Potterton Puma 80 Diverter valve

[paul.martland]

I've just had my Potteton Puma 80 combi repaired. It was firing up for hot water but no central heating. The diverter valve was replaced and for three whole days we had CH and HW. But now no CH again. Could the diverter valve have gone so quickly??

Any suggestions gratefully received

 

[doitall]

yes especially if the system is full of crud

 

[croydoncorgi]

First things first.

Make absolutely sure that there are no dripping hot water taps. This will stop central heating from a Puma absolutely dead!

When the CH is turned on, does the boiler fire up at all? Does the pump run?

 

[paul.martland]

Thanks for the reply

I've found a very slight drip from the sensor that screws into the body of the diverter valve. When I turn the bolier to central heating constant, room stat up nothing happens, no fan, no motor - nothing. Hot water still working fine.

Paul

 

[croydoncorgi]

Are you sure you're looking at the diverter valve? It's to the RIGHT of the boiler towards the back, under the pump. On the LEFT side of the boiler there's the DHW flow switch, which has a microswitch clearly in view on the end of it (and often leaks!).

Problem you describe is difficult to diagnose because with the CH switched ON the boiler would normally start up from cold, run for a while and then switch off on overheat or on its own internal thermisters, even with the diverter valve stuck in the HW position and no water running. Also, the diverter is quite reliable on the Puma. There is no sensor on the diverter which actually fires the boiler. If the water pressure switch is seeing low pressure, the boiler will not work at all.

What is NOT reliable on the Puma is the PCB and associated connections. But the PCB carries MAINS voltages and is NOT a DIY area.

 

[just-thinking]

puma can deliver a sharp bite to your wallet.
pcb will last a long time as long as pcb houseing is never lowered.but lowering houseing always necessary to do most repairs will cause a poor electrical connection to become defective.look on back of pcb for burning mark,top left hand corner.if burnt change it.can be repaired if you know what you are doing.
have you got 240 volts at room stat ? no probaly pcb

 

[ChrisR]

If the Puma thinks there's a tap on - which as above can be a tiny drip, there will be a red LED on on the pcb. Have a look. Then turn the power off, remove and inspect corner of the pcb. Can get you a new pcb for about £40.

 

[croydoncorgi]

The favourite Puma PCB burnup location starts around the Live header pin on the top left hand corner of the PCB. But if that happens the boiler usually stops altogether.

I'm thinking more likely there's a bad connection between the PCB and the control panel, or maybe to the thermostat. These connections are (ISTR) further down the left hand edge of the PCB. Anyway - prolly makes no difference... PCB failure is still likely. Be nice to nail definitely before sending you to get a new one fitted. BTW, there is a pot. setup adjustment on the new board - which is why changing it is not a DIY job.

 

[croydoncorgi]

which as above can be a tiny drip, there will be a red LED on on the pcb

Sorry Chris. not true. The red DHW demand light comes on when the DHW flow microswitch closes. Usually, a 'tiny drip' is just enough to cool the waxstat but not to trigger the switch, so the boiler THINKS it's doing CH but ACTUALLY the diverter is sending water round inside the boiler with no HW flow to remove the heat. So boiler constantly cycles: short burn... long time cooling down... short burn, etc.

 

[paul.martland]

Thanks for all the replies. All useful. Drip from sensor that goes into diverter valve now fixed. Seems to be a PCB - left hand side - problem as when pressed boiler fires up. It's been on for two whole days now and a new PCB board is on its way which my local plumber is going to fit.


Ta

 

[fredbear]

Sorry Chris. not true. The red DHW demand light comes on when the DHW flow microswitch closes. Usually, a 'tiny drip' is just enough to cool the waxstat but not to trigger the switch, so the boiler THINKS it's doing CH but ACTUALLY the diverter is sending water round inside the boiler with no HW flow to remove the heat. So boiler constantly cycles: short burn... long time cooling down... short burn, etc.

A full 11 years later and your post has just helped me out. I was all set to pull the diverter valve when I read your comment about a dripping tap and explanation of the problem. Which is the problem I have intermittently. Have just had the boiler do as you describe (short burn / long cool down, pump / fan etc working but no CH flow), shut the dripping HW tap down in the kitchen and voila, CH flow restored!! I dont expect a reply but just wanted to say a big thankyou. From a long term puma 80se sufferer.

 

[Dan Robinson]

CroydonCorgi is no longer with us. He passed away rather suddenly a few years ago. RIP.

 

[Agile]

You should not blame your boiler!

The blame rests squarely on the lazy owner of the dripping tap!

Tony

 

[fredbear]

CroydonCorgi is no longer with us. He passed away rather suddenly a few years ago. RIP.

ahhh sad news. RIP

 

[fredbear]

You should not blame your boiler!

The blame rests squarely on the lazy owner of the dripping tap!

Tony

Tony, youre a plumber right, but unless youre a psychic plumber im guessing you wont be aware of the of the seemingly endless list of view forming problems this boiler has had since day dot. You also wont be aware of the length of time the tap has been dripping, and as you dont know the owner, youve no real idea as to the degree of importance theyd place on a mildly dripping tap. The owner was to blame for this particular problem, the owner is also grateful to the knowledgeable folks of this forum who helped him improve his understanding of the problem.
Heres to levels of understanding mate