Lennox LDT Series Information page 15

4-Terminal Block TB13
TB13 terminal block distributes line voltage power to the
line voltage items in the unit.
5-Outdoor Fan Motor Fuse Block & Fuses
F10 Power Exhaust Fan Motor Fuse
Block and Fuses F6.
STD SCCR 240V, 300V and higher rated SCCR units have
three line voltage fuses F10 provide overcurrent protection
to all condenser fans. Two line voltage fuses F6 provide
overcurrent protection to the two optional power exhaust
fans. The fuses are rated at 30A in all 208/230V units but
10A in the 208/230V 240U and 300U models.
6-Compressor Contactor K1 and K2
All compressor contactors are three‐pole‐double‐break
contactors with 24VAC coils. In all units, K1 (energized by
A55) energizes compressors B1 in response to first stage
cool demand, and K2 (energized by A55) energizes B2 in
response to second stage cool demand.
7-Blower Contactor K3
Blower contactor K3,
three‐pole‐double‐break contactor with a 24VAC coil used
to energize the indoor blower motor B3 in response to
blower demand. K3 is energized by Unit Controller (A55).
Optional Staged-Blower units which are not equipped with
a bypass option will not have a K3.
8-Ultraviolet Germicidal Lamp (UVC)
Transformer T49
UVC transformer T49 is used in 460V and 575V units which
are equipped with a UVC. The auto voltage to 230VAC
transformer is installed in the control box. The transformer
has an output rating of 0.5 amps. T49 transformer supplies
230VAC power to the UVC lamp.
9-Burner Controls A3 & A12
Units have two burner controls. A3 controls gas heat
section one and A12 controls gas heat section two. The first
gas heat section and the second gas heat section burner
controls are identical. Both burner controls are factory set
and are not adjustable. The control makes three attempts
at ignition and then locks out the system if ignition is not
obtained after the third trial. Reset after lockout requires
only breaking and remaking thermostat demand. The
control shuts off gas flow immediately in the event of a gas
or power failure. Upon restoration of gas and power, the
used in all units, is
control will restart the ignition sequence and continue until
flame is established or system locks out. For a more
detailed description see the Gas Heat Components
section.
10-Power Exhaust Relay K65 & K231 (PED
units)
Power exhaust relays K65 and K231 are N.O. DPDT relays
with a 24VAC coil. The relay are used in units equipped with
the optional power exhaust dampers. K65 and K231 are
energized by the A55 Unit Controller, after the economizer
dampers reach 50% open (adjustable in ECTO). When K65
closes, exhaust fan B10 is energized and when K231
closes B11 is energized.
11-Variable Frequency Drive A96 (optional)
Staged-Blower units are equipped with a VFD which alters
the supply power frequency and voltage to the blower
motor. Blower speed is staged depending on the
compressor stages, heating demand, ventilation demand,
or smoke alarm. The amount of airflow for each stage is
preset from the factory. Airflow can be adjusted by
changing ECTO parameters in the A55 Unit Controller. The
a
VFD is located below the Unit Controller.
12-VFD Power To Motor Contactor K202
(optional)
Contactor is used in Staged-Blower units equipped with a
VFD bypass option. The three pole 40 amp contactor with a
24VAC coil is energized by the A55 Unit Controller. K202
allows power from the VFD to the B3 blower motor in
response to blower demand.
13-Inverter Start Forward Rotation Relay
K203 (optional)
Relay is used in optional Staged-Blower units and is a
three-pole double-throw relay with a 24VAC coil. K203 is
energized by the A55 Unit Controller and provides input to
the A96 VFD to start blower forward rotation. K203 also
de-energizes K3 allowing A96 to control B3 blower.
14-Unit Controller A55
The Unit Controller provides all unit control functions, unit
status information, unit diagnostics, programmable
parameters and USB verification and profile sharing. Refer
to the Unit Controller guide provided with the unit.
Thermostat wires are connected to J297 on the Unit
Controller.
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