Head:
ht = hf + hch + hct
ht = Total pump’s head (ft)
hf = Friction loss in developed length of longest pipe run in system per 4’/100’ 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)
hch = Pressure loss in chiller’s condenser
hct = Pressure loss in cooling tower
Flow:
gpm = Q/500∆T
Q = Total chiller’s load (Btuh)
500 = Factor for converting lb of water to gpm – Btuh
∆T = The temperature difference between condenser water supply and return (℉)
