Heating constantly on - Drayton zone actuator problem??

27 Dec 2011
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United Kingdom
Please can anyone advise me on a problem I have with my heating. All of my radiators are constantly on despite my thermostat being turned down and heating switched off.
I've read quite a few threads on this forum and think it could be a problem with a Drayton ZA5 zone valve actuator in my airing cupboard. I found that the switch that should move from A to B wasn't moving when the heating was turned on or off.
I have dismantled the zone valve actuator and have found that:
• I can manually move the arm on top of the box to turn the valve on or off.
• The motor seems to be whirling around okay inside the circular part of the actuator when I turn the heating on and off.

What I can't figure out is why the heating isn't switching on and off properly if the valve arm has movement and the motor inside the actuator seems to be working.

Can anyone help??

I am a complete novice and have to admit to not even knowing what a zone valve actuator was until yesterday so please be kind! :D
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If the motor is operating correctly and the valve opens but does not fire the boiler, then chances are the end switch is faulty and its better to replace the powerhead as a complete unit. It is possible to repair, but long term get a new one. Wiring is like for like.
Thank you for your advice. Yes it does seem that the motor is working inside the circular unit, but when assembled its not moving the valve as it should do. Can I replace the ZA5 unit safely myself by just turning the electrics off in the house and as you say, wiring like for like?
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As you said you are a novice and safe working practices are a skill to be acquired. In your case, I would advise calling a pro to do this relatively easy task and its not expensive. The wires are identical and the easiest way is to use an in line connector as this saves going into any wiring centre.
You must isolate electrics and prove isolation before attempting any work of this kind.
Check the valve body spindle moves freely as these can stick. There is approx 30 degrees of movement on the spindle from open to closed.

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