Sealed System Pressure Issues

[sniperkmydj]

Hello all, Thank you for taking the time to read my post. Background: Micron Glow worm 40FF boiler. Modern 4 bed, 2 floor house, 11 radiators. Leaking pressure relief valve, failed expansion tank behind boiler. Work undertaken so far: I have fitted a new expansion tank, specified by online plumbing merchant (18L) in the airing cupboard with a new 3 bar pressure relief valve. I emptied the system and filled again including inhibitor, I set the system up at 1 bar cold pressure, bled all radiators and topped up to 1 bar. All radiators are as hot as each other and only a tiny about of air comes out of the radiators when bleeding if at all. Issue: The system has been running for 2 weeks now and I still have a pressure drop from 1 bar to 0.4-0.5 bar after each use. I hear noises in the pipes, like air is moving around. The pressure I don't believe is increasing above 3 bar. I have two gauges one on the boiler in the kitchen reading 1 bar cold, and one in the airing cupboard on expansion tank reading 2-2.5 bar cold. Can someone please give me an indication of what is going on? Many thanks, Kieran

 

[Last Plumber]

Hello all, Thank you for taking the time to read my post. Background: Micron Glow worm 40FF boiler. Modern 4 bed, 2 floor house, 11 radiators. Leaking pressure relief valve, failed expansion tank behind boiler. Work undertaken so far: I have fitted a new expansion tank, specified by online plumbing merchant (18L) in the airing cupboard with a new 3 bar pressure relief valve. I emptied the system and filled again including inhibitor, I set the system up at 1 bar cold pressure, bled all radiators and topped up to 1 bar. All radiators are as hot as each other and only a tiny about of air comes out of the radiators when bleeding if at all. Issue: The system has been running for 2 weeks now and I still have a pressure drop from 1 bar to 0.4-0.5 bar after each use. I hear noises in the pipes, like air is moving around. The pressure I don't believe is increasing above 3 bar. I have two gauges one on the boiler in the kitchen reading 1 bar cold, and one in the airing cupboard on expansion tank reading 2-2.5 bar cold. Can someone please give me an indication of what is going on? Many thanks, Kieran

You've not set the expansion vessel pressure by the sounds of it.
if you work on the boiler you're supposed to be gas safe registered, you know that don't you ?

 

[Best]

What did you do with the original expansion vessel that was part of the boiler?
If you are not Gas Safe qualified you cannot work at the gas boilers. (I am a heating engineer, but I am not gas, so can't touch them.)
You are better to pay a heating engineer to check the system and any work on boiler needs to be a gas engineer

 

[sniperkmydj]

Many thanks for your responses.

The expansion tank behind the boiler has been left connected and in-situ. I have not touched the boiler as I am not gas safe. I have spoken to three local plumbers who have all advised that I am ok to work on any part of the system providing it is not the boiler.

The expansion vessel I fitted came pre-charged at 1.5 bar, should I reduce this to 1 bar to match cold pressure?

If its not exceeding 3 bar, how can air get in as no water is being vented?

 

[sniperkmydj]

You've not set the expansion vessel pressure by the sounds of it.
if you work on the boiler you're supposed to be gas safe registered, you know that don't you ?

Many thanks for your responses.

The expansion tank behind the boiler has been left connected and in-situ. I have not touched the boiler as I am not gas safe. I have spoken to three local plumbers who have all advised that I am ok to work on any part of the system providing it is not the boiler.

The expansion vessel I fitted came pre-charged at 1.5 bar, should I reduce this to 1 bar to match cold pressure?

If its not exceeding 3 bar, how can air get in as no water is being vented?

 

[Last Plumber]

Let the pressure out of the system until it reaches zero.
Set the vessel pressure to 0.8-1.0 bar.
Recharge system to 1.0-1.2 bar.
You can set both to same if you like.

 

[Scott_D]

Did you replace the leaky PRV?

 

[sniperkmydj]

Let the pressure out of the system until it reaches zero.
Set the vessel pressure to 0.8-1.0 bar.
Recharge system to 1.0-1.2 bar.
You can set both to same if you like.

Thank you for your response.

I have followed your instructions and after running the system for 2 hours now, the pressure on both gauges is at 2.5 bar, which is still too high. What do I try next?

 

[sniperkmydj]

Did you replace the leaky PRV?

I did at the time I replace the expansion vessel

 

[Last Plumber]

Is the vessel big enough ?
I know you have 11 rads but you need to know water vol to calculate vessel size.

What temp have you got boiler on ?

 

[sniperkmydj]

Is the vessel big enough ?
I know you have 11 rads but you need to know water vol to calculate vessel size.

What temp have you got boiler on ?

I presume so, as the plumbers murchant I purchased it from took my details and recommended the 18l version. The vessel seems much larger in size than the original behind the boiler.
The boiler does not have a temperature gauge as such, just a dial, which is 3 quarters of the way round .
Maybe I should calculate the volume myself, how is best to do that?

Thank you for your time

 

[Billy Bob Bob]

He has not worked on the boiler,just fitted a remote EV,my first thoughts would be why a 18l EV ? 12l would have been oversized but thats what i would have used,Either the vessel you have is too big and not absorbing the system expansion rate or you have a leak somewhere

 

[Scott_D]

Pictures needed

 

[sniperkmydj]

What would you like to see, the expansion tank setup?

One added bit of info, the water side of the expansion tank doesn't get warm, just checked. What if I don't have water in it, air pocket, would it impact on its operation?

Pictures needed

 

[sniperkmydj]

He has not worked on the boiler,just fitted a remote EV,my first thoughts would be why a 18l EV ? 12l would have been oversized but thats what i would have used,Either the vessel you have is too big and not absorbing the system expansion rate or you have a leak somewhere

I did query the size, but they sent the calculations to the manufacturer. I do also have a couple of double skinned radiators which will add to the volume requirement of the expansion vessel. Leak is possible, as hear tinking/ dripping in the wall cavities, but no one agrees with me lol

 

[sniperkmydj]

After the changes I made last night to the vessel I got home to find the system sitting cold at 3 bar. I have drained back to 1 bar. What the hell is going on lol

Pictures needed

 

[sniperkmydj]

New AAV installed also

 

[Jones82]

Reading your initial post, the pressure gauge near the expansion vessel must be getting to 2.5bar some how, perhaps fill the system to 1 bar then shut off the cold main, if the pressure doesn't rise to 2.5 again then the system must be filling from some where, eg a faulty filling loop

Or perhaps the gauge on the boiler is faulty and your overfilling the system?

 

[Jones82]

Looking at your pictures the filling loop looks like its constantly open, shut the valves and disconnect the loop after filling. This way you know for certain the heating system can't be constantly filling. Also there are two filling loops, one near the vessel and one near the pump and PRV