Greenheck MPX (472695) - Manual (Page 22)

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*
High Discharge
Temperature Trip
Blinks 2 Times Lockout
Code 3
Compressor
Protector Trip
Blinks 3 Times Lockout
Code 4* Locked Rotor Blinks 4 Times Lockout
Code 5
Demand Signal
Loss
Blinks 5 Times Lockout
Code 6
Discharge
Thermistor Fault
Blinks 6 Times
Reduce
Capacity
Code 7 Future N/A N/A
Code 8
Welded
Contactor
Blinks 8 Times
Unload
Compressor
Code 9 Low Voltage Blinks 9 Times Trip Compressor
*Protective faults that require manual reset.
Multiple Compressor Operation
100% Cooling
5 VDC Signal
System At Rest
1.0 VDC
Digital Scroll Compressor Runs
(Circuit A)
Digital Scroll
Compressor
Runs
(Circuit A)
Fixed Scroll Compressor Runs
(Circuit B)
Fixed Scroll Compressor Does Not Run
Until Call For Cooling Exceeds 50%
70% Cooling
Call for Cooling fr
om DDC
50% Cooling
10% Cooling
1.9 VDC Signal
22 Model MPX Make-Up Air Unit
®