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 (℉)
