Heat Miser

October 14, 2009 7:43 AM

Our house (with a recently replaced boiler) doesn't get heat in every room. I thought I had figured out the cause, but I was wrong.

We have a gas steam boiler installed about two years ago, and we live in Salem, Massachusetts.

The second floor of our house has four rooms: the office, the master bedroom, the bathroom, and the nursery. Each of these rooms has a radiator, and when each radiator is fully open and the heat is on, the radiators in the master bedroom and the office get warm while the other two rooms don't seem to have anything.

I think I had previously gotten heat in the other two rooms by closing the valve on the radiator in the office, making the office colder. However, when I did this last night, the radiator nursery still never got warm.

Is this a problem I could fix on my own? How could I investigate further? If not, is it expensive? If you're in the area, is there an HVAC person you could recommend?

posted by mkb to home & garden (11 answers total)

Do you need to bleed air from your radiators perhaps?
posted by wrok at 7:51 AM on October 14, 2009 [2 favorites]

I'm not familiar with gas steam boilers, but when I've come across these symptoms it has always been due to an air bubble preventing the heat transfer.

Can you bleed your radiators? On all the radiators I've seen (in the UK) there is a small bleed valve at the top and on the side that is either a knurled twisty thing you can operate by hand or a different type you need to buy an inexpensive key to turn. Just keep a wadded rag around the valve as you bleed it because it will spurt dirty water all over the place once you've got the air out.

Forgive me if I'm doing the grandmother/egg sucking thing but as you didn't mention bleeding the radiators, I thought it was worth mentioning.
posted by littleredspiders at 7:53 AM on October 14, 2009

Steam heat is tricky, but the most likely cause of uneven distribution is a clogged or poorly sized air vent.

Also, steam radiators aren't designed so that you can regulate the temperature with the valve. It should be either all the way open, or all the way closed. Pipe insulation can help, if your steam is condensing in the pipe, rather than in the radiator.

Unfortunately, the best way to solve your problem is with a HVAC professional with a lot of experience with steam heat. It's really a non-ideal way of heating a house (as opposed to hot water) because of the sensitivity of the system and the built-in inefficiency that comes with changing water from a liquid to a gas.
posted by electroboy at 7:55 AM on October 14, 2009

Oh, one more thing, if your radiators aren't sloped slightly towards the incoming pipe, you can get condensate in the radiator, which can make your system run inefficiently.
posted by electroboy at 7:56 AM on October 14, 2009

Since you say fully open I am assuming you have a two pipe radiator system. The valve that you open is on the inlet side which lets the steam in. Obviously this must be open to get heat. However, for the steam to fill the radiator you have to get the air out. There is a trap on the opposite side of the radiator near the floor. This trap works to let the air out and to drain condensate back to the boiler. Sometimes these get clogged. Also, bang on the radiator and make sure that it is not water logged near the bottom. Standing water will prevent the air from getting out via the trap. If the trap is functioning properly and the radiator is not water logged then you may have a clog in the pipe somewhere, most often on the return side, in which case it may be time to call a plumber.

Someone mentioned bleeding the air out by hand; that only applies to hot water systems.
posted by caddis at 9:22 AM on October 14, 2009

Here, I found a little primer on steam heating systems that may help you track down your particular problem.
posted by caddis at 9:35 AM on October 14, 2009

Following on caddis's post, it's important to know whether you have single or double pipe steam.
posted by electroboy at 10:36 AM on October 14, 2009

Just in case you do have a one pipe system here are some basics. There is one largish pipe which connects to the radiator. There is usually a valve but it is not for throttling only for turning the radiator on or off. There is also an automatic air vent, typically at the opposite end of the radiator from the inlet/outlet pipe and near but not at the top. This stays open and lets out the air until it gets hot from the steam and then it closes. If this valve is not functioning properly then the air will not leave the radiator when the steam comes up and the steam will not be able to flow into the radiator because of the air. A little steam will come up, but not enough to warm much of anything. If this is the type of system you have then check that vent and make sure it is operating (as per electroboy's comments). There can be blockages in the steam piping especially if the house has settled and the pipe is no longer sloped properly and allows condensate to accumulate and block the steam, but the most common problem is the vent. New ones are cheap.

There is another kind of system which is pretty rare, and I don't think they were ever installed in homes. These systems were like the one pipe system with an air vent but had a second smaller pipe without a trap for condensate return. These were for large buildings I think where they would sometimes get water hammer in one pipe systems from large amounts of condensate draining down the steam line.
posted by caddis at 11:57 AM on October 14, 2009

You are sure it's steam? Not trying to be a snot but it's not very common in residential applications: if you do, on each radiator there should be a valve, it'll look like a bullet or maybe a tiny silver drum, ( Hoffmann are a pretty all-over brand) and when the heat goes on and steam starts running around, they should whistle (very very softly) and then stop when the steam reaches them. If they are not opening (and thus 'whistling) pressure will prevent steam from getting to the radiator. Steam vents are cheap and easy to replace - a little teflon on the threads and a less-than ham-handed turn of the wrench.

If, on the other hand you have hydronic (aka hot water circulating) you could be faced with an undersized circulation pump (often packaged with the boiler and not designed for any installation that is far from a split-level rancher) or wonky piping from radiator to radiator. Hot water radiators also need to be vented but really they should only need it once. If you need to do that more than once a season you have a leak somewhere. Replacing these vents means shutting down the water inlet on the boiler and... best left to professionals.

That you are able to 'push' heat around by closing valves suggests the heating system is under-sized. Which you can't fix, but you can hold the installer accountable for.
posted by From Bklyn at 12:08 PM on October 14, 2009

Some more info on balancing one pipe steam systems. Browse around their website; They have a lot more info on steam systems than you'll get here.

Not trying to be a snot but it's not very common in residential applications

Depends on how old your house is. They're pretty typical in my neighborhood, but most of the houses here are from the 1920s and 30s.
posted by electroboy at 12:50 PM on October 14, 2009

If you are really heating with steam electroboy's link is the thing. I got out of steam before Dan Holohan put out his book, but I cannot emphasize how dearly I would have liked to have had it. Steam is a very beautiful and powerful thing and "The Deadmen" (the men who installed so many myriad steam systems from the 10's through the 70's and 80's) had more knowledge and understanding of how it works and how to apply it's strength precisely than was every written down. Dan Holohan has resurrected much of what was lost. I want to say that he used to give tours of different steam systems around Manhattan but that could be apocryphal.... anyway, thanks electroboy for the reminder and I heartily second the whole site.
posted by From Bklyn at 1:11 PM on October 14, 2009