Hussmann Proto-Aire EZ Manual Del Usuario página 28

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C. Low Pressure Control
The system controller will stage the compressor on and off based on a suction pressure
setpoint. The suction group includes an adjustable low-pressure control.
D. Discharge Temperature Sensor
Certain models of the digital compressor have a discharge temperature sensor installed
in the head of the compressor. It will be monitored for high discharge temperatures and
in the event excessive discharge temperatures are measured an alarm at the IDCM will
occur.
E. Circuit Breaker
Individual 208-volt compressor circuit breakers shall be provided per compressor. The
circuit breaker shall open on a fault and stop 208-volt power from entering the line side
of the compressor contactor. Circuit breakers shall trip on overcurrent, short circuit, and
overheating.
F. Thermal Overloads
Motor winding overheating is detected via internal compressor overloads. In the event
of excessive temperature-rise in the motor windings, the internal overload shall directly
open the high voltage power feeds to the motor windings and stop the compressor.
Motor winding trips shall auto-reset once the winding temperatures have dropped below
the design threshold.
G. Crankcase Heaters
A crankcase heater is used to alleviate liquid migration to the compressor during off cycle periods.
The crankcase heater is interlocked through the compressor contactor to be powered when the
compressor is not running.
H. Run Proof (if applied)
Upon delivering a compressor run command, the rack controller shall monitor the
panel-mounted compressor current sensing relay digital input for a run proof signal.
Lack of run proof input closure shall produce a run proof alarm. A run proof alarm
can occur if the compressor is not drawing current when the controller is expecting it to
be in operation. This could be due to, but not limited to, a compressor breaker trip, low
pressure control trip, high pressure control trip, oil level failure, or thermal overload trip.
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Proto-Aire EZ I/O Manual