ELECTRICAL
GENERAL (CONT.)
Master Satellite Connection (Medium Temp)
The “master satellite” connection system allows one condensing unit to be connected to multiple cases. Figure 32 on page 38 shows
a typical diagram for this system.
All of the display case controls, including the disconnect switch, time clock, and temperature control, are installed behind the kickplate
and prewired. The liquid line solenoid is prewired but is not installed in the liquid line.
The power to operate each display case is connected at each case’s disconnect switch. The power to operate the condensing unit
is connected at the condensing unit. There are no interconnecting wires between the condensing unit and display case. There are
interconnecting wires that need to be connected between the cases. The liquid line solenoid valve needs to be installed in the common
liquid line before the liquid is distributed to the cases.
The controls operate the system as a pump down defrost. When the display case begins defrost, the liquid line solenoid valve is de-
energized. The compressor continues to run and pumps down the coil.
The master case contains the time clock. Interconnecting case wiring allows the master case to control the satellite cases. When defrost
is initiated in the master case, it sends an electrical signal to each case to initiate a defrost in all of the satellite cases. A second set of
interconnecting wires is connected in series between each of the cases.
The liquid line solenoid is energized at the end of the defrost cycle. The suction line pressure rises and the compressor starts.
Electrical - General • 31
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