Worcester C1 pressure high

[Nogsx3]

We have British Gas branded Worcester Bosch C1 combi boiler. I spotted yesterday the pressure guage needle was over the red line limit of 4 and probably nearer where 5 would be if it was marked. We turned the system off immediately and its dropped down to 3, the start of the red zone where its stayed over night.

I've search on the forum and the common faults that cause this are HE failure, expansion tank failure or leaks. We have not leak, the flexi pipe where the filling value is looks normal. Nothing looks wrong but obiously something is and ironically BG are servicing the system in 2 days time.

Is there anything I can do to drop the pressure or is it safe for now to just leave it for the service ? I've found the manuals for the boiler online but I'm familier with boilers / heating systems.

 

[jjohn]

could just be that the expansion vessel need recharging simple fix for enginner best to get BG to come early as your paying them anyway youll probably find water dripping out of pressure relief pipe that has relieved pressure when system heats up may be best to get pressure relief valve replaced if so

 

[jjohn]

Since pressure has remained at 3bar when system has cooled lightly heat exchanger is leaking across to primary system cold supply to heating side.
Check by releasing pressure at pressure relief valve on boiler without topping system up at loop if H/E passing pressure will rise again

 

[Nogsx3]

Thanks for replies. I've released some pressure via PRV, its dropped to 2bar after about 15 minutes. I'll keep my eye on it...

 

[Nogsx3]

Its settled at just under 1 but even letting in water it doesn't seem to rise again.

well i got the pressure back up, turn valve off at 2 but pressure kept going up, i did turn it on for 20mins of heat. Outside over flow has a tricke. I#ve given up for now, service in the morning and find out whats wrong then.