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How to size a circulating pump for a closed circuit (hydronic)?

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148 views asked Mar 1, 2015 by Joe Mahini

1 Answer

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Pump’s Head:

                                   ht = hf + hvl + hcs + hco

                                   ht = Total pump’s head (ft)

hf = Friction loss for developed length of longest pipe run in system per 4ft/100ft friction loss (ft) 
     *Developed length is total length of supply and return including equivalent length for fittings                   (rule of thumb: 3 times of supply pipe)

          hvl = Pressure drop in control valve for most farthest coil (ft)

          hcs = Pressure drop in circuit setter for most farthest coil (ft)

         hco = Pressure drop in coil for most farthest coil (ft)


Pump’s Flow:

                                 gpm = Q/500∆T

         Q = Total heat gain (for cooling) or heat loss (for heating) 
         500 = Factor for converting lb of water to gpm-Btuh

         ∆T = the temperature difference between supply and return water (℉)

answered Mar 1, 2015 by Joe Mahini

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