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Table 9 — Fan Rpm at Motor Pulley Settings* (Factory-Supplied Drives)
UNIT
542J
0
1
⁄
2
150
†
†
1132
180
†
†
1010
*Approximate fan rpm shown.
†Due to belt and pulley size, pulley cannot be set to this number of turns
open.
Fig. 25 — Indoor-Fan Pulley Alignment
and Adjustment
C. Outdoor-Fan Adjustment (Fig. 26)
1. Turn off unit power supply.
2. Remove access panel(s) closest to the fan to be adjusted.
3. Loosen fan hub setscrews.
4. Adjust fan height on shaft using a straightedge placed
across the fan orifice.
5. Tighten setscrews and replace panel(s).
6. Turn on unit power.
D. Ventilation Sequence
If unit is equipped with economizer or two-position damper,
the damper will open to the minimum position whenever the
indoor fan runs.
MOTOR PULLEY TURNS OPEN
1
1
1
⁄
2
2
1105
1078
989
968
2
1
⁄
3
3
1
⁄
2
2
1051
1024
997
947
926
905
NOTE: To run units at speeds not listed, field-supplied drives are
required.
NOTE: Dimensions are in inches.
Fig. 26 — Outdoor Fan Adjustment
Two-Position Damper
Whenever the indoor fan is energized (during heating, cool-
ing, or continuous fan), 24-v power is on indoor fan contactor
(IFC) and the economizer or two-position damper control. The
damper motor will be energized at terminal TR, and the damper
will drive open to minimum vent position. The damper motor
will stop, and the damper will remain in the minimum ven-
tilation position until the indoor fan is shut off. When the in-
door fan is shut off, the damper motor will spring return to
the closed position.
Economizer
When unit is equipped with an economizer, additional out-
door air can be brought in through the damper to provide cool-
ing. If the unit calls for cooling and the outdoor-air tempera-
ture is below the outdoor-air thermostat setting, the economizer
motor starts. The damper drives open until it reaches full open
or until the mixed-air set point is met. When cooling load is
satisfied, or outdoor air is no longer below the outdoor-air ther-
mostat setting, the damper returns to the minimum position
if indoor fan is running, or closes if the indoor fan is not
running.
If the leaving-air thermistor (located on the indoor-fan blower
housing) senses a leaving-air temperature less than 50 F, the
damper closes until the leaving-air temperature is above
50 F.
—19—
4
4
1
⁄
5
2
970
943
916
883
862
841
5
1
⁄
6
2
889
862
820
799
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