Potterton Puma 80 mystery

[bobb]

My friend has a problem with a Puma 80 combi.

The central heating will only work when you close the valve on the cold water supply (not the filling loop) for domestic hot water.

So, when they want hot water they have to open the valve, and then close it again to get CH back.

This is baffling me.

Can anyone suggest why this is?

 

[ChrisR]

Do a search on "dripping" as in tap. Standard Puma fault. Boiler half thinks a tap's on.

Will raise a couple of issues I'm interested in so will ask others for comments! :

If you just change the waxstat, so you find they tend to leak?

What's your method for changing the diverter valve/rear nut access - bend the metal edge down?...

 

[gazthepottertonengineer]

personally just replace front of valve doing away with the need for getting at "that" nut

Ive never had any leak oh no now ive said that

 

[Soggy_weetabix]

I have always just removed the brass nut, lubricated the rod and replaced.

Not had a problem with leaks so far, but have only repaired 20 or so in the last couple of years, and only once has the whole valve needed changing.

That took 5 hours...all because of that nut!

David

 

[Mikeyboy]

ChrisR ,I have changed many wax capsules only with no leakage .The common problem with changing the full valve , is , the dreaded back-nut .Before I even isolate , or , drain boiler , a liberal spraying of wd.40 on the nut ensures that it will be easier to loosen . The 90 degree angle bend of galvanised steel ,which prevents proper access to nut , I use my dremel to cut away .Another point , we all know that if you even glance at the iso valves ,they will p**s out , so a full drain down . I always used to replace said iso valves with 22mm. gate valves , as they are the same length .

 

[Agile]

"""a liberal spraying of wd.40 on the nut ensures that """

the water pump pliars will slip ????

 

[bobb]

Do a search on "dripping" as in tap. Standard Puma fault. Boiler half thinks a tap's on.

Will raise a couple of issues I'm interested in so will ask others for comments! :

If you just change the waxstat, so you find they tend to leak?

What's your method for changing the diverter valve/rear nut access - bend the metal edge down?...

A bit too oblique for me Chris. Could you come down to my level? Why does shutting off the cold water allow the CH to run and what needs to be changed? I'd be grateful for Dummies' Guide.

 

[ACOperson]

Bobb,

if a tap is dripping or you have a leak somewhere, the boiler has a constant flow of mains water through it - albeit a small flow. The Puma diverter valve works thermostatically, with a flow of cold mains water cooling a capsule full of heated wax. This sends the heat in the primary circuit (ie water heated by the heat exchanger) to heat only the hot water, not the radiators.

When you have a call for CH, but a tap dripping, the diverter is being constantly cooled off by the mains water flow, therefore no heat will go to the radiators.

Find the leak & sort it and you should be right.

 

[Softus]

Will raise a couple of issues I'm interested in so will ask others for comments! :

If you just change the waxstat, so you find they tend to leak?

Only when the 'O' ring is damaged.

What's your method for changing the diverter valve/rear nut access - bend the metal edge down?...

Nope - I have a socket that's an exact fit and I use a 1/2" ratchet drive. if the nut is extraordinarily tight, or poor access makes it hard to get a grip, then I also have an 24" breaker bar (to fit onto the socket) that takes no prisoners.

The 90 degree angle bend of galvanised steel ,which prevents proper access to nut

Socket...ratchet...access problem solved.

 

[ChrisR]

You can't get a socket on the rear nut cos it's got a pipe coming through, unless you mean a crowfoot. Basin spanners, grips... or

or

at a pinch

 

[Softus]

I agree that there's a water connection on the rear of the DV, but once this is uncoupled (which it has to be when changing the whole valve) then it's simple to get a socket on the rear nut.

 

[corgiman]

I recently had some trouble with a combi 100 (cheap version of puma) I changed the wax capsule but got called back as it was leaking.

found that the two small hole on the head were letting by water at quite a rate!! so i changed the whole valve and so far no problem.

I must have changed 100's of wax capsules without a leak or a problem, Potty could not tell me why this happened either.

 

[ChrisR]

24" breaker bar - hmm, getting that in...!

One of these might be handy, you could put in an extension underneath as you look at it, which would come forward under the boiler:

I have all these things but don't carry them on the van!

 

[Softus]

I've had the breaker bar in once, where there was loads of access underneath but very little at the side. If no room then ratchet or 'T' bar will do it.

I don't recognise that cunning tool - it looks like high quality gear, but what is it exactly?

 

[ChrisR]

It's a normal ratchet head, which has the square holes in the end, and the one you can see goes right through. So you can put an extension in from three directions. Britool make square L bars which are handy with one of those.
It's a Snap-on, but others copy them.
Also have their indexing and flex-head ones up to 1/2". Not every length of handle though...