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Navien NCB-240 Internal Circulator Variable or Single Speed

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axeyal
axeyal Member Posts: 8
in THE MAIN WALL
I'm trying to balance my Primary / Secondary flow and would like to understand if the internal circulator in the Navien NCB-240 runs on a single speed or does it have more than one speed to modulate with the firing rate?

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  • Zman
    Zman Member Posts: 7,569
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    It's probably single speed. Do you know what model the circ is?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • axeyal
    axeyal Member Posts: 8
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    Thanks Zman,
    The model number is 30012768A Circulation Pump.
  • motoguy128
    motoguy128 Member Posts: 393
    edited November 2021
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    Its 3 fixed speeds manually adjustable only. Similar to a grundfos 15-58 3 speed. Its flow rate is only good enough for about 7 Gpm max I think. So the flow is about 4-7gpm

  • motoguy128
    motoguy128 Member Posts: 393
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    That’s one huge limitation of a combi. Depending on desired supply temp, the capacity is limited by primary loop flow. So if you have a bigger cast iron system and have lets say 14gpm on the secondary, if 150 gives you let’s say 15f delta t across the system and it comes back at 135f, you have to supply 165f water. Not a big deal but something to keep in mind.
  • axeyal
    axeyal Member Posts: 8
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    motoguy128 said:

    Its 3 fixed speeds manually adjustable only. Similar to a grundfos 15-58 3 speed. Its flow rate is only good enough for about 7 Gpm max I think. So the flow is about 4-7gpm

    The installation manual does not mention an adjustment on the circulator. That makes me believe it is a single speed. Do you have any documentation showing otherwise?
  • axeyal
    axeyal Member Posts: 8
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    I read somewhere in this forum before that the flow rate of the circulator is 5gpm. I am getting lower water temperature reading at the secondary loop supply than the primary loop supply temperature on the boiler. This makes me think that I need to reduce the flow in the secondary loop so there is less mixing of return water across the closely spaced Ts

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