Lennox LGT156H Installation Instructions Manual page 14

Instructions provided with the thermostat may also be
used to initiate blower only (G) demand. Unit will cycle on
thermostat demand. The following steps apply to
applications using a
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.
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.
WARNING
1-Make sure that unit is installed in accordance with the
installation instructions and applicable codes.
2-Inspect all electrical wiring, both field‐ and factory‐
installed, for loose connections. Tighten as required.
3-Check to ensure that refrigerant lines do not rub against
the cabinet or against other refrigerant lines.
4-Check voltage at disconnect switch. Voltage must be
within range listed on nameplate. If not, consult power
company and have voltage condition corrected before
starting unit.
5-Make sure filters are new and in place before start‐up.
B-Blower Access
LGT/LCT156, 180, 210, 240, 300
typical electro-mechanical
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 15.
3- Pull base toward outside of unit.
C-Determining Unit CFM
IMPORTANT - Multi-staged supply air 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.
Variable Air Volume Units - Refer to the Variable Air
Volume Start-Up section.
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 15. Do not exceed
minimum and maximum number of pulley turns as
shown in table 3.
MINIMUM AND MAXIMUM PULLEY ADJUSTMENT
Belt Minimum Turns Open
A Section
B Section
*No minimum number of turns open when B belt is used on
pulleys 6" O.D. or larger.
Page 14
TABLE 3
Maximum Turns Open
No minimum
1*
5
6