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• The “Diagnostic: Compressor X Proving Lockout” diagnostic point is activated and the alarm
output is activated.
Diagnostic: Compressor X Contactor Failure
If a compressor proving input becomes Active for 5 continuous seconds when the associated
compressor command output is Inactive, a Diagnostic: Compressor X Contactor Failure is
generated and the following occurs:
• All compressors on the associated circuit are de-energized immediately and they are locked
out until a Reset Diagnostic is initiated.
The “Compressor X Contactor Failure” diagnostic point is activated and the alarm output is
activated.
Diagnostics – Low Pressure Cutout
The following operation is enforced based on the state of the circuit’s LPC input:
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• If a compressor output is Off and its circuit’s LPC input is open, compressor operation is not
inhibited, and the DDiiaaggnnoossttiicc:: CCiirrccuuiitt XX LLPPCC TTrriipp point will not be annunciated.
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An LPC Bypass Delay function delays the setting of a low pressure cutout after compressor
startup on a circuit until a pre-determined amount of time passes in low ambient conditions. The
length of the delay is determined based on ambient temperature:
• If the Outdoor Air Temperature Active is less than 40°F, the LPC Bypass Delay is set to 60
seconds
• If the Outdoor Air Temperature Active is between 40°F and 50°F, the LPC Bypass Delay is set
to 30 seconds
• If the Outdoor Air Temperature Active is greater than 50°F, the LPC Bypass Delay is 0 seconds
There are two diagnostics that can be generated based on the Compressor Low Pressure Cutout
input:
Diagnostic: Circuit X LPC Trip
• All Compressors Outputs on the effected circuit are commanded OFF
• The Diagnostic: Circuit X LPC Trip point is annunciated
• The circuit is disabled for 3 minutes
• The circuit’s LPC trip counter is incremented
After the 3 minute low pressure event timeout has expired, if the unit is not under a lockout
event,
• The Diagnostic: Circuit X LPC Trip point is reset
• If the stage is still requested ON, the circuit is allowed to stage again
• If the Circuit runs for 3 minutes, its LPC Trip Count is reset to 0.
On Heat Pumps, if the Outdoor Air Temperature is less than 0° F or if the unit is in active defrost,
the low pressure cutout input state is ignored.
Diagnostic: Circuit X LPC Lockout
If a circuit’s LPC trip counter accumulates 4 low pressure events without the circuit running for
the 3 minute minimum on time (counter is not reset), a Diagnostic: Circuit X LPC Lockout” is
generated.
Once a Diagnostic: Circuit X LPC Lockout has been generated, the following occurs:
• All compressors on the associated circuit are de-energized immediately and they are locked
out until a Reset Diagnostic is initiated.
• The Diagnostic: Circuit X LPC Lockout point is activated and the alarm output is activated.
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