Potterton Promax HE24 Lockout problem

My Promax HE24 boiler has been working OK since new (4 years ago). 4 weeks ago the system developed a problem in that after it has been on for about 12 minutes the boiler switches itself off. In that 12 minutes the hot water and/or CH start to heat up OK. The only way to restart it is to use the reset switch on the front, but this will not work until the boiler has cooled down for up to one hour. I have insurance so they called in a local reputable heating company, who have focussed on the boiler as the problem. They have visited abot 6 times and changed: Flow temp thermistor, Fan thermostat, Safety thermostat, PCB, and checked the cover seats correctly.
Can anyone offer me any advice on what to do? The heating engineers do not or cannot do any detailed investigation to find out exactly what is causing the problem; they seem to be only able to guess and change parts hoping to get a fix ( they're now talking about changing the fan and pump).
I'm worried the insurance company will deem the problem to be beyond economic repair, without ever knowing the real cause. If they do this they will only provide about one eighth of the boiler replacement cost - and
the fault may not be the boiler!
Any advice or comments would be appreciated.

i would test the pump and then if working i would turn the pump valves off and remove the pump to see if there is a build up of sludge on the inlet side.is it open vented.

johnrow said:

Can anyone offer me any advice on what to do? The heating engineers do not or cannot do any detailed investigation to find out exactly what is causing the problem; they seem to be only able to guess and change parts hoping to get a fix ( they're now talking about changing the fan and pump).

Any advice or comments would be appreciated.

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This is the problem with these breakdown insurance schemes. They employ contractors to do the work and to keep the costs to a minimum they employ inexperienced people who have no diagnostic skills and just change parts until it hopefully works.

Sometimes further visits are paid for by the insurance so there is no incentive to actually fix it.

You have only three alternatives:-

Stick with them until they fix it.

Get a competent independent and send the bill to the insurance. But first tell the insurance you are not happy with their contractor and are going to do this!

Get the manufacturer's service team to do the work. Again advise that as above or even tell they to get them in.

You expect that a modern boiler should be completely repairable. You will have to keep on complaining but keep a log of exactly who you spoke to so that you can demonstrate that their service has not been adequate.

Its a common problem with these schemes. I often go when they have failed to diagnose the problem, often saying its not possible to do the repair.

A classic was an older boiler they said was sludged up and had to be replaced when it was only an air lock which I solved in 10 minutes!

Tony

Comb box door seals need replacing.

johnrow said:

They have visited abot 6 times and changed: Flow temp thermistor, Fan thermostat, Safety thermostat, PCB, and checked the cover seats correctly.

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May well be, but he says they checked that.

I went to one with a very intermittent lockout which I never solved.

Suspect it was the PCB as the agent called the manufacturers and it cost about £350 although I cannot see why it was so expensive with fixed price repairs.

Tony

Thanks to all for your comments and advice. The Insurance co. contractors have ordered a replacement pump, and another thermostat so I'll wait and see what happens after they've been replaced.