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I ** think it is a Danfoss RAS C2 via google images
Anyway even at off/lowest setting the rad is still boiling. With trv head off pin moves easily when pushed down (then springs back up)
With the old trvs I fixed this by adjusting a screw inside the trv so that the screw was a bit lower inside the trv so it pushed the pushed the pin in more for a given trv 'value'
I can't see how to do this on the Danfoss - is it adjustable, or do I need a new trv head or is it even more complicated
Ta
I'm not a plumber but if the pin is not seized then I'd just be assuming that the trv thermostat head or sensor is knackt.
I guess you could buy a like for like replacement and in the first place just try replacing the head, if that doesn't work then you'll have to replace the bottom bit unfortunately
Are you sure the TRV body hasn't come unscrewed from the valve, meaning that it's not completely closing the valve? It's quite a fine thing as the wax inside doesn't expand very much to push the pin.
I think so - appeared to be screwed on properly (but only hand tight as I took it off by hand) and the replaced as tight as I could (*one hand not going mental)
I've got Honeywell HR92 heads on Drayton RT212 bodies and hand tight for the securing ring is fine IMO
Try the head from a working radiator and see if that helps. If it does it's the head, if it doesn't the piston in the valve body might be seized even though the operating pin moves freely. You could try tapping the body to see if that frees it up but you'll probably need a new valve. I'd wait for the current cold snap to pass before doing anything though!
Try putting a copper penny or some other metal disc between the valve and the pin?