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Myson T6 Radiator Won't Heat Up after Bleeding
I installed a Myson T6 radiator using the center supply/return valves. It is installed on a loop. The loop has one other radiator on it (an old cast iron).
I bled both radiators until water came out the air valves. The system is filled and pressured to the max (15 PSI). All the other radiators in the house heat up without issue.
However, the two radiators on this loop won't heat up at all under normal operation. They DO heat up if I open one of the air valves and let it bleed water into a bucket for several minutes; then, hot water will eventually start to come out of the air valve and the radiator will heat up. But if I close the valves and just let the boiler run for a while, there is no heat on this loop. The pipes feeding the supply and return don't even get warm, so it seems that no hot water is entering the loop at all. (Yes, the valves that control the supply and return lines to this loop are fully open.)
This loop used to have just one radiator on it (the old cast iron) and that did heat up without issue. So I know the supply and return pipes work.
I'm at a loss as to what could be wrong. Any ideas?
I am a little confused by the Myson's built-in thermostat valve and am wondering if that is where I am screwing up. It's a green piece that came preinstalled on the righthand top side of the radiator (when you are facing it) that has the letter N on it, along with several numbers. I gather that this should control how much water enters or leaves the radiator, although I am confused by how one sets it (the comic book installation instructions that came with the radiator don't make it very clear). I have tried moving it to various positions and it doesn't make a difference, however.