How many btus per person

Note that incandescent lights waste energy by 1 consuming more electricity for the same amount of lighting and 2 making the cooling system work harder and longer to remove the heat given off. The energy consumed by the lights is dissipated by convection and radiation. The convection component of the heat constitutes about 40 percent for fluorescent lamps, and it represents the instantaneous part of the cooling load due to lighting.

The remaining part is in the form of radiation that is absorbed and reradiated by the walls, floors, ceiling, and the furniture, and thus they affect the cooling load with time delay. Therefore, lighting may continue contributing to the cooling load by reradiation even after the lights have been turned off. Sometimes it may be necessary to consider time lag effects when determining the design cooling load.

The ratio of the lighting wattage in use to the total wattage installed is called the usage factor, and it must be considered when determining the heat gain due to lighting at a given time since installed lighting does not give off heat unless it is on. For commercial applications such as supermarkets and shopping centers, the usage factor is taken to be unity. Most equipment and appliances are driven by electric motors, and thus the heat given off by an appliance in steady operation is simply the power consumed by its motor.

For a fan, for example, part of the power consumed by the motor is transmitted to the fan to drive it, while the rest is converted to heat because of the inefficiency of the motor. The fan transmits the energy to the air molecules and increases their kinetic energy.

But this energy is also converted to heat as the fast-moving molecules are slowed down by other molecules and stopped as a result of friction. Therefore, we can say that the entire energy consumed by the motor of the fan in a room is eventually converted to heat in that room.

Of course, if the motor is in one room say, room A and the fan is in another say, room B , then the heat gain of room B will be equal to the power transmitted to the fan only, while the heat gain of room A will be the heat generated by the motor due to its inefficiency Fig.

The power rating W motor on the label of a motor represents the power that the motor will supply under full load conditions. But a motor usually operates at part load, sometimes at as low as 30 to 40 percent, and thus it consumes and delivers much less power than the label indicates. Also, there is an inefficiency associated with the conversion of electrical energy to rotational mechanical energy. This is characterized by the motor efficiency h motor , which decreases with decreasing load factor.

Therefore, it is not a good idea to oversize the motor since oversized motors operate at a low load factor and thus at a lower efficiency. Another factor that affects the amount of heat generated by a motor is how long a motor actually operates. Motors with very low usage factors such as the motors of dock doors can be ignored in calculations.

The TRUE highest cost system is the system not installed properly I am yourmrfixit. Originally Posted by vstech. MOST people have absolutely no idea of the concept that people raise the heat load in a structure. Know Your Equipment Capabilities. Originally Posted by Shophound. Contractor locator map How-to-apply-for-Professional How many times must one fix something before it is fixed? Originally Posted by beenthere. There are some churches, that the congregation is at BTUs per person.

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