I've got a historically under-heating radiator in a converted porch room. It is quite obvious to me that this radiator was added significantly after the house was built (1929).
The radiator in question is supplied off one of two main branches, which then exits the basement through the foundation wall into the garage and has about 25 feet of minimally insulated horizontal-ish pipe until it comes out into the converted porch space.
Additionally, the radiator is connected to the supply and return at the top and bottom of the same side with an inlet valve and no trap whatsoever. This seems to me like it would "short circuit" the majority of the radiator.
When I bought the house 1.5 years ago, the radiator had an air vent on the far end. After some research about vapor-vacuum systems, I replaced this with a pipe plug, but this doesn't seem to have changed anything.
While investigating this, I've run the system with the air vent off. Result: lots of gurgling and minimal steam until quite some time into the heating cycle.
I've also run it with the radiator disconnected to see what was happening with the supply line. Result was minimal steam bubbling up through quite a bit of condensate in the supply line. Video of this experimenting : https://youtube.com/watch?v=GPsZoQJfGic
After 15 minutes of doing this, the supply eventually yielded a strong steady supply of steam (at which point I had the valve back on) but still didn't heat the radiator appreciably.
Quick summary of the rest of the system:
The rest of the radiators are very uniform in style, thin tube with graduated inlet regulating valves at the top, and hoffman thermostatic traps at the bottom of the opposite end. The boiler is a newer Weil Mclain. The steam mains drop into wet returns, and there is a parallel dry return dropping into the wet return at the same point. There is a crossover thermostatic trap at the end of the steam main into the dry return (similar to what is on each radiator). Near the boiler end, there is a hoffman differential loop between the steam main and dry return, with the appropriate overflow into the wet return and a Hoffman #15 vacuum vent at the highest end of the dry return.
What can I do to increase the heat output of this radiator?
My semi-informed guesswork:
1) replumb the return side to the opposite end of the radiator to force the entire radiator to fill.
2) correct the slope and/or insulate the horizontal run out to this radiator (which way?)
3) somehow add a trap or a drip to the supply side to remove the condensate and deliver steam faster
Thanks in advance!