Magaflo CL170 and Greenstar boiler

Heating engineer said a I had a leaking expansion vessel in the greenstar boiler and replaced it. No leaks at boiler now and no water going to vent but having to repressurise the heating system from the fill valve almost daily now or boiler cuts out.
No evidence of a leak in the house but due to construction of foundations cannot get under all sections of the house. Do I have to start ripping up wooden floors or is there a way to prove whether the fault is in the house or in the combined CL 170 and greenstar system which I have installed in the garage. Could it possibly be leaking into the hot water in the megaflo coil. Me heating engineer is baffled and has checked for leaks under the floor ( the bits he can get too ). Getting worried now , and help much appreciated. Installation is 10 years old with no real troubles.

It's not your cylinder that's at fault - if the coil was split the heating pressure would be rising, not falling, as your hot water pressure is greater than your heating pressure.

Sounds like a leak under the floor somewhere if there's no internal damp. A good quality thermal camera would be the best way of finding it, should be able to hire one...

thanks for the answer ,take your point but was clutching at straws.
Will have to lift floors I'm afraid.

See FAQ on this site for checking the boiler pressure relief vent is not leaking. Most likely cause.

What pressure does the cold system increase increase to when you put heating on and all rads hot? He may not have correctly set the new EXV air pressure. Many RGIs seem to think they come ready set!

Tony

Pressurise boiler.
Shutoff flow and return valves at the boiler and leave for a few hours cold.
If the boiler looses pressure the fault is in the boiler.
If it doesn't the fault is in the house.

Agile said:

See FAQ on this site for checking the boiler pressure relief vent is not leaking. Most likely cause

Tony

Click to expand...

Do try to read the original post Tony, the OP has already checked this...

try to isolate the parts of system under floor.