Carrier 58UXT Series, Operating Instructions Manual, Page: 22 / 24

k. Multiply gas rate cu ft/hr by heating value (Btu/cu ft).
l. Move setup switch SW-2 to OFF position and jumper R and
W2 thermostat connections. (See Fig. 18.) This keeps
furnace locked in high-heat operation. Repeat items h
through k for high-heat operation.
EXAMPLE: (High-heat operation at 0–2000 ft altitude)
Furnace input from rating plate is 85,000 Btuh
Btu heating input = Btu/cu ft X cu ft/hr
Heating value of gas = 1050 Btu/cu ft
Time for 1 revolution of 2-cu ft dial = 92 sec
Gas rate = 80 cu ft/hr (from Table 10) Btu heating input =
1050 X 80 = 84,000 Btuh. In this example, the orifice size
and manifold pressure adjustment is within ±2 percent of
the furnace input rate.
NOTE:
Measured gas inputs (high heat and low heat) 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.
m. Remove jumper across R, W/W1, and W2 thermostat
connections to terminate call for heat.
5. Set temperature rise.
Place SW-2 in ON position. Jumper R to W/W1 and W2 to
check high-gas-heat temperature rise. To check low-gas-heat
temperature rise, remove jumper to W2. Determine air tem-
perature rise for both high and low fire. Do not exceed
temperature rise ranges specified on unit rating plate for high
and low stage.
a. Place duct thermometers in return and supply ducts as near
furnace as possible. Be sure thermometers do not see heat
exchangers so that radiant heat will not affect thermometer
readings. This is particularly important with straight run
ducts.
b. When thermometer readings stabilize, subtract return-air
temperature from supply-air temperature to determine tem-
perature rise.
NOTE: If the temperature rise is outside this range, first check:
(1.) Gas input for low- and high-stage operation.
(2.) Derate for altitude if applicable.
(3.) Return and supply ducts for excessive restrictions
causing static pressures greater than 0.50-in. wc.
c. Adjust air temperature rise by adjusting blower speed.
Increase blower speed to reduce temperature rise. Decrease
blower speed to increase temperature rise. For high fire,
speed selection can be med-high, med (5-speed blowers
only), or med-low (factory setting). For low fire, speed
selection can be low (factory setting), med-low, or med
(5-speed blowers only).
Disconnect the electrical power before changing the speed tap
(or removing motor lead cap, if used, on 5-speed motors). A
failure to follow this warning can cause personal injury.
NOTE:
For units with 5-speed motors, make sure the unused
speed tap is either capped or placed on SPARE terminal on control
board before power is restored.
d. To change motor speed selection for high heat, remove
blower motor lead from control HIGH-GAS-HEAT termi-
nal. (See Fig. 17 and 19.) Select desired blower motor
speed lead from 1 of the other terminals and relocate it to
the HIGH-GAS-HEAT terminal. (See Table 11 for lead
color identification.) Reconnect original lead to the SPARE
terminal (or use insulating cap, if used, in furnaces using
5-speed blower motors). Follow this procedure for proper
selection of cool and low-gas-heat speed selection.
Table 10—Gas Rate (CU FT/HR)
SECONDS
FOR 1
REVOLUTION
SIZE OF TEST DIAL
SECONDS
FOR 1
REVOLUTION
SIZE OF TEST DIAL
I
Cu Ft
2
Cu Ft
5
Cu Ft
1
Cu Ft
2
Cu Ft
5
Cu Ft
10 360 720 1800 50 72 144 360
11 327 655 1636 51 71 141 355
12 300 600 1500 52 69 138 346
13 277 555 1385 53 68 136 340
14 257 514 1286 54 67 133 333
15 240 480 1200 55 65 131 327
16 225 450 1125 56 64 129 321
17 212 424 1059 57 63 126 316
18 200 400 1000 58 62 124 310
19 189 379 947 59 61 122 305
20 180 360 900 60 60 120 300
21 171 343 857 62 58 116 290
22 164 327 818 64 56 112 281
23 157 313 783 66 54 109 273
24 150 300 750 68 53 106 265
25 144 288 720 70 51 103 257
26 138 277 692 72 50 100 250
27 133 267 667 74 48 97 243
28 129 257 643 76 47 95 237
29 124 248 621 78 46 92 231
30 120 240 600 80 45 90 225
31 116 232 581 82 44 88 220
32 113 225 563 84 43 86 214
33 109 218 545 86 42 84 209
34 106 212 529 88 41 82 205
35 103 206 514 90 40 80 200
36 100 200 500 92 39 78 196
37 97 195 486 94 38 76 192
38 95 189 474 96 38 75 188
39 92 185 462 98 37 74 184
40 90 180 450 100 36 72 180
41 88 176 439 102 35 71 178
42 86 172 429 104 35 69 173
43 84 167 419 106 34 68 170
44 82 164 409 108 33 67 167
45 80 160 400 110 33 65 164
46 78 157 391 112 32 64 161
47 76 153 383 116 31 62 155
48 75 150 375 120 30 60 150
49 73 147 367
Table 11—Speed Selection
COLOR SPEED AS SHIPPED
White Common C
OM
Black High Cool
Yellow Med-High SPARE
Orange† Med SPARE or Capped
Blue Med-Low High-Gas Heat
Red Low* Low-Gas Heat
* Continuous blower speed
† Available on 5-speed blowers only
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