Page 13
507124-04 3/2016
Blower Operation and Adjustments
Supply Air Inverter Units -
The blower rotation will
always be correct on units equipped with an inverter.
Checking blower rotation is not a valid method of
determining voltage phasing for incoming power.
Supply Air Inverter Units and Units Equipped With
Optional Voltage or Phase Detection
- The Unit
Controller checks the incoming power during start-up. If
the voltage or phase is incorrect, the Unit Controller will
display an alarm and the unit will not start.
IMPORTANT
Three Phase Scroll Compressor Voltage Phasing
Three phase scroll compressors must be phased se
quentially to ensure correct compressor and blower*
rotation and operation. Compressor and blower are
wired in phase at the factory. Power wires are color-
coded as follows: line 1-red, line 2-yellow, line 3-blue.
1-Observe suction and discharge pressures and blow
er* rotation on unit start-up.
2-Suction pressure must drop, discharge pressure must
rise and blower* rotation must match rotation marking.
If pressure differential is not observed or blower* rota
tion is not correct:
3-Disconnect all remote electrical power supplies.
4-Reverse any two field-installed wires connected to
the line side of S48 disconnect or TB13 terminal strip.
Do not reverse wires at blower contactor.
5-Make sure the connections are tight.
Discharge and suction pressures should operate at
their normal start‐up ranges.
*Supply air inverter blower motors should rotate in the
correct direction; verify scroll compressor rotation
separately. Contact technical support if the blower is
rotating incorrectly.
A-Blower Operation
Initiate blower only (G) demand at thermostat according
to instructions provided with thermostat. Unit will cycle on
thermostat demand. The following steps apply to
applications using a typical electro-mechanical
thermostat.
1- Blower operation is manually set at the thermostat
subbase fan switch. With fan switch in
ON
position,
blowers will operate continuously.
2- With fan switch in
AUTO
position, the blowers will
cycle with demand. Blowers and entire unit will be off
when system switch is in
OFF
position.
B-Blower Access
1- Disconnect jack/plug connector to blower motor. Also
disconnect jack/plug connector heating limit switches
on gas units.
2- Remove screws on either side of blower assembly
sliding base. See figure 13.
3- Pull base toward outside of unit.
C-Determining Unit CFM
IMPORTANT -
Supply air inverter
units are factory-set
to run the blower at full speed when there is a blower (G)
demand without a heating or cooling demand. Refer to
the field-provided, design specified CFM for all modes
of operation. Use the following procedure to adjust
motor pulley to deliver the highest CFM called for in the
design spec. See Inverter Start-Up section to set blower
CFM for all modes once the motor pulley is set.
1- The following measurements must be made with a
dry indoor coil. Run blower (G demand) without a
cooling demand. Measure the indoor blower shaft
RPM. Air filters must be in place when measurements
are taken.
2- With all access panels in place, measure static
pressure external to unit (from supply to return).
Blower performance data is based on static pressure
readings taken in locations shown in figure 14.
Note - Static pressure readings can vary if not taken
where shown.
3- Referring to page 17, use static pressure and RPM
readings to determine unit CFM. Use page 18 when
installing units with any of the optional accessories
listed.
4- The blower RPM can be adjusted at the motor pulley.
Loosen Allen screw and turn adjustable pulley
clockwise to increase CFM. Turn counterclockwise to
decrease CFM. See figure 13. Do not exceed
minimum and maximum number of pulley turns as
shown in table 2.
TABLE 2
MINIMUM AND MAXIMUM PULLEY ADJUSTMENT
Belt
Minimum Turns Open
Maximum Turns Open
A Section
No minimum
5
B Section
1*
6
*No minimum number of turns open when B belt is used on
pulleys 6” O.D. or larger.
