Most motorised valves have an inbuilt switch
which is used to control the pump, if these are connected together then the
pump will only run when a valve is open.
The proper CH ones do, but I was
assuming Phil was going to use small solenoid type valves inline with the
radiator (there are some that various people including Ian Bird have found
>from
either open or closed.
The proper CH ones have a small
motor and microswitches inside - when power is applied, the motor operates
and
moves a lever which operates the valve. When the valve is opened, the
lever operates a microswitch at its limit which signals the pump/boiler to
fire. The lever is spring loaded, so that when power is removed from
the
motor (which runs continuously whilst the valve is open, typical power
consumption 6-10W) the lever returns and the microswitch is opened,
switching
the boiler/pump off. There are 2 port and 3 port mid-position
flavours -
the above certainly applies to the 3 port ones as I've disassembled one
;)
James
H
For
more information: http://www.automatedhome.co.uk
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