Central heating problem

[MadAlicesDad]

Over the last few weeks, the heating has not been responding to the thermostat and with the CH off and the HW on, the radiators get hot.

I suspect it's the actuator on the CH/HW valve that's dodgy. Any thoughts? If it is that, it's a Drayton MA1 fitted about 10 years ago; are the latest actuators a direct swap?

Another thing I found strange is that the override button on the (wireless) thermostat receiver does not light the green 'CH on' LED. Could this be something to do with the problem?

Any help/suggestions greatly appreciated.

TIA
Mike

 

[sloppytom]

The heads on those valve should pull off easy and change with a new one.
Check the pin moves freely on the valve body, if it doesnt then that may be the problem. The override button only works if the receiver and thermostat have lost connection. You would see a solid red light on the receiver if no connection, in which case the override button can then be used to turn the heating on and off ( green light)

 

[Agile]

But does the thermostat light the green light to bring on the heating?

Have you replaced the batteries and repaired the TX and RX units?

Tony

 

[MadAlicesDad]

But does the thermostat light the green light to bring on the heating?

Yes, and if the HW is off, the system seems to function correctly.

Have you replaced the batteries and repaired the TX and RX units?

No. As above, the thermostat transmitter turns the receiver on/off correctly and the battery symbol isn't showing.

Later I'll try a few more things like setting the system to different settings and removing the actuator to see what position it is in.

 

[MadAlicesDad]

I took the actuator off the valve to watch if it moved when the CH was switched on. I could feel the motor running but no movement, but I noticed the actuator rattled if shaken. I took it apart and found this:

Untitled

• MadAlicesDad
• 15 May 2015
• 1

The spring (circled) is supposed to go between A and B, but the retaining lug on the casing at A had snapped off. As well as no spring, the lug was jammed in the slot at C preventing the lever (and hence the actuator) from moving fully.

I glued the lug back into place with mitre bond (better than superglue on its own) and now all seems well. A preferable solution to a new £70 actuator! If it snaps again, I'll insert a metal lug to hold it.

Regarding the override switch, thanks for the info; one less thing to worry about!

Mike

 

[Agile]

I have actually seen exactly that same failure.

But I just replaced it with a new valve based on the Honeywell design.

Tony

 

[MadAlicesDad]

But was that for yourself or a paying customer? I've saved myself around £70 for 30 mins work, but I accept that replacement is a better option for a paying customer.

 

[75pete]

That's a good bit of DIY