Humidity Control; Dehumidification/Humidification Required; Dehumidification Operation, Compressorized Direct Expansion (Dx) Systems; Humidification Operation - Emerson VERTIV Liebert Mini-Mate2 Series User Manual

Silicon Controlled Rectifier Electric Reheat (SCR)
The SCR proportionally controls the stainless steel reheat feature to maintain the selected room
temperature. The rapid cycling made possible by the SCR controller provides precise temperature
control, while the constant element temperature improves heater life. During operation of the SCR
control, THE COMPRESSOR OPERATES CONTINUOUSLY. The heaters are modulated to provide
temperature control. The display status will show when the unit is cooling and heating. The control
will automatically lock the compressor cooling in the "ON" position, except when the temperature
falls below the low temperature alarm setpoint. Cooling will then be disabled until the room
temperature reaches this minimum temperature setpoint.
7.2

Humidity Control

7.2.1

Dehumidification/Humidification Required

The humidity control is based on a calculated percentage requirement for dehumidification or
humidification (i.e., the difference between the return air humidity and the humidity setpoint). As the
return air humidity rises above the humidity setpoint, the percent dehumidification required
increases proportionally from 0% to 100% over a humidity band equal to the humidity sensitivity
setting. The converse is true for percent humidification requirement.
7.2.2

Dehumidification Operation, Compressorized Direct Expansion (DX) Systems

Dehumidification with the standard configuration is accomplished by operating the compressor
without the hot gas bypass active. The fan will operate at low speed unless the cooling requirement
reaches 100%. At that point, the low speed fan is disabled (unless manually overridden by the user)
until the cooling requirement decreases to 0%. Dehumidification will also be disabled if the heating
requirement exceeds 125%. It will be re-enabled when the heating requirement reaches 50%.
7.2.3

Humidification Operation

The canister humidifier is activated when the humidity control calculates a requirement of 100%
humidification, and it is deactivated when the humidification requirement falls below 50%.
7.3

Load Control Features

The control system monitors the compressor and prevents it from turning on within a 3-minute period
of being off. If this on-off-on cycle occurs too often (e.g., 10 times in a one-hour period), a Short Cycle
Alarm will occur.
7.4

Communication

The control system uses a two-wire, RS-422 channel to communicate with Liebert Site Monitoring
Products via a proprietary protocol. A converter board (ECA2) is available to allow communications
with a "dumb" terminal or a computer using RS-232 channel. More details are provided in the Site
Products and ECA2 user manual.
The communications channel provides both monitoring and control options, including:
• TEMPERATURE/HUMIDITY: Current temperature and humidity readings.
• STATUS (%): Cooling/heating and humidify/dehumidify operating status.
• PRESENT ALARMS: Alarms currently activated.
• SETPOINTS:
• Temperature Setpoint
• Temperature Sensitivity
• Humidity Setpoint
• Humidity Sensitivity
• High Temperature Alarm
• Low Temperature Alarm
• High Humidity Alarm
• Low Humidity Alarm
• ON/OFF STATUS
• SILENCE ALARM
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Liebert Mini-Mate2
System Performance Microprocessor Controls
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