Carrier 58SX040-IBC - Manual (Page 7)

PILOT FLAME BURNER FLAME
4. High Altitude—Input ratings apply for altitudes up to
2000 feet. Ratings for altitudes above 2000 ft must be
4% less for each 1000 ft above sea level.
Temperature Rise— Do NOT operate furnace outside range
of temperature rise specified on unit rating plate. Determine
air temperature rise as follows:
1. Place thermometers in retmm and supply ducts as near
furnace as possible. Thermometers must not “see”
heating element or radiant heat may affect readings.
This practice is particularly important with straight-
run ducts.
2. When thermometer readings stabilize, subtract return-
air temperature from supply-air temperature to deter­
mine air temperature rise.
3. Adjust temperature rise by adjusting blower speed.
Increase blower speed to reduce temperature rise.
Decrease blower speed to increase temperature rise.
Thermostat Heat Anticipator Adjustment— Thermostat
heat anticipator must be set to match amp draw of compo­
nents in R-W circuit. Accurate amp draw measurements can
be obtained at thermostat subbase terminals R and W. Fig­
ure 8 illustrates an easy method of obtaining these measure­
ments. Amp reading should be taken after blower has
started on its heating speed.
Safety Check of Limit Control— Control shuts off combus­
tion gas supply and energizes circulating-air blower motor if
furnace overheats.
Recommended method of checking this limit control is to
gradually block off return air after furnace has been operat­
ing for at least 5 minutes. As soon as limit control func­
tions, return-air opening should be unblocked to permit
normal air circulation. By using this method to check limit
control, proper functioning can be determined and furnace
will fail-safe if circulating air supply is restricted or motor
fails. If limit control does not function during this test, iden­
tify and correct cause of malfunction.
Safety Check of Flow-Sensing Switch— This control
proves operation of draft inducer. Check switch operation as
follows:
1. Turn off 115-v power supply to furnace.
2. Remove control access panel and disconnect inducer-
motor lead wires from inducer printed-circuit board.
3. Turn on 115-v power supply to furnace.
4. Close thermostat switch as if making normal furnace
start. When flow-sensing switch is functioning prop­
erly, gas should not flow to pilot and ignitor should not
operate. If either pilot gas flow or ignitor operation
occurs when inducer motor is disconnected, shut fur­
nace down immediately. Determine cause of malfunc­
tion and correct condition.
5. Turn off 115-v power supply to furnace.
6. Reconnect inducer-motor leads, reinstall control access
panel, and turn on 115-v power supply.