Understanding hot water issue

[olbasoil]

My son has just bought a house with an indirect cylinder. The valve is a Myson MPE 222.


With the controller set to OFF (both heating and hot water) the valve remains lit up and the boiler is firing.

Surely this must be a fault in a system that was described by the vendor as fully working? If so is the fault likely to be in the valve, the wiring or the controller?

 

[SimonG]

One of them is faulty and providing live back to boiler. Testers out to confirm.

 

[townfanjon]

Sounds like the actuator nact , quick easy job on those .

 

[olbasoil]

Sounds like the actuator nact , quick easy job on those .

That's good to hear but I wouldn't want to replace it if the fault lies in the wiring or controller. I don't understand is how power is reaching the valve at all, if it is switched off at the controller?

 

[ShaunCorbs]

There a permanent live to the microswitch

 

[zzzjim]

..I don't understand is how power is reaching the valve at all, if it is switched off at the controller?

It's a bit like car wipers needing "Parking Power" to get back to their rest position , when you just turn them off !

System fully working ,but does it have a Magnetic filter to keep it clean ?

 

[olbasoil]

Thank you ShaunCorbs. That's a very instructive diagram. So if the valve was somehow stuck in the on position, that would make the connection between the grey/live coming from the controller and the orange supplying live to the boiler & pump.
Does the LED on the valve signify:
1) a live connection on the main motor between blue neutral & brown via thermostat
or
2) a live connection on the microswitch, which would normally be because of the above, but could also be because the microswitch has got stuck ?

The former suggests incorrect wiring or a faulty live coming from the controller. The latter suggests a faulty valve.

 

[Best]

Led light just means power is to the actuator motor I believe.

 

[ShaunCorbs]

i would say 2 but the 2 port always has power even when the controller isnt callling

 

[Gazzt]

Common fault on motorized valves. The valve stuck can keep the micro switch in contact so i would screw the actuator off and make sure the valve moves freely, you should be able to turn it with your fingers. But as said above the actuator will need replacing.