Vaillant Ecotec boiler losing pressure intermittently

BillG100

Would anyone like to hazard a guess about this behaviour:

1) Isolate one of the five underfloor heating circuits (uhc)
2) Pressure on boiler continues to fall over a 24 hour period from about 1.4 to 0.9
3) Switch uhc on because I assume that's not the cause of the problem
4) Repressurise boiler BUT this time it takes a LOT more water than it usually does to get from 0.9 to 1.4. The tap needed to be switched on for about 12 secs rather than 2 or 3.

PS: Leak detection are in on Monday.

Alex1983

I’d guess it’s more volume of water.

Ruski

Any update BillG - Did Mondays 'Ghostbusters' find the ectoplasm leaking anywhere?!?

Cheers

Russ

BillG100

Ruski wrote: »

Any update BillG - Did Mondays 'Ghostbusters' find the ectoplasm leaking anywhere?!?

Cheers

Russ

My wife and I were away for a couple of days last week. I've got a webcam on the boiler so was able to watch the pressure gauge steadily going down before the boiler generated an F.22 and cut out. It was left in that state for about 24 hours until we got home. Purely by chance (when the system was completely cold because of the length of time it had been off) we noticed a drip of water below the lockshield valve on the bathroom radiator. I re-pressurised the boiler and then "twiddled" the lockshield valve. That made the drip either better or worse depending on the position of the lockshield valve.

When "Leakbusters" turned up on Monday I showed them the drip on the lockshield valve. They drained the system and fixed the leaking valve. After doing that they:

1) Refilled the system and added an inert gas
2) Isolated the underfloor circuits and left for 2 hours
3) No pressure drop was detected so they opened the underfloor circuits
4) After another hour and no pressure drop was detected

"Leakbusters" concluded the problem was fixed and left.

Two days later the jury is still out but initial signs are the boiler seems to be holding pressure. Can't be sure because the weather is very mild and the pressure loss seemed to be worse when it was cold.

PS: we had checked all rads and valves several times previously but noticed nothing. It's possible the water was evaporating and it only became visible when the pipes / rads were completely cold.

If this turns out to be the cause BG will have unnecessarily fitted a new heat exchanger, schrader valve and pressure sensor on the Vaillant.

BillG100

After 10 days the boiler has started losing pressure again. Really was convinced the problem had been fixed! Back to square one.

J_B

We have a gradual 'pressure drop' problem.
Plumber has been today and scratched his head considerably and without stripping the boiler down to investigate all valves and seals, he has suggested that we try some 'leak-stop' type of compound (a bit like Radweld in a car!)
So, will let him do that and cross several fingers.

macman

This is fairly typical of BG: just swap out random components in the hope that you'll eventually cure the problem, rather than do proper methodical fault finding.
If you've ruled out the EV and a leak on the CH circuit, then it can only be the PRV. In post 11 you say that the PRV is 'OK', but don' explain how you'e come to that conclusion, unless it has been changed, or you used a bag to check for discharge from the overflow pipe (this is separate to the condensate pipe)?
This may be hepful:
http://www.vaillantservice.co.uk/ECOTEC_F.75_Fault_Code.html
Is the boiler still in warranty? If so, dump BG and get Vaillant involved instead. If not, get a Vaillant -competent RGI.

BillG100

One question I have is what volume of water needs to be lost from the system to make the pressure drop from 1.5 bar to 0.5 bar? I've been given various answers by plumbers/heating engineers, ranging from a "medium sized wine glass" to a "bucket".

Alex1983

How would you logically fault find this issue?

I’ve been in this situation many times working for big companies in the past and the sensible think to do is repressurise the expansion vessel, put a balloon on the PRV and isolate the flow and returns for a few days but Big companies customers tend not to allow that and want a fix, they pay yearly premium which usually includes parts so don’t care what is fitted, which means the big companies only have the option of replacing bits and hoping it cures it.

1.5bar to 0 is approximately 5litres.

BillG100

macman wrote: »

This is fairly typical of BG: just swap out random components in the hope that you'll eventually cure the problem, rather than do proper methodical fault finding.
If you've ruled out the EV and a leak on the CH circuit, then it can only be the PRV. In post 11 you say that the PRV is 'OK', but don' explain how you'e come to that conclusion, unless it has been changed, or you used a bag to check for discharge from the overflow pipe (this is separate to the condensate pipe)?
This may be hepful:
http://www.vaillantservice.co.uk/ECOTEC_F.75_Fault_Code.html
Is the boiler still in warranty? If so, dump BG and get Vaillant involved instead. If not, get a Vaillant -competent RGI.

WRT the PRV... BG engineer said it was ok because he'd taken it out and the washer hadn't gone. He also checked the overflow pipe and noted there was a dead spider in it which had clearly been there for a good while. Had water been dripping out the spider would have detached.