48
90+ HIGH ALTITUDE
INSTRUCTIONS
NATURAL GAS
INSTALLATION OF THIS FURNACE
AT ALTITUDES ABOVE 2000 FT (610
m) SHALL BE IN ACCORDANCE
WITH LOCAL CODES, OR IN THE
ABSENCE OF LOCAL CODES, THE
NATIONAL FUEL GAS CODE, ANSI
Z223.1/NFPA 54 OR NATIONAL
STANDARD OF CANADA, NATURAL
GAS AND PROPANE INSTALLATION
CODE, CAN B149.1.
INSTALLATION OF THIS APPLIANCE
AT OR ABOVE 5000 FT (1525 m)
SHALL BE MADE IN ACCORDANCE
WITH THE LISTED HIGH ALTITUDE
CONVERSION KIT AVAILABLE WITH
THIS FURNACE.
ELEVATIONS ABOVE 2000 FT
REQUIRE THAT THE FURNACE
INPUT RATING BE ADJUSTED AND
THAT THE SIZE OF THE BURNER
ORIFICES BE RE-CALCULATED
BASED ON ELEVATION AND GAS
HEATING VALUE. THE BURNER
ORIFICES MAY (OR MAY NOT) NEED
TO BE CHANGED. THE FOLLOWING
EXAMPLES SHOW HOW TO
DETERMINE IF AN ORIFICE CHANGE
WILL BE NECESSARY AND HOW TO
DETERMINE THE NEW ORIFICE SIZE.
IN CANADA, AS AN ALTERNATE TO
SIZING THE BURNER ORIFICE, THE
MANIFOLD GAS PRESSURE MAY BE
ADJUSTED. THIS METHOD IS
COVERED LATER IN THIS SECTION.
THIS METHOD OF ADJUSTING
MANIFOLD PRESSURE MAY ONLY
BE USED IN CANADIAN
INSTALLATIONS.
34" 90 Plus furnaces installed at high
elevations require the installation of a
high altitude kit for proper operation. The
high altitude kit consists of a high
altitude pressure switch that replaces
the pressure switch attached to the
induced draft blower.
The pressure switch must be installed
at elevations above 5000 ft. Elevations
above 2000 ft. require the furnace to be
de-rated 4% per thousand feet.
NOTE: 278 Option Code is available on
(-)GRK-12/(-)GRL models only.
Alternately, furnaces can be ordered
from the factory already converted for
high altitude elevations. The factory
option for high altitude elevations would
be ordered as a 278 option (example; a
105k BTU upflow furnace which is
factory converted for high altitude
elevations would have the model
number (-)GRL-10EZAJS278
). These
factory converted furnaces come with a
pressure switch for high-altitude
elevations already attached. Also,
different burner orifices are installed at
!
CAUTION
!
CAUTION
Natural Gas Orifice Drill Size (4% per 1000 ft. De-Rate)
IMPORTANT: 90 Plus Models only. Do not use this chart for any 80 Plus Models.
Burner Input (per burner) 15,000 BTU @ Sea Level
Sea level 2000 to 3000 to 4000 to 5000 to 6000 to 7000 to 8000 to
to 1999 ft 2999 ft 3999 ft 4999 ft 5999 ft 5999 ft 7999 ft 8999 ft
47 48 48 49 49 49 50 50
48 49 49 49 50 50 50 51
49 50 50 50 51 51 51 52
50 51 51 51 51 52 52 52
51 51 52 52 52 53 53 53
Annual Avg. Heat
Value (btu per ft
3
)
850
900
1000
1075
1170
TABLE 10
HIGH ALTITUDE KIT
Installer must make necessary burner
orifice and pressure switch changes as
indicated in the table below:
(-)GRK-12/(-)GRL PRESSURE SWITCH CHANGES
INPUT
HIGH ALTITUDE SET POINT SET POINT
KIT NO. HIGH FIRE LOW FIRE
45,000 RXGY-F18 -1.08 NO CHANGE
60,000 RXGY-F18 -1.08 NO CHANGE
75,000 (N) N/A NO CHANGE NO CHANGE
75,000 (W) N/A NO CHANGE NO CHANGE
90,000 RXGY-F20 -1.15 NO CHANGE
105,000 RXGY-42 -1.08 -0.50
120,000 RXGY-F21 -0.50 -0.30
(-)GTK PRESSURE SWITCH CHANGES
INPUT
HIGH ALTITUDE
KIT HIGH FIRE LOW FIRE
60,000 RXGY-F29 -1.0 -0.8
75,000 (N) RXGY-F30 -0.8 -0.6
75,000 (W) RXGY-F30 -0.8 -.06
90,000 RXGY-F31 -0.9 -.06
105,000 RXGY-F32 -0.7 -.04
120,000 RXGY-F33 -0.4 -0.3
NOTE: Orifices are no longer supplied
with kit.
the factory which are one drill size
smaller (#51 DMS) than standard
(-)GRL gas furnaces (#50 DMS). The
smaller orifice is installed to
accommodate for average heating
values expected in most high altitude
areas and a required 4% per
thousand feet reduction in input as
specified by the National Fuel Gas
Code (NFGC). Specific orifices
should always
be recalculated for all
high altitude installations as outlined
below. Orifices should be changed, if
necessary, based on gas heating
value and elevation.
NOTE: Factory installed orifices are
calculated and sized based on a sea
level Natural Gas heating value of
1075 BTU per cubic ft. Regional
reduced heating values may nullify
the need to change orifices except at
extreme altitudes.
The following are examples of orifice
sizing using the National Fuel Gas
Code Appendix F. For a simplified
estimation of orifice size based on
heating value and elevation, use
Tables 8 and 10, however
calculations are the best method.
Example: 900 BTU/ft
3
Regional
Natural Gas Heating Value
I / H = Q
15000 / 900 = 16.68 ft
3
/hr
I = Sea Level input (per burner):
15000
H = Sea Level Heating Value: 900
Q = 16.68 ft
3
Natural Gas per hour.
From Table F.1 of National Fuel Gas
Code Handbook, 2002 (3.5” w.c.
column)
Orifice required at Sea Level: #48
From Table F.4 of National Fuel Gas
Code Handbook, 2002
Orifice required at 5000 ft. elevation
(4% de-rate per thousand ft.): #50
Orifice required at 8000 ft. elevation
(4% de-rate per thousand ft.): #51
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