Do I have an air locked radiator?

scott2033

I have a 100 year old, small one story carriage house with a hot water circulation system that was converted from a gravity fed system.

The main supply line runs from the basement to a high point in the attic that utilizes an air vent at the high point (top) of the supply line. From that point the supply line is piped with a drop down the center of the length of the house. Supply lines then branch off (with a drop) to each of the five radiators.

My problem is with the radiator that is fed from the 2nd to the last branch off the main supply line. That radiator stays cold, as does the supply line that comes out of the wall to feed the radiator. All the other radiators function as expected.

Oh, and this is probably important. None of the radiators have any type of air bleed valves. I'm assuming this was due to the original gravity fed piping design and the "main" air vent at the high point of the system.

The system was completely drained last year so that I could do some work on the boiler (the circulator was bad, and I also replaced the autofill valve and pressure relief valve). I filled the system slowly and was up in the attic and opened the air vent up until I started getting water just to make sure I got all of the air out of the system.

Is adding an air bleeder to the cold radiator a possible solution? If so, are there common parts to replace the plug on the high side of the radiator opposite of the supply line with a plug w/air bleed valve available for this purpose? Or am I totally missing something and am totally off on my assessment of this being an air locked radiator?

I appreciate any feedback and advice on getting this cold radiator working!

EBEBRATT-Ed

It's always possible that it could be air locked. You can drain the system and install a bleeder. If their is no tapping you can dril and tap 1/8" IPS and put a bleeder in. Then fill the system and try it.

If you get air it's an air problem, if you only get water it's a flow problem

Big Ed_4

Sounds like a down feed mono flow system , they were installed in slab homes back in the early 50's . The proper circulator is very important to make it work . What circulator did you have before you tried to fix it with what ?