APi 748 V1.1 406
4.6
P/N 77500001
Back
REFRIGERATION SYSTEM
If the Refrigeration System compressor is
inoperative, perform the following checks before
replacing the unit. Be sure to hold the
Refrigeration Interlock Switch closed when
making the operational checks.
NOTE: When the Refrigeration Interlock Switch is
depressed, there is a one-minute power up delay
to the compressor circuit.
1. Measure the line voltage. If the line voltage is
below 105 volts, the compressor may fail to start
or run hot.
2. If the line voltage is correct, check the
automatic thermostat operation by connecting a
jumper wire across the terminal with power
disconnected.
3. The Start Capacitor, Run Capacitor, and Start
Relay are best tested by substituting them with
know good components. This way, there can be
no doubt of test results.
4. Check
Thermal Overload
for continuity.
5. With the motor leads disconnected from the
circuits, check the compressor motor windings
with a Volt/Ohm meter set on R x 1 scale.
(Readings ±10%)
Common to Start ................ 5 Ohms
Common to Run .................. 1 Ohm
Start to Run.......................... 6 Ohms
6. Check for a grounded winding with a Volt/Ohm
meter from the Start Capacitor to the metal
casing, and the Run Capacitor to the metal
casing. There should be no continuity. If there is,
replace the compressor.
COMPRESSOR CIRCUIT SYSTEM
The Compressor Motor is a Two-Value Capacitor
Motor. During start-up, both the Running and
Starting Capacitor are in the circuit. This makes
the total capacitance during start between 98 µF
and 113 µF.
The overall effects of a running Capacitor are:
• Increases break down torque 30%
• Reduces full-load current
• Reduces full-load noise
• Increases locked rotor torque 20%
• Increases overall efficiency
The Start Relay contact is normally closed. The
Start Relay has a voltage sensitive coil that
remains de-energized until the voltage across its
coil, caused by the voltage across the Start
Winding, exceeds 162 - 175 VAC. At this time the
compressor has broken away from the load and is
near its nominal running speed. As the
compressor shaft speed increases, the voltage on
the Start Winding also increases. When the Start
Winding voltage reaches the proper level, the
Start Relay coil will energize. This opens the
contacts to the Start Capacitor, disconnecting it
from the circuit. With the Start capacitor
disconnected, the current through the Start
Winding will drop 70%. The Bleeder Resistor
provides a safe discharge path for any stored
charge in the Start Capacitor. Failure to return to
the Start Relay and the Control Box to their
correct mounting position will cause the motor
starting voltages to be altered. This could result in
startup problems at low line voltages.
Always secure the Control Box before returning
the unit to service.
When power is applied to the black wire, the
Evaporator Blower should run immediately.
Connecting the black wire to the YL/BK wire
closed the refrigeration circuit. When the YL/BK
wire is hot, the condenser fan and compressor will
start to run. Until the compressor rotor shaft
reaches a minimum running speed, the start relay
contact (Terminal 1 & 2) will remain closed. This
allows the Start Capacitor to draw high current
through the Start Winding. This creates a high
torque at the rotor shaft in order to accelerate the
Compressor under load. As the rotor comes up to
speed, the voltage on the Start Relay coil
(Terminal 2 & 5) will rise. When the minimum
running speed is attained, the Start Relay coil will
energize and open the circuit to the Start
Capacitor. When repairing the refrigeration unit
only use EXACT replacement parts for the Start
Relay, Run, and Start Capacitors. Failure to do so
will void the warranty. Please note the placement
of the Start Relay and the Control Box. Both must
be returned to the proper orientation. Altering the
mounting position for either of these parts will
change the starting voltage (Relay, Run, and Start
Capacitors).
CAUTION! This is a HIGH Energy
Circuit. DO NOT use less than 16 gauge
wire or switches rated less than 15
amps. DO NOT connect the jumper wire
or switch while power is ON.
Summary of Contents for Showcase 748
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Page 75: ...APi 748 V1 1 406 6 4 P N 77500001 Back Message Center ...
Page 77: ...APi 748 V1 1 406 6 6 P N 77500001 Back Main Door Interior ...
Page 79: ...APi 748 V1 1 406 6 8 P N 77500001 Back Lower Main Door Components ...
Page 81: ...APi 748 V1 1 406 6 10 P N 77500001 Back Coin Mech Compartment ...
Page 83: ...APi 748 V1 1 406 6 12 P N 77500001 Back Door Assembly Coin Mech Compartment ...
Page 85: ...APi 748 V1 1 406 6 14 P N 77500001 Back Cabinet Final Assembly ...
Page 88: ...APi 748 V1 1 406 6 17 P N 77500001 Back This Page Intentionally Left Blank ...
Page 91: ...APi 748 V1 1 406 6 20 P N 77500001 Back Main Power Switch ...
Page 93: ...APi 748 V1 1 406 6 22 P N 77500001 Back Turret Drive Motor ...
Page 97: ...APi 748 V1 1 406 6 26 P N 77500001 Back Plate Assembly Locks Delivery Door ...
Page 99: ...APi 748 V1 1 406 6 28 P N 77500001 Back Refrigeration Unit 120 V Domestic Control Box Assem ...