Glow-worm ultracom - pcb or flow sensor?

[Andy Don]

Good morning. We have a 10 year old Ultracom which now very frequently thinks there's a demand for hot water, even though there isn't, so the boiler kicks into that mode, and sits there heating tap water that isn't going anywhere. Sometimes this happens if a cold tap has been used or the loo flushed but generally there's been nothing obvious to trigger it (I've heard it at 4 am doing this). Glow-worm's tech help suggest either the flow sensor or pcb. We've had 2 flow sensors die in the past, but on both occasions there was simply no hot water, not this random effect we're getting now. Glow-worm's fixed price is 299 pounds, presumably good value if it is the pcb, but not if just a flow sensor, in which case I'll get someone local again. Has anyone known a flow sensor fail with these sort of issues , or does it point more to the pcb? Thanks for any advice.
Andy

 

[Deleted member 120897]

Doesn’t sound like it’s the pcb. If it fires when a cold outlet is used, then it sounds like a dead leg with trapped air, so dead leg needs to be removed. Could be a few reasons why it’s firing for hot water, probably best with a local engineer to diagnose your problem properly.

 

[Andy Don]

Doesn’t sound like it’s the pcb. If it fires when a cold outlet is used, then it sounds like a dead leg with trapped air, so dead leg needs to be removed. Could be a few reasons why it’s firing for hot water, probably best with a local engineer to diagnose your problem properly.

Thanks for that. And yes, time for an engineer!