On Sun, 12 Nov 2017 13:48:20 +0000, Tim Watts wrote:

On 12/11/17 13:05, T i m wrote:
On Sun, 12 Nov 2017 12:41:34 +0000, Tim Watts


Normally you use a designated radiator.

So this would be on all the time, no stat-valve etc?

Yes.

And with lockshield valves both ends so normal users don't fiddle.

Or if you don't want to (or don't trust it not to be fiddled with),
you could do as I did and put a pressure bypass in, which should only
open to protect the boiler pump.

Ah, that makes more sense and as you eluded to above, less chance of
being 'fiddled with'.

It will be interesting to see how it all went on Friday (when the
plumbers were due back to replace both motorised valves) and whilst
they were there the other day I overheard talk of 'one of the motorised
valves not being moveable by hand' ... but are they all (as they could
have been different makes / designs)?

Usually they have an override lever that can be pushed and dropped into
a locking slot, for when the motor fails.

I believe the primary purpose of the locking lever is to force the 3
port diverter valve to keep both ports open to facilitate draining and
reduce air locks during refilling operations whilst the system is powered
down.

It doesn't (or shouldn't) stay in the latched position once the system
is powered up and running. I can't say whether this also applies to the
two port valves since I only have experience of the 35 yo single 3 port
diverter valve (Y or S plan ?) setup used here.

--
Johnny B Good