19
G
AS
S
UPPLY
AND
P
IPING
24 V
AC
H
UMIDIFIER
The yellow wire connected to the I.D. Blower pressure switch
is powered anytime the pressure switch is closed and
provides 24 VAC humidifier control. Remove the yellow wire
and connect the supplied brown jumper wire to the pressure
switch terminal. Reconnect the yellow wire to the “piggyback”
terminal on the brown jumper and then connect the 24 VAC
line of the humidifier to the stripped end of the brown wire.
Using a wire nut or a field-supplied quick connect terminal
can make this connection. The wiring must conform to all
local and national codes. Connect the COM side of the
humidifier to the B/C terminal on the furnace control board
(or to the COM side of the 24 VAC transformer).
DO NOT
CONNECT 115V HUMIDIFIER TO THESE TERMINALS.
G
AS
S
UPPLY
AND
P
IPING
The furnace rating plate includes the approved furnace gas in-
put 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.
CAUTION
T
O
PREVENT
UNRELIABLE
OPERATION
OR
EQUIPMENT
DAMAGE
,
THE
INLET
GAS
SUPPLY
PRESSURE
MUST
BE
AS
SPECIFIED
ON
THE
UNIT
RATING
PLATE
WITH
ALL
OTHER
HOUSEHOLD
GAS
FIRED
APPLIANCES
OPERATING
.
Inlet gas supply pressures must be maintained within the ranges
specified in the following table. The supply pressure must be
constant and available with all other household gas fired appli-
ances operating. The minimum gas supply pressure must be
maintained to prevent unreliable ignition. The maximum must
not be exceeded to prevent unit overfiring.
Natural Gas
Minimum: 5.0" w.c.
Maximum:10.0" w.c.
Propane Gas Minimum: 11.0" w.c.
Maximum:13.0" w.c.
Inlet Gas Supply Pressure
NOTE:
Adjusting the minimum supply pressure below the limits
in the above table could lead to unreliable ignition. Gas input to
the burners must not exceed the rated input shown on the
rating plate. Overfiring of the furnace can result in premature
heat exchanger failure. Gas pressures in excess of 13 inches
water column can also cause permanent damage to the gas
valve.
At all altitudes, the manifold pressure must be within 0.3 inches
w.c. of that listed in the Specification Sheet applicable to your
model for the fuel used. At all altitudes and with either fuel, the
air temperature rise must be within the range listed on the fur-
nace nameplate. Should this appliance be converted to LP,
refer to the instructions included in the factory authorized LP
conversion kit.
H
IGH
A
LTITUDE
D
ERATE
IMPORTANT NOTE:
The furnace will naturally derate itself with
altitude. Do not attempt to increase the firing rate by changing
orifices or increasing the manifold pressure. This can cause
poor combustion and equipment failure.
High altitude installations may require both a pressure switch
and an orifice change. These changes are necessary to com-
pensate for the natural reduction in the density of both the gas
fuel and the combustion air at higher altitude.
For installations above 7000 feet, please refer to your distribu-
tor for required kit(s).
Contact the distributor for a tabular listing of appropriate
manufacturer’s kits for propane gas and/or high altitude instal-
lations. The indicated kits must be used to insure safe and
proper furnace operation. All conversions must be performed
by a qualified installer, or service agency.
P
ROPANE
G
AS
C
ONVERSION
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
.
This unit is configured for natural gas. The appropriate
manufacturer’s propane gas conversion kit, must be applied for
propane gas installations. Refer to the “Propane Gas and/or
High Altitude Installations” section for details.
Models using Single Stage Gas Valves
Altitude
Gas
Kit
Orifice
Manifold
Pressure
Pressure
Switch
#55
10.0" w.c.
NOTE:
In Canada, gas furnaces are certified to 4500 feet.
NOTE:
GMS81405DN** models utilize #43 orifices in Natural gas
applications.
0-7000
Natural
None
#45
3.5" w.c.
None
Propane
LPT-03
Models using 2-Stage Gas Valves
High
Stage
Low
Stage
Natural
None
#45
3.5" w.c. 1.9" w.c.
None
Propane
LPM-06
#55
10.0" w.c. 6.0" w.c.
None
0-7000
NOTE:
In Canada, gas furnaces are only certified to 4500 feet.
NOTE:
GMH81405DN** models utilize #43 orifices in Natural gas
applications.
Gas
Altitude
Kit
Orifice
Manifold Pressure Pressure
Switch
Change
