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Can you mix a monoflo loop and a baseboard loop?

Joseph_4Joseph_4 Posts: 198Member
I have a customer who has a 3/4 or a 1 inch monoflo loop going around the entire house which is running off its own pump. There are 1/2 inch upfeed and downfeed loops using monoflo tees. I want to add a baseboard in an extension and I want to tie it on to that the same loop. If i would break in to the return supply on the 3/4 or 1inch line in the basement and run a 10ft piece of baseboard in another room that they are using as an extension, would this work? Would the water get to the baseboard properly or would it mess up the current monoflo radiators? Or is there a way that I could adjust it so that everything would work fine?


  • STEVEusaPASTEVEusaPA Posts: 3,691Member
    It could work if you are using monoflo tees. But you don't say how you intend to 'break in'.
    If you continue the main loop with the same size pipe, out to the addition, back to the main loop, and bring it back to continue the original loop. Supply and return to baseboard at least the width of the baseboard. Monoflow tee on the return if going up, on both if going down.
    Also, what make/model of circulator? You'd want to calculate if the existing is going to do the job or you need an upgrade.
    The 2 issues are flow of course, and based on the layout, is enough heat going to go all the radiation.
    If it's a big room, isolate the near boiler piping and make it it's own zone. If it's not big, could create a short cycling problem with the small load.
  • John RuhnkeJohn Ruhnke Posts: 880Member

    So the problem you are going to have is the heating style and characteristics that are different between cast iron radiators and hot water baseboard. Fin tube baseboard heats up quick and cools down quick. Cast iron takes longer to get to temperature but stays hot a very long time. When you mix the two together on the same zone the baseboard doesn't stay hot long enough to give off the proper amount of heat. The hot cast iron radiators shut off the thermostat. The solution might be to not mix different heater types. They make a cast iron baseboard. I would install cast iron baseboard because it acts the same way as the radiators do. You would need to use monoflo tees with that.
    I am the walking Deadman
    Hydronics Designer
    Hydronics is the most comfortable and energy efficient HVAC system.
  • Joseph_4Joseph_4 Posts: 198Member
    The Monoflo tees are supplying copper fin tube element type radiaitors that go in radiator cabinets.. not cast iron.. what do u think?
  • John RuhnkeJohn Ruhnke Posts: 880Member
    That should work fine. You just got to do a heatloss and figure how much is in each room and how much each room needs. If the rooms have 30% more heat per room then needed then the baseboard added needs to be 30% bigger to match. If the rooms average 20% less then the baseboard needs to be 20% less then needed.

    Also you need to add up the btu output of the whole house. You get 40,000 btus at a delta tee of 20 for 3/4 pipe. So make sure the load is less then 40,000.

    You may need to split the loop in two and increase the trunk to 1" . You cant run 1" pipe and then reduce down into the baseboard. That would limit the whole loop to 40,000 btu's.

    There is still a lot more to learn and I am not going to get you all the info you need without seeing the whole house. So you are going to have to either find some good books or do more internet research to put all the pieces together properly.
    I am the walking Deadman
    Hydronics Designer
    Hydronics is the most comfortable and energy efficient HVAC system.
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