Installation Guide
507052-04 Page 37 of 53Issue 1727
Electrical
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
blower deck, before performing any service procedure.
CAUTION
Figure 54. Interior Make-Up Box Installation
Figure 55. Interior Make-Up Box Installation
The unit is equipped with a eld makeup box. The makeup
box may be installed on the exterior of the right side of
the furnace to facilitate installation. Seal unused openings
on left side with plugs removed from right side. Secure
the excess wire to the existing harness to protect it from
damage.
Refer to Figure 58 for eld wiring and Figure 59 for
schematic wiring diagram and troubleshooting.
1. The power supply wiring must meet Class I restrictions.
Protected by either a fuse or circuit breaker, select
circuit protection and wire size according to unit
nameplate.
NOTE: Unit nameplate states maximum current draw.
Maximum over current protection allowed is shown in
Table 11.
2. Holes are on both sides of the furnace cabinet to
facilitate wiring.
3. Install a separate (properly sized) disconnect switch
near the furnace so that power can be turned off for
servicing.
Table 11.
Capacity
Maximum Over-Current
Protection (Amps)
045B12, 070B16 15
090C20, 110C20 20
4. Before connecting the thermostat, check to make sure
the wires will be long enough for servicing at a later
date. Make sure that thermostat wire is long enough to
facilitate future removal of blower for service.
5. Complete the wiring connections to the equipment.
Use the provided unit wiring diagram and the eld
wiring diagram shown in Figure 58. Use 18 gauge
wire or larger that is suitable for Class II rating for
thermostat connections.
6. Electrically ground the unit according to local codes or,
in the absence of local codes, according to the current
National Electric Code (ANSI/NFPA No. 70). A green
ground wire is provided in the eld make-up box.
NOTE: This furnace contains electronic components
that are polarity sensitive. Make sure that the furnace
is wired correctly and is properly grounded.
7. One line voltage “ACC” 1/4” spade terminal is provided
on the furnace integrated control. Any electronic air
cleaner or other accessory rated up to one amp can
be connected to this terminal with the neutral leg of the
circuit being connected to one of the provided neutral
terminals. This terminal is energized when the indoor
blower is operating.
8. One line voltage “HUM” 1/4” spade terminal is provided
on the furnace integrated control. Any humidier rated
up to one amp can be connected to this terminal
with the neutral leg of the circuit being connected to
one of the provided neutral terminals. This terminal
is energized in the heating mode whenever the
combustion air inducer is operating.
9. Install the room thermostat according to the instructions
provided with the thermostat. If the furnace is being
matched with a heat pump, refer to the instruction
packaged with the dual fuel thermostat.