Potterton Suprima 100L - Intermittant - not starting

[clockworkfrog]

Pulling my hair out on this one.

Symptoms are that the boiler does not always start and seems to cut out early. When not working, the lamp flashes orange which indicates heat demand but suggests to me that the boiler thinks that it has reached temperature.

The pump and fan do not run when it fails to start.

The lamp does not go to red as in the lockout faults I have read about here and reset doesn't help.

If it isn't working at night, the chances are it will come on by itself in the morning.

Could this be the temperature sensor? I don't think that it is the overheat sensor because the red light doesn't come on.

Any ideas gratefully received.

Regards

Steve

 

[gavinda]

had one of these failed today, and it is a cheap part.

 

[nickso]

ive replaced one suprima thermistor in 8 years, it could be at fault but i doubt it.

ill lay money on it having the classic version 3 pcb fault where it thinks its up to temp when its not. the only thing stopping me from being 100% sure is i recall it flashing green when it sits doing nothing, not orange.

 

[gavinda]

yeah.. ita the first one ive done.... i usually walk in carrying the board on a call out to these.


apparantly 9/10 boards returned to potterton arent faulty. although they've change the design twice and 10/10 customers whove boards ive swapped have never reported back to me that i was wrong.

 

[nickso]

apparantly 9/10 boards returned to potterton arent faulty. although they've change the design twice and 10/10 customers whove boards ive swapped have never reported back to me that i was wrong.

hmm, i have two problems with that.

1) you were no doubt told that by some ****y BG manager who got the information from an even more ****y BG warranty parts guy.

2) the ****y BG parts guy no doubt got that info from a really ****y potterton parts guy. the 1+2 pcb's were ****, why they can't just admit it and get over it i'll never know. i'm pretty sure the factory in outer mongolia they used to make these pcb's was making china dolls the week before and thought they would re-tool and have a go at pcb's. version 3 pcb's are good apart from the above mentioned fault which is very rare indeed.

 

[nickso]

3) swopping the pcb always cures it, apart from that one time when it was the gas valve.

 

[gavinda]

totally agree , the pcbs are meh..


always check that gas valve gauze too

 

[ollski]

apparantly 9/10 boards returned to potterton arent faulty.

The phrase Bg bullshit is so common now I believe it is about to get a dictionary entry as a single word.

 

[clockworkfrog]

Thanks Guys.

I have taken the PCB out to take a look at it and it is a Siemens PCB in a plastic casing it has LMU30.211A159 written on it. It didn't look anything like I was expecting from seeing the pictures of the clunky things shown on the internet in forums and it certainly didn't look like it had dry joints.

How do I identify which PCB I have? It sounds like the general opinion is that its not the thermistor although it is cheap to try a swap I suppose.

It was fitted about 4 years ago by the way.

Cheers

 

[clockworkfrog]

just going back to what nickso said. When doing nothing the lamp is flashing orange, with SL ON, and just orange with SL OFF.

Once it does start the lamp colours are correct but it seems to cut out early. Yesterday it ran all day without a problem then cut out (didnt restart) at about 6pm. (flashing orange) then without touching it, it came on again at about 9pm. (that sounds like cooling down time to me)

We once tried runing a bath to get rid of hot water and it fired up after that but it could have been coincidence because it was about 9pm and had been off for a while anyway.

I checked the voltage across the fan and the output to the pump and neither are ON and they both work fine once volatge is applied.

Because it is not try to start the fan I decided that it can't be the air pressure switch because its not even getting that far. Same probably applies to the gasflow valve.

Because it's not in lockout (RED) I decided that it cant be the overheat sensor.

From the diagram in the handbook it isn't getting into its control sequence because of temperature.

That leaves the sensor and the PCB I guess.

 

[gavinda]

apparantly 9/10 boards returned to potterton arent faulty.

The phrase Bg bulls**t is so common now I believe it is about to get a dictionary entry as a single word.

hey, i never said i believed it did i

 

[nickso]

That leaves the sensor and the PCB I guess.

ive never had to do this, i always replace the pcb for any stupid faults, but if you catch it when its flashing orange check the thermistor resistance. i'll almost guarantee it will be correct. that way you can pretty much rule out the thermistor.