler. The boiler does heating only. The boiler is 2 years old.

The boiler has been working fine until recently.

The gauge on the boiler shows, when cold, a system water pressure of just over 1 bar.

Lately the system has been losing water pressure. What is happening is this. The heating comes on and the gauge on the boiler slowly creeps up to 3 bar when the pressure relief valve opens and water is discharged to outside. The thermostat on the boiler seems to be working ok and shuts off the gas at

55c.

Any idea why this is happening?

Regards.

DAB.

[andrew]

Pressure vessel not working. Either the air has leaked out, in which case you can pump it up with a bicycle pump, or the diaphram has broken, in which case you need a new pressure vessel. If it's inside the boiler, it can sometimes be easier to fit a new one outside the boiler on the pipework, and just leave the failed one where it is.