Glowworm 30si - pressure loss

[Monomono]

All

I have a Glowworm 30si that is about 4 1/2 years old. We are currently experiencing pressure loss overnight, with the boiler pressure at 0.6 bar in the mornings.

I have had an engineer come and look at it about four times, and it would appear that they are completely lost. These are the things they have looked at:
1. They assumed that it was the PRV and replaced it, but this did not solve the problem.
2. They looked at the EV, which was full of water, so they drained the vessel and reinflated the bladder, but no solution
3. Now they think that the EV should be replaced "as they cannot think of anything else"

I cannot see any leak on the radiators, though I do have underfloor heating in the kitchen which I cannot check for leaks. I have isolated the boiler for a few hours and the pressure did not drop, though the system pressure was 1.6 bar (I put more water in to bring it up so that any leak would be visible) and as soon as I closed the inlet and outlet valves on the boiler, the pressure dropped to 1.2 bar and stayed there.

I don't mind having the EV changed if this is going to resolve the issue, but I am not convinced! It is difficult to see if the PRV is leaking as there is too much rain to tell whether it is dripping or not...

I have noticed someone mentioning the heat exchanger and possible condensate leaks - how would I check for this?

Thanks in advance
Monomono

 

[plumbnuts]

The expansion vessel should not be full of water. There is a diaphragm inside and if you momentarily push the center of the schreader valve you should hear a small amount of air escape. If wheen you do this you get water, you will need a new ex vessel or fit one externally. If the diaphragm is knackered, this would explain your pressure loss.

Steve

 

[Monomono]

Thanks Steve - I appreciate your response.

I will check and post whether there was water coming out, as the engineer emptied the EV ("these things can happen over time...."), reinflated the diaphragm and assured me that this meant the EV couldn't be the problem....

MM

 

[Monomono]

Steve

I did as you suggested and checked whether there was water in the diaphragm but only have air escaping, no water. I am assuming that this must mean that the EV is ok? I pumped a bit of air in, to replace what I had let out.

Any other ideas?

Thanks
MM

 

[gooba]

MM
ihave exactly the same boiler and it would seem exactly the same problem.I also have under floor heating through out the groundfloor. When I re-pressurize the the system to 1bar once the boiler starts up the pressure climbs to 3.3bar where it stays until it switches off at night, on waking up the house is freezing and the pressure has dropped to 0.6bar thus the boiler doesn't start.I have had a heating engineer out today who told me it could be the prv or the ev and the pump was beginning to sound noisy, he then said it would cost 'around' the £500 mark but thought it would probably be better to swap the boiler for a new one.
I noticed you wrote you had had anew prv valve so I think I can rule that out.I was wondering how you checked the diaghragm in the ev because in the manual it say's you have to remove the boiler to replace it and i can't see any way of getting to the schreader valve.
I have noticed that my prv discharges water but only when the pressure gets up to above 3bar this I would have thought was normal to relieve the excess pressure in the system.the cost of the new ev valve is £200 plus labour which is alot cheaper than anew boiler and I don't mind spending if I know this will cure it.
I have read in the manual that you can put an external epansion valve on
I would be gratefull for any advice you could give me or any information should you resolve your problem

thanks gooba(darren)

 

[plumbnuts]

MM
Put a plastic bag over the external outlet of the prv pipe for a day and see if you collect any water. Does your pressure rise significantly when the boiler is in operation?

Gooba
Your expansion vessel is most likely fooked. The cheap alternative, as suggested is to fit an external one. You would then leave the internal ev in place. This method is ok as long as you have space.

Steve

 

[Monomono]

Steve

I will put a bag over the outlet tomorrow and see whether there is any leakage. The pressure does not appear to go too high when the boiler is on - it only seems to go up to 1.4 bar or so.

I guess the bag would tell me whether it is a faulty PRV?

Thanks for your help
MM

 

[petit_pablo]

had a heating engineer out today who told me it could be the prv or the ev and the pump was beginning to sound noisy, he then said it would cost 'around' the £500 mark but thought it would probably be better to swap the boiler for a new one.


thanks gooba(darren)

Id sack him off straight away and get someone in who knows what they are doing. He's just fishing for a boiler swap, more in it for him that way.

To both the OPs, these guys are guessing at the fault and its a pretty basic fault. The EV should be repressured 1st then the PRV replaced if it has been passing.

 

[Monomono]

Just to let people know the outcome for future reference - my issue was that the flexible hose that connected the expansion vessel to the rest of the boiler became blocked.

Therefore, no matter what the pressure was in the EV, the pressure on the other side of the bockage kept building until it was high enough to bypass the PRV, after which the system cooled and the pressure dropped to below the minimum pressure cut-off point.

I think the piping loop has been redesigned on future systems, so hopefully this shouldn't happen on newer boilers.

MM