Basement Radiator Issues

Discussion in 'Boiler Forum' started by BrettY, Oct 28, 2009.

  1. BrettY

    BrettY New Member

    Messages:
    1
    Location:
    PA
    Hello to everyone! I have a two-pipe oil-fired hot-water boiler system in a two story house that uses radiators. The radiators on the first and second floor heat just fine, however, there are two radiators in the basement that will not heat. Each radiator comes off of the supply using a monoflow T, and returns back to the supply (not the return) using a monoflow T. Both radiators are one of the first to come off of the supply. The monoflow Ts are installed correctly. The radiators are always ice cold. The pipes from the main running horizontal over to the radiators are warm, but nothing goes down the verticle. There are bleeders right at the elbows going down to radiators. I have bled the radiators and have no air. Now once in a while when the boiler is under a heavy load, one of the radiators will get hot, the other one remains cold. However, after trying to bleed them on last time (I have a manual fill for the boiler) I must have put too much water in the system because the next morning, the pressure was up around 30+ psi, but guess what...both radiators were hot! Why will they work at the extreme pressure but not at 12-18psi? One thing is that the monoflow Ts are only separated by about 6 inches or pipe. What can I do to get flow through these radiators?
  2. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    If there is only 6" between the tees then you are probably never going to get them to heat correctly. there needs to be at least 18", preferably a lot more.
  3. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,143
    Location:
    South*East
    If it is a two pipe system then one end of the radiator should go to the supply and the other end to the return. By trying to do it with monoflow tees not only will it not work you are restricting the rest of the system. That is reason you get some heat on a long call. The water is moving to slow through the system.

    John
  4. patsfan78

    patsfan78 Web Development | HVAC

    Messages:
    33
    Location:
    Maine
    The radiators require more than just 6 inches between the tees if the flow is going down. Hot water is buoyant and needs to be piped right in order to get that water to go down. The tees should be as far apart as the radiator is wide at least.
  5. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,143
    Location:
    South*East
    According to there post it is a two pipe system the monoflow tees should not be there. A two pipe system is not a loop. There are two separate lines extending from the boiler they do not tie into each other. For each radiator there is one tee in feed and one in the return.

    John
  6. julio.caluori

    julio.caluori New Member

    Messages:
    7
    Location:
    Montreal, QC
    Also, not only are you supposed to NOT have monoflow T's on your two-pipe system, but you are supposed to have a circulator on you supply line and a BFP on your return line. But seeing you have monoflows, a circulator wouldn't be needed in this context.

    Correct me if I am wrong.
    Julio
  7. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,143
    Location:
    South*East
    Every system I have installed had the circulator on the return with the flow check on the feed. Is that what you call a BFP? The first two pipe systems had no circulators. They ran by gravity. From there it went to one pipe systems with monoflow tees.

    John
  8. julio.caluori

    julio.caluori New Member

    Messages:
    7
    Location:
    Montreal, QC
    Yes, a BFP is a "Back Flow Preventer". Yes, no pumps were installed back in the day, these systems work by thermosiphon, the hot water would raise and the cold would drop, creating movement.
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