Pressure Loss in system with Vaillant ECOmax 226EH

[Tristar]

Hi guys, looking for some ideas as to where my pressure leak is, with no visible water leak, and which is not from the pressure relief valve.
With ALL underfloor pipes isolated, pressure still drops.
With the above AND indirect hot water coil isolated, pressure still drops.
Only pipes fed now are all above ground floor level, yet still no visible signs of leaks, yet system requires about two pints (measured by pressure drop when draining down) every day. Boiler works normally.
This situation has been ongoing for about 3 weeks now, and my Corgi man is as baffled as me. Vaillant unable to give any useful advice, which seems fair, as without a leak from the pressure relief valve where can it leak to in the boiler?
Any ideas chaps?

 

[kevplumb]

1st isolate the boiler and see if the press drops

 

[Tristar]

1st isolate the boiler and see if the press drops

Thanks Kev, will try that next.

 

[Tristar]

Tried Isolating boiler, pressure remained OK. So appears only to drop when on demand. Exhaust is quite steamy, has anyone experience of a leak into the burner chamber which could account for such a pressure loss? Condensate drain v. diff to access, but will check for excess discharge also.

:

 

[kevplumb]

if the leak was in the boiler the pressure would have dropped when you isolated it

 

[Tristar]

Point taken Kev, but does that still apply with the boiler shut down? In other words, could it leak internally only with heat applied, and therefore expansion of metal? (As you can tell, I am groping in the dark here).

 

[kevplumb]

have known it with cast heat exchangers so i suppose its poss

 

[Tristar]

Thanks Kev, will keep you posted on the outcome. Whats the weather like out there? Probably quite cool now.

 

[Tristar]

Latest sitrep, having run each section of system separately, taking pressure readings after 12 hours for each, indications were that the indirect heater coil was leaking in the tank (This did not show up in my original checks, but am now operating the motorised valve manually to ensure correct feed). However, having now turned all CH sections AND HW back on, there is now no apparent leak! This after having to top up twice a day for three weeks. What is going on? HELP required.
I suppose I will have to wait until it recurs and start all over again.

Thanks in anticipation of some sound advice.

 

[Tristar]

Thanks very much for all your help last year. The leak WAS in the indirect coil in the tank, which was changed, now all OK.

Once more many thanks, and apologies for the long silence!