507388-03
Issue 2110
Page 7 of 19
Electrical Connections
All wiring must be done in accordance with the National
Electrical Code, ANSI/NFPA No. 70 (latest edition); or local
codes, where they prevail. Any alteration of internal wiring
will void certification and warranty.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
Electrostatic discharge can affect electronic components.
Take precautions during furnace installation and service
to protect the furnace’s electronic controls. Precautions
will help to avoid control exposure to electrostatic
discharge by putting the furnace, the control and
the technician at the same electrostatic potential.
Neutralize electrostatic charge by touching hand and
all tools on an unpainted unit surface, such as the gas
valve or vestibule panel, before performing any service
procedure.
CAUTION
The rating plate indicates the operating voltage, phase,
minimum circuit ampacity, maximum fuse size, and
minimum voltage. Units must never be installed where
voltage exceeds 10% over the voltage indicated on the
rating plate.
Units are factory wired for a 230 volt power supply. If power
supply is 208 volts, it will be necessary to change a wire
connection on unit transformer from 240 volt terminal to
208 volt terminal as shown on the wiring diagram.
Failure of the compressor as a result of operation on
improper voltage voids the compressor replacement
warranty.
A separate electric line with wire having a temperature rating
of 60°C should be run directly from the main supply panel
to the leads in the unit. Refer to the rating plate located on
the unit for proper fuse or breaker size. Make sure the unit
is electrically grounded in accordance with local codes or,
in the absence of local codes, with the National Electrical
Code, ANSI/NFPA No. 70 (latest edition) for installations
in the U.S.
See rating plate for minimum wire ampacity and size wire
accordingly.
Exterior Junction Box and Switch
If local codes allow, a field supplied junction box and
optional switch may be installed on the top panel to provide
an exterior electrical wiring point and disconnect. A suitable
junction box cover must be used. If a switch is used it must
meet or exceed the electrical specifications shown on the
unit rating plate. The junction box, cover, and (if used)
switch are standard items that are locally available.
Installing an Exterior Junction Box
1. Remove the two screws that secure the factory-
supplied cover over the rear half of the internal junction
box. Keep the front cover in place. See Figure 4.
2. Position a 4x4 junction box over the opening as shown
in Figure 5. Make sure the junction box is pulled up
against the front cover so that there is no gap. Remove
a knock-out in the box to allow the unit wiring leads
to extend into the bottom of the box. Pull the leads
through the knock-out and into the box. Remove a
knock-out for the main power supply leads.
3. Secure the junction box to the top panel using screws.
4. Connect the unit wiring leads to the main power supply
or the switch as desired. Securely attach the cover to
the junction box. When complete, the junction box
should be as shown in Figure 6.
5. The rear cover that was removed in Step 1 is not used
and may be discarded.
Rear Cover
Front Cover
(Leave in place)
Figure 4.