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baseboard on monoflo system

lisfjoelisfjoe Member Posts: 13
I have a customer with no heat from a 3 ft piece of baseboard where there was once a convector on a monoflo system. Is the cause of no heat due to the excessive pressure drop of the baseboard?

How could I correct this situation?


  • was the

    Was the baseboard installed without vent???
  • lisfjoelisfjoe Member Posts: 13
    it has a vent

    but i get no air, but can't tell if vent is on supply or return side, though it really shouldn't matter when the circ is off, right?
  • JStarJStar Member Posts: 2,668
    edited December 2013

    How far apart are the venturi tees? What size, and how much piping to the baseboard?
    - Joe Starosielec
    [email protected]
  • lisfjoelisfjoe Member Posts: 13
    3 feet apart

    each run is about 3 feet long of 1/2 inch tube.
  • Paul48Paul48 Member Posts: 4,256
    No Flow?

    Did you verify no flow? Three feet of  baseboard vs. a convector is "no heat".
  • billtwocasebilltwocase Member Posts: 2,385

    You either need to bleed the baseboard, or open a closed valve. You should be able to determine if the bleeder is on the supply or return. If it is on the supply, with the circ off, lift up the bleeder end of the baseboard while bleeding it. Air rises
  • Steamfitter66Steamfitter66 Member Posts: 117
    edited December 2013
    Is the baseboard warm?

    If so you have flow. Whats the heat loss of the room?

    Whats the heat output of the baseboard at your systems water temp?

    Those 2 things will answer your question.
  • lisfjoelisfjoe Member Posts: 13
    re:no flow

    how can I verify no flow? Except that the supply and returns don't get hot, which I assume that verifies no flow which really was my original question. Why no flow? Is it because of the pressure drop or air?

    Also, 3 feet of BB = 1500 btus. Maybe not enough for the room but pipes are not hot.
  • Paul48Paul48 Member Posts: 4,256

    Wasn't sure if you had put hands on the system,, or were just wondering about a "no heat" complaint. Like removing a cast iron radiator and replacing it with a section of BB, I could see a homeowner complaining of no heat.
  • lisfjoelisfjoe Member Posts: 13
    thanks guys but

    still no answer to my question but does 3/4 tube have that much more pressure drop than a convector to cause no flow? I am now thinking it shouldn't have and my problem is probably air. Any comments?.
  • WeezboWeezbo Member Posts: 6,232

    rjb mentioned ,you probably need to get rid of the air and give it another go ...

    heat should arrive at the emitter when you get that happening .

    it may not produce much heat even at that due to it being possibly less of a heat emitter than the pipes transmitting the heat to the emitter , the overall scheme of things within the building envelope.

  • Steamfitter66Steamfitter66 Member Posts: 117
    I have worked on quite a few monoflow systems

    most of them installed in the 60s and 70s. most single stories had no coin vents and pumped on the return yet would work the air out of the system after a good initial purge.

    Are you sure the T are installed properly....
  • JasonJason Member Posts: 294

    You probably have an air lock. I bet one of the pipes does not run uphill all the time. Add a purge valve.

    See,click on general hydronic sand than scroll down to monoflo bleeding.
  • SWEISWEI Member Posts: 7,356
    It also helps

    to lower the surface tension of the water.  Most hydronic conditioners and cleaners contain a bit of surfactant along with their inhibitors, but if all else fails you can add a bit of clear dish detergent (Dawn, Joy, etc.)
  • lisfjoelisfjoe Member Posts: 13
    thanks for all your suggestions

    I will let you know the outcome.
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