Zero Zone 3RMCC30WA, Installation & Operation Manual

Page: 33 / 49

ELECTRICAL
GENERAL
!
Caution!
DISCONNECT POWER TO THE CASE BEFORE SERVICING ELECTRICAL COMPONENTS TO AVOID PERSONAL INJURY AND DAMAGE
TO THE UNIT.
Figure 26 on page 32
for 30" and 24" door cases shows the typical wiring diagram for a low temperature case equipped with electric
defrost.
Figure 27 on page 33
shows the typical wiring diagram for a low temperature case equipped with hot gas defrost.
Figure 30
on page 36 shows the typical wiring diagram for a medium temperature case. Each case is provided with a wiring diagram located in
the electric box that shows the exact wiring of the case.
There are many control options available for multiple case defrost systems. Wiring diagrams and instructions can be obtained by
contacting Zero Zone’s Service Department.
External wiring should be sized according to the amperage rating stamped on the serial plate. The serial plate is located on the ceiling
inside the left-hand door. Typical electrical values are shown on specification sheets for each of these cases in the bag attached to the
case or are available at www.zero-zone.com. All internal wiring has been done at the factory. Cases with standard wiring have their control
wires terminated in the electrical compartment located behind the kick rail at the right end of the case. A terminal block has been used
to simplify field connections. An electrical box is mounted on the top of the unit for cases equipped with the optional top mount electrical
connections.
All wiring must comply with the National Electrical Code and all local codes. After installation of the equipment, correct operation of the
electrical circuits and controls and defrost operation and termination should be verified. All operating voltages and amperages should be
measured and recorded.
OPTIONAL ELECTRICAL WIRING
Single Point Connection (Low Temp)
The “single point” connection system is designed to reduce the time required to install and wire one display case with one condensing
unit.
Figure 28 on page 34 is a typical diagram for this system.
All of the display case controls, including the disconnect switch and the electronic case controls are installed behind the kickplate and
prewired. The liquid line solenoid valve is installed in the liquid line and wired.
The power to operate the display case is connected at the case disconnect switch. The power to operate the condensing unit is
connected in the condensing unit control panel. There are no interconnecting wires between the condensing unit and display case.
The controls operate the system as a pump down defrost. When the display case begins defrost, the liquid line solenoid valve, fans and
anti-sweat heaters are de-energized. The defrost heaters are energized. The compressor continues to run and pumps down the coil. The
compressor cycles off on its low-pressure control. If there is any residual liquid left in the coil, the suction line pressure will rise and the
compressor may turn on and pump down the coil.
The liquid line solenoid is energized at the end of the defrost cycle and the defrost heaters are de-energized. The suction line pressure
rises and the compressor starts. When the low temperature evaporator reaches operating temperature, the fans and anti-condensate door
heaters are energized.
Electrical - General • 29