One Cast Iron Radiator Not Working (Tried everything)

ThisOldFurnace

Hi All,



I am extremely new to the oil-fired hot water boiler world. Just recently, I ran into alot of trouble with the hot water boiler. I had to fix a leaking water coil (domestic hot water also heated via this furnace), I had to replace the recirculation pump, then I found out the Pressure Reducing valve was shot and not letting any water in the system. Needless to say this had to be replaced as well. (All of this completed by myself, a friend and Google) Now that i'm done with the history of my last 2 weeks, here is the problem:



After the above mentioned repairs, the furnace and now heating the home as it was 5 months ago when I moved in. In essence, back to "normal". However, I have always had one radiator in my hallway that does not work AT ALL. Its a "2-pipe" radiator, if I continuously bleed this radiator, I can get one of the two pipes on the radiator "hot" but the radiator does not heat up at all, and that once hot pipe will be cold again minutes after bleeding the radiator. The other 4 radiators get so hot you can not hold your hand on them. I'm going to list some items about the furnace and what I have tried below, please bare in mind that I do not know much about this system except what I learned in the last 2 weeks:



-This system is a "Crane" branded hot-water boiler

-The system has ONE cirulator pump (GRUNDFOS) and is not "Zoned"

-System Pressure is around 12-15 PSI

-5 radiators on the system (4 first level, one second level, most of the upstairs is electric heat)

-System has an old-style ceiling mounted expansion tank mounted near the boiler in the basement between the 1st floor joists. (Seems to be correctly presureized as well

-System was recently completely drained empty due the previous house owners thinking it was not nessessary to install a shut-off valve to prevent the rediators from draining in the event I need to replace the recirc pump.

-System has since been refilled and bled (extremely long process) and is heating the way it was before all these issues had occured. again, back to "Normal".

-If I contiually bleed the non-working radiator in the hall, one of the two pipes connecting to it will heat up but the radiator never gets hot. The other pipe connected to it remains cold at all times.

-Radiator has lots of water and I have bled the air out of all the other radiators over the past few days. I not get no more air when bleeding.

-The radiators do not have any temperature controled valves. (i.e. Boiler heats up, recirc turns on, ALL radiators heat up , with the exception of the one in the hall)



Do you guys have any idea on what may be wrong with this radiator? Sorry for the long-winded first-post but the above is absolutly everything I know about this system. Thanks in advance for any information.

Ironman

Believe it or Not...

It's probably still air bound. You may only be bleeding air from one side of the system. There are too many variables to list without seeing the system. Can you you post some pics of the boiler, near boiler piping and piping at and near the rad?

Paul48

Pipe

And the only pipe that gets hot when bleeding is the one without the valve? I'm assuming it has a regular radiator valve on it?

Paul Pollets

Pump Location

I'll bet you have the circulator pump on the return header of the boiler pumping towards to the expansion tank. If the pump is on the supply header pushing away from the expansion tank, you'll have no air in the system after the first purge. Are you familiar with "Pumping Away"? Read it if you haven't.

You should also consider replacing the expansion tank with a pre-charged tank and make sure the piping conforms with "Pumping Away" !