puma 80 nightmare

yodaboda · 5 Jul 2006

Hi All
I have got a puma potterton 80 which is turning into a nightmare 8 months ago the heating wasnt coming on as it should have been but hot water was working fine the problem was diagnosed as being due to the wax capsule in the diverter valve sticking in the hot water position a new diverter valve was fitted as well as new pump and thermister (h/w & c/h) the boiler is now showing similar sympoms the central heating doesnt come on at all and sporadically the pilot light goes out coupled with loud banging noise and steam overheating i think but this happens even when not being used.My gas fitter who is a good friend is a bit stumped as numerous checks on all components suggest it needs a new diverter valve again wondered if anybody had experienced similar probs and can think of anything that we have overlooked any help would be great thanks

Baxmax · 5 Jul 2006

First post eh

Agile · 5 Jul 2006

Your gas fitter is evidently not very experienced with Pumas! He seems to be better at just changing parts rather than diagnosing faults!

Tell him the DHW flow switch is sticking in the on position.

You should also check that none of your hot taps are dripping!

Tony Glazier

yodaboda · 5 Jul 2006

hi Tony

there are no leaking taps

dhw flow switch has been tested and is working
unless u mean it can occasionally stick?

croydoncorgi · 5 Jul 2006

The wax-stat diverter valve on Pumas is virtually bullet-proof (hardly any moving parts...) but if the boiler is firing and then overheating (noise, steam and the pilot lights goes off)b chances are the DHW switch is sticking open and therefore the boiler fires AFTER the tap has been turned off. There's nowhere for the heat to go, so kettle, kettle , whoosh, clunk!

But then you say that the boiler may be firing with no HW demand at all! That's very worrying: it's carefully designed NOT to do that!

What is the indicated system pressure (gauge under boiler, right hand side)?

ChrisR · 5 Jul 2006

If the DHW flow switch thinks tap water is flowing, a red led comes on on the pcb, which is obvious with the case front panel off. SUggest you look for that.

If it works for HW but bangs and goes out when you try CH, your pump's not going, or there's a serious blockage. DV could be stuck in HW position, but it's unlikely unless there's a tap dripping. Would be easy to check with a surface thermometer.

Was the whole dv renewed or just the wax capsule at the front?

Agile · 5 Jul 2006

The boiler fires with no CH or HW demand BECAUSE the DHW demand switch is jammed in the demand position ( electrically closed not open ) so the boiler starts up and Chris's red light on the PCB comes on.

The switch may well be working but the shaft which activates it can jam!

Just because he thinks its OK does not mean that it IS working !

This is a very common fault with Pumas and any competent boiler engineer should be aware of it.

Tony

Gasguru · 5 Jul 2006

Unscrew DHW microswitch, put a long M4 bolt into the end of the flowswitch assembly.

Get customer to turn the hot tap on/off several times - you can "feel" on the end of the bolt if the pin is sticking and not fully retracting.

Agile · 5 Jul 2006

Even easier is to just watch the gap ( should be about 1 mm ) between the operating rod and the switch actuating cam.

Can help to put white card behind the viewing hole and or use a torch.

When DHW demand exceeds 2 li/min switch should have actuated.

When DHW is turned off the rod should retract quickly and re-establish the gap within 1/2 second.

Tony

yodaboda · 6 Jul 2006

Hi and thanks to everyone who has taken the time to help

I will try to answer all the points mentioned as best as i can

firstly yes the whole diverter valve was replaced aprox 8 months ago

The red light on the pcb does come on and off when you turn the hot water on and off and you can hear it clicking, that was what i meant when i said it had been tested

is it possible it can still be sticking even though red light coming on and off? or occasionally sticking?

pump also working fine it doesnt bang when ch put on, cental heating just doesnt come on at all banging occurs sporadically with steam and then over heat stat kicks in and pilot goes out

taps are fine too no drips whatsoever

I will get my friend to unscrew dhw microswitch as suggested

my gas fitter also mentioned something about the frost protection thermostat but cant remember what it was. does anyone think it may be relevant

thanks again for your help

Agile · 6 Jul 2006

The question is what does the red light do when its banging! Its ON I expect !

Its JUST possible the diverter is stuck or faulty but again unlikely. It helps to put silicone grease on the moving seals when installing.

Did you see the NEW diverter or did he just tell you !!!

The frost stat can have one wire disconnected to remove it from the equation but I have NEVER heard of a faulty one !!!

Tony

ChrisR · 6 Jul 2006

Yodoaboda. as far as I can see, for ALL that you say to be true, the boiler would
a) have to be coming on for no reason and
b) have to be ignoring the CH temp sensor.

It's pretty unlikely to be doing that though it's possible that there's a pcb/connection error.
But a "red light" condition WOULD do both those things, so its worth checking again.

yodaboda · 6 Jul 2006

hi Tony

not sure if red light is on when its banging will try to check when it next happens

diverter valve definatly changed i bought it myself £88.00 if i remember rightly and a real pig to change my friend is an honest fitter and has done numerous checks and really is stumped he says it all points to diverter valve but almost doesnt want to believe it can be

he also wondered whether the overheat stat could have become over sensitive? could that be of any relivance

thanks

yodaboda · 6 Jul 2006

hi Chris

will get these checked out prob not till friday though

thanks for your help

ChrisR · 6 Jul 2006

has done numerous checks and really is stumped he says it all points to diverter valve but almost doesnt want to believe it can be

Best to check it with a surface temp probe cos it's quite slow. But that can't possibly bring the boiler on.

he also wondered whether the overheat stat could have become over sensitive? could that be of any relivance

Oooerr, seriously, he isn't very bright then - that wouldn't make it pop bang and steam.

I'm not sure, but now I think I just remember someone having got water onto the relevant connector on the pcb bringing the CH on. It would be worth taking the pcb out, it's always possible some pcb "reconditioner" has got hold of it and put car body filler and bits of wire all over it, too.

diynot

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puma 80 nightmare

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