8
unit and for proper grounding. Field supplied bushings for the
power supply cables must be added to support and protect
the power supply cables.
• All 208/230 Volt units are shipped from the factory wired for
240 volt operation. For 208V operation, remove the lead from
the transformer terminal marked 240V and connect it to the
terminal marked 208V.
Thermostat Connections
• Thermostat connections shall be in accordance with the
instructions supplied with the thermostat. The thermostat
used with this equipment must operate in conjunction with
any installed accessories. Typical AC and air handler hookups
are shown in
.
CAUTION:
Isolation must be maintained from the external
Class 2 output of any transformer in a cooling
circuit. Use a thermostat with isolating contacts
to prevent inter-connection of Class 2 outputs.
• Where local codes require that the thermostat wiring
must be routed through a conduit or raceway, splices
can be made inside the unit; however, all wiring must
be NEC Class 1 and must be separated from incoming power
leads.
• The thermostat should be mounted about 5 feet above the
floor on an inside wall. DO NOT install the thermostat on
an outside wall or any other location where its operation
may be adversely affected by radiant heat from fireplaces,
sunlight, or lighting fixtures, and convective heat from warm
air registers or electrical appliances. Refer to the thermostat
manufacturer’s instruction sheet for detailed mounting and
installation information.
• Install the grommet, which is packed with the unit, in the hole
for low-voltage wires. Properly connect the low-voltage wiring
between the thermostat, outdoor unit, and control board.
NOTE:
When the low voltage wires are positioned in this
grommet, the grommet will prevent chafing and/or shorting
of the low voltage leads
Important!
On variable speed models when the unit is used
in an air conditioning system, connect the
O
terminal to the
Y
Grounding
WARNING:
The unit cabinet must have an uninterrupted or
unbroken electrical ground to minimize personal
injury if an electrical fault should occur. Do not
use gas piping as an electrical ground!
This unit must be electrically grounded in accordance with
local codes or, in the absence of local codes, with the National
Electrical Code (ANSI/NFPA 70) or the CSA C22.1 Electrical
Code. Use the grounding lug provided in the control box for
grounding the unit.
Control Board
The control board in the air handler controls the timing sequence
of the elements. Depending on the thermostat connection, there
are multiple timing sequence variations that can be chosen. The
board also is equipped with a 3 second blower on delay, a 15
second blower off delay in electric heat mode and a 40 second
ELECTRICAL CONNECTIONS
WARNING:
ELECTRICAL SHOCK, FIRE OR
EXPLOSION HAZARD
Failure to follow safety warnings exactly could
result in serious injury or property damage.
Improper servicing could result in dangerous
operation, serious injury, death or property
damage.
• Before servicing, disconnect all electrical
power to the indoor blower.
• When servicing controls, label all wires prior
to disconnecting. Reconnect wires correctly.
• Verify proper operation after servicing.
• Electrical connections must be in compliance with
all applicable local codes and ordinances, and with
the current revision of the National Electric Code
(ANSI/NFPA 70).
• For Canadian installations, the electrical connections and
grounding shall comply with the current Canadian Electrical
Code (CSA C22.1 and/or local codes).
Pre-Electrical Checklist
√
Verify the voltage, frequency, and phase of the supply source
match the specifications on the unit rating plate.
√
Verify that the service provided by the utility is sufficient to
handle the additional load imposed by this equipment. See
the unit wiring label or
& MOP information.
√
Verify factory wiring is in accordance with the unit wiring
diagram. See
Verify none of the connections loosened during shipping or
installation.
Line Voltage
•
An electrical disconnect must be located within sight
of and readily accessible to the unit
. This switch shall be
capable of electrically de-energizing the outdoor unit. See unit
data label for proper incoming field wiring. Any other wiring
methods must be acceptable to authority having jurisdiction.
• It is recommended that the line voltage to the unit be supplied
from a dedicated branch circuit containing the correct fuse or
circuit breaker for the unit.
• Overcurrent protection must be provided at the branch circuit
distribution panel and sized as shown on the unit rating label
and according to applicable local codes. See the unit rating
and maximum overcurrent protection limits.
• The installer should become familiar with the wiring diagram/
schematic before making any electrical connections to the
unit. See the unit wiring label or
&
• Use only copper wire for the line voltage power supply to this
unit. Use proper code agency listed conduit and a conduit
connector for connecting the supply wires to the unit. Aluminum
supply wire may be used if a heater kit is installed.
• If replacing any of the original wires supplied with the unit,
the replacement wire must be copper wire consisting of the
same gauge and temperature rating.
• Provide power supply for the unit in accordance with the unit
wiring diagram, and the unit rating plate. Use UL listed conduit
and conduit connectors for connecting the supply wires to the
Summary of Contents for MB7EM 3-PHASE Series
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