I-Unit Components - Lennox LGH094U Unit Information

I-UNIT COMPONENTS

WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon­
nect switch(es). Unit may have multiple
power supplies.
All 7.5 through 12.5 ton (38.1 through 70.3 kW) units are
configure to order units (CTO). The LGH unit compo­
nents are shown in figure 1, 2 or 3. All units come stan­
dard with hinged unit panels. All L1, L2 and L3 wiring is
color coded; L1 is red, L2 is yellow and L3 is blue.
A-Control Box Components
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can affect electronic com­
ponents. Take precautions during unit installation
and service to protect the unit's electronic con­
trols. Precautions will help to avoid control expo­
sure to electrostatic discharge by putting the unit,
the control and the technician at the same electro­
static potential. Neutralize electrostatic charge by
touching hand and all tools on an unpainted unit
surface, such as the gas valve or blower deck, be­
fore performing any service procedure.
LGH control box components are shown in figures 4, 5 and
6. The control box is located in the upper portion of the com­
pressor compartment.
1-Disconnect Switch S48 (Optional)
All units may be equipped with an optional disconnect switch
S48. Other factory or field installed optional circuit breakers
may be used, such as CB10. S48 and CB10 are toggle
switches, which can be used by the service technician to dis­
connect power to the unit.
2-Control Transformer T1
All use a single line voltage to 24VAC transformer mounted
in the control box. Transformer supplies power to control
circuits in the unit. The transformer is rated at 70VA and is
protected by a 3.5 amp circuit breaker (CB8). The 208/230
(Y) voltage transformers use primary voltage taps as
shown in figure 7, while 460 (G) and 575 (J) voltage trans­
formers use a single primary voltage tap.
3-Outdoor Fan Relay K10, K68
Outdoor fan relays K10 and K68 are DPDT relays with a
24VAC coil. In standard and high efficiency units, K10 and
K68 energize condenser fans B4 and B5. In ultra high effi­
ciency units, K10 and K68 energize compressor 1 and 2
crankcase heaters.
4-Outdoor Fan Capacitors C1, C2 (non-Ultra
units)
Fan capacitors C1 and C2 370V / 10 MFD capacitors are
used to assist in the start up of condenser fans B4 and B5.
208/230V TRANSFORMER
ORANGE
5-C. A. I. Transformers T3 all 460V &575V units
All LGH 460 (G) and 575 (J) voltage units use transformer
T3. The auto voltage to 230VAC transformer is mounted in
the control box. The transformer has an output rating of
0.5A. T3 transformer supplies 230 VAC power to combus­
tion air blower motor (B6).
6-Compressor Contactor K1, K2
All compressor contactors are three‐pole, double‐break con­
tactors with 24VAC coils. K1 and K2 (both energized by A55)
energize compressors B1 and B2. On CE M-volt units, contac­
tor is CE approved by manufacturer (Siemens). See figure 8.
7-Combustion Air Inducer Relay K13
Combustion air inducer relay K13, used in all LGH units, is a
DPDT relay with a 24VAC coil. K13 is energized by the A55
Unit Controller. K13 remains energized throughout the heat­
ing demand. When energized, K13 N.O. contacts close to
energize combustion air blower and begin a heating se­
quence. Pressure switch S18, located in the compressor
compartment, closes as combustion air static pressure
falls to "prove" combustion air inducer operation. When
S18 closes, the ignition controls and gas valves are ener­
gized to begin a heating sequence.
8-Blower Contactor K3
K3 is used in units with a constant blower speed or a staged
blower which is not equipped with a bypass option. K3 is a
three‐pole‐double‐break contactor with a 24VAC coil used
to energize the indoor blower motor B3 in response to blow­
er demand. K3 is energized by A55 Unit Controller. On
M-volt CE units, the contactor is CE approved by manufac­
turer (Siemens). See figure 8.
Page 28
BLUE YELLOW
SECONDARY
208 VOLTS
RED
230 VOLTS
PRIMARY
BLACK
FIGURE 7
CONTACTOR
FIGURE 8