High pressure

[steq184]

I have a Baxi Platinum Combi HE boiler.
My problem is that it has just run out of warranty and now the pressure is up to the maximum 3 bar on the gauge.
I have drained some water out of the system getting the pressure down to 1.5 bar.
24 hours later the pressure was up to 2 bar and next day back to 3 bar.
the heating is turned off but the hot water still on and working.
Anyone know what the problem is and how easy to repair, I am a competent person and don't fancy paying out the £300 quoted by Baxi even before I had told them what the fault was.

 

[Dan Robinson]

Filling loop

 

[steq184]

How much should this cost to repair?

 

[45yearsagasman]

View media item 35799Either your filling loop is passing, or the plate heat exchanger is pinholed internally. Check your fill loop first to make sure it's not letting water into your system. A severe rise in pressure during operation can also indicate a pressure vessel fault