Suprima 80 Heat Exchanger / Losing pressure

[SurreyPlumb]

Hi

I wonder if anyone has come across the following type of central heating problem-

Sealed system, fully pumped, S plan, sealed, Potty Suprima 80, CH pipework is a mixture of copper and Poly.

System loses 1 bar of pressure in about 3 hours but only when heating is running. I have pressure tested the whole system for 10hours at 2.5 bar with no significant loss (and boiler switched off).

Having checked the heat exchanger there would appear to be a significant amount of corrosion around the drain point at the bottom LHS and rusting to the plate on the LHS of the burner. Could it be that the Heat Exchanger is cracked? I've ran the system flat out and then removed the case but cannot see any evidence of water coming through. Unfortunately this is a CH system that we did not install and all pipework is buried in concrete screed.

Has anyone seen a similar problem i.e. losing this much pressure through the HE without signs of water. Is the only option to isolate the boiler after getting it hot, and then pressure test it?

Any advice greatly appreciated.

 

[gas4you]

Have you drained the expansion vessel and tested the pressure in it?

If water comes out of the valve it needs replacing.

See FAQ's on how to test the exp vessel.

 

[petit_pablo]

1 bar of pressure and no sign of a leak suggests its in the screed somewhere. If it was in heat exchanger 1) you would see it and it would fill the bottom of the case 2) it would do it on hw too

 

[SurreyPlumb]

Hi

Just to clarify, the system leaks when hot water or heating is on. But not when the boiler is switched off. Pressure vessel & PRV are fine. No loss from safety pipe and no significant increse in pressure when system running.

Thanks.

 

[petit_pablo]

Id say its in the screed

If its only doing it when its on then the heat can be expanding a joint somewhere and leaking, as its cooling down the joint shrinks back again

 

[SurreyPlumb]

Thanks guys for the replies. Anyone had any experience with leak detection companies? The last one we used was not to be recommended....

 

[gas4you]

Strangely enough I was talking to someone a few days ago who had used a company from Cambridge , I think, they couldn't praise them enough.

In the end the bloke placed a 10p piece on the floor and said that's where your leak is and it was spot on.

Can't remember their name though (old age methinks )

They used thermal imaging to acheive this.

 

[petit_pablo]

Thanks guys for the replies. Anyone had any experience with leak detection companies? The last one we used was not to be recommended....

Munters do leak detection using a gas in pipes. Seemed quite good when we used them, we thought there was 1 leak they found 3