Baxi Bermuda firing up when CH/HW switched off

[vichighrise]

I'm hoping to pick the brains of the Baxi enthusiasts in this group...

Recently moved into a property where the Baxi Bermuda (15 years old) was firing up even when the CH/HW was switched off and overheating the hot water in the cylinder.

British Gas checked it out, replaced the ACL Synchron Motor and cleaned the Baxi at the start of the week but the boiler is still firing up even when the CH/HW is switched off (although the HW cylinder appears to be okay)

Is this normal, or should I be on the phone to BG again?

[Roger Mills]

It certainly shouldn't fire when there is no demand for heat from either HW or central heating - unless it's being brought on by a frost stat located elsewhere, but I think we can probably discount that.

How many motorised valves have you got in the system, and what type (2-port or 3-port)?

[I suspect that you've probably got an S-Plan system with two 2-port valves, and that one or other of these is jammed in the open position.]

It's very unlikely to be a boiler problem per se - the boiler only runs when told to do so by the external controls.

[Mark]

My Baxi bermuda was older that yours but all it had was a thermostat in the boiler itself. Therefore it used to fire up from time to time unless it was completely switched off.

M

[the.highrise]

Thanks, Mark (and Roger) The mystery deepens, though; on Thursday evening when the CH/HW went off so did the boiler - thought the problem was solved. However on Friday, Saturday and Sunday it kept firing up after CH/HW went off - and then today, after both am and pm cycles of CH/HW switched off so did the boiler. Very odd indeed.

Still, I have BG coming round again tomorrow so will ask them to investigate.

[the.highrise]

Thanks, Mark (and Roger) The mystery deepens, though; on Thursday evening when the CH/HW went off so did the boiler - thought the problem was solved. However on Friday, Saturday and Sunday it kept firing up after CH/HW went off - and then today, after both am and pm cycles of CH/HW switched off so did the boiler. Very odd indeed.

Still, I have BG coming round again tomorrow so will ask them to investigate.