CA / CT SERIES
CAP600
Page 6 of 30
REV D July 2013
Duplex Units
1
2
3
4
5
6
Air Intake
Air Compressor
Intercooler
Alternator
Pressure Switch
Vibration Isolator pads
with hardware mounts
2
Exact orientation of your system's
components may be different from the
layout in the figure. Please see your model's
general arrangement diagram for a precise
configuration of system components.
1
1
2
3
3
4
5
5
6
Fig. (2) Duplex unit system diagram.
Refer to the simplex diagram for a description of the compression cycle.
Duplex units operate in much the same way as simplex units, only there are two compressors.
The key difference is in the pressure switch and starter. In a duplex unit, there are two
pressure switches, a “lead” pressure switch and a “lag” pressure switch set 10 psi lower than
the lead switch. The alternator utilizes both compressors to fill the tank. Once the tank
approaches the cutoff “lag” pressure, the alternator selects one compressor to be the “lag”
compressor and cycles it off, using only the “lead” compressor to provide the remaining
pressure. The alternator then cycles between both compressors, switching the “lead” and “lag”
compressor and ensuring roughly equal wear between them. If air usage exceeds the output
of a single compressor, the alternator utilizes both the “lead” and the “lag compressor to fulfill
operating conditions, once again cycling off the “lag” compressor when its cutoff pressure is
reached.
