Isolating Radiators Part 2 - Mystery Pressure Drop

[DavidGee]

Firstly, thank you to everyone who commented on the last post with regard to this issue ... the post were appreciated.

Just to recap I have a pressurized central heating system which is losing pressure ... an engineer having checked the system informed me that I have a leak under the floor (the pipes are buried in concrete) the previous post basically asked if if I could help locate the leak by isolating the radiators .... clearly I can't.

Since the last post the following has happened.

Valves have been fitted on the pipework to separate the upstairs and downstairs heating. When the upstairs heating only is on everything works perfectly, when these valves are opened to allow to whole system to operate (upstairs and downstairs) the pressure drops quite rapidly thus giving the impression that the leak is downstairs.

Given this a thermal survey was undertaken of all the downstairs heating pipework, no leak was found and as most of the pipework ran against the walls moisture readings were taken along these piperuns and no evidence of moisture was found in the walls.

This survey was repeated again upstairs with the same results ... no leaks were found were found or moisture detected.

Does anyone have any suggestions as to what could be causing this situation?

The amount of water being lost is quite significant the pressure fell from 1.5 bar to 1 bar quite quickly and I had to top up the system three time in the afternoon whist the survey was being undertaken. There is no evidence of water escaping from the external expansion pipe and the boiler when only heating upstairs seems to be working fine with no loss of pressure.

If anyone has any thoughts on this one it would be appreciated.

As an aside due to the size and open plan nature of the house the piping can't be dropped in from above to avoid the downstairs piping (which does not appear to have leak in any case)

Thank you

D

 

[Chalked]

Leaking heat exchanger?. Is it a worcester?

 

[IDCHAPPY]

Can't quite remember from the first thread but have you ruled out the PRV?

 

[LPC]

I commented in the other thread but i'll lay out what I would check:

1)Make 100% it isn't the PRV. If it holds pressure upstairs only this is unlikely, but tie a carrier bag around the outlet for a day or two to be 100% there isn't anything coming out of it (it'll likely be a bit of 15mm copper terminating outside).

2)Do you have a hot water cylinder or is it a combi boiler? If it is the former you need to isolate the cylinder flow and return to make sure it isn't a split in the cylinder coil.

3)Has an engineer definitely had the combustion chamber open to check the main heat ex isn't leaking? Some boilers can leak internally but never show because the heat inside the boiler evaporates it before it can leave the sealed chamber.

 

[DavidGee]

Thanks for the reply

The boiler is a Gloworm which is about 6 years old .. the engineer did mention the heat exchanger but thought is unlikely due to the age of the boiler.

Will certainly get it checked out properly though

 

[DavidGee]

The PRV seems to be OK (albeit I will check it out again) it certainly holds pressure when only the upstairs heating is usedn

 

[DavidGee]

Thanks for your reply

!. I will most certainly check that the PRV is OK by attaching a bag, thanks for the suggestion

2. It's a Gloworm Flexicom boiler so I would think that it is a combination boiler (it's about six years old)

3. I don't think that the engineer has checked the combustion chamber, once it was seen that the upstairs heating was working well and the pressure was holding he seemed to think that the leak was the most plausible reason for the drop in pressure

Thanks again

D

 

[lame plumber]

chalked has the answer esp if its a wb, been there several times, isolate the boiler overnight to check

 

[DavidGee]

Thanks for your reply

!. I will most certainly check that the PRV is OK by attaching a bag, thanks for the suggestion

2. It's a Gloworm Flexicom boiler so I would think that it is a combination boiler (it's about six years old)

3. I don't think that the engineer has checked the combustion chamber, once it was seen that the upstairs heating was working well and the pressure was holding he seemed to think that the leak was the most plausible reason for the drop in pressure

Thanks again

D

 

[LPC]

I think you'd do well to find an engineer that wants to solve it due to the curiosity aspect. I know if you rang me up with this tale i'd be interested to find it and only charge for what I fix, not time for finding the problem. Maybe ring a few local engineers?

 

[Ermintrude]

Isolate pipework on ground floor connect a water test rig and bump it up to 6 bar. If it's still got 6 bar 24hrs later it's an expansion issue. Hire the pump from hire shop for. £39 a week.

 

[lame plumber]

I think you'd do well to find an engineer that wants to solve it due to the curiosity aspect. I know if you rang me up with this tale i'd be interested to find it and only charge for what I fix, not time for finding the problem. Maybe ring a few local engineers?

???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? come work for me, I'll be able to retire quicker

 

[Ermintrude]

???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? come work for me, I'll be able to retire quicker

Thought you were retired.?

 

[lame plumber]

Thought you were retired.?

nope, still looking for a source of foot n mouth to send your way

 

[Ermintrude]

nope, still looking for a source of foot n mouth to send your way

My foot usually in my mouth

 

[DavidGee]

Hi Thanks again for the information ... just for my information would a leaking heat exchanger only affect the ground floor (as when only the 1st floor is heated everything is fine .... or would it be the volume of the whole house which it could not cope with?

Many thanks

D

 

[Ermintrude]

If it's volume related it's not the hex. But it would only drop in pressure when system had been hot if it was pressure issue

 

[DavidGee]

Thanks for the reply, its appreciated ... this is what I find puzzling - when only the upstairs heating is on (via the isolation valves on the flow and return pipes downstairs) the system works fine with the radiators providing the necessary heat ... once these valves are open to heat the whole house the pressure gauge drops quite rapidly.

Given that no leaks have been found in the pipework, the PRV seems to be fine and if it's not the heat exchanger as it seems fine heating the first floor I am not too sure what else it could be.

Is there anything else that could have been missed?

David

 

[Ermintrude]

The pipes in the floor have a hole in them. Have you isolated the ground floor and pressure tested as said above?

 

[DavidGee]

I am currently trying to arrange someone to do this as it is beyond my abilities.

The thermal survey (which included basic moisture testing of the walls) did not seem to come up with anything suggesting a leaking pipe which makes this whole thing very puzzling.

I am just wondering if it may be easier to have the PRV replaced and if the pressure still drops it can only be a leak in the pipes....

 

[Ermintrude]

Thermal test and moisture test won't show squat. Concrete is a heat guzzler and unless the camera has an amazingly high resolution and uber fast refresh rate?

 

[DavidGee]

The survey was done by a professional company using a FLIR T440BX camera.

I have to say the images are pretty sharp and I would have thought shown up a water leak.

A number of people suggested this approach on this site and it seemed a sensible thing to try.

Just wish I could get to the bottom of this one ...

D

 

[Ermintrude]

If pipes cold ain't showing squat. Those cameras are ok for wood floors and massive red hot leaks and rads that are full of sludge. Thermal cameras ok but if 200mm concrete u will struggle with anything less than the Hubble ! Pressurise the gauge won't lie. Test with water and not air! As air will expand on compression and contract when system settles down leading to false measurements.

 

[Billy Bob Bob]

Firstly, thank you to everyone who commented on the last post with regard to this issue ... the post were appreciated.

Just to recap I have a pressurized central heating system which is losing pressure ... an engineer having checked the system informed me that I have a leak under the floor (the pipes are buried in concrete) the previous post basically asked if if I could help locate the leak by isolating the radiators .... clearly I can't.

Since the last post the following has happened.

Valves have been fitted on the pipework to separate the upstairs and downstairs heating. When the upstairs heating only is on everything works perfectly, when these valves are opened to allow to whole system to operate (upstairs and downstairs) the pressure drops quite rapidly thus giving the impression that the leak is downstairs.

Given this a thermal survey was undertaken of all the downstairs heating pipework, no leak was found and as most of the pipework ran against the walls moisture readings were taken along these piperuns and no evidence of moisture was found in the walls.

This survey was repeated again upstairs with the same results ... no leaks were found were found or moisture detected.

Does anyone have any suggestions as to what could be causing this situation?

The amount of water being lost is quite significant the pressure fell from 1.5 bar to 1 bar quite quickly and I had to top up the system three time in the afternoon whist the survey was being undertaken. There is no evidence of water escaping from the external expansion pipe and the boiler when only heating upstairs seems to be working fine with no loss of pressure.

If anyone has any thoughts on this one it would be appreciated.

As an aside due to the size and open plan nature of the house the piping can't be dropped in from above to avoid the downstairs piping (which does not appear to have leak in any case)

Thank you

D

quite a easy,mechanical,non BS answer my friend leaks down stairs thermal imaging is pants

 

[armyash]

Dodgy expansion vessel?