provides a detailed formula and example for calculating the horsepower (HP) of a pump in an HVAC chilled water system. The equation for HP is given as: HP = (GPM x Head Loss x Specific Gravity of Water) / (3960 x Efficiency of Motor). In the example, the formula uses values for GPM (gallons per minute), Head Loss (in feet), Specific Gravity of Water (assumed to be 1), and Efficiency of the Motor (75%). The example shows the calculation for a chilled water pump, with a result of 8.1 HP. The image also includes a breakdown of how to calculate GPM using the formula GPM = (TR x 24) / ΔT where TR represents tonnage and ΔT represents the temperature difference. This formula helps determine the required horsepower for pumps in HVAC systems based on their operating parameters.