Heat exchanger died on my watch today...

[WaterTight]

Was changing 3 rad valves on a combi in a flat. Create a vaccuum to avoid drain down, changed the valves, re-filled and then when I turned off the filling loop noticed the pressur guage kept creeping up. Checked filling loop wasn't passing. Even when detatched and with the house mains off (i was trying everything to reassure myself) it kept creeping up until I let the pressure out again. I phoned tech support (i'm not gas safe, don't know nowt about boilers) for Worcester (was a greenstar junior 24) and they said it meant heat exchanger went. They said it couldn't have been anything I did. Landlord was totally cool about it, I recommended a local gas safe guy to look at it.

My questions are:

1) Was tech support correct?

2) How common is this? I've done this kind of job many hundreds of times and not had it but may have been unusually lucky.

3) How was the pressure going up? Where was the extra water coming from?

 

[ShaunCorbs]

how did you create the vacuum ? also doesnt sound like the heat exchanger if the mains water was off

 

[WaterTight]

Actually I'm not 100% sure now but I think I saw it rising very very slowly with mains off. But def rising with mains on.

I created vacuum by running off some water from filling loop into a bucket. Something I've only done for second time today - hope it's not a bad idea for some reason...

Usually I do it from a rad valve but sometimes when they don't shut off or look knackered it's a pain. Have tried releasing some pressure from bleed screw on small systems but takes ages.

 

[ShaunCorbs]

Actually I'm not 100% sure now but I think I saw it rising very very slowly with mains off. But def rising with mains on.

I created vacuum by running off some water from filling loop into a bucket. Something I've only done for second time today - hope it's not a bad idea for some reason...

Usually I do it from a rad valve but sometimes when they don't shut off or look knackered it's a pain. Have tried releasing some pressure from bleed screw on small systems but takes ages.

sounds like it but as your not gas safe cant go into detail

and never done that before just normally drain down

 

[WaterTight]

Is it a bad idea? Makes it lots quicker. I was done in 45 mins.

 

[ShaunCorbs]

Is it a bad idea? Makes it lots quicker. I was done in 45 mins.

tbh i dont know as ive never done it maybe one of the other lads/ladys have and can say yes or no

 

[mfgs]

I do it all the time, either from a drain off or a rad valve. The fact you did it from a filling loop wont have made any difference. Its much easier than a full drain down, exactly like bunging a vented system.
Its either an unlucky coincidence or it just want picked up on before as the pressure had levelled out between the water main and the central heating system. If the mains only has a standing pressure of 1.5-2 bar then it could easily go unnoticed.