I have a downstairs rad that has a 23 year old TRV and it's barely heating up. I bled it, and removed the TRV head and it still just gets a bit warm. It seems to be warm over all the rad, not just at the bottom. The rest of the system heats up fine with the other rads getting hot. It's sealed system with one of those tank thingies that you have to pressurise - pressure is set to 1 bar. I'm guessing it's sludged up, but maybe it could be the TRV valve, or something else. What's the protocol for figuring it out, before calling a professional?
