In article ,
"Christian McArdle" writes:

Part L does not allow any heating appliance to be uncontrolled. Every heat
outlet has to have either a TRV or thermally controlled zone valve in its
circuit, so can't be relied on as a bypass.

Well, I did mine before Part L came into effect, but I thought it
conformed to the draft. I use the rads in the room with the thermostat
as the bypass loop. They have lockshield valves only, and are controlled
by the thermostat which cuts off the boiler when there's no call for
heat.

--
Andrew Gabriel