ASHRAE Journal - February 2024 - 30

FIGURE 3 Dedicated space.
FIGURE 4 Working space.
interlock wiring needs, which might include a restroom
exhaust fan controlled from a light switch or a VAV box
controlled from a room lighting occupancy sensor.
Information the mechanical designer needs from
the electrical designer includes: voltage/phase
availability and preference; total kVA of transformers
in each electrical room (to calculate heat gain for
cooling load); AFC at equipment (so equipment can
be specified with the correct SCCR); location of large
conduit banks, electrical distribution equipment and
electrical panelboards (to coordinate duct routing and
mechanical equipment location); lighting loads and
locations; electrical equipment that produces heat,
which could include distribution equipment, inverters,
uninterruptable power supply (UPS), transformers,
generators and elevator equipment; equipment cooling
requirements, which could include UPS, fire alarm
control panels, inverters, elevator controllers and
lighting controls; and electrical metering integration
with the building automation system.
Electrical Equipment Coordination
Electrical items that need to be discussed and
and 4 ft (0.9 m and 1.2 m). The mechanical designer
should consult a knowledgeable electrical designer or
the NEC for specifics. The National Electrical Code Handbook
includes helpful diagrams useful for interpreting
working space requirements.
Electrical and Mechanical Needs
Information the electrical designer needs from
the mechanical designer regarding mechanical
equipment includes: equipment and control
panel locations; voltage/phase options; equipment
horsepower, ampacity and connection locations;
emergency or standby power requirements;
disconnecting means; starter or VFD information; and
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coordinated with the mechanical designer are
highlighted in this paragraph. Disconnect switches can
be fused or non-fused, heavy duty or toggle and can be
furnished integral with some equipment or furnished
separately by the Division 26 contractor. Starters may
be integral to the mechanical equipment or furnished
separately. Note that electronically commutated (EC)
motors do not require external starters. If there is
a VFD, it may provide the starting function. It may
also provide the disconnecting means, but if it is not
located within line of sight of the equipment, a separate
disconnect switch would be required. The VFD may also
be furnished integral to the mechanical equipment or
furnished separately by either the Division 23 contractor
or the Division 26 contractor. All of these items need to
be coordinated and communicated in the mechanical
equipment schedules and on the electrical plans.
Mechanical Equipment Coordination
Mechanical equipment features that must be
coordinated include voltage, amperage, MOCP,
disconnecting means, starters, control requirements
and equipment options. Options that might be powered
separately from the main equipment feed may include
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ASHRAE Journal - February 2024

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