Pressure increases when heating turned on!

[debrag]

I have a valliant turbomax boiler. When I moved in the pressure was low so I opened the valve and increased it, unfortunatly too much and it went over 2. Bleed the radiators and go it down into the green area but it won't go down that far.

When I turn the heating on everything works fine but the pressure gauage goes up over 2 after a while and the radiator indicator starts flashing. The heating stays on.

I'm not sure what I shouldbe doing as the valve is now closed.

 

[plumbnuts]

The pressure when the system is stone cold should be just above 1 bar. As the system heats up the pressure will rise as the water expands. 2 bars when the system is hot is quite normal.
Steve

 

[debrag]

Thanks but the pressure is currently over 2 and the heating isn't on.

 

[Alz0r]

I would hazard a guess that the valve on the filling loop is letting by.

 

[simond]

As long as the pressure doesn't get much above 2.5 you haven't got a problem.

The flashing radiator symbol has nothing to do with water pressure in the circuit; it is saying that the boiler is currently being asked to come on by your thermostat/timer but the water inside the boiler has reached temperature, so just the pump is running until the temperature dissipates.

 

[debrag]

UPDATE:

The pressure still increases. Sometimes almost to 3.

I just blead one radiator and the pressure went from almost 3 to around 1.5 when I blead another radiator the pressure went back up but now it has gone down to 1.5 again. It won't stay there for too long though.
Is the pressure meant to change all the time.

All required valves are closed as far as I'm aware.

 

[alwest197]

Had a similar problem with my combi boiler...might be different with yours however.
Mine was caused by pinholes in the Plate heat exchanger allowing water in which slowly built up the pressue. I had to keep letting pressure out through a radiator until it was fixed.

An extra check that the loop is fully closed and not leaking water is a good idea esp if it had not been opened for some time until you did it.