507582-04
Page 35 of 54
Issue 2220
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 field 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 56 or Figure 57 for field wiring 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
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.
Model
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 field
wiring diagram shown in Figure 56 or Figure 57. 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 field 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. See Figure
58 or Figure 59 for integrated control configuration.
This terminal is energized when the indoor blower is
operating. Any 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. If an accessory rated at greater than one
amp is connected to this terminal, it is necessary to
use an external relay.