One zone failing to heat rads: controller or valve?

[Kester_holmes]

Zone 1 rads working, zone 2 doesn’t switch pump on so rads don’t operate.

Trying to work out whether it’s the motorised valve, or wall controller.

When you remove the electrical box from zone 2 valve , the metal valve operates left and right freely, and when zone 1 is pumping heat , you can use that to open zone 2 which then heats rads.

However when zone 1 controller is off, zone 2 controller won’t turn pump on.

Any suggestions how to test? Should I be able to see zone 2 motorised valve operate/move when it’s heating controller is turned on?

Big thanks

 

[Murdochcat]

Does zone 2 have its own thermostat

 

[Kester_holmes]

Neither zone had its own room thermostat, TRVs only.

I should’ve said this had all worked for 15 years, zone 1 only just stopped working.

 

[gazfen]

Manual override should fire up your boiler zone 2 head sounds knackered

 

[RandomGrinch]

What is the make of your controller, and have you tried linking it out?

 

[Kester_holmes]

Thanks for your answers/suggestions.

Manual override turns the pump on but it stops after 1 sec.

Controller is a newlec centaur plus NLC21.

I’m not sure how to link the controller out. Just disconnect it and ensure the wire to pump is connected to live?

 

[RandomGrinch]

Controller is a newlec centaur plus NLC21.

I’m not sure how to link the controller out.

If you're happy to, take a photo of the wiring of the backplate behind the centaur plus - you can link the wires out there.

As @gazfen says, it may very well be the valve head, but at least linking out the controller will rule it out.

 

[Kester_holmes]

Will do, cheers.

 

[Madrab]

Manual override should fire up your boiler zone 2 head sounds knackered

Not usually, manual override usually won't keep the microswitch closed, once it latches back

Any suggestions how to test?

I find the easiest way to test the valve is have a plug and extension. Disconnect the valves wiring and wire the zone valves blue/brown and earth to a mains plug - put a connector block on the grey and orange and power the valve, if the valve motor activates then motors ok. Turn off, bridge/connect grey to live and turn on again, once valve opens tests for 240v on the orange. If that all is ok, then look elsewhere - if the other valve is working then won't be the programmer, poss bad connection in the centre

One glaring question though, why have 2 zones without their own thermostats, pointless having separate zones then.

 

[gazfen]

Easiest way is to link out the thermostat check for 240 on brown at the valve. If 240 not at orange yer head is knackered. Mega easy repair

 

[Madrab]

Easiest way is to link out the thermostat check for 240 on brown at the valve. If 240 not at orange yer head is knackered. Mega easy repair

Neither zone had its own room thermostat

 

[gazfen]

Than what tells it to fire up. Trv heads won’t fire the boiler. Is it a smart thermostat. Get a decent heat engineer out.

 

[Kester_holmes]

Thanks for all your replies and suggestions.

The system was installed 15 years ago when house was renovated, without thermostats. The two zones are two sides of the house (ours, and our kind in-laws who let us build on!), each with own controller to call for heat (or at least for pump to be switched on).

Ive been lazy, but need to test for live on orange. I also realised that I can test by swapping the working zone valve actualtor in place of the suspect one.

Will report back in due course. Cheers

 

[Madrab]

Than what tells it to fire up.

Programmer - live straight to the the valve and SL back to call the boiler, system will rely on boiler stat to modulate, not very efficient especially these day though relatively easy to upgrade.

 

[Madrab]

need to test for live on orange

Do the whole end to end test - Test for live out of programmer and then brown into valve, then check motor is energised, then test for live on grey and when valve open, live on orange