Potterton Boiler not firing sometimes

[Simon Hill]

My potterton profile 40 has started to become intermittent, woke up on Friday to no hot water. Demand was there and pump to tank running but boiler was doing nothing. Switched mains supply off, then back on and it burst into life for a couple of minutes then went off again. Did the same thing, this time it stayed on until water was hot. Saturday morning did the same thing but this time one on/off cycle seemed to sort it. Was fine yesterday but this morning did the same again. I have heard odd clicking type sounds coming from the boiler when it's been on, could this be connected?

Any help gratefully received.

Cheers

[Simon Hill]

Oh, forgot to add it's a Boilermate thermalstore system.

[Ed Sirett]

Perhaps the themrostat is on the blink? The thermostat on these boilers is fairly low tech; consisting of a liquid in a phial located in the heat exchanger connected to a capilliary tube connected to some gubbins; This is altered by the dial with numbers on the front. AFAIK the over heat stat is manually resetable so it is not over-heating.

Some questions: When the boiler goes out does the fan keep running? Does the fan keep stopping and starting? Does moving the thermostat stop or start the boiler when it is running/not running? How well is the pump running? How sre are you that water is actually circulating?

[geoff]

I thought that was the netaheat, does the profile work the same way ?

[Simon Hill]

Hmm, not sure how to tell, there's no noises coming from it at all when it's out? When I do the mains reset, I think I can hear the fan start before the igntion begins.

Not that I can tell, see above. It's making some bl00dy loud clicking when on now though! Although not all the time, I can't seem to get to it while it's making the clicking noises.

running/not

Will try this as soon as it fails again and let you know.

When it's working it's perfect, the CH is v hot and there's loads of hot water from stone cold in about 15mins. I've had the pump out in the past and cleaned the scale out etc, all looks ok. Again what's the best way to check?

[Simon Hill]

OK, I have some more info. When it's not on but demand is there, the fan is running. Moving the thermostat a little does not change anything but if I reduce the thermostat knob right down until it clicks off then back up again, the boiler does burst into life. Does this give you any more clues?

Cheers

over-heating.

[geoff]

In message , Simon Hill writes

What, check the pump ?

There should be a large chrome screw at the back of the pump which if you unscrew it, you should be able to see the shaft rotating

[BigWallop]

When you're using the 'stat to fire the boiler and it responds but nothing else happens, then it could be a zone valve that's the cause. When the 'stat is switched off then straight back on, the signal will over ride everything and set the boiler going. If the zone valves don't respond to this situation, then the system will fail again due the break in signalling from the rest of the components.

Hope this makes sense.

[Ed Sirett]

I will double check next time I'm at one of the flats I look after. I'm nigh on certain it's a manual reset job which cuts the power to the entire boiler if it ever trips - ecept possible for pump over-run.

Having read the OPs reply I'm tending to the idea that there maybe some sort of thermostat problem.