Cooling Load - Misc. Equip.




The heat gains from miscellaneous equipment can be found by the following equations.

The first equation is used for motors, where P is equal to the nominal horsepower of the motor. Dividing the horsepower of the motor by the efficiency of the motor allows the heat gains due to the motor and the heat gains due to the inefficiency of the motor to be taken into account. If the motor is used continuously then the usage factor will be 1.0. Otherwise the usage factor will be the fraction of the time that it is used divided by the total time the space is occupied. The load factor of the motor takes into account the fact that motors rarely run at its nominally rated capacity. For example, if a 1 HP motor actually operates at 0.75 HP then the load factor will by 0.75.

Heat Transfer Cooling Load Misc Equip for the Mechanical PE Exam

The second equation describes heat gain from everyday appliances like microwaves, toasters, ranges, ovens and computers. The input energy is found by researching the manufacturer's product data or by referring to typical values reported in ASHRAE Fundamentals. ASHRAE Fundamentals also has typical usage factors and radiated heat fractions for typical equipment. Also shown in ASHRAE Fundamentals are the sensible heat gains for typical pieces of equipment, which bypasses the formula below.

Heat Transfer Cooling Load Misc Equip for the Mechanical PE Exam