FIGURE 11
BLUE
YELLOW
ORANGE
RED
BLACK
230 VOLTS
PRIMARY SECONDARY
TRANSFORMER T1 208/230V
SHOWN
208 VOLTS
Page 23
FIGURE 10
LOW VOLTAGE
TERMINAL STRIP TB1
GCS16 LOW VOLTAGE TERMINAL STRIP
ALL UNITS
TO INSERT OR RELEASE
WIRE, DEPRESS CENTER
WITH PEN OR SMALL
SLOT SCREWDRIVER .
3-Terminal Block TB17 (2553, 2753, 3003)
TB17 is a low voltage terminal block located in the control
box of 18.5 ton and larger units. The terminal strip is de
signed for diagnostic troubleshooting and test running the
unit from the control box area. TB17 terminals are desig
nated as shown in table 1:
TABLE 1
TB17 TERMINAL DESIGNATIONS
TERMINAL
NUMBER
1
2
3
4
5
6
24 VAC Power
Input to pilot relay K66
(24VAC applied here will energize 1st stage cooling)
Input to pilot relay K67
(24VAC applied here will energize 2nd stage cooling)
24 VAC Common
First stage thermostat Y1
Second stage thermostat Y2
4-Transformer T1 (all units)
All GCS16 series units
use a single line volt
age to 24VAC trans
former mounted in the
control box. The trans
former supplies power
to control circuits in the
unit (except the heat
ing section). Transformer is rated at 70VA. 208/230 (P) volt
age transformers use two primary voltage taps as shown in
figure 11.
In 18.5 ton and larger units, T1 is used only to supply 24VAC
power to the pilot control circuit and all 24VAC devices other
than the contactors and transformer T18 is used to supply
24VAC power to the contactors.
5-Transformer Fuse F1 (all units)
T1 transformer is equipped with an integral fuse connected in
series with the blue secondary voltage wire. The fuse may be
accessed outside the transformer and is rated 3.5A.
6-Transformer T18 (2553, 2753, 3003 only)
T18 is a line voltage to 24VAC transformer used in 18.5 ton
and larger units. T18 is identical to transformer T1 and is used
to supply 24VAC power to contactors.
7-Transformer T3 (all 460V and 575V units)
460 (G) and 575 (J) voltage units use a line voltage to 230V
autotransformer to power the combustion air blower. The
autotransformer is connected directly to line voltage and is
powered at all times. It has an output rating of 0.5A. In units
over 12.5 ton capacity, T3 is located in the heating control
box in the heating section.
8-Condenser Fan Motor Fuse F10
(2553, 2753, 3003 only)
Line voltage fuses F10 are used to provide overcurrent
protection to all condenser fans (and optional power ex
haust fans) in the unit. The fuses are rated at 20A in
208/230V units and 15A in all others.
9-Unit Line Voltage Fuses F16
(1853, 2553, 2753, 3003)
Line voltage fuses F16 are used to provide overcurrent
protection to all line voltage components in the unit (except
compressors, crankcase heaters and optional electric
heat). The fuses are rated at 35A in 208/230V units and
30A in all others.
10-Circuit Breaker CB4, CB5
(1603 Y voltage only)
Circuit breaker CB4 provides overcurrent protection to
condenser fan B4 in 12.5 ton units and CB5 provides over
current protection to condenser fan B5. Both circuit break
ers are twopole 240V manual reset switches with a 15A
rating.
11-Compressor Contactor K1 (all units)
K1 is a 24V to line voltage contactor used to energize the
first compressor (B1) in response to first stage cooling de
mand. All units use threepoledoublebreak contactors for
threephase operation with a 24VAC coil.
NOTE-Contactor K1 is energized by the thermostat
control system. Depending on the control system
installed, the contactors may or may not be immediately
energized upon demand. Refer to the operation se
quence for the control system installed.
12-Blower Motor Overload Relay S42
(5 & 10 HP Motors only)
Units equipped with 5 and 10 horsepower indoor blower
motors are also equipped with a thermal overload relay
connected inline with the blower motor. The relay monitors
the current flowing to the blower motor. When the relay
senses an overload condition, a set of N.C. contacts in the
relay open to deenergize all control voltage in the unit.
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