20
WIRE SIZE, AWG
lamps, televisions, radios or air streams
from registers. Refer to instructions packed
with the thermostat for “heater” selection or
adjustment.
The following is a list of recommended
thermostats to be used with or without an
economizer:
B. HOOK-UP
To wire unit, refer to the following hook-
up diagram.
Refer to Figures 2 and 21 for location of
wiring entrances.
Wiring to be done in the field between
the unit and devices not attached to the
unit, or between separate devices which
are field installed and located, shall
conform with the temperature limitation
for Type T wire [63°F rise (35°C)] when
installed in accordance with the
manufacturer’s instructions.
C. INTERNAL WIRING
A diagram of the internal wiring of this unit
is located on the inside of control access
panel and in this manual. If any of the
original wire as supplied with the
appliance must be replaced, the wire
gauge and insulation must be same as
original wiring.
Transformer is factory wired for 230 volts
on 208/230 volt models and must be
changed for 208 volt applications. See
unit wiring diagram for 208 volt wiring.
D. THERMOSTAT
The room thermostat must be compatible
with the spark ignition control on the unit.
Generally, all thermostats that are not of
the “current robbing” type are compatible
with the integrated furnace control. The low
voltage wiring should be sized as shown in
Table 7.
Install the room thermostat in accordance
with the instruction sheet packed in the box
with the thermostat. Run the thermostat
lead wires through control entry opening
(Figure 2 or Figure 21) and connect to the
low voltage thermostat connections (see
wiring diagram). Never install the
thermostat on an outside wall or where it
will be influenced by drafts, concealed hot
or cold water pipes or ducts, lighting
fixtures, radiation from fireplace, sun rays,
FIELD WIRE SIZE FOR 24 VOLT THERMOSTAT CIRCUITS
SOLID COPPER WIRE - AWG.
3.0 16 14 12 10 10 10
2.5 16 14 12 12 12 10
2.0 18 16 14 12 12 10
50 100 150 200 250 300
Length of Run – Feet (1)
Thermostat Load -
Amps
TABLE 8
(1) The total wire length is the distance from the unit to the thermostat
and back to the unit.
NOTE: DO NOT USE CONTROL WIRING SMALLER THAN NO. 18
AWG.
FIGURE 21. BASE ENTRY LOCATIONS
FIGURE 22. TYPICAL THERMOSTAT WIRING
14
1/2(
7/8(
12
1/2(
7/8(
10
1/2(
7/8(
8
3/4(
1-31/32(
6
1(
1-23/64(
4
1(
1-23/64(
3
1-1/4(
1-23/32(
2
1-1/4(
1-23/32(
1
1-1/2(
1-31/32(
0
1-1/2(
1-31/32(
00
2(
2-15/32(
000
2(
2-15/32(
CONDUIT SIZE
HOLE SIZE
ST-A0886-14
Two Stage Cool/
Two Stage Heat Part #
W/O Economizer
Robertshaw -
Model #09710
41-32971-01
Honeywell -
Model #T874D1959
41-21444-01
White Rodgers -
Model #1F91-7
41-21015-04
Honeywell -
Model #T7300AORB
41-21615-06
NOTES: 1. DETERMINE REQUIRED WIRE SIZE FROM MINIMUM CIRCUITAMPACITY SHOWN IN INSTALLATION & OPERATING INSTRUCTION.
2. BOTTOM POWER ENTRY WILL NOT ACCOMMODATE WIRE LARGER THAN #2 AWG (SHADED AREA).
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