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compressor rotation, disconnect unit power and switch two
of the unit's main power leads. Restore unit power and re-
check compressor operation.
Reset thermostat cooling set point to a position above the
space temperature.
Both compressors will shut off. Indoor fan motor will stop
immediately.
Operating Fan for Test and Balance
During the Test and Balance procedure, it is necessary to
operate the supply fan in High Speed without concurrent op-
eration of the Cooling or Heating systems. Use the following
procedure to force the fan speed to High.
1. Set the space thermostat to SYSTEM OFF and FAN in
AUTO.
2. Disconnect unit power. Lock-out/tag out.
3. Open the fan access panel and remove the cover of
control box.
4. Adjust the Low Speed 2-Pin DIP switches on the Unit
Control Board. Set both switches to "OFF." This will
allow the motor to run at full speed in ventilation only.
5. Locate pressure ports or pitot tubes in the return duct
and supply duct to measure external static pressure.
6. Replace control box cover.
7. Restore unit power.
8. Set the space thermostat to FAN CONT.
9. Check the motor speed with stroboscope or similar tool.
Motor shaft speed must be in 1725 to 1760 rpm (28.8 to
29.3 r/s) range for High Speed.
10. Replace the fan access panel.
11. Perform test and balance procedure.
12. Adjust the supply fan speed according to the Pulley and
Drive Adjustment section to deliver the project selection
cfm value. Ensure the selection cfm value is not lower
that the "Min cfm Per Fan Motor Type" for this unit-size
as found in Table 8. See Fan Speed Set-Up section for
alternate method of adjusting supply fan speed through
the Unit Control Board.
To restore the unit to ready-to-start condition, disconnect the
unit power and lock-out/tag-out, set the space thermostat to
FAN AUTO, remove the test pressure ports from the exter-
nal duct locations, and re-set Low Speed 2-Pin DIP switch-
es to factory setting (refer to wiring diagram on control box
cover). Replace the supply fan access panel. Restore unit
power.
Table 8 — FAS/FHS Min Cfm Per Fan Motor Type
2-SPEED FAN
UNIT
MOTOR (AT HIGH
FAS240
FHS240
FAS300
FAS336
Fan Speed Set-Up
These units contain a variable frequency drive (VFD) fan
assembly. The fan operates from a 0-10 Vdc signal.
NOTE: The indoor fan motors are equipped with protection
relays designed to disable unit operation when a problem is
detected. See Typical Wiring Diagram (see Fig. 16) for the
red wires in the Indoor fan control.
Fan motor is wired to connect the motor protection relays in
series.
28
2-SPEED FAN
MOTOR (AT LOW
SPEED)
SPEED)
7,500
5,000
8,450
5,633
10,140
6,760
Specifications subject to change without notice.
UNITS WITH ELECTRO-MECHANICAL CONTROLS
The fan speed set up controls are located on the lower sec-
tion of the Unit Control Board (UCB). (See Fig. 28.)
The Unit Control Board (UCB) voltage is set for 10 Vdc from
the factory to allow for full speed with belt/pulley
adjustments.
The following procedure will allow for fan speed reduction if
desired.
1. Check the job specifications for the cfm (cubic feet per
minute) and ESP (external static pressure) required.
2. Connect a multimeter to the Vdc terminals on the UCB.
3. Set the Range Switch to either A, B, or C per the Switch
Range table. A is the lowest speed range, B is the
middle speed range and C is the highest speed range.
4. Using a straight blade screwdriver, turn the Vdc control
dial to fine tune the Vdc reading until the unit matches
the required airflow setting.
5. Record the reading in the Field Setting field.
NOTE: Fan set-up Vdc is not affected by the operating
stage of the unit.
Fig. 28 — Unit Control Board
FAS-FHS-240-336-02SI
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