Central heating not working on Potterton (hot water is ok)

[pototea]

I have a Potterton Combi 80 boiler. This evening the central heating won't come on (it was working fine this afternoon).

The hot water works fine. The flame light comes on when I open the hot tap & hot water comes out.

When I try to use the central heating, the flame light won't come on (either when I use the timer setting or switch it to constant). I have checked the pressure & this seems ok. I changed the temperature on the thermostat to max which is 30'C & it still won't come on. I hear a click when I move the thermostat past 17'C. But the flame just won't come on!

Any ideas of what could be wrong?

 

[Rob]

need to prove your timer and roomstat are working first. If they are and there is still no activity from the boiler then its likely the PCB.

 

[fred48]

I rather suspect that this might be due to a sticking diverter valve - I have had this problem with a Potterton Combi 100. It seems you can only purchase the entire valve assembly at around £80 though I think it is usually just the wax thermostat that packs in.

 

[pototea]

Thanks for the replies. It is difficult to see if it is the timer or the thermostat which is causing a problem as my hot water is constant. The clock is still going round but the heating didn't come on this morning so I presume the timer is working. I have a plumber coming this afternoon to take a look at it.

 

[pototea]

The plumber has just been. He said the diverter valve needs replacing. He is going to see if he can find somewhere that sells a replacement part but said as it is an old model then he may not be able to find anywhere that sells it in which case I would need a new boiler.

Are spare parts hard to come by?

 

[fred48]

Try www.keeptheheaton.com - I managed to get a diverter valve from them last year for about £80. That was for a Potterton Combi 100: the 80 might just have the same part - not sure. Hang on a mo..........

Yes, just checked on www.mjtcontrols.co.uk and I see that the 80 and the 100 share the same valve - it was 929651 but it's been superceded by 10/20351. Keeptheheaton have them for £74.08 plus VaT and carriage - I think mine came in a couple of days.

Best of Luck. Have fun!

Let us know how you get on - by the way, you'll need some washers too - none came with mine - just the bare valve. Pity you don't seem to be able to source just the wax thermostat bit that's at the end of the valve - seems you have to buy the whole caboodle.

 

[pototea]

Thanks fred48 . I did already see that website. If the plumber can't find the spare part locally then I will order it from keetheheaton & get him to fit it.

 

[fred48]

Best of Luck - I hope all goes well. Might go have a Pot o' Tea now!

 

[pototea]

Just thought I would post a little update on this.

The (Corgi in NW London) plumber has bought a part for £87, which is £10 cheaper than keeptheheaton. He is charging £100 for labour. Does that sound about right?

Also last night the central heating started to work again & it came on this morning. The flame comes on for about 15 minutes, heats the radiators up, then goes off for a few minutes, then comes back on etc. That sounds like a thermostat problem to me. Would a faulty diverter valve produce those symptoms?

 

[Rob]

if it were a faulty diverter valve the boiler would still fire up initially providing the boiler isnt still hot from a HW demand. Or have you not given us the correct info.

and yes £100 labour is about right, its not a nice job.

 

[fred48]

I'd ordered my new diverter valve last year as my Combi 100 was starting to display some problems with the CH not coming on for long periods (an hour or more) occasionally after the hot water had been run. It seemed to cure itself for a wee while so it wasn't until yesterday, when I had a bit of spare time, that I fitted it. Quite a fiddly job but I took me less than 2 hours.

The thing, touch wood, seems to be working fine now - the CH locks out for just about 4 mins if the radiators are hot and the hot water is run. That seems all right, I think.

I decided today to take the old valve apart and my assumptions were correct - the thermostat mechanism was almost completely stuck. Taken apart, it looks just like the thermostat capsule in a car cooling system thermostat - a small cylindrical capsule with a pin sticking out of it - there's no temperature marking on it but it just makes me wonder if I should keep the old valve and try and renovate it with a new thermostatic element (if I can get one).

I do get the impression that Potterton do have problems with diverter valves, but I hope you get yours sorted out. Let us know if the new valve helps the problem - I hope it does.

By the way, in this day and age, I suspect £100 labour charge is not at all excessive.

Best Wishes.

 

[Agile]

The wax bit usually fails after a number of years and is available unofficially and is quite easy to change on its own.

However, in this case he is saying nothing about the boiler firing up for a few seconds when heating is started as it would if the diverter had failed.

Based on what he has said it would be something else!

Tony

 

[pototea]

Hi, the plumber came yesterday & fit the new part. So now the central heating problem should be fixed.

My only problem now is that the thermostat is in the kitchen, which is the hottest room in the house so the heating does go off quite quickly and stay off for awhile until the kitchen has cooled down!

 

[2face]

move it to the hall . ?? strange place to put a stat ??

or purchase a wireless 1 .. much easier ..