Glow worm 35ci problem

[tawelfryn]

Hello all, great forum, made interesting reading. OK, I have a glowworm 35 ci, about 18 months old. On the weekend I noticed a rapid drop in pressure all the time, kept filling back up to 1 bar then it would fire up last for an hour then cut off with low pressure. The water was being dumped out the back from the pipe outside. Having read other posts, I have checked the expansion vessell it was about 1.25 bar, then last night i managed to get a new prv (pressure release valve) and fitted it. Filled to 1 bar, bled radiators, opened air release on top of pump (left it open as book says) Fired up and it started dumping hot water straight out again, but then it stopped and the heating was on for around 5 hrs all evening with no probs. Great i thought fixed, but when i got up this morning it was 0.6 bar low pressure red led and system was off, i have refilled to 1 bar the same has happened, water dumped outside and now I have turned it off to see if it goes below 0.6. It seems to me that when the boiler is fired up the pressure must be going over 3 bar (release pressure of prv) dumping it outside till it gets below 3 bar, keeps working as the pressure is in the norm range, then when everything cools the pressure is below 0.6 from water loss, so I think it is pressurising too much whilst the boiler is on, but, I dont know what is causing this, Im not a plumber Im a brickie!
Any thoughts greatly appreciated,
Cheers guys

 

[Agile]

Look at the FAQ section on this web site and see the instructions for pressurising the expansion vessel.

Tony

 

[tawelfryn]

ok, been a few hours now, heating thermo set @19c to let the boiler switch on and off. Dare I say it , its been working ok. Its as if by filling it to 1 bar is too much, although thats what the book says, and then when the boiler is on the digi thermometer on the boiler reads around the 70c. When the boiler cuts out, I can then see the bar pressure, its about 1.9, then it drops slowly, i have seen it go to 0.8, as long as it doesn't reach 0.6 it will be fine. Its as if you have to "fine tune" a happy medium of pressure to work within the boundaries of hot "blow off pressure" to cold "shut down lack of pressure" I think that by putting too much cold pressure in, when it reaches operating temperature, too much water is lost, then when it cools, theres not enough.
Does this sound feasible to you guys?

 

[MOORJOHN]

hI, I've got this problem too. had a glowworm engineer over 6 months ago who said it was because the braided hose was blocked. He replaced it. Now that the winters coming and the central heating is on again, the prv fires about 4 times a day, and we have to keep re pressurising through the filling loop.

I've tried waggling the braided hose in to relieve blocks. See whether the situation has improved.

This has been a consistent problem since the boiler was 6 months old. We have worn out 2 prv's with the repeated venting.

Design fault in glowworms?

any way of stopping the hose blocking - cos I bet that's what it is. Or does anyone know of other possible explanations

 

[mickyg]

if the hose is blocked then its because your system is full of carp. It needs flushing out in that case. It may, however, just be the expansion vessel needs repressurising.

 

[Elkato531]

Are you making sure that the system pressure is zero and the system open (drain tap or rad vents) when you test and re-pressurise the expansion vessel. As Agile said, instructions are in the FAQ section.

 

[nclarke8]

I have the same problem on my 35CI. I changed the PRV as the old one wasn't holding pressure with cold water at 1.5 Bar, but its still leaking with heating on. Looking at the manual and you have to take the boiler off the wall to get to the expansion vessel, so 'we' cant check the pressure and i will change the simple fittings but not going to touch the gas pipes. time for a friendly plumber who can take back an expansion vessel if not required !!

 

[mrjinxster]

Where is the GAQ on here I can't see it

 

[JohnD]

Where is the GAQ on here I can't see it

look again.

https://www.diynot.com/diy/forums/plumbing/