Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

primary/ secondary piping ( how to wire the primary pump)

aaron_4 Member Posts: 42
1) How long should your Primary loop be in your primary / Seconday pumping designe?

2) In John Siegenthaler book Modern Hydronic Heating 2nd Edition, he talks about sizing the Primary circulator. How do you know what the temperature drop is. He uses 15 in the example.

Thanks Aaron


  • Dan_15
    Dan_15 Member Posts: 388
    primary/ secondary piping (how to wire the primary pump)

    I'm setting up a boiler with primary/ secondary piping. 3 zones. 2 radiant and an indirect. My question is how do i wire the circ on the primary loop to run whenever any of the secondary pumps come on? I'm using a taco sr504 expandible 4 zone switching relay with priority (If i can).
  • Steve_35
    Steve_35 Member Posts: 546
    What are you using to fire the boiler?

  • Ron Schroeder
    Ron Schroeder Member Posts: 998

    I wire circulator to C1 C2 on Aquastat, then whenever the SR504 pulls in Aquastat C1 will be powered. Think you can also wire it to ZR on the SR504
  • Dan_15
    Dan_15 Member Posts: 388

    It's a biasi boiler with a riello oil burner
    Thanks fo the help,
  • Jed_2
    Jed_2 Member Posts: 781
    That's the \"Zig\"

    with Biasi boilers. You have an L4006 operating control. No C1, C2. So with many control strategy's, you need that exta 120V relay to pull in. ZR does the trick many times, but I've had to add an extra external relay on accasion.

  • Dennis
    Dennis Member Posts: 101
    Primary wiring

    The easy way is to let it run 24/7 if you are worried about heat loss from the boiler you could insulate the primary loop. You could however use circulator relays with an extra set of normally open contacts in parallel to bring on the primary, if the primary draws more current than the contacts can handle, power an isolation relay to bring on the primary. The boiler can cycle based on the high limit setting or the reset temperature.
    Just do it, right.
  • Dan_15
    Dan_15 Member Posts: 388

    Thanks for the help, If I try ZR Do i leave the jumper in?
  • Ron Schroeder
    Ron Schroeder Member Posts: 998

    If I remember right yes try page 23

  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124
    if you use an....

    HW 8148 tie the primary in of the c1/c2 on that relay every time tt is made that will go on...that simplifies a lot....kpc

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
This discussion has been closed.