Lennox ALLIED Commercial TCA180S2B Standard Manual page 21

12−Blower Motor Overload Relay S42
S42 is a manual reset overload relay, used in all TCA units
equipped with 10 or more HP standard efficiency motors.
The relay is connected in line with the blower motor to mon-
itor the current flow to the motor. When the relay senses an
overload condition, a set of normally closed contacts opens
de−energizing the 24 volt output of T1. See figure figure 4.
13−Power Exhaust Relay K65 (PED units)
Power exhaust relay K65 is a DPDT relay with a 24VAC
coil. K65 is used in Y voltage units equipped with the
field installed optional power exhaust dampers. K65 is
energized by the economizer enthalpy control A6, after
the economizer dampers reach 50% open (adjustable)
When K65 closes, exhaust fans B10 and B11 are ener-
gized.
Adjust relay amp setting according to value given on the blower motor nameplate. Proper relay amp
Use small slotted screwdriver to adjust control mode from automatic reset (A) to manual reset (H).
Control must be in the manual reset mode (H) to perform a test. Press the red test button. Green trip
SIEMENS OVERLOAD RELAY
setting equals motor nameplate FLA X service factor of 1.15 X .95.
indicator should pop out. Press the blue reset screw to reset the relay.
14−MCC Control A45
The main control module A45 (figure 6) controls all cool-
ing operation and serves as a staging point for all internal
inputs to the appropriate components of the TCA unit. The
MCC control receives and sends out 24 volts to the com-
ponents located in the TCA control box, economizer and
supply/return compartments. The control communicates to
compressors contactors K1, K2 , condenser fan relay K10 and
indoor blower contactor K3. Thermostat hook ups (TB1) and
low voltage hook ups (TB14) are located on the board. See
tables 2 and 3 for terminal designations. Tables 4, 5 , 6 and 7
show pin terminal designations.
Features
The MCC A45 is equipped with a green LED for board sta-
tus. See table 1 for LED flash codes. While in the cooling
mode the board will incorporate AUTO−STAGING. If the
board receives a Y3 demand (if applicable) the board will
energize Y1, Y2 and Y3 in successive order. In the same
manner a Y2, will be interpreted as a Y1/Y2. The MCC
control also incorporates a minimum run time of 4 minutes
for up to 3 independent cooling stages. This 4 minute run
time can be interrupted by pushing SW1 located on the
board. If pressed for 3 seconds or more, the control goes
into TEST mode disabling AUTO−STAGING. The MCC
control board is used for all T class units. A dip switch,
factory set, is provided to configure to unit type (TGA
gas, TCA cooling/electric heat, THA heat pump) See fig-
ure 5.
BLUE RESET BUTTON IN
FACTORY-SET AUTO MODE
(Turn clockwise to H for
manual reset)
GREEN TRIP INDICATOR
(Flush with surface −− not tripped;
Above surface −− tripped)
RED TEST BUTTON
AMP ADJUSTMENT DIAL
FIGURE 4
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