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FIGURE 12
OVERLOAD RELAY S42
MANUAL/AUTO RESET ADJUSTMENT
DIAL ADJUSTMENT
TRIP INDICATION
WINDOW
TRIP RANGE
ADJUSTMENT
TEST BUTTON
PUSH TO
TEST
MANUAL/AUTO
RESET SWITCH
H=MANUAL RESET
A=AUTO RESET
LINE VOLTAGE IN
SWITCHED VOLTAGE OUT
FIND FULLLOAD AMPS (FLA) OF
INDOOR BLOWER MOTOR
MARKED ON UNIT RATING
PLATE. SET DIAL TO
THIS VALUE. RELAY
WILL THEN AU
TOMATICALLY TRIP
WHEN FLA EX
CEEDS 125% OF
SET VALUE.
ADJUST TO
POINTER
13-Compressor Contactor K2 (all units)
K2 is a 24V to line voltage contactor used to energize the
second compressor (B2) in response to cooling demand.
All units use threepoledoublebreak contactors for three
phase operation with a 24VAC coil. In 1853 units, contac
tor K2 is used for the second first stage compressor. In all
other units, K2 is used to energize the second stage com
pressor.
In 1603 and 1853 units, K2 is energized after a 30 second
delay is initiated by time delay DL15. The time delay is used
to stagger the electrical load and limit the effects of electri
cal inrush on unit components.
14-Compressor Contactor K14 (1853 only)
K14 is a 24V to line voltage contactor used to energize the
3rd compressor (B13) in response to second stage cooling
demand. Contactor K14 is identical to contactor K1. All units
use threepoledoublebreak contactors.
15-Indoor Blower Contactor K3 (all units)
K3 is a 24V to line voltage contactor used to energize the
indoor blower motor in response to blower demand. In cool
ing mode K3 is energized by pilot relay K46 in response to
cooling or constant fan demand. In heating mode K3 is en
ergized by relays K20 or K25 (in the heating section) in re
sponse to heating demand. All units use threepoledouble
break contactors.
16-Condenser Fan Contactor K10
(all units except 1353)
K10 is a 24V to line voltage contactor used to energize
both condenser fans (B4 and B5) in response to demand.
Both condenser fans are energized with the first compres
sor upon receiving a cooling demand. Both fans operate
throughout all cooling (compressor) demand. All units use
threepoledoublebreak contactors with a 24VAC coil.
17-Combustion Air Blower Relay K13
(all units)
Relay K13 is a DPDT relay located inside the control box of
12.5 ton and smaller units. K13 is energized by 1st stage
heating demand from thermostat and is energized throughout
the heating demand. When energized, K13 normally open
contacts close to energize combustion air blower and begin a
heating sequence. A centrifugal prove" switch located in
combustion air blower motor closes as the motor nears full
speed to prove" combustion air blower operation. When the
switch closes, the ignition control and gas valve are energized
to begin a heating sequence. In 15 ton and larger units, K13 is
located in the heating controls section of the unit.
18-Condenser Outdoor Fan Contactor K68
(2553, 2753, 3003 only)
CHA16 18.5 ton and larger units are equipped with sepa
rate condenser fan contactors for each stage of cooling.
K68 is identical to K10. In units equipped with two con
denser fan contactors, K10 operates with the first stage
circuit on a call for first stage cooling and K68 operates
with the second stage circuit on a call for second stage
cooling.
19-Pilot Relay Board A11
(1853, 2553, 2753, 3003 only)
A11 is a pilot relay board (figure 13) used in all GCS1615
ton and larger units. Pilot relays are used in 24VAC control
circuits to limit voltage drop caused by a long run of thermo
stat wire. The relays on the circuit board are added electri
cally in between the thermostat (or thermostat control sys
tem) and the contactors in the unit. The relays draw much
less current from the transformer than the unit contactors.
When a long run of thermostat wire is used from the unit to
the thermostat and back to energize unit contactors, the
current drawn by
the contactors
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