about radiator heat

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by donk, Dec 17, 2008.

  1. donk

    donk New Member

    Messages:
    34
    Hi - I'm asking for my son who bought a circa 1940's house with radiator heat...

    He's had central air/heat installed on the top 2 floors. Now he wants to keep the radiator heat only in basement. The boiler is in basement and the system has a loop of pipe going around the ceiling. Off of this loop, each upstairs radiator has 2 small pipes going to it (I assume supply and return?).

    He wants to cut these supply/return pipes and cap them - thereby making it a closed system only in the basement. Of course then he can remove the upstairs radiators.

    Is there any obvious prob with doing this?
    Thx,
    Donk
  2. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Nope...................
  3. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Woops.. Sorry. I have been chastized previously for the brevity of some of my posts so perhaps I should elaborate. Uh....nope......
  4. NLRicker

    NLRicker New Member

    Messages:
    6
    If he'll continue to use the boiler the system will need an expansion tank. If the remaining loop includes that it seems OK to me. But my old natural convection system had a tank in the attic.
  5. donk

    donk New Member

    Messages:
    34
    Yeah, he wants to continue heating the basement with the current boiler.
    What's an expansion tank, and why would he need one? I was thinking the boiler would be "too" powerful - since it only has to heat 1 floor instead of 3 now?
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    22,180
    Location:
    New England
    Your system probably already contains an expansion tank. Except with a steam system, the pipes in a hot water heat system are normally entirely filled with water - air would cause blockages and could prevent circulation. So, when the boiler heats the water, it expands, so if you don't have an expansion tank, you could split a seam or fitting with the pressure.

    A boiler sized to heat the entire house modified to only heat a small portion could end up short cycling which makes it less efficient. Depending on the unit, it may support the use of a different jet to the burner, which would decrease its maximum output. You'd have to read the spec sheets/installation manual to see.
  7. donk

    donk New Member

    Messages:
    34
    Yeah, I think it does have an expansion tank. There's a big, cylindrical tank mounted on the ceiling, with a faucet-type valve attached to it. About the size of maybe 10 or 15 gallons.
  8. donk

    donk New Member

    Messages:
    34
    "A boiler sized to heat the entire house modified to only heat a small portion could end up short cycling which makes it less efficient. Depending on the unit, it may support the use of a different jet to the burner, which would decrease its maximum output. You'd have to read the spec sheets/installation manual to see."

    Can you tell me what you "short cycling" is? And how he will know if it is short cycling? Does that mean the boiler will run all the time?

    And also about the "different jet to the burner"... does that mean he could shut off or remove some of the gas jets that heat the water - to compensate for the reduced number of radiators?

    Thx,
    Donk
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,180
    Location:
    New England
    Any heating equipment is more efficient if it runs all of the time. Obviously, that doesn't work as the weather and load changes. But if you've got a boiler that is oversized, it only needs to run a very short time to make enough heat (the circulators may and probably should run longer). This is very inefficient and just like on a car, short runs means it may not get up to normal operating temp and you can end up with the burner and flue staying moist since it never got fully warmed up and rusting out. So, short cycling means when it does turn on, it only runs for a very short amount of time.

    Depending on how the burner is configured, it might be possible to put in a smaller jet to effectively make it operate as a smaller boiler. Depends on the design and whether parts are available. Not all systems can be modified like this and remain certified (and thus remain safe and legal). The older the system, the harder it may be to find parts. Some manufacturers offer the same exact burner, but adjust the parts to make them output more or less. The last boiler I had could be adjusted over about a 60K BTU range. the newest, highest efficiency ones can do that automatically on their own. The one I have can adjust from full output down to 20% of that - it adjusts to the load so it can run longer and become more efficient.

    A short shot of hot, followed by a longer period of cold is less comfortable than constant warm at the proper level.
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,869
    Location:
    Cave Creek, Arizona
    piping

    The system the way it works now is that some water is diverted to the upstairs radiators and then it comes back into the line on the way to the next ones. IF you just cap the lines you will reduce the flow available downstream. It would be best tp remove the unused tees, but the next best is to reconnect the two lines together to restore full flow.
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