Potterton promax HE 24 unreliable please help

[DIYDaveB]

Ok I'm stumped...

My Potterton Promax HE 24 (Heat only) boiler started becoming unreliable with it starting to fire up less often without using the reset switch on the front. It has now basically got to the point where it won't fire without a reset or unless it has been on recently. Once reset it starts like a charm and runs the full heating cycle without issue, making me think that the issue can't be that serious.

When it won't fire you can hear the transformer come on and a single relay click from the control board but no other activity at all; no fan, no pump, no ignition attempts...

After reading all the posts on the bolier and following the diagnostics in the manual I have eliminated the following:

• Thermister
  All safety thermostats
  Condensate trap, and sensor
  Dry joints on the PCB's (Only one found on the ignition board)
  Transformer
  DC voltage on control board
  3 Way valve actuator
  Tank stat
  Room stat
  Control board (changed for new one with no affect)
  Pump

As you can see I'm stuck; the boiler engineer I got out was as much use as a chocolate teapot as he said "You seem to know more than me; I would just change parts at random now."

I hope some Baxi/Potterton engineer are reading and give me some ideas, or recommend a good boiler engineer in Gloucestershire.

Please help as my Mrs is getting fed up of cold water in the mornings.

 

[Agile]

You dont actually say it, but I presume that you mean that its going to lockout?

I think that its a relatively simple gas related problem which any competent engineer should be able to diagnose.

Whilst I expect that I know the cause, as its gas related, for safety reasons I dont encourage DIY gas work.

As long as you ensure that you get an engineer who will give a no-fix no-fee and agrees not to charge you for any parts not required to effect a cure. I expect the part that may be required is about £23 ! Pretty cheap as far as boiler parts go.

You also need an engineer with a flue gas analyser! Some still dont have them!

Tony

 

[DIYDaveB]

Hi Agile, well I assume it is locked out and the reset switch clears this, but the bolier literally has no feedback indicators so hard to say.

I am happy to work on the electronics but as you point out only a qualified gas safe engineer should touch the gas systems. Can you give me an idea of what your thinking so I can mention it to the engineer please.

Can anyone recommend anyone in the Gloucestershire area?

Cheers

 

[misterdubya]

There is another topic on this, posted quite recenty aswell. Maybe Tony is using this as his reference, as he seems to be vague.

But, if he is thinking what I'm thinking he's thinking (oh lordy) he cannot elaborate due to forum rules.

Namsag may be along soon, and will just tell you anyway. DIYnot forum rules are different in Scotland).

Mr. W.

 

[DIYDaveB]

Cheers Mr W; couldn't find the post you were referring to as its all a bit vague; could someone PM me their ideas. I will definitely get an engineer to do the work, just would like to find me a good one, as the few I have met haven't even serviced the boiler properly so far , but reading these forums gives me hope as I know there are good ones out there.

 

[DIYDaveB]

One thing I don't understand though; if I have a gas flow issue of some kind how come when I reset it it fires up instantly and runs as if nothing is wrong with a clear strong blue flame? I guess I would have expected this kind of issue to cause a constant issue instead of a lockout after a prolonged (about 2 hours) period of intactivity?

 

[DIYDaveB]

One thing I don't understand though; if I have a gas flow issue of some kind how come when I reset it it fires up instantly and runs as if nothing is wrong with a clear strong blue flame? I guess I would have expected this kind of issue to cause a constant issue instead of a lockout after a prolonged (about 2 hours) period of intactivity?

Strike that once the gas gets going there is a yellowly burn to it.

 

[DIYDaveB]

Had an engineer out today and he did a combustion check and all was fine. After some puzzeling and testing we discovered that dosconnecting the water flow switch caused the same lock out scenario, so it looks like a intermittant fault of the water flow switch.

Just thought I'd let people know, as it is a perplexing problem and all Potterton keep saying is change the control board even though I had.

 

[DIYDaveB]

All fixed; it was the water flow switch (dry fire protection); it would seem that I didn't need a new switch but to simply remove it and clean it of debris. The switch uses a hinged magnet to operate a magnetic reed switch and the magnet had iron oxide debris covering it, which affected the swing making it intermittant.

FYI

Dave

 

[michael Shilling]

I know this is an old thread, but was interested as I had diagnosed a faulty flow switch causing the apparent lock out myself. But it proved to be a false lead as, after replacing the flow switch, the boiler still exhibited the same lock out symptoms, that is sometimes will not restart after running normally. Again I had replaced all the safety cut out button devices and the thermister on the flow pipe.
So I am taking the nuclear option and replacing this now 15 year old boiler with another brand. Therefore NOT Potterton Baxi