Possible fault two-port valve

[MrGatch]

Hoping you guys can help confirm the diagnosis of a fault before I call a plumber.

I've lost heating to the upstairs zone on my heating sysem.

System boiler is working fine feeding two other zones and the hot water.

The zone is connected via a Nest, which is saying its calling for heat but isn't translating into anything.

The same Nest is controlling the hot water and that is fine.

I've checked the voltage from the Nest through the wiring centre and up the the two-port valve for the zone and all seems sound. The valve is powered, the switch-live energizes when the Nest calls for heat, however no activity on the valve.

If I manually open the valve then it energizes one of the cores which triggers the boiler correctly.

Am I right to assume this is a faulty two-valve or could it be something more complicated?

Its a Flomasta 8982G and has been in for 3 years.

 

[John.g]

Looks that way as long as the switched brown? wire is live, and you have checked that it is switching on/off, the other grey? wire is permanently live.

 

[MrGatch]

Would I just get away with replacing the actuator or is it a whole replacement unit and need to drain the system?

I'm confident I can replace an actuator, but might leave draining the system to a pro!

 

[John.g]

Just ensure that the Flomasta 8982G actuator is detachable, (most are, these days I think), You might then consider just removing your own one, and ensure the valve spindle moves freely, then power the (removed) actuator on/off to see that it doesn't move, then renew actuator only.

Edit: Had a quick google but didn't see a head only for sale but someone on here or any plumbers suppliers will inform if separately available.

 

[MrGatch]

Great! Thanks for that!

Checked and the actuator head does clip off easily. The head says Flomasta 8982G which seems to be a identical to the 27900SX in Screwfix for £55. Will give that a try. Fingers crossed.

 

[MrGatch]

It was the motor on the two-port valve.

Bought a new one from ScrewFix and clipped on just the actuator to the existing valve, wired it up and it works a treat again.

Thank you for the advice.