Carrier 58MXB Series, Installation, Start-Up, And Operating Instructions Manual, Page: 55 / 60

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 16)
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
UNIT DAMAGE HAZARD
Failure to follow this caution may result in overheating the
heat exchangers or condensing flue gases in heat exchanger
areas not designed for condensate.
Temperature rise must be within limits specified on furnace
rating plate. Recommended operation is at midpoint of rise
range or slightly above.
Determine and adjust air temperature rise as follows:
1. Place thermometers in return and supply ducts as close to
furnace as possible. Be sure thermometers do not see heat
exchangers so that radiant heat does not affect readings. This
practice is particularly important with straight-run ducts.
2. When thermometer readings 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.
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.
Disconnect 115-v electrical power before changing speed tap.
4. To change blower motor speed selections for heating mode,
remove blower motor lead from control HEAT terminal. (See
Fig. 36.) Select desired blower motor speed lead from 1 of the
other motor leads and relocate it to HEAT terminal. See Table
17 for lead color identification. Reconnect original lead on
SPARE terminal.
Follow this same procedure for proper selection of COOL
speed selection.
ADJUST BLOWER OFF DELAY (HEAT MODE)
The blower off delay has 4 adjustable settings from 90 sec to 180
sec. (See Table 18.) The blower off delay jumpers are located on
the furnace control (See Fig. 31). To change the blower off delay
setting, move the jumper from one set of pins on the control to the
pins used for the desired blower off delay. Factory blower off
delay setting is 120 sec.
SET THERMOSTAT HEAT ANTICIPATOR
When using a nonelectronic thermostat, the thermostat heat
anticipator must be set to match the amp draw of the electrical
components in R-W circuit. Accurate amp draw readings can be
obtained at thermostat subbase terminals R and W. Fig. 58
illustrates the easy method of obtaining actual amp draw. The amp
reading should be taken after blower motor has started and furnace
is heating. Connect ammeter wires as shown in Fig. 58. The
thermostat anticipator should NOT be in the curcuit while mea-
suring current. If thermostat has no subbase, the thermostat must
Table 15–Altitude Derate Multipler for U.S.A.
ALTITUDE
(FT)
PERCENT
OF DERATE
DERATE MULTIPLIER
FACTOR*
0–2000 0 1.00
2001–3000 4–6 0.95
3001–4000 6–8 0.93
4001–5000 8–10 0.91
5001–6000 10–12 0.89
6001–7000 12–14 0.87
7001–8000 14–16 0.85
8001–9000 16–18 0.83
9001–10,000 18–20 0.81
* Derate multiplier factors are based on midpoint altitude for altitude range.
Table 16—Gas Rate (cu ft/hr)
SECONDS
FOR 1
REVOLUTION
SIZE OF TEST DIAL
SECONDS
FOR 1
REVOLUTION
SIZE OF TEST DIAL
1
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 73 147 367 124 29 58 145
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