Compressor Timing-Short-Cycle Protection; Compressor Sequencing On Two-Compressor Units; Motorized Ball Valve In Digital Scroll Units - Emerson Liebert Challenger 3000 User Manual

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
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.
3.1.4

Compressor Sequencing on Two-Compressor Units

Compressor Sequencing parameter (Service Menu, Options Setup) is intended to maintain equal run
times between compressors. This setting has three selection possibilities:
• Always use Compressor 1 as lead compressor
• Always use Compressor 2 as lead compressor
• Auto:
• First priority: if the safety timings are acceptable for only one compressor, then it is the next
to be started/stopped.
• If both compressors are off: the one with fewer working hours is the next to start.
• If both compressors are in operation: the one that has been operating longer since the last
start is the next to be stopped.
NOTE
The Auto setting attempts to maintain equal run times between compressors.
3.1.5

Motorized Ball Valve in Digital Scroll Units

On water/glycol-cooled digital scroll units, discharge pressure is controlled by a motorized ball valve
(MBV). During unloaded operation, pressure changes during each digital cycle could cause a pres-
sure-controlled water regulating valve to open and close an excessive number of times. The motorized
ball valve is designed to maintain a consistent peak discharge pressure.
The control algorithm for the motorized ball valve uses an intelligent sampling rate and adjustable
pressure thresholds to reduce the number of times the valve opens and closes. The valve assembly
consists of the brass valve, linkage and actuator.
Each compressor has one motorized ball valve that is driven by the analog output of the Liebert iCOM
control board based on discharge pressure. If there is a call for cooling, the compressor start is delayed
by a 30-second timer. During this delay, the motorized ball valve is set to 50% open to allow fluid flow
through the unit condenser. The compressor will start after the 30-second timer elapses.
Motorized Ball Valve Manual Mode: (Service/Service) Manual operation can be selected to allow
service personnel to control the motorized ball valve from the Liebert iCOM control.
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Operation