High Pressure 3 Bar - Potterton Performa 28

Hi,

Just joined DIYnot in the hope that someone out there can help me as I'm at the end of my tether and feel that I am in posession of the bionic boiler (as it seems to have had so many new parts) in the last 18 months.

My Potterton Performa 28 is about 4 years old and has had numerous problems over the last 18 months, possibly all related,possibly not, I will give you all of the details...

The start of the problem was that the hot water was fine but had very limited heat in rads, excessive pressure, discharge of water from prv and boiler was noisy & occasionally overheated in a very short space of time and then would switch itself off.

Plumbers were called in and we had a complete new pump fitted & divertor valve, heat exchagers were checked and found to be ok, however return pipework to boiler was cold and problems continued.

Since then we have a new diaprahm for the expansion vessel fitted, still no improvement, next, an external expansion vessel has been fitted, still no improvement and in addition we awoke to a large flood from the boiler.

We have breakdown insurance cover, so engineers were called out (again), to inform us that the old (internal) expansion vessel had split as it hadn't been capped off properly. They then capped it off, however pressure was still too high and boiler overheating so they fiddled with the filling loop (took it off), then returned a couple of days later to put it back on, still had the same problem. By now some head scratching and we were told in need of a system & heat exchanger flush

We had the powerflush 10 days ago and we now have full heat (hooray), however still have the high pressure problem at almost 3 bar and there is still a constant trickle/flow outside, the boiler dumped/emptied today and it has also been making a boiling sound as well as the odd banging/hammering.

I am so fed up with engineers who keep scratching their heads and have been really impressed with the level of knowledge on this site, please can anyone help??

JoH

Disconnect one end of the filling loop, as it should be when not in use.

Drain water out of system until reading 1bar, do not use heating over night and tell us in the morning what the gauge is reading.

Ensure the filling loop is not passing.

With the filling loop detached and if you still get rising pressure in the boiler leading to the prv operating, then there is only one logical reason for this.

Your secondary heat exchanger is perforated and is allowing mains water to enter the system side via the HE.

To prove this, pressure the boiler to 1 bar. Isolate the cold feed and run the heating system for a while. Whilst the pressure will increase it should return to it's normal level when cold and certainly should not get anywhere near 3 bar.

Obviously, you will not have hot water whilst doing all of this.

Dont work on these things, but have just looked at the PDF manual and the plate HE is my dianosis as well if loop aint passing.

Besides EH you articulated better than I.