Main heat exchanger overheating when heating off

[Knappers]

I'm glad you went to the effort but it was more the advice to turn the gas valve on and off that I take issue with!
It's not even a usefull test for the consumer as obviously turning off valve will stop the issue regardless.
If you hadn't mentioned the letby then I'd probably not have picked up the issue but the idea of considering a significant amount of letby and not advising shutting off permanently (especially on a premix burner with open venturi) is dumbfounding!

 

[Knappers]

I suppose atleast now the OP can put his multimeter to good use

 

[oz-plumber]

HI Knackers,

Most parasitic flames are cancelled by the high limit thermostat.
Generally, the consensus is a gas valve fault.
Secondly, PCB Fault.
Thirdly - Fame sensor fault.

If you read through the Baxi Technical Manual - ( not the boiler installed ) - but generic through most boilers.

Change PCB - if this does not rectify problem, change gas valve.
Change Gas Valve - if this does not rectify problem, change flame sense electrode.
Change flame sense electrode!!

Generally, I start with the cheapest option - Flame Sense Electrode - and this 8 times out of 10 fixes the problem.

Understanding boilers operations, that is why I suggested turning off the gas valve when not in use.
My understanding from the OP was that the boiler shut down on 'overheat', which stopped the gas to the burner.

That is why I suggested turning off the gas valve when not in use.
If I thought the problem was more serious than that, I would have suggested turning off the boiler completely.

Thanks for your informed comments

 

[Knappers]

I wouldnt be quoting texhnical manuals for consumer advice.
Each to their own oz-pumber

 

[oz-plumber]

FYI Knappers - All available online
You don't have to search hard to find anything about any boiler.

Most of the UK spare parts supplier have boiler manuals online - available for anyone to look at.
Including fault finding and service manuals.

Oh...and then there's Youtube...............

 

[Knappers]

OK dude
All the best to the guy with the problem.
Please don't be tempted to change a gas valve or get stuck into your boiler - testing parts.
If you suspect a serious issue with your boiler or even if you have to regularly reset a fault, please seek professional assistance from a gas engineer - in person.
A lack of hot water is not normally potentially life threatening, just a bit of an inconvenience.

If you fancy making a rotating belt of knives tho then I think that's a cool idea and can point you at a YouTube video that shows how to do it

 

[oz-plumber]

Post the link to the video........Dude!!!

 

[Knappers]

Must be OK

 

[Bob6464]

Thanks for the replies and help all, had no hot water for a few days but new boiler is being installed tomorrow, i have always been happy to descale plate heat exchangers with spirit of salts but i do not have the skill or knowledge to go further than that, so decided to live with cold water for a few days rather than mess with things that our beyond me.

Thanks Again

 

[oz-plumber]

Thanks Bob6464,

Tried to help you as much as I could without getting into too much trouble.
All of the solutions provided are freely available on the net.

My point was that you could have hot water for showering / bathing if you manually switched the gas valve at the boiler on and off at / for your convenience. PITA, but, you could at least have a hot shower and heating sporadically when required.

Apologies from me - and I don't speak for the forum, about the Knob - Knappers, who in his own right took it upon himself to have ago at me for trying to give you some help and sabotage your post.

I went slightly off track also, posting information freely available on the net.
Obviously some of the information, on your situation in particular, he has or had no knowledge of.
Sharing information - helping others..........I hope I gave you some assistance.

We're here to help each other, if I crossed some line, I haven't been informed as of yet......still waiting.

I haven't looked at Knapper's video he posted, if it had something to do with Plumbing I may have.
Did you? - Did it help your boiler issues?

Over and out,

Hope your new boiler gives you years of trouble free hot water & heating.

Oz