Potterton Performa 24 Tripping

[Degs]

Hi

Can anyone help with an anoying problem with my Potterton Performa 24 boiler?

Most morning we wake up to find the boiler has tripped and can only be started by resetting the high temperature cut-out inside. This has been going on for a while now and to overcome this in the recent past the plate heat exchanger has been replaced along with the actual safety cut-out, but the problem remains.
Something I have notced whilst doing the reset routine in the mornings is that the boiler pressure varies greatly from day to day (sometimes requiring top up) not sure if this is related.

Hope someone can help
Thanks
Degs

 

[Baxi-Remeha]

there is a kit that can be fitted, what is happening is the boiler will be overheating once the demand for heat has stopped, and with there being no pump over run the residual heat causes the boiler to over heat. basicly what the kit dose is it interupts the flame sensing device, so it can only lock out if the boiler is firing

part no. 5115349.

there are other things that can cause the boiler to lock out, so i would advise you get it checked out by a corgi, just to be sure...

 

[Agile]

It sounds to me as if your boiler has several different problems.

The pressure aspects point to the expansion vessel needing checking as well as the PRV and filling loop.

Overheating AFTER DHW demand has ceased is usually caused by limescale in the main heat exchanger. Latent heat with no pump over run.

Overheating DURING DHW ( or sometimes CH as well ) would point to a circulation problem, pump or blockage etc.

All these would be investigated after the gas valve min/max settings had been first checked.

Tony Glazier

 

[Degs]

Thanks for the info (Jason and Agile).
Since I posted the initial question and with regards to the pressure aspect I have place a tin under the PRV pipe. This morning I found about a pint of water in it which means the presuure at some stage rose above 3 bar and of course the boiler had tripped.

The expansion chamber and the possibility of a blockage could well be a cause as when the heat exchanger was repaced all sorts of black scale came out of the old one.
Can you recommend a good de-scaler or any other chemical for flushing the sytem out.
Thanks

 

[Agile]

That confirms my suspicion that the expansion vessel needs checking or repressurising.

Tony