15
Low Voltage Wiring
• The furnace is designed to be controlled by a 24 VAC
thermostat. The thermostat’s wiring must comply with
the current provisions of the NEC (ANSI/NFPA 70) and
with applicable local codes having jurisdiction.
• The thermostat must be installed according to the
instructions supplied by the thermostat manufacturer.
Low voltage connections (24 VAC) from the thermostat
are wired to the terminal strip on the integrated control
in the furnace.
• The thermostat should be mounted about 5 feet above
the floor on an inside wall. DO NOT install the thermostat
on an outside wall or any other location where its
operation may be adversely affected by radiant heat from
fireplaces, sunlight, or lighting fixtures, and convective
heat from warm air registers or electrical appliances.
Refer to the thermostat manufacturer’s instruction sheet
for detailed mounting information.
• The nominal anticipator setting is 0.4. Refer to the
thermostat literature for additional information.
• Best practice is to use five-wire conductor thermostat
wire for 24 volt low-voltage circuit (2-wire is required
for furnace only; 5-wire for heating and optional cooling
wire information.
Connecting Thermostat Wires
1. Insert 24 volt wires through the plastic grommet just
above the control panel.
2. Connect the thermostat wires to the furnace low voltage
pigtails (dependent on the installation application). See
Figure 25 and Figure 26 (page 14)
. NOTE:
If AC is
installed with the furnace, a Y connection is required
to be made at the furnace. See
and
3. Connect low-voltage circuit to the wall thermostat.
4. A hole may be made in the furnace cabinet to ease
thermostat wiring. Make sure that the wiring is protected
from the sharp edge of the added hole.
Table 5. Voltage Specifications & Thermostat Wire Gauge
FURNACE
MODEL
NUMBER-
FURNACE
INPUT
(BTUH)
CABINET
WIDTH
(IN.)
NOMINAL
ELECTRICAL
SUPPLY
MINIMUM
OPERATING
VOLTAGE
MAXIMUM
OPERATING
VOLTAGE
MAXIMUM
FURNACE
AMPERES
MAXIMUM
FUSE OR CIRCUIT
BREAKER AMPS*
MINIMUM
CIRCUIT
AMPACITY
1
MG1E-056
56,000
19 3/4
115-1-60
103
127
9.4
15
11.8
MG1E-070
70,000
19 3/4
115-1-60
103
127
9.4
15
11.8
MG1E-077
77,000
19 3/4
115-1-60
103
127
9.4
15
11.8
MG1E-090
85,000
19 3/4
115-1-60
103
127
9.4
15
11.8
NOTE:
Minimum wire gauge and maximum fuse/circuit breaker amperage are based on MCA and MOP calculations. This furnace is approved
for installation with a 15 amp fuse/circuit breaker however. Wire sizing must adhere to current version of the NEC and/or applicable local codes
depending upon the overcurrent protection.
* Non-time-delay fuses or circuit breakers are required.
THERMOSTAT WIRE GAUGE
RECOMMENDED THERMOSTAT WIRE LENGTH (TOTAL LENGTH)
2 - WIRE - HEATING
4 OR 5 WIRE - COOLING
24
55 ft.
25 ft.
22
90 ft.
45 ft.
20
140 ft.
70 ft.
18
225 ft.
110 ft.
Total wire length includes wire from furnace to the thermostat, from thermostat to outdoor unit, & from outdoor unit back to the furnace.
Verifying Anticipator Setting
After the furnace is installed, check the thermostat
anticipator against the nominal setting of 0.4.
1. Connect the milliamp meter in series with one of the
gas valve’s low voltage terminals.
2. Energize the gas valve.
3. Read the value of the milliamps.
4. Adjust the heat anticipator of the thermostat to the
value on the milliamp meter. If the heat anticipator is
set too high, the furnace may delay turning on. If set too
low, the furnace may cycle frequently and not provide
comfort to the homeowner.
Grounding
WARNING:
To minimize personal injury, the furnace cabinet
must have an uninterrupted or unbroken electrical
ground. The controls used in this furnace require
an earth ground to operate properly. Acceptable
methods include electrical wire or conduit
approved for ground service. Do not use gas
piping as an electrical ground!
Summary of Contents for MG1 Series
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