Potterton Promax FSB 30 HE - Help

[RobGra]

Evening,

Looking for some help & advice please. I've read similar problems in other threads, so bear with me.

The boiler is locking-out in overheat. Its pretty irregular and so far my local engineer has checked or replaced the thermostats, thermistor, changed the door seal and checked wiring etc. Pump has also been checked and is fine.
Its already cost me a few £'s, however engineer is now suggesting changing the PCB - not cheap and no guarantee. Incidentally, Baxi technical department advised the engineer to double up the door seal, which he's also done?

I'm now considering biting the bullet and getting Baxi out, or getting rid of the boiler altogether! Its around 9 years old and otherwise looks in good condition, and runs well until it locks out!

The overheating lockout only happens when the heating and hot water are asking for heat at the same time. If theyre on separately, it doesn't lockout.
The boiler will fire up ok and runs for 20 minutes or so before going into lockout, again only if hot water and central heating are on at same time. Also, after resetting the boiler, it seems to run fine after that.
I was wondering if both hot water and heating on at same time = increased heat, or something that's affecting the thermostats?

I'm loathe to pay > £250 for a PCB if it doesn't fix it!

Therefore if anyone who has experience with this boiler could advise I'd appreciate some help, or advice. And i hope I've described everything properly...

Thanks

 

[Vic Spanner]

Get Baxi out on a FPR.

 

[RobGra]

Get Baxi out on a FPR.

Thanks, I'm leaning towards that. It isn't cheap mind. £335 or £28 per month...

https://www.baxi.co.uk/service-and-...arts, labour and VAT,off payment from £335.88

 

[kidgreen61]

Horrid boiler, I'd get rid if I were you.

 

[RobGra]

Horrid boiler, I'd get rid if I were you.

I hear you! I'm actively considering that option.

Its a "system" free standing boiler, therefore any recommendations for a new system boiler or even changing to a combi would be appreciated? It will all least let me explore options.

Anything but Baxi!!

 

[ianmcd]

What system do you have ? Y plan or S plan

 

[RobGra]

What system do you have ? Y plan or S plan

Hi its an S plan - 2 motorised valves, both are relatively new

 

[ianmcd]

Hi thanks, have had problems with that boiler on Y plan, overheating, do you have a by-pass fitted before the 2 port valves ?

 

[RobGra]

Hi thanks, have had problems with that boiler on Y plan, overheating, do you have a by-pass fitted before the 2 port valves ?

Yeah, there's what looks like a pressure relief valve?

 

[ianmcd]

no a pressure release valve is a completely different thing

 

[RobGra]

Sorry my mistake, yes its a bypass valve. It looks like it's set quite high 0.5? Theres also a towel radiator without a TRV in the system too.

 

[Gasguru]

If it's 0.5 bar it's barely going to open if at all....given a 5m pump can only provide 0.5 bar of pressure when the flow has reduced to zero and a 6m pump not much more.
Try setting it around 0.1 or 0.2 to see if there's an improvement.

 

[RobGra]

If it's 0.5 bar it's barely going to open if at all....given a 5m pump can only provide 0.5 bar of pressure when the flow has reduced to zero and a 6m pump not much more.
Try setting it around 0.1 or 0.2 to see if there's an improvement.

Ok will try that, thanks. Remember theres a radiator without a TRV fitted in the system.

 

[ianmcd]

Ok will try that, thanks. Remember theres a radiator without a TRV fitted in the system.

Wont make any difference if the CH is set to off, that is why you have a by-pass

 

[RobGra]

Wont make any difference if the CH is set to off, that is why you have a by-pass

Understood, thanks.

Bit of an unfolding drama: When I was looking at the by-pass valve, I noticed one of the pump isolation valves was seeping a bit, when I looked closer, both of the isolation valves are completely seized. This got me thinking about the pump and how old it is - probably 8-9 years old. Its 3 speed Grunfoss pump. Did a quick Google search on checking pumps and and use a screwdriver to check - its working ok, however it could be stopped relatively easily. I wonder if the pump might be the source of the problem ie: whilst its turning, it might not have sufficient oomph to shift water quickly enough? Engineers did check the pump recently, but more to see it it was actually spinning.

So I need to get the isolation valves changed anyway, therefore a new pump will be fitted too. System will need to be drained as well - sigh.

I'll update this later.