Chaffoteaux Britony SE80 Ionisation fault?

[Chudley]

Hi,

I year ago I bought a house with a Chaffoteaux Britony SE80 (dont laugh). At the time the boiler wasnt working - when it tried to light it would lockout after a while with a flashing 60 degress LED (the manual says this is a fault with the Ionisation PCB). Anyway, about 1 time in 30 it would actually light. I stipped it down, cleaned dust off the pcb etc (obviously never been serviced given its general state). Somehow, the boiler started locking out less frequently, and eventually started running without any problems. Since then, it has locked out only a few times, and in the last 5 months or so not at all.

Anyway, 2 days ago it locked out again with the same error. The next day a couple more times, then yesterday it stopped working entirely, all with the same error code. I've measured voltage to the ionisation electrode at 24v when it is trying to light, so there seems to be no issue there. The spark generator never fires, so my guess is this is the problem. It's not the electrodes as there is never any voltage at the generator spade terminals, and if this actually fires without the spade plugs in, it arcs across the terminals. Currently it isnt doing this. The pressure is OK at around 1 bar cold, the fan runs without a problem, pump is fine. I havent managed to measure any voltage at the gas valve currently however - when should this open during the firing sequence?

I'm guessing the PCB is dead or intermittent at best, but I dont want to pay £120+ for this until I'm sure. Although I don't have the luxury of time given the prospect of cold showers! Can anyone suggest anything I can do to find out more, or what might be wrong?

Many thanks

Ben

 

[The Baker]

Just an outside chance but have you considered checking the said pcb for dry joints?
When looked at through a strong lens, the solder spots on the back of the pcb may have some solder joints that resemble a volcano with a bit sticking up in the middle (excuse my simplistic description).
If you carefuly resolder any dry joints found you may solve your promlem.

RegardsTim

 

[Chudley]

The Baker,

Thanks for the suggestion - I've already checked for dry joints as given the intermittent nature of the problem it was my first thought - unfortunately the board looks like it came out of the factory only yesterday!

I'm going to recheck anyway just in case but everything looked fine. I've confirmed that whilst waiting to fire, there is no voltage to the gas valve at all....

 

[Agile]

"""It's not the electrodes as there is never any voltage at the generator spade terminals, and if this actually fires without the spade plugs in, it arcs across the terminals. Currently it isnt doing this"""

I dont really understand what you are trying to say above. HT leads to the spark electrodes can sometimes fail.

You should not try to measure the spark generator output which is about 10,000 - 12,000 volts and pulsed.

Can you clarify what you wanted to say?

Tony

 

[Chudley]

Agile,

What I mean to say is that if the HT leads are disconnected from the generator, which then fires, the current arcs across the two spade terminals on the generator itself. If this doesnt happen when the spade plugs are removed, then it cant be the HT leads which have failed, as they werent plugged in!

Thanks for the warning on voltage, but no need to worry - i'm well aware of how high a voltage these things put out, or at least would if it did anything. Occasionally, say 1 time in 50 it will work as it should, but when this happens, the time between the boiler starting up its firing sequence and the spark firing varies considerably. When it was working normally it was always fairly quick.

Ben

 

[boilerbeasty]

Mine (SE100 rather than 80 but essentially the same boiler) behaves in a similar way when the heating has been on for a while. The boiler's in a cupboard which gets quite warm after a while. Perhaps this suggests it could be a dry joint -i.e. an intermittent problem which gets worse with thermal expansion. That's my guess.

Haven't sorted it yet, cos I moved in April and didn't have many cold days before the CH was turned off for the summer.

I would be interested to hear what the root cause is, if you manage to find out and get it fixed...

 

[cross thread]

had this prob on older model ,solenoid sticking on its seating ,means splitting gas section so qualified only

 

[Chudley]

Hi,

I've ordered a replacement PCB as thats my best guess given what I know so far. I'll post back when it arrives and i've fitted it. I'll then investigate the existing PCB in more detail if it is at fault. I don't think it's the solenoid in this case as no voltage is ever applied to it before it locks out. I'll be gutted at spending £140 if it isnt the PCB!

To be honest, I would probably be better burning the boiler for warmth given the problems I've had with it (diaphragm, 3 way valve, water control all replaced, thermistor leaking, PRV leaking, you name it it seems to have been a problem).

Bah

 

[Chudley]

Well, I've replaced the PCB and now all works well.

The odd thing is that after testing the old PCB with a multimeter at various points it started working flawlessly again - which suggests a poor connection was disturbed somewhere. Cant find it however - all joints look fine.

One thing I did notice was that the voltage at one of the diodes (i forget which one) was found to be rising slowly until lockout, where it had only reached around 8v DC. When the spark generator fired however, voltage lept immediately to +25v, so there was definitely a problem with the board before the spark generator itself. Frustrating I cant see anything that may have caused it however..

Oh well..

 

[ChrisR]

Thanks for letting us know

 

[geoff@cetltd]

There you go ... black magic