Glow-worm 30Cxi Pressure Drop

[kk4v07]

Hi all,

I am seeking some advice regarding a glow worm boiler that has been in the house since we moved in 3 years ago.

I recently bled the upstairs towel rad, as it was heating only half way. I repressurised the boiler and fired the heating up for an hour. After 30 minutes all rads (8 in total) heating up fine so went to bed. Woke up, boiler stuck at 0.4 bar pressure and refusing to fire up.

Opened the blue plastic filling tap, water came gushing out of what I assume is a safety valve on the left of the boiler. Shut the tap and called in an engineer.

The filling loop and pressure sensor were both replaced, however after a couple of hours with the heating on the boiler cut out again and the pressure dropped to 0.0!

Opened filling tap and repressurised to 1 bar, also checked all rads for leaks around pipes, couldn't spot anything obvious, all bleeding valves tight too. We checked outside and the pipe leading out from the boiler is sending a steady stream of hot water out, so is the PRV valve a goner now?

Or could it possibly be the Expansion Vessel (as well)? The boiler will drop back to 0 after the course of an hour or two.

Tired of filling the boiler as I understand this is diluting any inhibitor in the system (something else to renew I guess!).

I am interested to know anyone's opinions on why bleeding one radiator could have kickstarted this failure, the boiler has been perfectly fine until now (despite sitting 0.7 bar for most of the time before this, handling HW and CH perfectly fine)

Many thanks for any help in advance.

 

[muggles]

Your half-full radiators were most likely providing additional expansion space for the heated water, and bleeding them has taken this away. I suspect your expansion vessel was already knackered, and it's not uncommon to find that a PRV doesn't reseal once activated

 

[ReganAndCarter]

The filling loops/valves on these boilers are rubbish. It's normal for them to have a couple of drips when using them to refill. Often this gets worse and they start dripping a lot more. Time for replacement. Can't understand why your engineer didn't check the expansion vessel's charge when he had it drained down for the new loop and pressure sensor. Would have saved you the cost of the last item, as it probably wasn't needed.

 

[kk4v07]

Thanks Regan & Muggles.

I was afraid as much, I did not have much time to do any research prior to calling the engineer out. I have since confirmed with another engineer who echo'd your comments. Hopefully I can get this fixed soon, am I right to assume the twice daily (morning + evening) repressurising to enable us to shower / whack the heating on for an hour to test it's still working / do the dishes, is damaging the overall health of the system by letting fresh water in?