CH on when HW selected

[chris23]

Boiler is Ideal Classic FF360, the timer is a Honeywell ST699 and there is a Drayton MA1 mid position actuator. The problem is that when Hot water only is selected on the timer the central heating comes on as well. So I looked at the actuator and realised that it was not working and replaced it making sure that the wires were connected correctly. Great I thought as the actuator leaver moved when I selected central heating. Then I selected central heating and hot water and it moved to mid position. But when I put it to hot water only, it stayed in the mid position. When I disconnect the power supply the actuator moves to the hot water only position so the valve is free to move. Any ideas please.

 

[Bamber gaspipe]

Have you checked the valve itself? it could be seized in the mid position, remove the actuator head & see if the spindle turns easily ( use a pair of pliers).

 

[wilhelm]

sounds like the ball or shoe (whatever...) in the valve itself is letting by.
change the lot.

 

[chris23]

I have tested the valve and it does move freely. When I disconnect the power supply, the actuator does move to the hot water only position, I assume this is its resting place when there is no power. I reconnect the power and select hot water only on the timer and the actuator moves to the mid position. Could the old actuator burning out cause a problem with the timer. When central heating only is selected the actuator moves to heating only position. When central heating and hot water are selected the actuator moves to the mid position. If I can get the actuator to move to the hot water only position and the central heating is still coming on, then I will change the valve.