TerenceBooth wrote:
I have a Horstmann timer controlling a fully pumped sytem with a
mid-position valve. If HW and CH are selected and running, then
switching CH off does not cause the valve to move even at the end of
the on/off cycle. The only solution is to disconnect the mains from
the system sometime during the off period when the spring moves the
valve to the correct HW-only position.
Is this a wiring error on my system or a problem with this type of
valve?. Can anyone help with a solution?

Alan Booth

Do your rads actually continue to get hot when CH is satisfied?
I ask this because you usually can't tell what the actuator of the valve is
doing by merely looking at the lever which is for manual override.