Liebert Mini-Mate2 MMD24E User Manual

System Performance Microprocessor Controls
55 Liebert
®
Mini-Mate2
™
SCR Electric Reheat
The SCR (Silicon Controlled Rectifier) controller 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 to “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. On cooling units with direct drive motors, 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.
7.3.1 Communication
The control system uses a two-wire, RS-422 channel to communicate with Liebert Site 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

Liebert Mini-Mate2 MMD24E Specifications

General

Brand	Liebert
Model	Mini-Mate2 MMD24E
Category	Air Conditioner
Language	English