User manual

Operation
16
High Pressure Alarm
When the compressor is initially activated, the system will be monitored for a high pressure situation.
When a high pressure situation is detected during the first 10 minutes of operation, the unit will
attempt to correct the problem several times without notification. If the unit is unsuccessful in
correcting the problem, an alarm will occur and the affected compressor will be locked off. If high head
pressure alarm trips three times in a rolling 12 hour period, the affected compressor will be locked off.
After the compressor has been running for 10 minutes, if a high head pressure situation is detected,
an alarm will occur and the affected compressor will be immediately locked off without the unit trying
to correct the problem.
Once the compressor is locked off, it will not come back on until main power is reset, or until the
HP Alarm Counters (Service Menu, Diagnostics) are reset to 0. Setting the counter to 0 will auto-reset
the alarm without the need of pressing the reset button on the display. Even if the pressure in the
system drops below the alarm point, the compressor will remain off until the system is reset.
Digital Scroll High Temperature
A protective maximum operating compressor temperature limit is imposed on units with digital scroll
compressor(s) with thermistor. If the digital scroll temperature reaches the maximum temperature
threshold, the compressor will be locked out for at least 30 minutes and an alarm will be annunciated.
If after 30 minutes the temperature has cooled to a safe operating temperature, the compressor will
resume operation.
Each time a high-temperature alarm occurs, HT 1 Alarm Counter (Service Menu, Diagnostics) or
HT 2 Alarm Counter (Service Menu, Diagnostics) is increased by one. Once these counters reach five
occurrences in a rolling four-hour period, the compressor will be locked out. The alarm can be reset
once the temperature returns to a safe level by:
1. Setting the counter back to 0 from the display and pressing the alarm reset button.
2. Shutting off power to the control board by turning the cooling unit's main power disconnect switch
Off and On.
3.1.3 Compressor Timing—Short-Cycle Protection
To help maximize the life of your compressor(s), there is a start-to-next start delay for each single
compressor.
NOTE
If the unit is equipped with manual reset high head pressure switches, or if the auto reset high
head pressure switches don’t reset, the compressor will not be turned back on, but there will be
a 30-second delay from when the high head pressure situation occurs and when the alarm is
annunciated.
NOTE
This delay may cause a short cycle if there is a very light room load. A short cycle means that
the compressor has cycled On and Off 10 times in the past hour. Should this occur, contact
your local Emerson representative to adjust the minimum compressor off delay.