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ELECTRIC HEAT CONTROL SECTION
(45 − 120 kW electric heat only)
17−Electric Heat Relay K9
All LCA/LCC series units with 45 − 120 kW electric heat use an
electric heat relay K9. K9 is a N.O. SPST pilot relay intended to
electrically isolate the unit’s 24V circuit from the electric heat
24V circuit. K9 is energized by the main control board A55.
K9−1 closes, enabling T2 to energize the electric heat con-
trol panel A60 and contactors K17 and K18.
18−Electric Heat Transformer T2
All LCA/LCC series units with 45 − 120 kW electric heat
use a single line voltage to 24VAC transformer mounted
in the electric heat control hat section in the control box.
The transformer supplies power to all electric heat con-
trols (contactors and coils). The transformer is rated at
70VA and is protected by a 3.5 amp circuit breaker CB13.
The 208/230 (Y) voltage transformers use two primary
voltage taps as shown in figure 4. Transformer T2 is iden-
tical to T1.
INTEGRATED MODULAR CONTROL BOARDS
The Integrated Modular Control (IMC) is a series of control
boards which integrates most control functions required for the
LGA/LGC/LCA/LCC units. The control boards are located in
the upper left hand corner of the control box. The control
includes complete unit diagnostics with permanent code
storage, field programmable control parameters and
control options, on-site testing, and serial communica-
tions. Seven different printed circuit boards (see figure 7)
make-up the modular configurations for the LGA/LGC/
LCA/LCC units. See table 1 for a list of control panels
used for each unit. See figure 7 for control location. For fur-
ther information refer to Integrated Modular Control Guide sent
with each unit.
TABLE 1
UNIT
CONTROL PANELS
A55 A57 A59 A58 A60 A61 A56
LGA/LGC X X X X OPT
LCA/LCC X X X X OPT
19−Main Control Module A55 (all units)
The main control module A55 is the heart of the system. It
controls one compressor, one two-stage gas valve (first
stage), one bank of electric heat, one outdoor fan, and one
blower. A55 includes the thermostat inputs, serial commu-
nications ports, diagnostic code display, control pushbutton,
system configuration dip switches, and four expansion ports. A
diagnostic code list is located on the back side of the left ac-
cess panel.
20−Compressor 2 Control Module A57
(all units)
The compressor 2 control module A57 controls one addi-
tional compressor stage for the LGA/LGC/LCA/LCC units.
A57 includes all inputs and outputs required for compressor
and fan control, compressor stages diagnostics, and low
ambient control.
21−Compressor 3 & 4 Control Module
A59 (all units)
The compressor 3 & 4 control module A59 controls two addi-
tional compressor stages for the LGA/LGC/LCA/LCC units.
A59 includes all inputs and outputs required for compressor
and fan control, compressor stage diagnostics, and low ambi-
ent control.
22−Gas Valve Control Module A58
(LGA/LGC units)
The gas valve control module A58 controls an additional burn-
er with a two-stage gas valve. A58 includes all inputs and out-
puts required for control and diagnostics of one two-stage gas
valve burner (second stage).
23−Electric Heat Control Module A60
(LCA/LCC units if 45 − 120 kW
electric heat is used)
The electric heat control module A60 is used to control a
second electric heat bank. A60 is used on the LCA/LCC
units.
24−Economizer Control Module A56
(Economizer only)
The economizer control module A56 controls the econo-
mizer. A56 has four different cooling modes, sensible
temperature, outdoor enthalpy, differential enthalpy, and
global control.
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