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Primary pump sizing

EBEBRATT-Ed
EBEBRATT-Ed Member Posts: 16,479
in THE MAIN WALL
Determine the feet of head by adding the resistance of each pipe, fitting, boiler and valves and anything else the water flows through at the 28 gpm you require. Total it up to get the total

Comments

  • Todd_12
    Todd_12 Member Posts: 55
    Primary pump sizing

    I'm trying to size a primary loop pump for twin Ultra 155's. Does this sound right? 2boilers @ 139mbh each = 278mbh(DOE capacity)/10,000 = 27.8gpm. So then do I find a pump that will give me 28gpm at a low head? What should I use for head since its only a small loop?
  • Todd_12
    Todd_12 Member Posts: 55
    Thank you

    I am thinking out loud and wanted to bounce this off you guys. Again, thanks.
  • hr
    hr Member Posts: 6,106
    I'll bet a

    Grundfos 26-64 would be ideal 28 gpm at about 3 feet.

    You have some of the data. GPM total, temperature drop for the primary loop could be included, then the head loss through anything in that primary loop. Y strainer, ball valves, fittings, and pipe lengths. Generally this is a few feet of head. Ideally it would be calculated with a tool or program like the B&G System Sizer or other programs. The HDS works nicely also.

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  • Todd_12
    Todd_12 Member Posts: 55
    Sizing

    As far as delta t on the primary loop, I assumed that it wasn't very important. This is basiclly being used so that the two boilers could be tied into a 10 zone system. 4 zones are radiant, with their own mixing beyond the primary loop. The remaining 6 zones are for fan coil zones that will need high(er) temps. The more I think about it, the more I realize the need to think beyond the primary loop.

    The interesting thing is that I was asked this because the engineer on the job decided to remove the primary pump after the installed started asking about the size/model for this pump. He actually changed his diagram and told the guy "do whatever you normally do" when the questions started.

    I have to remind myself to keep bar raised, and not let anothers complacency steer my thinking. Thanks again guys, I guess I'll dust off the System Syzer and check it myself.
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