I-Unit Components - Lennox LDT DUAL FUEL Series 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 disconnect
switch(es). Unit may have multiple power
supplies.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic
electronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
The LDT unit parts arrangement are shown in FIGURE
1. All L1, L2, and L3 wiring is color coded; L1 is red, L2 is
yellow, and L3 is blue. See wiring diagrams in the back of
this manual for complete call out of components per LDT
unit. All 7.5 through 12.5 ton units are configure to order
units (CTO).
A-Control Box Components
LDT control box components are shown in FIGURE 2. The
control box is located in the upper portion of the compres-
sor 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 techni-
cian to disconnect power to the unit.
2-Control Transformer T1
All use a single line voltage to 24VAC transformer mount-
ed in the control box. Transformer supplies power to con-
trol circuits in the unit. The transformer is rated at 92VA
and is protected by a 6 amp circuit breaker (CB8). The
208/230 (Y) voltage transformers use primary voltage
taps as shown in FIGURE 3, while 460 (G) and 575 (J)
voltage transformers use a single primary voltage tap.
discharge can affect
208/230V TRANSFORMER
BLUE
ORANGE
3-C. A. I. Transformers T3 575V Units
All LDT 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 combustion air
blower motor (B6).
4-Transformer T18
T18 is a single line voltage to 24VAC transformer used in
all LDT units. T18 is rated at 70VAC and is protected by a
3.5 amp circuit breaker (CB18).
5-Compressor Contactor K1, K2
All compressor contactors are three-pole, double-break
contactors with 24VAC coils. K1 and K2 (both energized
by A55) energize compressors B1 and B2.
6-Power Exhaust Relay K65 (PED units)
Power exhaust relay K65 is a N.O. DPDT relay with a
24VAC coil. K65 is used in all LDT units equipped with
the optional power exhaust dampers. K65 is energized by
the economizer control panel (A56), after the economizer
dampers reach 50% open (adjustable in CORE). When
K65 closes, the exhaust fan B10 is are energized.
7-Terminal Block (TB13)
TB13 terminal block distributes line voltage power to the
line voltage items in the unit.
Page 14
YELLOW
SECONDARY
208 VOLTS
RED
230 VOLTS
PRIMARY
BLACK
FIGURE 3