puma 80, DHW works, no CH ?

[oliew]

Hi there, I have a potterton puma 80 combi, recently i replaced the extractor fan through your advice it worked beautifully thanks for that!,
this morning i came downstairs and thought it was pretty cold!!! i checked the boiler it was set to be on CH but the radiators are cold!
i turned the hot tap on and it fired up, hot water comes out of the tap then i turn the tap off and the boiler continues to fire for about 20 seconds, then i hear this little gurling, sort of a filling up noise then something clicks and it stops firing.

i took the front off and checked the pcb joints and wires all looks good, the pump is very hot! but its turning as i checked with the central nut thinking it was siezed.

the pipe to the central heating flow with the red valve on is hot before the valve but cold after the valve.
so this made me think could there be a blockage??? maybe the pump is not pumping, maybe a valve is stuck as the pump is trying to pump the water round the flow system but cannot because something is stopping it, i dont want to burn the pump out, so ive turned the CH to off.

p.s one other thing i do have a dripping tap in the kitchen near the boiler but ive never had this problem in 2 years since ive been here, but i have read about dripping taps affecting puma boilers.

its freezing today!!!

thanks in advance
Oli

 

[Gasguru]

Dripping hot water taps will stop the heating.

 

[gazthepottertonengineer]

yes only takes slight drip from tap to keep the wax capsule in the hot water position
to test it is that simply turn off ballofix isolator cold water mains into boiler off and see if heating stays on

 

[oliew]

ive just isolated the tap that was dripping turning the valve under the sink so that should eliminate that.

if i wait a bit and then click the boiler to constant it fires up, give it 30/40 seconds then i hear it filling up then it makes a little high pitched noise as if it starts to push the new hot water through and then click, stop.

i can feel the pump spinning all the time even when its stopped firing as if its trying to push the water through.
again pipes before the red flow valve is red hot, but after the flow valve its slightly warm but only for the first 10 inches, could this be blocked???

thanks for the quick reply
Oli

 

[oliew]

gaz,
ill try your advice thanks! , i just looked under the boiler and the water inlet has a stop valve on it with 2 screwdriver valves next to each other in the same fitting, do i just need to turn one of them to cut the water off.
cheers
Oli

 

[ChrisR]

Turn that CW isolator off anyway. Yes the more sticky-out screw, 1/4 turn.
They get very fussy with age
If you leave it on CH, does the front (wax capsule) end of the diverter valve get hot?

The pumps get slow and the diverter valves stick. Had one blocked one but that was ptfe tape stretched across a fitting !

 

[oliew]

ok isolated that main cold water inlet valve, also turned the tap valve off under sink so it wont drip.

both CH flow and return are as normal, not shut off.
the end of the wax doesnt get very hot at all no.


im leaving it on constant now...

5 mins later it fired up, hot water coming out to the radiators, still going now as im writing this message!

thanks!!
so what does this tell me now, what needs replacing?

thankyou!
Oli

 

[ChrisR]

1) Tap washer!

The diverter valve wax thermostat has got old. Normal procedure is to change the whole valve, though some change just the front part, or use a non-potty wax bit , and deal with the common leaks you can get doing that.

The DV is a little awkward to change if the bottom of the boiler is 4" over a worktop

 

[oliew]

yes it is 4" over a worktop i had trouble even getting a screwdriver in to turn off the cold water inlet!!!
ill go out and get a tap washer today!!
thanks for all your help again

this forum is great!
Oli

 

[ChrisR]

I'm sure it must say in the manual somewhere
"Thou shallt put Pumas in daft places".

If you buy a whole diverter valve, you can remove the front ends and swap, The hard nut is at the back.

 

[oliew]

ive changed the tap washer, it was a mixer tap so a half turn fitting was needed, the washer was built into it.

since doing that and turning all the water back on, the boiler still only does the ch when the main water inlet is turned off at the valve
would this mean i definetly need a new diverter valve, or at least the end piece you talk of?

cheers
Oli

 

[ChrisR]

I fink it means you have another leaking tap!
But , also,
yes.

 

[oliew]

thanks chris, ive just realised my bath hot tap is leaking too but its not noticeable only when you put your hand on the underside of it!!!
ill see how it goes now, if my ch stops i know i need a new diverter piece!
hey ive learnt something about combis today anyway!
thanks for all your help
Oli

 

[gazthepottertonengineer]

!
hey ive learnt something about combis today anyway!

Oli

No youve learnt something new about pumas as this is the only combi i know of that this applies too !