GMES96-U Installation Manual
22
To ensure proper unit grounding, the ground wire should run
from the furnace ground screw located inside the furnace junc-
tion box all the way back to the electrical panel. NOTE: Do not
use gas piping as an electrical ground. To confirm proper unit
grounding, turn off the electrical power and perform the follow-
ing check.
1. Measure resistance between the neutral (white) connection
and any unpainted surface.
2. Resistance should measure 10 ohms or less.
This furnace is equipped with a blower door interlock switch
which interrupts unit voltage when the blower door is opened
for servicing. Do not defeat this switch.
24 VOLT THERMOSTAT WIRING
NOTE: Wire routing must not interfere with circulator blower
operation, filter removal or routine maintenance.
Low voltage connections can be made through either the right or
left side panel. Thermostat wiring entrance holes are located in
the blower compartment. The following figure shows connec-
tions for a “heat/cool system”.
This furnace is equipped with a 40 VA transformer to facilitate
use with most cooling equipment. Consult the wiring diagram,
located on the blower compartment door, for further details of
115 Volt and 24 Volt wiring.
HIGH VOLTAGE !
T
O
AVOID
PERSONAL
INJURY
OR
DEATH
DUE
TO
ELECTRICAL
SHOCK
,
DISCONNECT
ELECTRICAL
POWER
BEFORE
SERVICING
OR
CHANGING
ANY
ELECTRICAL
WIRING
.
WARNING
R
C
Furnace Integrated
Control Module
Remote Condensing Unit
(Single-Stage Cooling)
R
Room
Thermostat
Figure 27
SINGLE-STAGE HEATING THERMOSTAT APPLICATION
A single-stage thermostat with only one heating stage is
needed to control this furnace.
FOSSIL FUEL APPLICATIONS
This furnace can be used in conjunction with a heat pump in a
fossil fuel application. A fossil fuel application refers to a com-
bined gas furnace and heat pump installation which uses an out-
door temperature sensor to determine the most cost efficient
means of heating (heat pump or gas furnace).
Strictly follow the wiring guidelines in the fossil fuel kit installa-
tion instructions. All furnace connections must be made to the
furnace integrated control module and the “FURNACE” termi-
nal strip on the fossil fuel control board.
G
AS
S
UPPLY
AND
P
IPING
T
O
PREVENT
UNRELIABLE
OPERATION
OR
EQUIPMENT
DAMAGE
,
THE
GAS
MANIFOLD
PRESSURE
MUST
BE
AS
SPECIFIED
ON
THE
UNIT
RATING
PLATE
. O
NLY
MINOR
ADJUSTMENTS
SHOULD
BE
MADE
BY
ADJUSTING
THE
GAS
VALVE
PRESSURE
REGULATOR
.
CAUTION
WARNING
P
OSSIBLE
PROPERTY
DAMAGE
,
PERSONAL
INJURY
OR
DEATH
MAY
OCCUR
IF
THE
CORRECT
CONVERSION
KITS
ARE
NOT
INSTALLED
. T
HE
APPROPRIATE
KITS
MUST
BE
APPLIED
TO
ENSURE
SAFE
AND
PROPER
FURNACE
OPERATION
. A
LL
CONVERSIONS
MUST
BE
PERFORMED
BY
A
QUALIFIED
INSTALLER
OR
SERVICE
AGENCY
.
The furnace rating plate includes the approved furnace gas
input rating and gas types. The furnace must be equipped to
operate on the type of gas applied. This includes any conver-
sion kits required for alternate fuels and/or high altitude.
Natural Gas Minimum: 4.5" W.C. Maximum: 10.0" W.C.
INLET GAS SUPPLY PRESSURE
Table 5
Inlet gas supply pressures must be maintained within the ranges
specified in the table 5. The supply pressure must be constant
and available with all other household gas fired appliances op-
erating. The minimum gas supply pressure must be main-
tained to prevent unreliable ignition. The maximum must not
be exceeded to prevent unit overfiring.
T
O
AVOID
POSSIBLE
UNSATISFACTORY
OPERATION
OF
EQUIPMENT
DAMAGE
DUE
TO
UNDERFIRING
OR
EQUIPMENT
,
USE
THE
PROPER
SIZE
OF
NATURAL
GAS
PIPING
NEEDED
WHEN
RUNNING
PIPE
FROM
THE
METER
/
TANK
TO
THE
FURNACE
.
WARNING
HIGH ALTITUDE DERATE
The furnace shall be installed within 0-4500’ of altitude.
GAS VALVE
This unit is equipped with a 24 volt gas valve controlled during
furnace operation by the integrated control module. As shipped,
the valve is configured for natural gas. Taps for measuring the
gas supply pressure and manifold pressure are provided on the
valve.
The gas valve has a manual ON/OFF control located on the
valve itself. This control may be set only to the “ON” or “OFF”