Think getting wrong circulator for pex flex

Rugar Posted By Rugar, Nov 6, 2017 at 10:06 PM

  1. Rugar

    Rugar
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    Oct 12, 2008
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    A company is sending me 150 ft of 1 pex flex and a 70 plate exchanger for my unpressurized primary loop. There also sending me a grundfos UPS 26-99 circulator. I have 90 ft of old baseboard and can't imagine more load than 60,000 btu. May add dhw in the future. I'm thinking this circulator is way over sized or am I missing something. Furnace will be located 150 ft away and 4-5 ft lower in elevation.
     
  2. maple1

    maple1
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    Sep 15, 2011
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    Napkin scratch:

    60,000 btu/hr at 20dt =60,000/60/20/8 = 6.25gpm.

    Pipe specs (google) for that 1" say at 10gpm = 4fps = 2.5psi/100'=around 9' of head for 150'. Extrapolating to say 7gpm gives 6' of head - I don't think that's a linear relationship though so say 7' of head.

    Add another 5' for elevation and that's 12' of head.

    Pump chart puts 12' of head just a hair over 7gpm on speed 1. So marginal for speed 1, but I didn't throw anything in for anything else head related like fittings or the bigger kicker, the HX. Do you know the pressure drop for that HX at 7gpm? You would most likely have to run in speed 2.

    Lots of assumptions & guesses in the above - and I might have screwed something up, did it in a hurry.

    I guess my first guess is that the 26-99 would not be oversized for this application and is likely a good fit. It will draw 180 watts on speed 2. At my rates, that would be 4.3kwh/day = $0.77/day. Not terrible but not the best, that's about what I spend to heat our DHW with electricity in the summer.

    I might have gone with 1-1/4" pipe.
     
  3. Rugar

    Rugar
    Member 2.
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    Oct 12, 2008
    130
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    Loc:
    East central KS
    This pipe is the 32 mm logstor pex flex so it more resembles 1 1/4 pex even though it's called inch. I was trying to calculate head closer to 18-22 but don't have all the right numbers to calculate. The pump I thought shows 30 something gpm. I'm guessing that is on speed three. However every where I looked up the pump the data was different.
    7-10 gpm is my rough figures for system but I'm lost
     
  4. JRemington

    JRemington
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    Nov 4, 2017
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    Have you thought about getting the Grundfus Alpha pump? It's the only pump we use. There's no guessing the flow. It has a digital readout and multiple adjustments for flow.
     
  5. maple1

    maple1
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    Do they make an Alpha with the same capacity as the one discussed above?
     
  6. JRemington

    JRemington
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    Nov 4, 2017
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  7. maple1

    maple1
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    Sep 15, 2011
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    I'm a huge Alpha fan too - I have one as my main load circ, pumping thru 4 heating zones & a DHW zone. Don't think you could find a better circ for pumping multiple varying loads with one circ. But I don't think it would have the flow for the above situation. Plus it would (I think) be just acting as a single load constant flow pump - which an ordinary circ would be suited just as well to. Aside from using a bit more electricity.
     
  8. JRemington

    JRemington
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    If I get a chance today I'll call the Amish down at DSMachine in Lancaster. They got a guy that's phenomenal with boiler set ups.
     
  9. TCaldwell

    TCaldwell
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    Oct 26, 2007
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    Just a thought what about 2 alphas in series or parallel?
     

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