Went to a Glowworm Compact 100e the other day and found out it was a lose electrical connection. Problem solved i thought, however was called back the following day as the boiler failed to light on C/H mode, found out that the pressure had dropped, repressurised the system and waited to confirm that the heating came on and yes it did, however i did notice that the pressure kept on rising while on heating mode, then the PRV cut in and the boiler lost pressure as it should. Dont understand why the pressure keeps on rising when the CH is on and it drops when its off. The Room stat and boiler stat are working i think it most be something to do about the expansion vessel.

Anyone shed some light on why a boiler pressure keep on rising when on CH and dropping when CH is off.

Bob the plumber, February 2009

Thanks for that PDN, as it happens i have to go back there tommorrow as the pressure has dropped again, i suspect due to the PRV operating. However i think i will be stopping of at Halfords for pump and Tyre pressure guage. As it happens i'm guessing that those symptoms are not specific to glowworms as i have come across this a few times, if the pressure keeps rising the problem is that the EV has lost its air and just needs re-pressurising.

Thank again (if it works)

Bob the Plumber, February 2009

The expansion vessel has lost it's air or needs replacing, to test remove the shreader valve cap on the EV and depress until the air stops if you get water time to replace EV. Otherwise get the bike pump out and pump up to 10psi. open a drain point and leave open until you reach 10psi, as your pumping your pushing the water out of the EV and recreating the expansion space

PDN, February 2009