ELECTRICAL ROOM INSTALLATION IN HVAC DESIGN BASIC INFORMATION


While most HVAC designers will have the support of a competent electrical design staff, it is important to understand certain fundamentals of electricity, power distribution, and utilization, because so many HVAC system devices are mechanically driven and controlled.

In building construction, HVAC design is interwoven with the electrical design, and each discipline needs to be conversant with the other. Electrical-mechanical interfaces need to be fully communicated for complete designs to be achieved.

The HVAC designer should have a working background in the fundamentals of electricity and electric control. Full presentation of the electrical needs of the HVAC system must be part of the HVAC design work, as must a complete understanding of the impacts of electrical heat releases on the building environment.

In rooms where electric devices consume electricity and give off heat, some sort of ventilation for cooling is required. Electronic installations may require mechanical refrigeration.

Natural convection ventilation usually assumes a 10 to 20#F rise in the space which allows calculation of the probably required ventilating airflow quantities, assuming that the heat release can be estimated. The following estimating factors may be helpful.

Transformers:
Assume that 3 to 5 percent of the active load will be dissipated in transformation. This may drop to 2 to 3 percent for more efficient units.

Elevator machine rooms:
Figure all the elevator motor horsepower times a factor for the estimated percentage of time in use. Peak-use hours approach 100 percent.

Consult the elevator vendor for temperature constraints and secondary losses from control panels, etc.

Motor control centers:
These units generate some heat from control transformers and starter holding coils. This equipment does not hold up well in hot environments. Carry this observation over into plant design considerations.

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