On a number of
issues the HVAC designer must interface with the electrical designer,
each sharing information and responding appropriately.
Motor loads: Motor
sizes and locations derive from the HVAC equipment selections and
equipment layouts.
Motor control
features: HVAC control schemes determine many of the needed starter
characteristics, e.g., hand-off-auto or start-stop, auxilary contact
types and number, pilot light requirements, and control voltage
transformer size if external devices needing control power are
involved. Be sure to coordinate the specification and control of two
speed motors and motor starters.
Fire and smoke
detection and alarm: The electrical designer is usually responsible
for fire detection and alarm, if such is required. But building codes
require smoke detectors in the airstream of recirculation fan systems
larger than 2000 ft3 /min.
If smoke is
detected, fan systems are required to shut down. Similarly, if the
building detection systems go into alarm, the fan systems must turn
off. Further sophistication gets into smoke control in buildings, a
separate topic by itself.
Lighting systems:
The HVAC designer must fully understand the building lighting systems
to be able to correctly respond to the cooling loads which develop.
Any inordinately
high lighting loads may stimulate discussion and evaluation of
lighting fixture selection. Automated lighting control may be
included as a feature of a building automation system.
Transformer
vaults: Electric transformers typically lose 2 to 5 percent of the
power load (winding losses) to the ambient air. Building transformers
may wind up in underground vaults, in secure rooms, in janitor
closets, or in ceiling spaces.
Dissipation of the
heat with ventilation is often a challenge. Note that even though the
load may decrease, transformers seldom sleep; 24 h/day ventilation is
required.
Building HVAC
systems which follow a time-clock schedule are inadequate for
transformer rooms. Some electronic monitoring and control devices
cannot tolerate ambient air temperatures above
about 100 deg F.
No comments:
Post a Comment