In article .com,
Don wrote:
I've been going through severe problems with my Heatline Compact S30
combi-boiler and recently had an engineer out to it under warranty. He
noted that the TRV's the instaler had fitted were one-directional, said
this would cause knocking and stress on the boiler and advised that
they be changed to bi-directional. He also advised a room-stat which
the installer also neglected.

Nothing wrong with directional TVRs provided they are fitted correctly.
Fit them the wrong way round and they may be noisy in operation.

If you have a room stat there mustn't be TVRs in that room.

--
*A bicycle can't stand alone because it's two tyred.*

Dave Plowman London SW
To e-mail, change noise into sound.