3. Verify natural gas input rate by clocking gas meter.
a. Calculate high-altitude adjustment (if required).
UNITED STATES
At installation altitudes above 2000 ft, this furnace has been approved for a 4 percent derate for each 1000 ft above sea level. See Table
4 for derate multiplier factor and example.
EXAMPLE: (For upflow and upflow/horizontal furnaces)
80,000 Btuh input furnace installed at 4300 ft.
Furnace Input Rate at Sea Level
X
Derate Multiplier Factor
=
Furnace Input Rate at Installation Altitude
80,000
X
0.82
=
65,600
CANADA
At installation altitudes from 2000 to 4500 ft, this furnace must be derated 10 percent by an authorized Gas Conversion Station or Dealer.
To determine correct input rate for altitude, see example above and use 0.90 as derate multiplier factor.
b. Turn off all other gas appliances and pilots.
c. Turn setup switch SW-2 (on control board) to ON position. (See Fig. 6 and 7.)
d. Jumper R to W/W1 and R to W2 thermostat connections.
e. Let furnace operate for 3 minutes in high-heat stage.
f. Measure time (in sec) for gas meter test dial to complete 1 revolution.
g. Refer to Table 5 for cu ft of gas per hr.
h. Multiply gas rate (cu ft/hr) X heating value (Btu/cu ft) using natural gas heating value from local gas utility/supplier.
EXAMPLE: (High-heat operation for upflow and upflow/horizontal furnaces at 0—2000 ft altitude)
Furnace input from rating plate is 80,000 Btuh.
Btu heating input = Btu/cu ft X cu ft/hr
Heating value of gas = 975 Btu/cu ft
Time for 1 revolution of 2-cu ft dial = 88 sec
Gas rate = 82 cu ft/hr (from Table 5)
Btu heating input = 82 X 975 = 79,950 Btuh
In this example, the orifice size and manifold pressure adjustment is within
±
2 percent of the furnace input rate.
i. Remove jumper across R and W2 thermostat connections and repeat items d through h for low-heat stage.
NOTE:
Measured gas inputs (high-heat and low-heat stage) must be within
±
2 percent of that stated on furnace rating plate when installed at sea
level or derated per that stated above when installed at higher altitudes.
j. Turn setup switch SW-2 (on control board) to OFF position. (See Fig. 6 and 7.)
4. Remove jumper across R and W/W1 thermostat connections to terminate call for heat.
5. Turn furnace gas valve control knob or electric switch to OFF position.
6. Turn off furnace power supply.
7. Remove manometer and replace manifold pressure tap plug. (See Fig. 4.)
NOTE:
Use propane-gas-resistant pipe dope to prevent gas leaks. DO NOT use Teflon tape.
8. Turn furnace gas valve control knob or electric switch to ON position.
9. Turn on furnace power supply.
10. Set room thermostat to call for heat.
Table 4—Altitude Derate Multiplier for U.S.A.
ALTITUDE (FT)
% OF DERATE
DERATE MULTIPLIER FACTOR FOR U.S.A.*
0—2000
0
1.00
2001—3000
8—12
0.90
3001—4000
12—16
0.86
4001—5000
16—20
0.82
5001—6000
20—24
0.78
6001—7000
24—28
0.74
7001—8000
28—32
0.70
8001—9000
32—36
0.66
9001—10,000
36—40
0.62
* Derate multiplier factor is based on midpoint altitude for altitude range.
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