I have recently had a Glowworm combi (30cxi) installed - everything appear to be working fine, but I have noticed that after turning on a cold tap quite often the boiler will spring into life, showing a rising or falling temperature on the display. The bolier doesn't appear to be heating, just the motor kicking in. I assume this is pressure related..? - The system appears fine otherwise, displaying a pressure just over 1 bar and delivers heating & hot water when needed. Is it normal for the cold tap operation to cause this or do I have a problem?

NewCombiMan, May 2008

Fit a check valve in the cold water supply to the combi.
When you draw cold water the combi does not see any
pressure drop due to the check valve, and this stops the
DHW triggering.

Simon, August 2008

Thanks T - Much appreciated..

New CombiMan, May 2008

sorry, call back your installer on this one, if not contact Gloworm for an engineer site visit (this should all be done under warranty, do not pay for it!)

T, May 2008

sounds like a plumbing issue, when cold it running it must be taking feed somehwere that is triggering the boiler dhw flow switch.

one of those problems that would need investigation onsite!

T, May 2008