Glowworm 30cxi pressure drops

[ma6mkd]

Hello,

My glowworm 30cxi was fitted back in 2005 and until a couple of weeks ago I have not had any problems with it. However, just before Christmas I decided to bleed my radiators and since then the pressure has started to continually drop. I am having to repressurize by using the refill loop every 1.5 to 2 days as once the pressure drops below 0.7 bars, the boiler ceases to work. I repressurize to 1.4 bars.

My observations since I've been trying to figure out what's happening are:

• 1. The pressure only drops when the CH is off.

• 2. The pressure tends to increase (!) when the CH is on. When increasing it's only by approx 0.2 bars and then it drops more than that in the time the CH is off, but I'm a bit stumped as to why the pressure would increase and then drop back down again.

I've taken some pressure readings from the expansion vessel and these seem to be pretty stable so don't think that's the cause of the problem. However, I've only started taking measurements over the last couple of days so need to build up a larger set of data I think before being able to say that definitively.

Assuming the expansion vessel isn't the problem, what else could be at fault. My guess would be the prv but would the symptoms I'm seeing be consistent with that?

If anyone on here has any comments / ideas of what the problem is or what I can try next to identify a solution it'd be appreciated.

Thanks.

 

[ma6mkd]

I've taken some more pressure readings from the expansion vessel over the course of the day and the pressure has remained consistent at 1.6 bars over the last three days so I don't feel that is at fault.

Is there anything I can check to determine if it's the prv that's the problem?

Thanks.

 

[tj351011]

check to see if water is leaking from the pressure relief pipe outside if so its either the PEV or PRV

 

[ma6mkd]

Hi,

Thanks for replying. There is a lot of water coming from the pressure relief pipe and I am now having to repressurise every few hours. I will replace the prv and see if that solves the problem.

Thanks for your help,

Mark

 

[ma6mkd]

Hi,

Apologies for the dealy. Things have been a bit busy recently. Anyway, I have replaced the PRV today so I shall monitor the situation over the next couple of days and let you know if this has done the trick.

Thanks,

Mark

 

[kitch0978]

its also possible that the expansion vessel pipe is blocked..............

 

[ma6mkd]

Hi,

The expansion vessel will be the next part to be replaced if the PRV hasn't done the trick. As I could not determine if the PRV or expansion vessel was the problem I opted for the cheaper part first. And 24 hours in, things are looking better

Thanks,

Mark

 

[hym]

Expansion vessel pressure should be checked depressurized and only be usually as rule of thumb 0.7/0.9 bar. As previous thread said vessel could be ok but supply tube to it could be blocked, all be it rare but very much worth checking.

 

[ma6mkd]

Hello,

Sorry, I had misread the previous post. I understand now that the issue could be the pipe leading to the expansion vessel and not the expansion vessel itself. I shall keep that in mind should I start experiencing problems agains.

The pressure in the expansion vessel is still approx 1.6 bars (when boiler is cold). Going from the above, I guess I should decrease the pressure to approx 0.7 bars. I'll do that this evening.

Can someone also let me know if the expansion vessel's pressure should remain constant whether the boiler is in use or not?

To finish on some good news, the boiler pressure is still holding steady so it does seem the replacement PRV has done the trick. But it would be good to ensure everything else is as it should be if possible.

Thank you,

Mark

 

[ma6mkd]

Hi,

A final message on this topic. Almost two weeks after fitting the new PRV the pressure is remaining stable so normal service has resumed. Thanks to those who replied to this thread and to the contributors of other threads as well. This site is an excellent source of information.

Thanks,

Mark