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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