How do radiators work?

October 5, 2005 7:35 AM

How do radiators heat my apartment?

I've always assumed that heated water went in one side and out the other. I've just moved into an apartment with exposed radiators on the ceiling, and there's only one pipe going in, so that theory's out.

For some of the radiators, when I turn them on, air starts hissing out of what I thought was a safety valve. Others remain silent. Which one of these means it's broken?

posted by RobotHero to home & garden (7 comments total)

Maybe the out pipe is concealed by the radiator itself?

Radiators should not hiss or leak.
posted by Pollomacho at 7:38 AM on October 5, 2005

You most likely have steam radiators. With 1-pipe steam radiators steam goes in the pipe, condenses as it loses heat, and goes back out the same pipe as water. (The hissing means that it is steam for sure).

Regarding the hissing, Heating Help has an answer (and a lot of useful info in general).
posted by true at 7:41 AM on October 5, 2005

Old steam radiators can hiss. As I understand them, steam goes up the pipe into the radiator, condenses, and then flows back out the single pipe. The hissing is from a pressure regulator.
posted by stoney at 7:41 AM on October 5, 2005

I stand corrected!
posted by Pollomacho at 7:53 AM on October 5, 2005

The pressure regulator, if correctly maintained, should hiss only briefly and periodically. If it's hissing continuously you should clean it (screw it off and leave it in a bowl of vinegar overnight) or replace it.
posted by nicwolff at 8:42 AM on October 5, 2005

Also, with these one-pipe steam radiators, I believe you are supposed to either fully open or fully close the valve. Apparently if you try to moderate the heat by partially opening the valve, you'll just get into trouble.
posted by TheOnlyCoolTim at 12:13 PM on October 5, 2005

I call you lucky: I miss radiators. Forced-air heat gives me allergies and headaches even with new furnace filters and small filters covering the output vents in my room.
posted by davy at 2:18 PM on October 5, 2005