Carrier 58MXA Operating And Instruction Manual page 36

Table 7—Model 58MXA Orifice Size and Manifold Pressure for Correct Input
(Tabulated Data Based on 20,000 Btuh per Burner, Derated 2% for Each 1000 Ft Above Sea Level)
AVG GAS
ALTITUDE
HEAT VALUE
RANGE
AT ALTITUDE
(FT)
(BTU/CU FT)
575
600
9001 625
650
to 675
700
10,000 725
750
775
BURNER FLAME
MANIFOLD
Fig. 46—Burner Flame
3. Verify natural gas input rate by clocking gas meter.
NOTE: Be sure all pressure tubing, combustion-air and vent
pipes, and burner enclosure front are in place when checking input
by clocking gas meter.
a. Calculate high-altitude adjustment (if required).
UNITED STATES
At altitudes above 2000 ft, this furnace has been approved
for a 2% derate for each 1000 ft above sea level. See Table
8 for derate multiplier factor.
Table 8—Altitude Derate Multiplier for U.S.A.
ALTITUDE % OF
(FT) DERATE
0—2000 0
2001—3000 4—6
3001—4000 6—8
4001—5000 8—10
5001—6000 10—12
6001—7000 12—14
7001—8000 14—16
8001—9000 16—18
9001—10,000 18—20
* Derate multiplier factor is based on midpoint altitude for altitude range.
0.58 0.60
Orifice Manifold Orifice
No. Pressure No.
43 3.8 42
43 3.5 43
44 3.7 44
44 3.4 44
45 3.8 44
45 3.6 45
45 3.3 45
45 3.1 45
45 2.9 45
BURNER
A89020
DERATE MULTIPLIER
FACTOR FOR U.S.A*
1.00
0.95
0.93
0.91
0.89
0.87
0.85
0.83
0.81
SPECIFIC GRAVITY OF NATURAL GAS
0.62
Manifold Orifice Manifold
Pressure No. Pressure
3.2 42 3.3
3.6 43 3.7
3.8 43 3.5
3.5 44 3.7
3.3 44 3.4
3.7 45 3.8
3.4 45 3.6
3.2 45 3.3
3.0 45 3.1
EXAMPLE:
100,000 Btuh input furnace installed at 4300 ft.
Furnace Input
Rate at
Sea Level
100,000 X 0.91 = 91,000
CANADA
At installation altitudes from 2000 to 4500 ft, this furnace
must be derated 5% by an authorized Gas Conversion
Station. To determine correct input rate for altitude, see
example above and use 0.95 as derate multiplier factor.
b. Turn off all other gas appliances and pilots.
c. Start furnace and let operate for 3 minutes.
d. Measure time (in sec) for gas meter test dial to complete 1
revolution.
e. Refer to Table 9 for cu ft of gas per hr.
f. Multiply gas rate (cu ft/hr) X heating value (Btu/cu ft) using
natural gas heating value from local gas utility/supplier.
EXAMPLE: (0—2000 ft altitude)
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 = 70 sec
Gas rate = 103 cu ft/hr (from Table 9)
Btu heating input = 103 X 975 = 100,425 Btuh
In this example, the orifice size and manifold pressure
adjustment is within ±2 percent of the furnace input rate.
36
Continued
0.64
Orifice Manifold Orifice
No. Pressure No.
42 3.5 42
42 3.2 42
43 3.6 43
44 3.8 43
44 3.5 44
44 3.3 44
45 3.7 45
45 3.4 45
45 3.2 45
Derate Furnace Input Rate
X Multiplier = at Installation
Factor Altitude
0.66
Manifold
Pressure
3.6
3.3
3.7
3.4
3.6
3.4
3.8
3.5
3.3