I have 3 big radiators in my 1902 house, UNDER the first floor, connected via duct work to a another register in the floor. When the radiator heats up, it draws air from the other register, through the duct work, due to convection and voila - air flow over radiator and up into the first floor..
These radiators are big, and appear to have a supply line and a return line for condensant that drops down right into a wet return line. They each have 1/2", 3/4" air vents (not1/8).
I mistakenly put Main air vents on these rads and they did NOT work properly (spitting, opening and closing randomly).
Any idea what air vents I should use on these bad boys?
Do they sound like true two-pipe rads or something else? I don't see any traps on them (but the rads are mostly hidden in their ductwork enclosures, so can't see everything going on without disassembling some of the box casing the rad).
Anyone have any knowledge of systems like this? THX!