"Set Square" wrote :

Not necessarily. If the stat is set low, the heating may not come on at
all because it will take a while for the house to cool below the lower
setting. If it *does* come on, it will only do so sufficiently to bring
the room with the stat up to the reduced stat setting. The other rooms
will get a bit warm - but probably not sufficiently so for their TRVs to
operate - so the fact that the TRVs are set higher than you want under
these circumstances is probably not relevant.

The point I was trying to make, though, is that when the house has cooled
down to the lower setting, then whenever there is demand it is likely to be
with the TRVs at full bore. The energy usage is therefore higher than
necessary.

Steve S