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Hot water system piping

Dave8699Dave8699 Member Posts: 31
So i have customer that would like to convert his 1 zone system to a 2 zone. The system has 14 cast iron radiators 7 on each floor with the feed and return going into the basement. My tought was running two 1" pex lines feeds and two 1" pex returns with tees to each radiator. My question is will the system work correctly and be balanced or will the first radiator on the main line be hotter then the last rad on the main line. I will attach a diagram of what I was thinking.


  • John RuhnkeJohn Ruhnke Member Posts: 880
    It might be cheaper to put in some thermostatic radiator valves on each radiator. Then you can leave the piping alone and every radiator becomes its own zone.
    I am the walking Deadman
    Hydronics Designer
    Hydronics is the most comfortable and energy efficient HVAC system.
  • Danny ScullyDanny Scully Member Posts: 1,219
    edited September 5
    Those thermostatic radiator valves, however, will not start and/or stop the boiler. This isn’t to say it’s a bad approach, but does it offer the result you desire? If you were to re-pipe it, I would suggest 2-pipe reverse return. This would address the potential balance issues you’re concerned with.
  • Dave8699Dave8699 Member Posts: 31
    I thought about the TRV but like Danny said, but I would not be able to turn on 1st floor from the 2 zone. So that would not be an option.

    Danny what do you mean by 2-pipe reverse return. I was thinking of running two 1 " feeds and two 1" returns 7 rads each.
  • Danny ScullyDanny Scully Member Posts: 1,219
    Look up 2-pipe reverse return piping schematic. Essentially, the first radiator to be supplied with water is the last radiator to return water to the boiler.
  • Dave8699Dave8699 Member Posts: 31
    ok so thats the technical term so the schematic I posted is a 2- reverse return.
  • Danny ScullyDanny Scully Member Posts: 1,219
    Yes, I apologize.
  • Dave8699Dave8699 Member Posts: 31
    No worries I appreciate the conformation, on another note I'm assuming that you use regular tees not monoflow tees?

    Also will 1" uponor hepex be big enough for the feed and return for 7 Rads which are all different pipe sizes 3/4 and 1".

    my plan is to have Two 1" feeds and two 1" returns back to the boiler with a 11/4" feed and return with a Alpha 2 pump .
  • Danny ScullyDanny Scully Member Posts: 1,219
    What is the BTU load of the radiators?
  • Jamie HallJamie Hall Member Posts: 11,442
    Yes regular Ts
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Dave8699Dave8699 Member Posts: 31
    Thanks to everyone who helped out, next visit ill measure rads and come up with a EDR and ill post them.
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