Low pressure on the system

[Adam HB]

Hi,

I'm a customer who knows very little.
I have just had a wet UFH system added to an existing central heating system. The oil boiler is now supplying one half of the house with UFH and the other half radiators and a hot water tank.
The problem is that both the pressure gauges on the hot water tank and the UFH manifold will slowly work their way down to zero bar, eventually cutting out the boiler.

I have been advised by the builder that the expansion vessel on the boiler might be to blame. When I top it up with air the pressure gauges rise, so every day I top it up to around 1.5 BAR and the heating works.
The system has also been topped up with water following the UFH installation.

Is it likely my builder is correct that I should install a new expansion vessel? Or is there something more sinister going on?

Thanks in advance,

Adam

 

[ShaunCorbs]

Would say there's a leak some where

 

[lucas121]

Do you know where your pressure relieve valve terminates? If so is there signs of water dripping there?

 

[king of pipes]

Did the installer fit a extra heating expansion vessel to allow for the extra volume of water in the ufh, tape a clear ploy bag on the saftey valve discharge while the system heats up you will soon see if its passing you will need a engineer to rectify the problem .

 

[Adam HB]

Do you know where your pressure relieve valve terminates? If so is there signs of water dripping there?

I think that's the pipe sticking outside and I haven't seen signs of water dripping.

 

[Adam HB]

Hi,
no, the original expansion vessel has been used.
When you say the "safety valve discharge" is that the pipe exiting the house that lucas121 called the "pressure relieve valve", or is it a valve on the actual expansion vessel?

 

[ShaunCorbs]

Hi,
no, the original expansion vessel has been used.
When you say the "safety valve discharge" is that the pipe exiting the house that lucas121 called the "pressure relieve valve", or is it a valve on the actual expansion vessel?

Depends your best bet would be to get a heating engy to just check the system

 

[king of pipes]

Get your engineer to check the system over including the boiler

 

[Adam HB]

An update to this problem:

A heating engineer looked over the system and fixed a leak on a radiator. Bled where there were airlocks, topped up the water in the system so we had the regular 1 BAR of pressure back. Problem solved, or so we thought.

Over the next 24 hours the pressure had dropped back to near zero.

I contacted the UFH installer who said the system was pressure tested to 3BAR and should be fine. He said to check for drips on the Manifold and to make sure an auto air vent is not closed. I will do that this evening.

My question is this: if there is no water coming from the outlet pipe from the expansion vessel then does it mean the vessel is ok? The heating engineer seems to think so.
Surely if I have had to replace air in the expansion vessel at all (I have several times) then this means it's membrane has failed and it needs replacing?

 

[Adam HB]

king of pipes,

the safety valve discharge is not passing water.
We have shut off the UFH but are still getting (a much slower) drop in pressure.
Can the wrong size expansion vessel account for a slow drop in pressure without the safety valve showing any water?

 

[Adam HB]

king of pipes,

the safety valve discharge is not passing water.
We have shut off the UFH but are still getting (a much slower) drop in pressure.
Can the wrong size expansion vessel account for a slow drop in pressure without the safety valve showing any water?

 

[king of pipes]

If your pressure is dropping then you still have a leak , it may be down to the expansion vessel if it has failed but you would see water at the saftey valve when the system heats up and the pressure gauge would register above 3bar does this happen ? truthfully you could loose it from lots of places get your engineer back bud .

 

[Nishikigoi]

If it's not an obvious leak then it might be time to try either renting a thermal imaging camera or get a leak detection company out as they have all this kit plus trace gas and acoustic detection. Google is your friend here, but if your London area then UK Leak Detection are good.