Puma 80 problem - PLEASE HELP...

[CptGreg]

PLEASE HELP.....?

Hi,

I require an experienced and competent gas engineer/boiler technician, to repair my boiler please.

Boiler: Potterton Puma 80 (permanent pilot).

Problem: If I run the hot water CONTINOUSLY for more than 15 minutes, or CONTINOUSLY run the central heating for more than 2 hours, the boiler cuts-out (with a click) and the pilot light goes out. If I then re-light it, it's back to square one.

So far, I've had two different engineers attempt to fix the problem, without success.

Between them, they have already replaced the following parts in the boiler :-

- Extractor fan assembly,
- Wax capsule,
- Thermocouple,
- auto air vent,
- flowswitch assembly,
- microswitch,
- overheat stat.

Unfortunatelly, replacing ALL of the above still hasn't fixed the problem.....

They have run out of ideas.......

Can YOU help ??? PLEASE ? If so, please leave your contact details and I will call you.


Additional info: The boiler pressure remains constant and perfect: 1 Bar with the central heating not running and 1.5 Bar with the central heating running.
There are NO unusual noises, etc. When the bolier is running it works and sounds perfect, heating works great and hot water is hot.

Also, this seems to be a WINTER-ONLY problem. During the summer, when only hot water is being used, the boiler NEVER cuts-out, and works PERFECTLY, no matter how much I use it, or how long I run it for.
The problem ONLY occurs in the winter, when central heating is being used in conjunction with the hot water.

I need your help please. Can you fix my boiler ? I can't afford a new boiler at present, so I must get this one fixed for now. Your help will be MUCH appeciated.
Please leave your contact details.

Thank You

 

[Axel]

According to your list, they haven't replaced the PCB yet, which controls everything.

ADLINK in Wembley sell refurbished ones cheap for this boiler. I'm not supporting the practice of using used parts, but if a PCB is only £ 30 from them, and easy to replace (as it is for this boiler), then it's a viable option, considering the mystery.

 

[CptGreg]

Thanks Axel, but both engineers checked the PCB board and said it's perfectly fine.

 

[holty]

doubt they properly checked the pcb.

 

[Axel]

Possibility: Flue gas is being recirculated in the flue due to defective / corroded co-axial flue pipe. Potterton even do a repair kit for the flue of this boiler. I'm speculating that after a certain period of operation (which could be shorter in Winter than Summer) the air for the boiler has got sufficiently contaminated with combustion products to cause it to lock out. Haven't got the manual so can't study this in detail, but I've heard of this type of mysterios fault before being caused by a flue terminal problem, and I know for a fact that those Potterton Puma boilers have an issue with the coaxial flue pipe that goes through the wall corroding so that the flue gases leak from the inner pipe into the outer pipe where the air intake is, leading to symptoms similar to those described.

 

[CptGreg]

Thanks Axel, but the PCB is fine. It's been checked. Any other ideas ? Is there anyone out there who successfully dealt with the same problem ? Do you have any experience with this particular boiler ?

 

[Axel]

I have seen the flue pipe problem before on this model of boiler. It can be hard to check depending on where the corroded bit of flue is, but with a torch looking from outside terminal, you might be able to see any corroded away bits of the inner tube. Potterton do a retro-fit insert that sleeves the corroded inner tube. HRPC sell them for about £ 20 or less.

 

[CptGreg]

Hmmmm. Thanks Axel. It will be extremely difficult to check the flue pipe with a torch though, as it is located on top of the first floor, and I don't have a ladder big enough for the job.

 

[Axel]

Next time you get a heating engineer in, ask him to buy and fit the £ 20 flue repair kit - just in case. Even if it doesn't solve the problem, it will have ruled out that possibility.

 

[picasso]

I will have a £1 on the gas valve and 50p each way on the pcb.

 

[holty]

has your engineer ruled out the overheat stat tripping by continuity test.when it does lock out.replacing is one thing testing is another.

 

[CptGreg]

Holty, please tell me more about this continuity test....

 

[gassafeman]

Heat Exchanger. Its latent heat.

Your engineers have replaced all the easy parts hoping it wasnt that.

Your PCB is fine. Why waste more money on a part that wont fix it.

Paul.

 

[CptGreg]

Hi Picasso,

Gas valve is very expensive, how certain are you it is the cause ?

 

[rojaca]

I would be looking at the Heat exchanger as well. It might be an idea to take the temperature of the flow pipe at the point the pilot is dropping out, checking for continuity across the overheat sta at this point and perhaps performing a flue gas analysis up to this point , whilst watching your flame picture and pilot flame to determine if the pilots dropping out due to overheat or thermocouple dropping out.