10
Packaged and Split Rooftop Ventilator
WARNING
The roof lining contains high voltage wiring. To prevent
electrocution, do not puncture the interior or exterior
panels of the roof.
WARNING
To prevent injury or death due to electrocution or
contact with moving parts, lock disconnect switch open.
For units with a gas furnace, if you turn off the power
supply, turn off the gas.
IMPORTANT
Before connecting power to the unit, read and
understand the following instructions and wiring
diagrams. Complete wiring diagrams are attached on
the inside of the control center door(s).
IMPORTANT
All wiring should be done in accordance with the latest
edition of the National Electric Code ANSI/NFPA 70
and any local codes that may apply. In Canada, wiring
should be done in accordance with the Canadian
Electrical Code.
IMPORTANT
The equipment must be properly grounded and
bonded. Any wiring running through the unit in the
airstream must be protected by metal conduit, metal
clad cable or raceways.
CAUTION
If replacement wire is required, it must have a
temperature rating of at least 105ºC, except for an
energy cut-off or sensor lead wire which must be rated
to 150ºC.
DANGER
High voltage electrical input is needed for this
equipment. This work should be performed by a
qualified electrician.
CAUTION
Any wiring deviations may result in personal injury
or property damage. Manufacturer is not responsible
for any damage to, or failure of the unit caused by
incorrect final wiring.
Electrical Information
Determine the Size of the Main Power Lines
The unit’s nameplate, located on the outside of the
control panel side, states the voltage and the unit’s
MCA. The main power lines to the unit should be sized
accordingly. Model MPF is provided with a separate
condensing unit with its own disconnect that requires a
separate power feed from the unit.
Determine the Size of Electric Heater Wiring
An optional electric heater may require a separate power
supply. The power connection should be made to the
factory-provided electric heater disconnect and must be
compatible with the ratings on the nameplate, supply
power voltage, phase and amperage. Consult ANSI/
NFPA 70 and CSA C22.1 for proper conductor sizing.
Provide the Opening(s) for the Electrical
Connections
Electrical openings vary by unit size and arrangement
and are field-supplied.
Connect the Power Supplies
Connect the main power lines and electric heater power
lines to the disconnect switches or terminal blocks and main
grounding lug(s). Torque field connections to manufacturer’s
recommendations.
Wire the Optional Convenience Outlet
The convenience outlet requires a separate 115V power
supply circuit. The circuit must include short circuit
protection which may need to be supplied by others.
Connect Field-Wired Low Voltage
Components
Most factory-supplied electrical components are
prewired. To determine what electrical accessories
require additional field-wiring, refer to the unit-specific
wiring diagram located on the inside of the control center
access door.
Control wires should not be run inside the same conduit
as that carrying the supply power. Make sure that field-
supplied conduit does not interfere with access panel
operation. All low voltage wiring should be run in conduit
wherever it may be exposed to the weather.
The low voltage control circuit is 24 VAC and control
wiring should not exceed 0.75 ohms. If wire resistance
exceeds 0.75 ohms, an industrial-style, plug-in relay
should be added to the unit control center and wired in
place of the remote switch (typically between terminal
blocks R and G on the terminal strip. The relay must
be rated for at least 5 amps and have a 24 VAC coil.
Failure to comply with these guidelines may cause
motor starters to “chatter” or not pull in which can cause
contactor failures and/or motor failures.
Field-Provided Disconnect
If field-installing an additional disconnect switch, it
is recommended that there is at least four feet of
service room between the switch and system access
panels. When providing or replacing fuses in a fusible
disconnect, use dual element time delay fuses and size
according to the rating plate.
WARNING
Consult your dealer when the following issues on Y
system are the key concern.
•
Warm air
may flow out from the indoor unit during
heating Thermo-OFF.
•
Refrigerant flow
sound may occur in the rooms
with low background noise such as hotel rooms,
hospital rooms, bedrooms, or conference rooms.
To avoid the above issues on Y system, changing
board settings on the indoor and outdoor units is
required.
© 2017 Mitsubishi Electric US, Inc.
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