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Cast baseboard + copper fin on the same zone?

woobagooba Member Posts: 93
edited March 28 in THE MAIN WALL
Folks, a follow up to this discussion ...

Are there issues with running cast baseboard and fin tube on the same loop? I guess I am asking if they can run adequately at the same water temperature. Thank you.


  • STEVEusaPA
    STEVEusaPA Member Posts: 4,925
    If sized properly, probably.
  • bob eck
    bob eck Member Posts: 925
    does copper baseboard heat up faster than cast iron baseboard?
    I would think it does.
    Is the copper baseboard near the thermostat? If so could the thermostat be satisfied from the heat coming off the copper baseboard and the areas or rooms with cast iron baseboard be cooler than they should be.
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 15,260
    If memory serves, copper heats nine times faster than cast iron, and cools at the same ratio. That’s the problem with having the two on the same zone. 
    Retired and loving it.
  • Jamie Hall
    Jamie Hall Member Posts: 15,742
    As @STEVEusaPA says -- no reason they can't -- if they are sized properly. Any baseboard or whatever construction -- for that matter, any radiator -- will produce X BTUh of heat when fed water at a temperature of Y, and that rating is given for the radiating unit -- and is independent of the material of construction. The rating is given as the EDR -- equivalent direct radiation -- and a unit with a certain EDR will produce the same amount of heat as any other unit with the same EDR in the same setting, regardless of material.

    With that said, as @bob eck speculated, there is a real difference between cast iron, finned steel, and finned copper for baseboard, and that is related to the material. In that order, the former will heat up to temperature much more slowly than the latter -- and, correspondingly, cool down much more slowly. This doesn't affect the total heat delivered, only the rate at which the rate increases or decreases with time. This may make a difference in the perception of heat from the unit, but also makes a difference in control -- as he says, if the control thermostat is in a space with copper fin, it may be turned off sooner than might be needed for another space on the same loop which has cast iron.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Steve Minnich
    Steve Minnich Member Posts: 2,650
    I’ve yet to meet a happy homeowner where both are controlled by the same thermostat. There’s sound reasons for that mentioned above. 
    Author - Hard Knocks: My Life Inside Boiler Rooms
    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
  • JohnNY
    JohnNY Member Posts: 2,650
    It's a bad idea. The only time I've seen it work is on a system with constant circulation and a good outdoor reset system.
    Contact John "JohnNY" Cataneo, Master Plumber
    in New York
    in New Jersey
    for Consulting Work
    or take his class.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,091
    edited March 29
    Is there an easy way to have the CI and Cop/Alu on separate loops? If so then use some zone valves to separate them with their own thermostats. At first glance, they have similar output per linear foot, but the difference in warm-up and cool-down will make for difficult comfort control. My experience bears this out. Never mix types of emitters on the same thermostat. Never mix different types of construction on the same thermostat. (ie: Sun porch with lots of glass, with standard rooms with a 15% glass to wall ratio.)

    There are too many options available to live with poorly conceived designs.

    Respectfully submitted,
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 15,260
    The irony of this is that the Btuh output of copper- and cast-iron baseboard per linear foot is basically the same. It’s really about the two not being in sync. It’s a donkey trying to run with a stallion, while being reigned together. It’s never going to stay on a straight path.
    Retired and loving it.
  • GW
    GW Member Posts: 4,083
    Do it, if it drives you nutty then deal with later. But I think the world offers bigger problems than this at this point 😀
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
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