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6.0 — SMART UNLOADING & PWM VALVE
The SMART controller is designed to operate the compres-
sor cylinder head unloaders or a PWM Valve installed in the
compressor's suction line using Pulse Width Modulation
(PWM).
See Application Guide 574-078 at www.carlylecompres-
sor.com
6.1 — Functional Overview
The SMART unloading controller allows continuous modu-
lation of the compressor capacity using the steps of mechan-
ical unloading or the PWM Valve. Here is how it works:
An analog output signal from the system rack controller pro-
vides a 0-10 VDC signal to the SMART controller. Based
on the signal, the SMART controller continuously modu-
lates the compressor unloader coils to deliver an equivalent
linear change in the compressor capacity output to precisely
meet thermal load demand. In addition, the SMART control-
ler will control discharge temperature by operating the
accessory cylinder head fan and liquid injection valve as
required, maintaining safe and reliable operation. If dis-
charge temperature exceeds allowable limits, the SMART
controller will automatically turn the compressor off to pro-
tect against compressor failure.
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