we had last year a plumber in that replaced all of our radiator valves. Now that it is winter time, I started the heating and figured out that one radiator stays cold. Bleeding the radiators and checking the pressure didn't do the trick, so the last thing I can think of is that the lockshield valve is not open. Unfortunately, the type he installed is different to the one we had (I could just use a bleed-key to open it): https://drive.google.com/open?id=0B5hJCFfDddTSZU5LVU9VbktJZ3c
I guess the topmost bit (the pin) needs to be opened, but it doesn't move even when using a plier. As I do not know this type of valve (why is it even threaded?), would someone please confirm if the pin should (easily) move?
Hello That looks like a normal lock shield valve ,minus its plastic cap. The threads are for a screw to hold the cap on. I use a 6 mm spanner to open the valve, or a small adjustable wrench. If it is tight squirt a bit of WD 40 down the valve and wait a bit. Frees off stubborn TRVs in the past for me.