Pressure too high

[eddiemoe]

BOILER 20-80 RS Flowmatic combi boiler.
PROBLEM at first i thought my safety valve was damaged as it continually was dripping through the overflow so I replaced this...
While replacing the safety valve i drained the whole system, but it never ever seemed to be fully drained.....now my boiler exceeds 3bar when the heat is on, then the safety valve blows until the pressure lowers,
I am sure that the hotwater supply is leaking into the radiator water somewhere in the boiler housing......
I am sure this is happening because my system is never draining down.
My setup is 10yrs old
Can anyone tell me where this is most likely to be happening???????????
A job for oilman me thinks eh?????????????

 

[BDL]

Sounds like your filling loop is either not turned off or letting by

 

[eddiemoe]

sorry meant to say that filling loop is off / not connected thanks, any other ideas?

 

[oilman]

It could be the heat exchanger leaking. You can test it in situ, but you will need to be able to work out how to do it yourself. I could tell you a way but it will get complex and it's not reliable. You have to look for signs of what's going on and react to the changes. Alternatively take it out and block up the port to the outlet. Connect the inlet to the mains and see if water leaks out of the other ports.

Let me know how you get on..

 

[eddiemoe]

i gave the system a few flushes too,
i think it might be the heat exchanger too, can you send me your test please..... thanks guys???????????
what £rice will a heat exchanger come in at? roughly?

 

[oilman]

Your posts are faster than I can edit, phew!!!!!
Heat exchangers are sometimes very expensive. You need to be sure before buying.
To clean the system adequately you will probably need to powerflush it.

 

[eddiemoe]

all water from the over flow is sparklingly clear...

 

[oilman]

The cleaning suggestion was in my post before I edited it because I misread your original query as being a problem with a leaking PRV

 

[BDL]

Isolate cold supply to boiler at inlet valve, see if pressure stays stable.
i.e. you still have the heating system pressure at 1.5 bar but have turned the cold mains off to boiler(or use your main stop cock) if this solves the problem you need a new heat exchanger.

Alternatively it may be your expansion vessel that is defective, this will cause pressure to rise to 3 bar and blow safety valve when the heating is in operation.

 

[eddiemoe]

thank you very much, you guys have been very helpful..