System losing pressure.

[lemmy999]

I have an Intergas HRE 36/30 boiler. Some time ago the boiler was showing either zero pressure or high pressure. I figured it was the pressure sensor. Saw some advice about fitting an external filling loop with a gauge which I did. I have been using that for a while.

Recently i have been experiencing pressure loss from the CH system. I figured it might be within the pipework and was going to take up boards in the likely areas to check. Prior to that I thought I'd check the overflow from the boiler. I connected it to a 5L bottle and waited. I'm still experiencing loss of pressure and the bottle has been filled. I believe that boilers vent to the overflow when they are over-pressure but that doesn't explain why I am still losing pressure in the system.

Is it possible that I am experiencing two different issues here? Or are they all past of a single issue?

 

[Deleted member 120897]

If you’re experiencing pressure loss, and given the description, I’d say expansion related issue, pressure relief valve (prv) not seating correctly or both. Is the pressure rising with heating on at all?

 

[lemmy999]

If you’re experiencing pressure loss, and given the description, I’d say expansion related issue, pressure relief valve (prv) not seating correctly or both. Is the pressure rising with heating on at all?

No. Its strange. I'm losing water from the overflow and know that there is air in the system so there can be no way that the system is overpressure.

 

[Brambles]

As soon as you loose system pressure air will enter the system.

Likely causes if there are no system leaks and the PrV is operating / passing:

Expansion vessel air valve is leaking - so there is no or low air pressure in the expansion vessel and / or vessel bladder has failed and / or Prv has not resealed after opening.

Most likely combination is that the boiler expansion vessel and Prv require replacing

 

[lemmy999]

Likely causes if there are no system leaks and the PrV is operating / passing:

Hmm, I really need to pressure test the system just to make sure that there are no leaks.

 

[Brambles]

The system is probably over pressurising because the expansion vessel has no air in it. As soon as the system gets hot, there is no area for the water to expand to, pressure rises, PrV opens, pressure falls, prv closes( may or may not seat properly). You top up the system pressure and the cycle starts again.

The expansion vessel is rear mounted - you need a competent person to change it. Alternatively fit a suitably sized external expansion vessel.

You will probably need to replace the PRV too. They can be problematic after they have been called into use a few times and don’t reseal properly.

 

[lemmy999]

@Brambles
??
Are you suggesting that I may be wrong??

 

[Brambles]

What you have described is s common problem on sealed systems.

The area to check first is that under pressure the PRV is sealed and not passing.
Then test the expansion vessel: Is there water on the air side - if so the bladder has failed. If there is no water, test the air valve is not leaking and that the charge pressure is correct.

If that is all ok, then go looking for leaks else where.

In your case you say the PRV is passing - so if the PRV is sealing then the issue is most likely the expansion vessel - either the bladder has failed or it has lost its air precharge.

If you had a system leak and the expansion vessel was working, the PRV would not open.

If you want to test the system for leaks:

Switch the boiler off completely. When it is cold, pressurise the system to 2 bar leave it for 24 hours and then note the pressure loss ( if any).

 

[EvilDrPorkChop]

Agreed with others. Sounds like a classic Expansion Vessel related issue down to lack of servicing.

Plus I believe the Intergas Vessels are only 6L which is tiny and not adequate for most systems.

 

[lemmy999]

Agreed with others. Sounds like a classic Expansion Vessel related issue down to lack of servicing.

Plus I believe the Intergas Vessels are only 6L which is tiny and not adequate for most systems.

I now believe that this particular boiler may have been recommended by a plumber who was getting some sort of bonus/payment from Intergas. I think they may have had some sort of promotion on several years ago when it was installed.

Too late to do anything now.

 

[EvilDrPorkChop]

I now believe that this particular boiler may have been recommended by a plumber who was getting some sort of bonus/payment from Intergas. I think they may have had some sort of promotion on several years ago when it was installed.

Too late to do anything now.

Not really an issue, you can add additional expansion onto a system if required.

But sounds like your current expansion vessel needs either recharging or replacing.

 

[lemmy999]

The system is probably over pressurising because the expansion vessel has no air in it. As soon as the system gets hot, there is no area for the water to expand to, pressure rises, PrV opens, pressure falls, prv closes( may or may not seat properly). You top up the system pressure and the cycle starts again.

The expansion vessel is rear mounted - you need a competent person to change it. Alternatively fit a suitably sized external expansion vessel.

You will probably need to replace the PRV too. They can be problematic after they have been called into use a few times and don’t reseal properly.

Thanks. I am pretty useful but I do not think I could realistically call myself competent with regard to CH. I know that Intergas do a "all in service " for about £400 which is probably the way to go.

 

[Deleted member 120897]

Being an intergas, it’s possible to be the communication hose to the vessel being blocked.

 

[EvilDrPorkChop]

Being an intergas, it’s possible to be the communication hose to the vessel being blocked.

Good call. I get this a fair bit on the Worcester Juniors/Sis too.