On Fri, 12 Dec 2003 16:05:30 +0000, The Natural Philosopher
wrote:

BillP wrote:

"stuart noble" wrote in message
...

My neighbour has just had a new Baxi combi installed. They've put TRVs on
all the rads bar one and have ripped out the old room thermostat. Is this
normal? I find being able to set that to 15 or so useful if you're leaving
the house unoccupied for a few days but maybe that's not how it's done

With a TRV system, the idea is to pump more or less continuously, and
let the TRV's decide on demand. The boiler merely cuts in when the
return flow has dropped to the boiler stat level.

Use of TRV's with an overall zone stat makes them essentially useless.
Either they are still demanding heat when the main stat cuts out, or
they have shutdown before it itself does, in which case it never
does.... you cannot have a romm or area controlled by two stats on
essentally the same zone.

With all due respect, you and Christian are talking what appears to be
twaddle.


FWIW I have a full TRV system (i.e. no rads without TRVs), with an
auto-bypass loop at the boiler, *and* a programmable room stat in the
hall.

The TRVs are set so that, in the evening, the rooms are each at the
desired comfort level - thereby fulfilling the aims of a full-TRV
system as you describe it.

However, the hall-stat is set (at 21C in the evening) to shut down the
boiler when all rooms are up to temperature.

In the morning we have the hall stat set to 19C, as we're rushing
around and don't like it too warm in the mornings. There's no way we
could do this without that stat in the hall, unless we went around and
altered the TRVs all the time.

We do get in the situation where some rooms are not up to temperature
and the hall stat shuts the boiler down - this is as you predict, so
against all advice I have fitted a TRV on the radiator in the hall
too. This I set a little cooler than we'd ideally like, so the hall is
the last to warm up - it needs heat "leaking" from other rooms to
finally hit 21.

It's a bit of a fudge, but I can't find a better way of doing it! I
suppose you might argue that that we might as well set the stat to 45C
in the evenings and let the TRVs do their job, which is fair enough,
but we still need the stat to achieve a lower temperature than the
TRVs would allow.

So, with all due respect you are talking what appears to be twaddle
:-) Well, partial twaddle maybe.




Tim Hardisty.
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