Potterton Puma 80E gas cutting out

[jimjam]

Hi all,

I have a Potterton Puma 80E combi boiler, several years old.

This has not been sounding good for a while. A couple of weeks ago it stopped working, I had a sparky friend look at it and we found a failed solder joint on the main circuit board which was repaired.

Boiler was then working again - until last couple of days when clanging noise got worse and boiler failed again. This tme we found that the fan assembly had died (motor, brushes the works). So replaced this.

Have been through the fault finding diagram and made all checks and all seems to be working according to this.

However the problem is that when turning on either CH or HW the pilot light/thermocouple ignite the main burners which then only stay lit for 5 seconds before gong out. This obviously means we have no CH/HW.

I am thinking that this may be a problem with a switch/valve rather than anything gas related. Any ideas greatly appreciated.

 

[ollski]

the same on hot water only?

 

[jimjam]

Yes, it's the same for HW only, CH only or CH/HW together.

 

[boxster]

that could be down to the spillage device. when it cuts off does it light back up again or does the LOCK OUT button come on and you have to re-set?

 

[jimjam]

It does not restart after going out. I don't think the LOCK OUT button comes on either. To restart I simply have to relight the pilot light - no electrical failure appears to take place and I do not need to alter any switches. . . .

 

[boxster]

mmmm does it bang and clatter when the pilot goes out kind of like someone hitting it with a hammer?

 

[jimjam]

nope. The only thing I can see is that the main burner comes on moe strongly than it did before (probably due o the new fan) however just before the burner goes out there seems to be a sl;ight increase in the strength of flame from the burner.

 

[ChrisR]

Don't help him lads it's a wind up! 80E with a pilot!!??

Jimjam we'll assume that you do have a pilot. SO it isn't an "E" and you don't have a lock-out button! (unless there are more models than I'm aware of, which wouldn't surprise me...) I'm not sure what the SE was - loses the horrid water pressure switch?? And I didn't know there was a spillage sensor... after the lynx?

It sounds a bit like the boiler has air in it. Top left there's a leaky brass thing which is an automatic air vent. Its cap is supposed to be loose - perhaps yours isn't? [/u]

 

[jimjam]

no not a wind up - I wasn't aware that 80E didn't have a pilot! I was making the assumption that mine was an 80E or 80 SE. It has all of 80/80E/80SE written on it at some point. The fault finding guide in the manual that seemed to fit best was that for the 80E hence my assumption that this was it. . . .

You are right in that I can't find a lock-out button. From what you've said it must be a plain old 80 . . . unless someone else knows different?

Thanks for the tip about the leaky brass thing I'll check it out.

 

[jimjam]

The automatic air vent wasn't lose so I have loosned it. This doesn't seem to have made any difference to the way the boiler cuts out. I am assuming that your 'leaky' description refers to the tiny amount of water that is present around the small plastic screw?

Thanks for the help anyway.

 

[boxster]

i think the problem is your gas valve pressure. You need to mke sure the INCOMMING pressure is correct and the OUTGOING pressure is what the boiler needs. The baxi 105 has a similar problem with this. I would bet my life this is the problem. check the valve pressures...

chris i thought that but then i thought on, the lynx does have a pilot but no lock out.

also air may be a possibltiy or even blockage, this may sound crazy but if all your radiator valves are closed the heat has no where to go or the valves may be turned off slightly on the boiler. i still rekon its the gas valve pressure comming into the valve. get transco 0800 111 999 to come and check your gas meter standing and working pressure. if they wont do it for free you may have to get someone else. make sure the pressure into the GASVALVE is correct

 

[ChrisR]

That's the leaky thing. It should have been loose, so here's a chance it is blocked and trapping air, though if there was some water there, maybe not. If you can get at it well enough you could loosen it from its nut underneath - if water starts to come out then you know it's ok. I think it's worth doing because the boiler is overheating so quickly - no switch that I know of is going to make it do that. (It would be ok-ish on HW if the pump had stopped - does it take longer to cut off when you put the tap on full?)

If you get nice and wet, then I'd call sparky back. Apart from the usual melted joint at the top left corner of the board there are often a couple of dozen other joints which have fine dark lines across them if you search very closely. Those are cracks in the solder which will give you trouble. just reflow the solder, no need to remove the old stuff.

If it really isn't actually overheating(!) then you're looking at a faulty boiler overheat stat (shouldn't switch off until about 95ºC , or the flame is lifting off the pilot when the main burner lights, which you should be able to see.
I would see what the temp is when it cuts out, with a thermometer which you won't have - but if the pipes near the overheat stat are near boiling point you should be able to tell...

 

[jimjam]

Chris, I've loosened the nut and water does start to come out. The time taken to cut off appears to be the same whatever combination of heating or water I use, even if tap is on full. The pipes near the Overheat stat don't appear to be overly hot - they are warm but not more than I would expect - at 95ºC I would think that I couldn't even touch the pipe - correct?

I have got my sparky coming to look again at lunchtime today, but from what I can tell there does not appear to be any fine dark lines on any joints . . . ?

If I can't get to the bottom of this before tomorrow I guess I'm gonna have to call out a heating engineer - thanks for your help guys it will certainly help me understand and avoid any bs if Ihave to get someone out. In any case I'll post a relpy to let you know what the problem was - if and when I get it fixed!

Any further suggestions in the meatime greatly appreciated.

 

[ChrisR]

The confuddlking thing here is the clanging noise - which strongly indicates overheating, but yes you'd sure find 95º very hot. If air was stopping you feeling the hot(water) it would stop the stat feeling it too!

So it doesn't make sense - we'd have to be there, something in the evidence is wrong.

The other day I was told that 2 sparkies could smell gas near a pipe I'd put in a couple of months before. Thinking they'd bashed something I checked quickly at the meter and sure enough, the pressure (of gas you trap in the pipe, for testing) dropped. So I spent ages with a detector and bubble spray trying to find the leak. Later I left the gas trapped again and had a cup of coffee - for half an hour. Then found that the pressure hadn't dropped any more.

What I'd seen was the effect of the gas cooling in the pipe. It's a big long pipe so the drop was much more than usual. Everything appeared to point to a leak, but there isn't one! The plasterer had had an Indian meal the night before, so that was the smell!

 

[boxster]

lol..

i went on an emegency call at 8.00pm a few nights back for a smell of gas. The pipe only fed a cooker with no cooker connected around 1 meter long it was the smallest gas pipe i have ever seen. i had 2 elbows off the meter and 1 elbow to the cooker with a york cap on the end.


it was leaking 3 mbr.... i tested it 5 times and again 3 mbr. i socked it in leak detector and no bubbles... i re-tested and again 3 mbr. I used a brand new gauge and again 3 mbr... so i pulled the pipe out and installed another, tested my new pipe it was fine. So i took the old pipe home and socked it again in leak detector and blew in it. still nothing... I put the pipe in water and blew still nothing...

anyone got any ideas how the is?? it should leak!