i have a steam heating system in my home. when the heat is on only 2 out of the 5 radiators get hot. need fix?

what is the problem and how can i fix it.

thank in advance for any help

6 Answers

  • Anonymous
    1 decade ago
    Favorite Answer

    You probably don't have steam heat- you have hot water heat. It's easy to check which one by looking at the radiators. If the radiators have two pipes (supply and return) it's hot water heat. Hot water heat is much more common in homes.

    Why the problem? You've got air in the water lines. With a hot water heating system the boiler heats water and an electric pump sends it up to the radiators. The water travels through the radiators to heat them up and then back to the boiler to be heated again.

    When the system gets too hot water is drained off the boiler to keep the water pressure from getting too high. When the system cools back down an electric valve is supposed to open and let more water back in so the system doesn't develop air pockets. I would guess this valve is the heart of your problem. If it's not working and the water level in the boiler drops the system will start pumping air to the radiators instead of water (I would bet that the radiators that don't work are the ones farthest from the boiler) and the radiators won't heat up.

    Here is how to get the air out of the system but DON'T try this yourself the first time because you could over pressurize the boiler!! Call a heating and air contractor and schedule a service call- they should look at the electric valve to make sure it's working and ask the service tech to show you how to bleed the air out of the system.

    1.) Open the manual valve to let more water into the boiler- I can't tell you how much water to let in... that's why you don't want to do this yourself the first time!

    2.) Turn the heat on and when the 2 radiators get hot go to the radiator closest to the boiler (even if it's one that works) and open the bleed valve. You will need a little key-like wrench with a square opening that you insert into the bleed valve to open it. On the bleed valve you will see a little nozzle that should be facing the floor. Hold a cup under this when you open the valve. When the valve is open you will hear a rush of air hiss out- this is the air that causing the problem. Keep it open until the air stops and water is flowing out of the valve without any spits of air. CAREFUL HERE- THE WATER THAT COMES OUT IS GOING TO BE HOT!!

    3.) Check the pressure on the boiler- you may have to add more water before moving on because you let some out when you bled the first radiator. If you let the level drop you'll just bring in more air and recreate the problem. Add more water with the manual valve (again, this is why you want a pro with the first time!) to get the pressure back up and then repeat the process at the next radiator.

    That's it- once you've done all the radiators the air is out and they will all heat up again. Keep in mind though that if the electric valve is bad the problem will come back. Some water will evaporate off in the summer as well so it's a good idea to bleed the system every fall before using your heat.

    I hope this helps but you really don't want to overheat the system- there is an emergency blow valve on the boiler that will go if you overheat to keep the boiler from bursting. If you are standing next to it when that happen you're going to get hosed with scalding hot water! Schedule a service call and have a professional walk you through this the first time.

    P.S.- If I'm wrong about your system don't hold it against me! I'm not a heating and air contractor but I lived in a house that had this system for five years and had exactly the same problem- I became an expert at bleeding radiators!


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  • 1 decade ago

    In a low pressure steam system, that is working at the boiler and some of the radiators, the problem usually is the steam traps. This permits the air to escape when the system comes on, and then shuts off when the steam gets to that point. The steam traps should be rebuilt or replaced every 5 years to prevent failure

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  • If you have steam the air must get out for the steam to get in check the vents on the radiators that are not working some have an adjustment they may be closed,some are fixed,if not working,shut off boiler and replace after steam pressure goes to zero.

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  • Anonymous
    4 years ago

    What 'me' said, plus, try to find the order of the rads by following the pipes from the boiler and do the first rad closest to the boiler first. Do the rest of them in order.

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    Lv 4
    1 decade ago

    TRY BLEEDING EACH RADIATOR. you can find out how by checking on the net under heating and plumbing repairs

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  • Enigma
    Lv 6
    1 decade ago

    they prb need to be flushed out

    google flushing a home radiator

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