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Circulator pump zone control wiring

Raymo Member Posts: 7
Hi everyone. I'm in processing to change out my federal gas boiler 150k BTU input with well McClain cga-4 series 3 input 100k btu DOE=85k IBR=73k BTU for 3 story of 860 sq feet each semi detach house in Queens new York using pumps for zoning of 2.

My question 1, this replacement boiler will be big enough for this house?
Question 2. how I connect pump wires to the boiler? I'm using taco relay switch 504 , I understand both pump wire go to that box according to taco wiring diagram. Is that also means no wire going to main pump connectors on boiler control side? How can set pump to run ONLY boiler temperature reached low limit settings? Is have to wire differently? How?


  • Jamie Hall
    Jamie Hall Member Posts: 16,063
    On will the boiler be big enough -- if you haven't done a heat loss calculation on the structure it is quite impossible to say. It may be. It may be much too big. It may be too small. You -- and we -- have absolutely no way of knowing.

    On controls. In general, the thermostats will control the zone valves or pumps. They in turn -- either directly or through the Taco -- will control the boiler either directly or indirectly with the boiler having its own controls, such as an aquastat. Each application tends to be somewhat different, although there are some general principles.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Raymo
    Raymo Member Posts: 7
    Thanks for the reply.. boiler manufactory try to boost the boiler efficiency # by doing control pump run time. With the single zone will be no issues. If you add multiple zone with additional relay or switch to it , you have to run wire differently to meet manufactory question is how to do it?
  • Jamie Hall
    Jamie Hall Member Posts: 16,063
    This should be piped primary/secondary. The boiler will fire to maintain the temperature in the primary loop -- that's an aquastat or, if the WM will accept it, an outdoor reset and aquastat. The primary loop is circulating any time the boiler is firing. The zone thermostats control the secondary loops with the zone pumps.

    You still have no idea as to whether the boiler is the right size for the structure. A very rough guess tells me it's probably around twice as big as you need, but that's a guess. If it is, you'll probably need a buffer tank to help reduce boiler cycling.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    HVACNUT Member Posts: 3,945
    Download the manual. Everything you need is there.
  • GroundUp
    GroundUp Member Posts: 1,204
    Read the manual. If still confused, hire a professional before it's too late.
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