Puma 80 DHW problem

[Softus]

Hello

I am a general plumber but not CORGI qualified, hence I do not intend to work on this appliance. However, I would appreciate some advice as I would like to save my mother-in-law some money by having a likely solution available before the callout to a CORGI engineer. Can anyone can diagnose my problem from the following information?

1) Boiler make / model (gas or oil)
Potterton Puma 80 (gas)

2) What is / is not happening
CH is working as per specification, but not DHW.
DHW at the taps is very hot for a few seconds, then goes warm/tepid/warm/tepid (etc. etc.)
When a tap is opened, the flow switch audibly operates, a red LED lights up on the circuit board, the boiler fires and the fan operates.

3) Has ANYTHING else been done / changed recently
Nothing at all.

4) When did it (problem) start
Several months ago, but she was afraid to seek help because of the potential cost.

5) When does it happen? eg, heating coming on or going off
At any and all times of day and days of the year.

6) Anything else you feel may be of relevance
The boiler was brand new and fitted three years ago.
Water pressure at the boiler gauge is 2.5 bar.
The area is mid-Herts, which is a renowned hard water area.


Many thanks.
Winston

 

[Baxi-Remeha]

dhw thermistor has gone. located on vertical pipe to left hand side of the boiler whith 2 red wires going to it. you may find the old one is blue and the new one is cream, this just shows you are getting the upgraded one.

i must remind you that you need to be corgi to repair it, but it shouldn't cost much....

 

[Softus]

Hi Jason

Thanks for your incredibly prompt reply

Just to double check... do you believe it definitely is *not* the diverter valve? I ask not in doubt of your wisdom but because I received some advice just now that this component commonly sticks and/or fails.

I can see the thermistor - exactly as you describe it (although I think the wires might be purple); is there a way to test the diagnosis without replacing the part? For example, by putting a resistor across the connection to the DHW thermistor?

Kind regards
Winston

 

[Baxi-Remeha]

to test the thermistor, you need to do a resistance test across the thermistor with it being disconnected from the boiler......

when the boiuler is running, do you notice the flames going up and down.

if so this indicates that the thermistor is giving a false reading and telling the boiler to modulate down. hense the luke warm or even cold water.

i changed 1 today with the same problem as you (well from what you have described)

you need to make sure the corgi engineer who replaces the part puts some heat sink on the thermistor b4 putting back in.





when you replace th

 

[Softus]

Hi Jason

Thanks again!

Next questions, if I may...

1. Assuming that you're CORGI registered, does the area that you cover include Hertfordshire?

2. I have a DVM and a good understanding of electrical principles and safe practices (since I also repair computers), so can you tell me the specification for the resistance of a functional thermistor?

3. Based on the work you did today, what would an *estimate* of your fee for fixing this?

Thanks
Winston

 

[breezer]

what would an *estimate* of your fee for fixing this?

get several quotes then you will know.

i say this because it depends on access to boiler, how easy job is to do ...yak yak yak

 

[Baxi-Remeha]

sorry softus, i dont live in hearfordshire, i live in the midlands. i also have no idea how much a quote would be as i am a service engineer for baxi potterton and dont deal with quotes......

(wait for the kingfisher rant from pedantic).......

but the thermistors only cost a couple of quid, so it shouldnt be too much.

it sits in a dry pocket and so only unscrews, a 2 min job.

 

[kevplumb]

stuck your head right on the block there mate

 

[Baxi-Remeha]

you can all say what u like, i just work for them..........

i dont have a choice so i dont care.

 

[kevplumb]

do you want to borrow my pliers ?

 

[Baxi-Remeha]

only if i can keep them............

 

[kevplumb]

might help you get that hook out of your mouth

 

[Baxi-Remeha]

they better be strong to reel me in.......................

 

[kevplumb]

touche click on name and e mail me

 

[Softus]

touche click on name and e mail me

I still don't get how to do this "click on name" business - can anyone please help a newbie?