Hot water but no Central Heating!

17 Jan 2011
Reaction score
United Kingdom
my boiler fires when hot water is called for but not the central heating.
the programmer is on and calling for heating
the thermostat is calling for heat
the pump does not go when heating is called.
the mid position actuator does not move from hot water.

I have manually moved the actuator to the mid position (both water and heating) and the radiators get warm.

Any ideas which bit is at fault or a way or how I can find out?


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as above so long as your roomstats not faulty and isnt just appearing to be in the calling for heat position without any contacts made.
what type of actuator is it?
Drayton mid position actuator
I will check the voltage later but it moves back when I put into auto.
How can I overridethe room stat?
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it will move back when on auto as the spring pulls it back to relaxed position, HW.

check if you have 230v on white wire when stat calling.
if not check stat has 230v going to it from programmer.
ok really confused now!

with everything off the actuator valve is in the W pos (HW)

call for HW and the boiler fires and pump runs.
turn off HW and the boiler goes off and he pump over runs
call for CH and nothing happens. although 240v at the white
when the pumps has finished its over run I can physically take the actuator off the valve and manually put it to M (both)
as i do this the actuator physically moves to the H (CH) and the pump starts - but there is no call for CH
I can then set the programmer to CH and flick the Thermostat and the boiler fires and the rads get hot.
the actuator stays in CH until HW is called.
has the programmer got confused cause I can't work out which bit is at fault!

the fault is the actuator.
once the valve gets to mid position live on the grey will take over and put he valve in H only position and hold it there till you take power of the grey.
call for hw.

so the fault poss lies with the pcb in the actuator.
you can check the motor by removing and placing 230v across it.
thanks for that!

the actuator was going to be the first thing I replaced.

thanks again everyone!


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