Potterton Promax FSB 30 HE - Help

Discussion in 'Plumbing and Central Heating' started by RobGra, 11 Apr 2021.

  1. RobGra

    RobGra

    Joined:
    11 Apr 2021
    Messages:
    31
    Thanks Received:
    1
    Country:
    United Kingdom
    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
     
  2. Sponsored Links
  3. Parrot.

    Parrot.

    Joined:
    24 Nov 2005
    Messages:
    682
    Thanks Received:
    93
    Country:
    United Kingdom
    Get Baxi out on a FPR.
     
    • Thanks Thanks x 1
  4. RobGra

    RobGra

    Joined:
    11 Apr 2021
    Messages:
    31
    Thanks Received:
    1
    Country:
    United Kingdom
  5. kidgreen61

    kidgreen61

    Joined:
    8 Mar 2009
    Messages:
    2,497
    Thanks Received:
    604
    Location:
    Staffordshire
    Country:
    United Kingdom
    Horrid boiler, I'd get rid if I were you.
     
    • Thanks Thanks x 1
  6. RobGra

    RobGra

    Joined:
    11 Apr 2021
    Messages:
    31
    Thanks Received:
    1
    Country:
    United Kingdom
    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!!
     
  7. ianmcd

    ianmcd

    Joined:
    15 Aug 2010
    Messages:
    24,055
    Thanks Received:
    10,136
    Location:
    Livingston
    Country:
    United Kingdom
    What system do you have ? Y plan or S plan
     
    • Thanks Thanks x 1
  8. RobGra

    RobGra

    Joined:
    11 Apr 2021
    Messages:
    31
    Thanks Received:
    1
    Country:
    United Kingdom
    Hi its an S plan - 2 motorised valves, both are relatively new
     
  9. ianmcd

    ianmcd

    Joined:
    15 Aug 2010
    Messages:
    24,055
    Thanks Received:
    10,136
    Location:
    Livingston
    Country:
    United Kingdom
    Hi thanks, have had problems with that boiler on Y plan, overheating, do you have a by-pass fitted before the 2 port valves ?
     
    • Thanks Thanks x 1
  10. Sponsored Links
  11. RobGra

    RobGra

    Joined:
    11 Apr 2021
    Messages:
    31
    Thanks Received:
    1
    Country:
    United Kingdom
    Yeah, there's what looks like a pressure relief valve?
     
  12. ianmcd

    ianmcd

    Joined:
    15 Aug 2010
    Messages:
    24,055
    Thanks Received:
    10,136
    Location:
    Livingston
    Country:
    United Kingdom
    no a pressure release valve is a completely different thing
     
  13. RobGra

    RobGra

    Joined:
    11 Apr 2021
    Messages:
    31
    Thanks Received:
    1
    Country:
    United Kingdom
    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.
     
    Last edited: 12 Apr 2021
  14. Gasguru

    Gasguru

    Joined:
    9 Sep 2005
    Messages:
    12,675
    Thanks Received:
    3,412
    Location:
    Sussex
    Country:
    United Kingdom
    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.
     
    • Thanks Thanks x 1
  15. RobGra

    RobGra

    Joined:
    11 Apr 2021
    Messages:
    31
    Thanks Received:
    1
    Country:
    United Kingdom
    Ok will try that, thanks. Remember theres a radiator without a TRV fitted in the system.
     
  16. ianmcd

    ianmcd

    Joined:
    15 Aug 2010
    Messages:
    24,055
    Thanks Received:
    10,136
    Location:
    Livingston
    Country:
    United Kingdom
    Wont make any difference if the CH is set to off, that is why you have a by-pass
     
    • Thanks Thanks x 1
  17. RobGra

    RobGra

    Joined:
    11 Apr 2021
    Messages:
    31
    Thanks Received:
    1
    Country:
    United Kingdom
    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.
     
Loading...

Share This Page