Faulty actuators or valves?

[Kolash]

The quality label top right of your manifold suggests a date of Oct 2016, and after a quick look, found the UK website below showing an installation in 2014, which looks similar!' Would that tie up with the date of yours?

Henco don't seem to be making it any more, though their brass version looks similar.
Polypipe spares seem to claim some of their spares are compatible with Henco, and I think the Polypipe blue caps might fit:

Thank you that is brilliant! I have not been able to identify the manifold brand but yes it looks similar.

I am guessing mine was installed between 2016 and 2018 before I owned the property. The BC certificate for the extension is 2018.

The blue caps look just like the one on the spare return port so I have purchased a set and will give the quick fix a go.

One day I will have a got a removing a valve and then compare to parts available. Maybe summer time!

 

[oz-plumber]

Questioning the piping setup on that manifold?
Unless the boiler is set to 45-50C

If it's a mixing header/ manifold, I think it plumbed wrong.

 

[Kolash]

Questioning the piping setup on that manifold?
Unless the boiler is set to 45-50C

If it's a mixing header/ manifold, I think it plumbed wrong.

I don’t know. The boiler is not set that low. The system works fine all zones warm up, it’s just the x4 loops in question are always on.

 

[Basher]

I don't see there is anything different in the way it's plumbed from the Henco example setup (admittedly incomplete!) I posted.
The mixing valve is set at about 47 which seems a tad high to me, but otherwise I don't see anything wrong.

 

[Kolash]

Fitted the blue cap and keeps the valve closed. Was not in anyway difficult to tighten. Maybe there is an issue with the actuator maybe not compatible with the pin valve but doesn’t explain why the others work!