In an earlier contribution to this discussion,
Michael D wrote:

I had a new boiler (Potterton 80 combi) fitted about 5 years ago & had
TRV's fitted (on all radiators) at the same time. Subsequently
someone said to me that I should have at least 1 radiator without a
TRV. When I mentioned this to the British Gas engineer doing my
annual service during the summer he removed the one from my bathroom
(he didn't seem to check whether or not I had a bypass).

The problem now is that my bathroom is very warm - uncomfortably so at
times, so I'd like to put the TRV back on. As I don't actually know
for sure whether or not I've got a bypass fitted I don't know whether
I can safely put the TRV back on. As the pipework around the boiler
is boxed in I can't tell if there's a bypass there without slightly
trashing the 'boxing-in'.

Any advice on whether or not it's likely I've got a bypass or how I
could find out would be useful.

Many thanks,

Michael

There seems to be some muddled thinking here! The idea of having one
radiator without a TRV is that you must *also* have a room stat in the area
served by that radiator, which switches the *whole lot* off when it gets up
to temperature - otherwise known as a boiler interlock.

Have you got such a room stat? Without it, there was no point whatsoever in
removing the TRV!

Whether or nor you need a by-pass depends on a number of factors. Does your
boiler have a pump over-run stat, and is the pump connected to it? Do you
have an S-Plan (2 x 2-port zone valves) system or a Y-Plan (3-port
mid-position valve) system? If the latter, and if one rad is always on,
there should always be a flow path open - thus not needing a by-pass.
--
Cheers,
Set Square
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