Puma 80e

[s.holmes]

I have searched all the topics on puma`s, but cant find the fault similar to mine. The problem is when we want hot water we have to turn the heating on i.e turn up the room thermostat, I have looked at the manufactures instructions and they do not show this fault. Please note i have a engineer booked to come on Wednesday and so will be grateful if i could pass on any advice.

 

[andsam]

flow switch

 

[ChrisR]

Well done I think that's a fault we haven't answered in a long time if ever!
Just to elaborate, there's a red light on the circuit board which should come on when the tap's on. You see it easily if you lower the front of the boiler - or in your case you presumably won't. It's a 0.2 inch diameter red led.

 

[Agile]

Its more often the shaft which is seized and might be more likely to happen after the boiler had not been used for DHW for a while.

Might be the traditional fault of the diaphragm unit failed. They have to be replaced as a unit although when stuck I once used a diaphragm from an instant water heater ( I think ) with success.

Tony

 

[Softus]

ChrisR and Agile - isn't there more to this than meets the eye?

With the CH on, if the DHW is alternating tepid/cold, then I can see how this could be a faulty, sticking or poorly adjusted flow switch. However, if the DHW is hot, then how is the burner pressure being modulated?

s.holmes - does the flow LED come on? And is your hot tap water really hot, or just tepid?

 

[ChrisR]

Softus I did mention the flow light.
There may of course be all sorts not as new, but I assume from what we are told:

• the boiler doesn't come on when the HW's turned on, and that
  there is HW if the CH is on.

It doesn't take much HW flow to take all the energy out of a puma 80 , without need for burner modulation.

 

[Softus]

ChrisR, I know you mentioned the flow light, but we hadn't had the answer yet so my intent was just to reiterate the question.

I think we have crossed wires about modulation - maybe I didn't explain my reasoning very well...

My understanding of the Puma 80 is that a separate GV soleniod operates (via the PCB) when the flow switch actuates. If the DHW is hot enough at the tap, then this implies that the flow switch is actuating, because, as you pointed out, there isn't enough heat for much flow on DHW when the boiler is burning for CH only.

If the DHW is not hot enough at the tap, then the fault could, amongst other things, be a flow switch problem.

Does this make sense?