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creating a real reverse return system

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naphelge
naphelge Member Posts: 9
in Gas Heating
I will be installing modcon hydronic heating system with 7 cast iron rads supplied/returned via manifolds. I just read up on reverse return, but was wondering, if the supply/return manifolds are located in the same general area, on the same wall in the laundry room is what I was planning, then I can't really see how a reverse return could really be realized. Even if the rad fed on the first port of the supply manifold is returned on the last port of the return manifold, the overall length of the run to that rad is essentially unchanged and as I read it, the idea of the reverse return is to try and make all the runs to each of the emitters essentially the same in order to create (almost) equal flow balance in the system.

The only way I can see this happening in my situation, is either locate the return manifold close to the furthest heat emitter in the system, so that while the furthest heat emitter's supply is furthest from the supply manifold its return is closest to the return manifold, and so on down the line for all the heat emitters, thereby creating somewhat equal length in each heat emitter's total supply-return pipe length.

Or alternatively, if one wishes to keep the manifolds together in the same general vicinity, then change each heat emitter's supply and-or return pipe length, by either taking longer piping routes than necessary, or perhaps by looping coils of pipe for some runs to physically increase the lengths necessary so as to make all heat emitter's overall supply-return pipe length generally equal.

I hope I have explained myself in a way that makes sense, even if what I explained is not entirely correct.

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  • SWEI
    SWEI Member Posts: 7,356
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    Home run manifolds and reverse return are two different piping schemes. If you have more than one pair (supply/return) of manifolds then you can reverse return pipe the manifold supplies, but with a single set you will need to choose one or the other. What is the layout like? One floor or two, what kind of access underneath, etc?
  • naphelge
    naphelge Member Posts: 9
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    [quote]What is the layout like? One floor or two, what kind of access underneath, etc? [/quote]
    Two floor house, but 95% of our time is spent upstairs, so we keep the lower level considerably cooler during the winter the upstairs.

    5 of the 7 rads going in will be upstairs to maintain a desired temp of ~70 degrees, with 2 going downstairs to maintain a temp of about 60 degrees.

    Because all of the runs are quite short, nothing longer than ~36 feet, I thought it would best and easiest to keep the entire house as a single zone run off a single supply/return manifold pair.

    I was initially leaning toward a trunk/branch system because I didn't want to turn my floor joists supporting the upper level into swiss cheese. However, I have since figured out a decent way to run all my PAP along a support beam overhead downstairs, supporting the joists, that will allow me to route the PAP runs to along the joists I need without needing to drill them out, popping up through the floor/walls where the rads are located upstairs. So I have since decided to go with a manifold pair that will lend greater flexibility to the layout.

    I based the BTUH of the rads based on a heat analysis of my house breaking the requirement down for each room. To be honest the rads don't quite cover the BTUH requirements laid out in the heat analysis, but they don't fall so far short that it wont be a problem to add an additional rad if the 7 going in can't heat the house as well as we hope.

    I will use 1/2" PAP, an 80K BTUH modcon gas boiler, which although it is twice as much as what our house requires, again according to the heat analysis, modulates down to 8k BTUH, so the additional headroom the boiler provides might lend peace of mind without any need to sacrifice efficiency.

    So I guess considering my intended layout, home running to each rad, there is no need to concern myself with reverse return since it is not really an option.

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