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So i have a boiler with 3 zones. 2 to my apartment, 1 to the upstairs tenant apartment. All heaters in the house are cast-iron radiators. The zones in my apartment are all ran 3/4" pex while upstairs is 1/2" due to adapting with what is in the walls. The zones on my floor run and heat normal. When upstairs calls for heat it takes the boiler at least 4 start and stops to achieve the set temp. Is the 1/2" pipe restricting the flow? Or is the run too long?


  • Jamie Hall
    Jamie Hall Member Posts: 22,073
    What is in the walls? I think your first thought is probably correct, that the small pipe is restricting the flow too much (it has 4 times the resistance, or very roughly a quarter of the flow, of the three quarter). Bigger pump or change pipe size...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Seanmckiernan76
    Seanmckiernan76 Member Posts: 2
    What if i split the upstairs loop into 2 zones? Each zone will only have 2 radiators