My mother had her central eating boiler replaced a couple of months
ago, and I went up to see her for the first time last week (I know, I
know, but I do phone her every week). I was amazed at what has been
installed.

The original system dated from the 1970s, with no room thermostats.
TRVs were added later to all radiators. The new boiler has been
installed, but there is no by-pass circuit, much less a valve or flow
switch, so one radiator must be left on permanently. The only
effective control over heat is the boiler thermostat. I don't know
whether the system had a by-pass circuit before. Could there have
been a flow switch in the old boiler?

Putting aside the question of complying with the Building Regulations
(which it doesn't), how dangerous is it to have a heating circuit
entirely controlled by TRVs with no by-pass? I tried closing all the
TRVs, but the boiler continued firing and I could hear the pump
beginning to strain. What would happen if i had let this continue, or
my mother (who's nearly 80, and a bit forgetful) decides to lower the
only open TRV?
--
Hugo Nebula
'What you have to ask yourself is, "if no-one on the internet wants
a piece of this, just how far from the pack have you strayed?"'