Exploding ( very loud *bangs*) Potterton Promax HE Boiler

[Rsian]

We had a Potterton HE boiler installed a couple of years ago.
Everything worked fine, except there would be an occasional *Bang* when it fired up. ( This bang usually happens when it fires up after it has been off for a period of time - several hours ).
We spoke to the person who installed it and he said there was nothing to worry about.
We had it serviced about nine months ago and told the different engineer about the loud bangs when it fired up.
He looked at it and said he could find nothing wrong with it, other than the 'whatever he called it' which creates the spark was a bit too far apart so he adjusted it slightly, other than that all was fine.
Anyway, the bangs continued and we just put up with it ( it is sometimes loud anough to wake you up ).

A neighbour whose garden backs on to our own came round the other day to say that in the morning she heard the *Bang* our boiler made, there was a flash of light from inside the flue, and a load of black smoke came out ( which immediately cleared and went back to white smoke - like it is supposed to be ).

I don't intend to play about with this myself, but can someone advise me what the problem might be before I get someone out again, all for them to say 'Nothing wrong with it'.

On a side note, water has leaked out of it a few of times ( from the pipes on the inside near the top ), only happened a few times, and has not happend for a few months, so I don't think this is tied in with the 'exploding' problem.

 

[slippyr4]

The boiler evidentally is struggling to ignite the gas. The bang is an explosion - too much unburnt gas/air mixture finally gets ignited. Black smoke is due to partial combustion.

You need to get this looked at as a priority. The bangs aren't so much of a worry as the fact that the boiler struggles to light the gas. Suggest you try and find an engineer with a specialism in potterton appliances; they'd be more likely to get to the cause.

 

[Rsian]

Cheers, I'll get it looked at.

It seems to fire up fine maybe nine times out of ten, it's just maybe once or twice a day that the *Bang* occurs.

 

[gazthepottertonengineer]

you can do a couple of things to sort this out firstly try removing the yellow jumper pin on the main pcb the one with several connections on the right as you look at it this will allow the boiler to fire up on a low gas rate and normally sorts this problem out

if this doesnt work try replacing the electrodes, ignition pcb and gas valve in that order to resolve problem

 

[Rsian]

you can do a couple of things to sort this out firstly try removing the yellow jumper pin on the main pcb the one with several connections on the right as you look at it this will allow the boiler to fire up on a low gas rate and normally sorts this problem out

Would you advise someone with no knowledge of boilers ( but who is fairly DIY capable ), to do the above ? ie, is it something 'doable' for your VERY average DIY'er,

if this doesnt work try replacing the electrodes, ignition pcb and gas valve in that order to resolve problem

I have no intention of even considering that.

 

[gazthepottertonengineer]

i didnt expect you to change gas valve thats for sure

removing jumper on pcb is quite straight forward though just make sure you turn electrics of though

 

[Agile]

it certainly reads that way !!!

you can do a couple of things to sort this, try replacing the electrodes, ignition pcb and gas valve in that order to resolve problem

 

[slippyr4]

given that the op said "I don't intend to play about with this myself, but can someone advise me what the problem might be before I get someone out again, all for them to say 'Nothing wrong with it'.", i don't think gaz was encouraging any dangerous practise.

 

[Rsian]

Hi.

Right, I'm just about to locate the jumper on my boiler pcb, and remove it, but before I do, would someone mind just answering me two quick questions?

1. I have actually noticed, that although the loud bangs do occasionally occur when it first fires up, it actually happens more often when it fires up after only a short period of time - say, if the boiler had been off for about 30 mins, it is much more likely to *bang* on that occasion.
I just find it hard to believe that the problem is down to the 'slow/fast gas rate' ( this is based on what I assume the previous term to mean ). Can this problem that occurs so sporadically, really be cured by doing this?

2. Why does my boiler fully switch off every time the water/heating has reached it's temperature, why does the pilot light not stay lit?

Cheers.

 

[Agile]

Firstly, your boiler does NOT have a "pilot light".

The problem you are experiencing is called "explosive ignition". It is caused because the gas/air mixture does not always ignite immediately.

This can be caused by many different things, burner pressure on ignition, spark power, timing, flue assembly, gas valve settings, etc.

You can try the PCB jumper adjustment as suggested if you feel competent to do that and see if that cures the problem.

I do have to say that most of these problems I see are caused by incorrect gas valve settings but yours could be caused by anything!

Tony

 

[Rsian]

Hi.

Right, I have just gone to try the jumper fix, but am not too certain what does what.

J1 has no jumper, both 2 & 3 have jumpers.

Below is a description on the page from the manual with the jumpers on it.

Which of these jumpers needs to be removed to do whatever it was needed to be done ( reduce the gas flow? ).

Thanks.

 

[Rsian]

Anyone?

 

[Mikeyboy]

Best course of action is,call Heat-Team[ number on baxi website], for a fixed price guaranteed repair.Alternatively arrange a call with British Gas to attend on a fixed price guaranteed repair of your boiler.On this boiler there have been quite a few modifications to the P.C.B.Re,moving fixed jumpers on the existing p.c.b.,alters the operation of the gas valve ,ignition and pressure to the burner.This type of work requiries a competant CORGI engineer.If you follow my advice,you will have a boiler with low start up ignition noise,smoother running, and you and your neighbours will be SAFE and happy.PLEASE LISTEN TO ME!Have the work carried out by a proffessionally competant engineer.Do not attempt any more hit and miss objectives,for your own safety.

 

[Agile]

It has not been stated yet which model of Promax HE he has.

Its easy enough to follow the book if one knows that.

I, for one, have no idea what the "yellow" jumper is or where it is or what its function is meant to be.

I would agree that either a competent independent engineer or the manufacturers engineer should be called. The first think I would check as a starting point would be the gas valve setup.

Tony

 

[Rsian]

Best course of action is,call Heat-Team[ number on baxi website], for a fixed price guaranteed repair.Alternatively arrange a call with British Gas to attend on a fixed price guaranteed repair of your boiler.On this boiler there have been quite a few modifications to the P.C.B.Re,moving fixed jumpers on the existing p.c.b.,alters the operation of the gas valve ,ignition and pressure to the burner.This type of work requiries a competant CORGI engineer.If you follow my advice,you will have a boiler with low start up ignition noise,smoother running, and you and your neighbours will be SAFE and happy.PLEASE LISTEN TO ME!Have the work carried out by a proffessionally competant engineer.Do not attempt any more hit and miss objectives,for your own safety.

Heat Team came out today and replaced the igntion...bit. Complete boiler guaranteed for 1 year, labour & parts. Cost about £250.00

Cheers.