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Digital Scroll Compressors

(continued)

Electronic Control

A Copeland Scroll Digital™ compressor also requires
the use of a digital scroll compressor controller

(see

Figure 4)

. This controller may be found in either

the compressor compartment of the unit or in the
main control center. The digital controller works in
conjunction with a DDC controller or possibly with a
BMS and it requires an analog input. The controller
is already programmed and wired and does not
require any further servicing by the owner. Detailed
information on the electronic control circuitry will be
found on the unit-speciﬁc wiring diagram found in the
control center. The digital scroll controller constantly
monitors and controls the operation of the digital
scroll compressor. LED indicator lights verify the
presence of power, operation of the unloader solenoid
and also indicate various alarm conditions.

See the Fault Code chart below. The Fault Code chart
is also printed on the back of the controller. Note that
if the controller generates either a Code 2 or a Code 4
Lockout, a manual reset must be performed. Manual
Reset is accomplished by shutting off main power to
the unit and then turning it back on.

Two Compressor Operation Concept

Whenever two compressors are used in a unit, the
digital scroll compressor is part of refrigerant circuit
“A”. A conventional ﬁxed scroll compressor is used
for circuit “B”. When the unit is at rest and there is no
call for cooling, a constant 1.0 volt signal is sent to the
digital scroll controller from the DDC to keep it from
going into lockup mode. The minimum input signal
that will cause the compressor to run is 1.9 volts and
the maximum is 5 volts (100% cooling). Whenever
there is a call for cooling, circuit A will be activated
ﬁrst. Circuit A will provide all necessary cooling until
the call for cooling exceeds 50%. When the call for
cooling reaches 50%, the digital scroll will shut down
and the ﬁxed scroll compressor will begin running.
Once the call for cooling exceeds 70%, then the
digital scroll will begin running again, in conjunction
with the ﬁxed scroll compressor (see below).

System Start-Up

During unit start-up, amperage draw readings are to
be taken on all three electric supply phases when
the unit is running. Because the digital scroll can run
without compressing the refrigerant, this can lead to
false amperage-draw readings during start-up of the
unit. Make certain that the amperage readings are
taken when the compressor is actually running under
load. Refer to the Refrigeration Start-Up portion of the
unit Installation, Operation and Maintenance manual
(IOM). All other temperature and pressure readings
should be taken as shown in the IOM, taking care
that refrigerant temperature and pressure readings
on the digital scroll compressor are taken while the
compressor is loaded.

Troubleshooting

If it is necessary to troubleshoot the refrigeration
system, the ﬁrst step is always to check the alarm
indicators on both the DDC and the digital scroll
compressor controller. Remember that the digital
scroll compressor may be running in a “no-load” state.

Copeland Scroll Digital™

Compressor Controller

Figure 4

Copeland Scroll Digital™ Compressor

Controller Fault Codes

Alert Code

System

Condition

Diagnostic

Alert Light

Action

Code 2*