Hi, I was wondering whether I could get some advice or tips regarding a small problem with our 5 month old Baxi Condensing Combi Boiler.  We have noticed that recently the pressure gauge is sitting idol at 2.3 and when the hot water is turned on it shoots up to 2.5 or even 3! It says on the instructions that normal operating pressure is between 1 and 2.5 and anything over this indicates a fault.  I've telephoned the installers who advised that this was ok and nothing to worry about, but I'm not too sure can anyone help  ???

Well it's certainly not normall to go that high and suggests a problem.

At about 3bar the boiler will discharge water, which could mean topping up when it cools.

2.3 bar cold is too high and should be lowered to 1-1.5 bar max, but how did it get that high in the first place, is the filler loop disconnected.

Another problem with larger system, and it will depend on the boiler model, but the expansion vessel is sized for about 130 litres anything over that will require an additional expansion vessel.

in other words more info on the system please.

The filler loop should be disconnected (water regs)

Lower the pressure to 1.5 bar maximum when the boiler and rads are cold, then record the high pressure when the system is hot.

To lower the pressure simple drain some water out the draincock or air vent, it will not be much.