Have protherm 100ec boiler british gas has replaced almost every part boiler will fire temp gauge rises to about 55 flame increase in strenght for about 10sec then boiler cuts out also they keep trying to sell me is a power flush at 740pounds would any one have any ideas thanks

The problem may not be just the pipes..IF you have a temperature setting lower it --as the heat causes to pressure to rise . The temp gauge may be faulty ..

Call British Gas. We are not them. Sorry.

Could be sludge in you system might need a flush ?

It sounds like you have a bad thermocouple. This apparatus senses when the temp is too low and sends an electric signal to turn on the gas to the heater. When it reaches it's preset temperature it sends a electric signal and the gas is turned off. It is best to call a repairman to fix this for a couple of reasons. One, he usually has the thrmocouple with him so you don;t have to wait on a part. Two, you"re messing with gas and if you screw up you can blow up the house and you along with it. Three it is a relatively quick and inexpensive service call, plus if there is anything else wrong he can fix it, save another service call and save you tons on your fuel costs.

3 Bar = 43.5 PSI When you heat water it always expands increasing pressure.
In a closed vessel volume can increase by 2-3%. Either expansion tanks allow for this and PSI is maintain or without an expansion outlet the PSI will increase in proportion to heat supplied.
Is this a low temp hydronic boiler operating at or <140F, a hi temp hydronic boiler @ >180F or steam boiler?

google your boiler it comes up with a manual go to page 26 it gives you 5 reasons why it goes to f1

Hello Mark
First of all turn on a hot water tap and keep it running whilst you check to see if your boiler is firing up, if it is not then try to restart it, you should hear the flame if its running, turn your tap off then just stand by the boiler for a few minutes to see if the pressure gauge starts to rise, if it doesn't rise you will never get any hot water, you will have to add some pressure to about 1 and a half on the dial, to do that is simply turn on the water valve in the bottom of your boiler and watch your pressure gauge rise to about 1 and a half then firmly turn it off again, it looks like a small tap like the one at the back of your washing machine pipe, it's ok you will hear the water rushing in, now with your gauge at about 1 and a half and your boiler running your water will get hot

Does the lit gas vary in amount of flame ? Are the gas jets clean?
Is the autovent screw opened at least 1/2 to 1 turn?
Possible resonance within the boiler casing - press and hold side & front panels to suppress the resonance frequency

You likely have a flame sensor problem.

If you can wath the ignition proccess, see if you ever notice a flame. If yes, and it then shuts downm, you have a flame sensor failure, replace the sensor and clean the flame burners and orifices.

If no flame at all, then your ignitor is failing, or you are not gatting gas to the ignitor.

This is the manual for 80E. It isn't a manual for the 80e, it's a manual for the 80E, dunno if they are the same or not.

http://www.protherm.cz/upload/1117176168.pdf

If that's is not it, you can browse here =>

http://www.protherm.cz/component.php?cocode=download&dcid=4