air in heating system

[rjmgas]

Hello all, Looking for some help on this one as i have stood around and scratched my head so much i have no hair left.
In november i fitted a combi boiler to an old system, all went fine until a few days before xmas, the client phoned to say there was cold spots on rads, i bled the 4 radiators in question and solved the problem, since then the clients need to bleed the 4 rads daily, however they dont need to top up the system. i Have investigated all pipework and there is no sign of a leak anywhere. I have checked all pipework when hot and cold. if the 4 rads arent bled daily the pressure increases. I am at my wits end, everything that happens is pretty much impossible, any suggestions would be greatly recieved:banghead:

 

[Simon F]

welcome to the forum.
how dirty was the system to start?
what level of cleaning did it get?
is the filling loop connected and passing water?
have you tested if its hydrogen or air being bled?

 

[rjmgas]

hi,
the system was well treated and it was powerflushed before the combi went in.
the filling loop isnt connected (was ment to state that in first post)
Tested to see if it was hydrogen but its not its air
Confusing one isnt it,
I did wonder if it was a cracked heat exchanger but theres no loss of pressure when the mains is off and taps are opened so that ruled that out.

 

[Ryan Jones]

Not sure if this would solve the air problem but a rise in pressure normally means the air pressure is lost in the expansion vessel so I would check that first

 

[Rob Sale]

Are there any long runs and dead legs. if there are try putting a AAT on it.