Page 20
Installer’s Guide
Control Wiring (Class II)
Low voltage control wiring should not be run in conduit with power
wiring unless Class 1 wire of proper voltage rating is used. Route
the thermostat cable or equivalent single leads of No. 18 AWG
colored wire from the thermostat subbase terminals through the
rubber grommet on the unit. See Figures 2 or 5 for the control
entry (24V Entry) location. Make connections as shown on the
unit wiring diagram.
Do not short thermostat wires since this will damage the control
transformer.
Table 6. Thermostat Wire Size and Maximum Length
Refer to Table 6 for recommended wire sizes and lengths for install
-
ing the unit thermostat. The total resistance of these low voltage
wires must not exceed one (1) ohm. Any resistance in excess of 1
ohm may cause the control to malfunction because of the exces-
sive voltage drop.
Contactor
Unit Ground Lug
Figure 20. Power Connections
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i
S
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h
W
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g
n
e
L
m
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m
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x
a
M
8
5
1
7
6
5
1
2
1
4
0
1
0
2
Electrical Power
It is important that proper electrical power be available for the unit.
Voltage variation should remain within the limits stamped on the
unit nameplate.
Disconnect Switch
Provide an approved weatherproof disconnect within close proxim-
ity to and
within sight of the unit.
If disconnect must be mounted
to the cabinet, the location shown in Figure 21 should be the only
one considered.
Over Current Protection
The branch circuit feeding the unit must be protected as shown on
the unit nameplate.
Power Wiring
The power supply lines must be run in weather-tight conduit to the
disconnect and into the side of the unit control box. Provide strain
relief for all conduit with suitable connectors.
Provide flexible conduit supports whenever vibration transmission
may cause a noise problem within the building structure.
1. Remove the Control/Heat access panel. Pass the power
wires through the Power Entry hole in the end of the unit.
See Figure 19.
2. Connect the high voltage wires to the appropriate contactor
terminals. Single phase units use a two (2) pole contactor
and three phase units use a two (2) pole contactor and a Blue
lead wire. Connect the ground to the ground lug on the chas-
sis. See Figure 20. Be sure all connections are tight.
GROUNDING: THE UNIT MUST BE ELECTRICALLY
GROUNDED IN ACCORDANCE WITH LOCAL CODES OR
THE NATIONAL ELECTRIC CODE.
NOTE:
Unit must be grounded for ignitor to operate properly.
Gas pipe to unit is not an adequate ground. Ground the unit
internally as provided.
Figure 21. Mounted Disconnect Location
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