Help with understanding hot water piping runs

Discussion in 'HVAC Heating & Cooling' started by tkoontz, May 25, 2008.

  1. tkoontz

    tkoontz New Member

    Messages:
    2
    I am switching from a one pipe steam system to a two pipe hot water baseboard system. Getting estimates, but getting different opinions on how to run the lines. Going to run 3 zones where there is currently 1. One zone to den which has a wood stove (no problem here, simple supply and return to furnace); one zone to first floor (no prob here either, unfinished basement gives access to run HW loop); 2nd floor is a doozey! 90 year old house with brick/tile exterior construction (no framing). Hardwood floors on 2nd floor.

    To be a little more descriptive, the second floor is basically a 25 foot square with 4 rooms. A pipe chase runs up the rear of the house into a bedroom closet. Go to the R and you are in a bedroom, go to the L and you have access to the bathroom. There are two bedrooms on the front of the house. Joists run from front to back. Not positive if there is a clear shot through the floor from rear to front, but it may be possible. The ceilings under the rear bedroom and bath are options for opening up the ceiling, because demo work will be done in here (hadn't planned on it, but hey, sometimes when you get lemons...).

    My basic question is how a loop for a zone can be configured if you can't run one continuous loop - supply from furnace to rad to rad to rad to rad and then return to furnace (this would require either running dummies practically around the entire perimeter, yuk, or busting open floors or the ceilings below, $$$). Can there be a T in the supply? Is the solution to just run a zone to one room if it is too challenging to tie it into a loop?

    Any advice is appreciated! Tracy
  2. hj

    hj Moderator & Master Plumber Staff Member

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    27,242
    Location:
    Cave Creek, Arizona
    piping

    Trying to balance flow to several radiators is almost impossible unless you use fittings such as MonoFlo tees which divert some of the water to the radiator and then mix the return water before it flows to the next one, and so on. You cannot do it with conventional PEX, or any other, fittings, unless you use a two pipe system and engineer the pipe sizes to create the necessary pressure imbalances.
  3. tkoontz

    tkoontz New Member

    Messages:
    2
    Thanks hj - I am woefully ignorant about the specifics of how the system works, having only basic understanding of how a hot water system operates, but have been doing some research to help.

    Seems like a forced system with reverse return is the way to go, maybe, but I don't understand what the reverse return is - more research is needed. I will check my plumbing book and see what it says.

    Some information I've read says (maybe on this site!) says that monoflows are obsolete - is that true? Is there just a better similar type product out there or a totally different approach?

    What is the best way to design a system if you had no constraints (ie. new construction) Seems like even if you could run a continuous loop (if this is ideal), there would be a limit to how long it could be without the water temp cooling before it gets to the end of the line, so then how to keep those end rads hot? What is the next best thing, if you do have issues that prevent the ideal design?

    Thanks again!
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    22,313
    Location:
    New England
    If it was new construction, or had easy access, the most comfortable heat is probably radiant floor hydronic heat. No cold spots, no restrictions on where to place furniture, very even, and often comfortable at lower temperatures. Your dog and cat will love it, too.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,242
    Location:
    Cave Creek, Arizona
    heating

    In a reverse return system you gradually decrease the main's pipe size to create a pressure imbalance to force water into the radiator branches, and then pipe the return, the same way so the water has a path back to the boiler. With this system you can turn off or cap radiators without affecting the operation of the radiators further down the line.
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