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chilled water cooling from a spring

I hope you guys have some insight on something I've been searching the web for info today.
Has a customer call who wants to gravity feed spring water down a hill into a coil in his heat pump for AC. I installed a wood boiler for him last year with a hot water coil in the duct. It heats great.
From what I'm reading a chilled water coil needs to be several times larger to get equal BTUs to a the output of a heating coil, plus he's not going to have water below 55F, rather than 40's like a chilled water coil would use (I presume).
I'm guessing he'll be down to an eighth or a tenth the heating capacity of an equivalent sized coil? I have no experience with chilled water so I'm guessing here.


    EBEBRATT-Ed Member Posts: 15,827
    You would have to oversize the coil to get adequate cooling. But the real problem is humidity control. You need to get a coil to about 50 deg to remove much humidity. And humidity removal (latent heat removal) is just as or maybe more important that sensible temperature change.

    Normal chilled water temperature is about 54 chiller return and 44 chiller supply putting the average coil temperature at about 49 deg. In chilled water a few degrees makes a huge difference. Normal water flow is 2-2.5 gpm / ton of cooling (12,000 btu/hr). 2 gpm will result in about a 12 degree change in water temperature, 2.5 is about 10 degrees
  • hot_rod
    hot_rod Member Posts: 22,467
    If you have enough gpm, run that water to a HP and then you could get the temperature you need and a high efficiency.

    The city of Toronto has some district cooling. They pull around 39°F water from deep in lake Ontario, they run through some large HX and chillers and the discharge water around 50F is the potable supply water for the city.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EYoder
    EYoder Member Posts: 60
    I appreciate the info. Thanks guys.