Carrier 58MXA Installation, Start-Up, And Operating Instructions Manual page 39

TABLE 8—MODEL 58MXA ORIFICE SIZE AND MANIFOLD PRESSURE FOR CORRECT INPUT (Continued)
(TABULATED DATA BASED ON 20,000 BTUH PER BURNER, DERATED 2 PERCENT FOR EACH 1000 FT
ALTITUDE AVG GAS
RANGE HEAT VALUE
(FT) (BTU/CU FT)
650
675
700
725
7001
to 750
8000
775
800
825
850
ALTITUDE AVG GAS
RANGE HEAT VALUE
(FT) (BTU/CU FT)
625
650
675
Altitudes
700
8001
to
725
9000
750
775
800
ALTITUDE AVG GAS
RANGE HEAT VALUE
(FT) (BTU/CU FT)
600
625
650
9001
675
to
700
10,000
725
750
775
*Orifice numbers shown in shading are factory installed.
EXAMPLE: (0-2000 ft altitude)
Furnace input from rating plate is 100,000 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 = 70 sec
Gas rate = 103 cu ft/hr (from Table 11)
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.
SET TEMPERATURE RISE
Temperature rise must be within limits specified on unit
rating plate. Recommended operation is at midpoint of rise or
above. Failure to follow this caution may result in condensing
or overheating the heat exchangers.
Determine and adjust air temperature rise as follows:
FOR USE WITH 040 THROUGH 120 SIZE FURNACES ONLY
ABOVE SEA LEVEL)
0.58
Orifice Manifold Orifice
no. Pressure no.
43 3.5 43
44 3.8 43
44 3.5 44
44 3.3 44
45 3.7 45
45 3.5 45
45 3.3 45
45 3.1 45
45 2.9 45
0.58
Orifice Manifold Orifice
no. Pressure no.
43 3.5 43
44 3.7 43
44 3.5 44
44 3.2 44
45 3.6 45
45 3.4 45
45 3.2 45
45 3.0 45
0.58
Orifice Manifold Orifice
no. Pressure no.
43 3.5 43
44 3.7 44
44 3.4 44
44 3.8 44
45 3.6 45
45 3.3 45
45 3.1 45
45 2.9 45
SPECIFIC GRAVITY OF NATURAL GAS
0.60 0.62
Manifold Orifice Manifold
Pressure no. Pressure
3.7 43 3.8
3.4 43 3.5
3.6 44 3.8
3.4 44 3.5
3.8 44 3.3
3.6 45 3.7
3.4 45 3.5
3.2 45 3.3
3.0 45 3.1
SPECIFIC GRAVITY OF NATURAL GAS
0.60 0.62
Manifold Orifice Manifold
Pressure no. Pressure
3.6 43 3.8
3.4 43 3.5
3.6 44 3.7
3.3 44 3.4
3.8 44 3.2
3.5 45 3.6
3.3 45 3.4
3.1 45 3.2
SPECIFIC GRAVITY OF NATURAL GAS
0.60 0.62
Manifold Orifice Manifold
Pressure no. Pressure
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
1. Place thermometers in return and supply ducts as close to
furnace as possible. Be sure thermometers do not see heat
exchanger so that radiant heat does not affect readings. This
practice is particularly important with straight-run ducts.
2. When thermometer dings stabilize, subtract return-air tem-
perature from supply-air temperature to determine air tem-
perature rise.
3. Adjust temperature rise by adjusting blower speed. Increase
blower speed to reduce temperature rise. Decrease blower
speed to increase temperature rise.
Disconnect 115-v electrical power before changing speed tap.
Failure to follow this warning could result in personal injury.
4. To change blower motor speed selections for heating mode,
remove blower motor lead from control center HEAT termi-
nal. (See Fig. 25.) Select desired blower motor speed lead
from 1 of the other terminals and relocate it to HEAT terminal.
See Table 12 for lead color identification. Reconnect original
39
0.64 0.66
Orifice Manifold Orifice
no. Pressure no.
42 3.2 42
43 3.6 43
43 3.4 43
44 3.6 44
44 3.4 44
45 3.8 44
45 3.6 45
45 3.4 45
45 3.2 45
0.64 0.66
Orifice Manifold Orifice
no. Pressure no.
42 3.2 42
43 3.6 43
44 3.8 43
44 3.6 44
44 3.3 44
45 3.8 44
45 3.5 45
45 3.3 45
0.64 0.66
Orifice Manifold Orifice
no. Pressure no.
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
Manifold
Pressure
3.3
3.7
3.5
3.7
3.5
3.3
3.7
3.5
3.3
Manifold
Pressure
3.3
3.7
3.4
3.7
3.4
3.2
3.6
3.4
Manifold
Pressure
3.3
3.7
3.4
3.6
3.4
3.8
3.5
3.3