[John Stumbles]

On Fri, 20 Apr 2007 22:14:34 +0000, nospam wrote:

Hello,

I am fitting TRVs to most of my radiators. I realise that I need to
fit a pressure valve so that the pump does not pack up if all the TRVs
close.

No that's not what they're used for. Please see these parts of the DIY
Wiki

http://wiki.diyfaq.org.uk/index.php?...re_to_fit_TRVs

http://wiki.diyfaq.org.uk/index.php?..._zones:_S-plan

[John Stumbles]

On Mon, 23 Apr 2007 14:18:00 +0000, nospam wrote:

On Sat, 21 Apr 2007 11:55:30 GMT, John Stumbles
wrote:

No that's not what they're used for. Please see these parts of the DIY
Wiki

http://wiki.diyfaq.org.uk/index.php?...re_to_fit_TRVs


This link says under bypass valves: "These let water flow from flow to
return when the pressure generated by the pump is high due to the zone
valves being closed, but don't pass a flow when any of the zone valves
are open". I can't see the difference between all the zone valve and
all the TRVs being closed. Surely the net result is the same: the pump
has nowhere to push the water?

Under the link you've left in above it says "... if TRVs are fitted to all
radiators and there is no room thermostat then energy will be wasted by
the boiler cycling when all rooms are up to temperature." I realise this
isn't clear about what happens if you have all TRVs and _do_ have a room
stat so I've added "The same problem can occur if TRVs are fitted to all
radiators in a system that /does/ have a room thermostat: if the TRV in
the area with the thermostat closes down while the thermostat is still
calling for heat it will continue to keep the boiler firing even when all
the TRVs are closed."

Does this clarify things (i.e. why you shouldn't have TRVs on all rads)?