Why don't the radiators in my apartment stay hot?
January 18, 2006 9:29 AM   Subscribe

Why don't the radiators in my apartment stay hot?

I have a two bedroom apartment with 5 radiators. One in each bedroom, one in the livingroom/diningroom, and one in the bathroom. Two of the radiators are broken. The two broken radiators are in the living room and in the bedroom directly behind the living room.

The problem is that the radiators will get hot but by morning they will be cold again. I've had maintenance up in apartment four or five times. And every time they adjust the boiler, bleed the radiators, and/or increase the pressure and the radiators start working again. But by the next morning they are cold again. Anyone have any idea what's going on?
posted by nooneyouknow to Home & Garden (8 answers total)
Radiators don't *stay* hot. They cycle. There are two settings on your thermostat: temperature (which you set) and offset (which is inside the thermostat). Say your thermostat is set at 70 and the offset is 5 (likely less, but...). The radiators will heat the place up to 75, then stay off until the place is back down to 65.

F'rinstance, here in St. Louis, the outside temp is around freezing. My house is drafty, but the radiators, best I can tell, haven't been on in about three hours.
posted by notsnot at 9:35 AM on January 18, 2006 [1 favorite]

Exactly what notsnot said. Radiators are hot when the heat "comes up" and then they slowly cool off.
posted by jdl at 10:21 AM on January 18, 2006

Response by poster: Okay. I guess I should've said these two radiators don't cycle back on. They get hot, go cool, and stay cool unlike the other three in my apartment which get hot, go cool, then get hot again.
posted by nooneyouknow at 11:26 AM on January 18, 2006

If you're at the end of a run a system can often fail like this sue toi the accumulation of air in the system. We have the same problem in our top floor apartment in Paris. All I can say is bleed, bleed, bleed. (You might want to talk to maintenance/landlord about automatic air release valves for the radiators/system.)
posted by Dick Paris at 11:52 AM on January 18, 2006

sue=due; toi=to!
posted by Dick Paris at 11:52 AM on January 18, 2006

Is this a one-pipe (steam) or two pipe (hot water) system? If steam, you might want to make sure that the radiators slant slightly downward, back toward the inlet, so the condensed steam (hot water) can flow back to the boiler.
posted by notsnot at 2:11 PM on January 18, 2006

Is this a hot water system? Since you said they were bleeding the radiators I am guessing it is. You could be getting air in the system. It usually does not get better until air is removed by bleeding. It starts with the top of the radiator not getting hot as it is filled with air and over time that part of the radiator that fails to heat grows with the increasing amount of air. If they can't sort out how the air is getting in perhaps they could get you automatic bleeder valves which allow air, but not water, to escape.
posted by caddis at 6:59 PM on January 18, 2006

Part of this follows previous advice posted here, but I'll try to add new stuff too. Were you around when they did the radiator bleeding? If you were, and you heard a lot of air hissing out of the valve for more than a couple of seconds, then you are getting excess air. Air in the lines is a situation which definitely affects the heating capability of radiators. That shouldn't keep happening frequently like you describe, but if you're sharing a boiler with several apartments and the problem radiators are at the high point or end of line, then you will get the worst of it. I guess an old boiler without an automatic bleeder setup that has ongoing leakage so it keeps taking in new water from an outside line might act like you describe. Outside water always has some air in it, and it usually travels to a high point or the end of the line.

If you weren't around during the bleeding, do you hear gurgling from the radiators? That's another indication of air in the line. In my house, when I hear gurgling, I know it is time to bleed the radiators. You may have to drain a quart or more of hot water before you hit the air pocket, then it will hiss for a while as the air comes out. Do you know how to bleed a radiator? It's pretty simple if you have the right key for it, which you can get at most hardware stores. My newer radiators are slotted so you could also use a small screwdriver for that type.

If you don't think air is a problem (e.g. you tried bleeding and it didn't help), then there is a good chance you have sludge gumming up your radiator lines and blocking the hot water flow. That's something your landlord will have to handle, since they have to flush the radiator lines to get the crap out of there. Not a real big deal, but you have to convince them its necessary. If it is an excess air problem, perhaps you can convince the landlord to install an automatic bleeder at the boiler, but it's a not-cheap plumber install and not something they'll likely volunteer to do out of the goodness of their heart.
posted by mdevore at 1:41 PM on January 19, 2006

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