Boiler firing 30 seconds, off 4 minutes, house not heating..

[simond]

I suggest you isolate the pump at the valves, and split it open using the allen screws.

Look into the hole in the centre of the impeller and check it is not full of detritous where it leads to the vanes. Bits of rust get lodged here and massively block flow, leading to poor circulation.

Especially if the system wasn't cleaned properly or you have a particularly crusty set of old rads.

Only once you have checked the circulation is it worth diving into the boiler.

 

[GasSafeTony]

I had exactly the same problem last week with a glow worm back boiler. Was scratching my head, checked all the basic things, even made a thread on Here for help but just got abuse from folk (specially agile). Turned out the old lady had been hoovering around the fire and had pulled out the connector from the pcb to the thermistor.

 

[sandybeach]

If you do a bit research online,you will find that this particular boiler is rather infamous when it comes to it's reliablity.Potterton were slated on Watchdog about 4 or 5 years ago due to the shear volume of complaints regarding faulty PCB's.
You should give Potterton a phone.I'm sure they were offering to replace the boards free of charge after the bad publicity.The offer has probably expired but it's worth a stab.

 

[ChrisR]

It expired quite a while ago.

 

[telegan]

very easy repair but you need to be rgi to do it as its inside the cc

 

[ChrisR]

mooky - you've already been inside the combustion chamber so you'll have already not done things you don't know about. Get a Registered guy to do any further work in accordance with the regs including section 26.9 .

 

[mooky]

I suggest you isolate the pump at the valves, and split it open using the allen screws.

Look into the hole in the centre of the impeller and check it is not full of detritous where it leads to the vanes. Bits of rust get lodged here and massively block flow, leading to poor circulation.

Especially if the system wasn't cleaned properly or you have a particularly crusty set of old rads.

Only once you have checked the circulation is it worth diving into the boiler.

Righto.
My suspicion is not the pump - for reasons mentioned before. But to completely eliminate it as a suspect, it's worthwhile checking it closely.
Do you need any sealant to re-assemble? Any gaskets likely to need replacing? It's a grundfos.

 

[mooky]

If you do a bit research online,you will find that this particular boiler is rather infamous when it comes to it's reliablity.Potterton were slated on Watchdog about 4 or 5 years ago due to the shear volume of complaints regarding faulty PCB's.
You should give Potterton a phone.I'm sure they were offering to replace the boards free of charge after the bad publicity.The offer has probably expired but it's worth a stab.

Yeah, well aware of the dodgy reputation of the Poterton Suprima boiler PCBs.
They tended to exhibit more fatal failures like tripping out for mysterious reasons. Still possible it's that...
Nothing to lose by giving them a call...

 

[mysteryman]

I've known a Suprima to exhibit all the pcb symptoms - but it was a blocked cold feed, running dry, and overheating. Check the circulation!

 

[mooky]

I've known a Suprima to exhibit all the pcb symptoms - but it was a blocked cold feed, running dry, and overheating. Check the circulation!

I'll check it. But from the behaviour described above (pump looks/sounds ok, boiler will happily run for an hour of constant firing without overtemp, radiators nice and hot) you still think its a circulation problem?

 

[sinfinity]

Had the same issue with our boiler, had British Gas out and they replace the temp sensor, has been working fine ever since. They did say that if this didn't fix the issue that the board was at fault and would need replacing.
If the boiler is working correctly once the rads and water are up to temp, the light should go constant orange. The flashing green means that there is a call for heat but the boiler thinks it up to max temp.
I had this issue for ages on and off, had the pump, tank temp sensor and auto valve replaced at various times. I went for a while then returned. turning up the speed of the pump seem to resolve it for a while, but eventually it never got up to temp on its own and required me to turn it on and off numerous times, I guess the boiler temp sensor was not completely dead.

Sounds like an issue with the thermostat selection on/in the boiler.


You've said the boiler flashes green to say it's reached it's set temperature,
it obviously thinks it has, even if the boiler thinks the desired temp is 35C ??
even though the thermostats are at "Max", are they actually at maximum??

what exactly is flashing / lit when it's not working as expected?

removing the thermo-resistor mean the boiler has no indication when it gets to your desired operating temp and the backup systems to prevent overheat are kicking in to stop it overheating/superheating the water above 90c.

I Don't know what's causing it to stop cycling before overheat protection (being a "layman" as well)

Suggest you get someone knowledgeable with potterton's out to look at it and let him know what symptoms you're getting.

When it's not working as expected, the led flashes green slowly after it stops firing. As far as I can gather this means it has reached the designated temp.
Since the thermistor was cleared as a suspect, it has to be something wrong with the control circuit. The pot for the temp control looks to be affixed to the PCB itself - so its a bit of open-boiler surgery to check that out.
New controller is about £200 I'm told...

 

[Putty1503]

Hi Mooky,
Did you ever resolve this problem?
I'm having exactly the same problem. British gas have replaced both PCB & Thermistor twice(!!) and it's still occurring as you described. It worked for a while but now becoming frequent again.
So if you resolved it, I would be grateful to know how.
Thanks in Advance.

 

[Agile]

Putty, you should start your own thread.

Whilst you may think your symptoms may seem similar to an existing post, to a professional your situation may well be completely different.

That's why your own post is likely to be more effective.

However, if BG are already on the job then what do you hope to achieve?

Tony

 

[Putty1503]

Hi Tony,
Thanks, maybe I will if Mooky's resolution doesn't work for me.
It may be completely different to a Professional but it could also be exactly the same and therefore will save time from everyone asking the same questions, to get the same answers Mooky gave.
If I knew how Mooky had resolved his/her problem then BG can investigate that possibility. BG are currently bewildered about what it could be and don't know what else to try. They've been out 10+ times, 3 different engineers all scratching their heads and drawing straws for who comes next. So any help/pointers have got to be worth trying.

Putty1503

 

[AGAS]

10+ times + 3 rgi . you will be waiting a long time for him to reply , it was posted 4 years ago , he probably has skipped it by now. do as agile says and start a new thread describing fault e.g. what are lights doing when you've turned fuse spur off and on ? etc etc