Section 4: Glossary of Control Functions
Running status. Standby units can be turned ON by Autochangeover,
Autosequencing, or Standby Testing.
Temperature Alarms
Temperature alarms are caused when the temperature detected by the
remote sensor in Zone 1 exceeds the programmed High or Low trip-
point. Trip-points are selected in 1 degree increments from the display.
Entering 00 disables an alarm. A Temperature Alarm activates the
Common Alarm output .
High Range—up to 90°F (32°C).
Low Range—down to 50°F (10°C).
Temperature Sensitivity
Refer to Temperature Staging.
Temperature Staging
The RAC2-8 can be programmed to use Standby units, along with
Running units, for increased capacity in Zone 1. If more than o ne
Standby unit is available, these units can be staged to turn on as
temperature increases. Temperature Staging is selected from the
display. This mode is the best way to control room temperature after
recovering from a power failure (a remote T/H sensor is required).
Normal Temperature
The temperature to be maintained when Temperature Staging is ON.
Normal Temperature is selected from the display.
Range—50 to 90°F (10 to 32°C), in 1 degree increments.
Temperature Sensitivity
The number of degrees from the Normal Temperature which causes the
next Standby unit to be turned ON. As temperature approaches Normal,
the Standby units are turned OFF in first-on/last-off order. Sensitivity is
selected from the display in 1 degree increments, and is a small number.
Terminal
A local terminal can be connected directly to the RAC2-8 or a remote
terminal can be connected through modems. Two EIA-232 ports are
available at the enclosure. All of the status information and control
functions available at the RAC2-8 local display are available from the
terminal. An additional function available at the terminal is Set Modem.
The terminal also displays a status message with time and date stamp
whenever a unit changes status (OFF or ON). The terminal baud rate is
selected by using switches inside the enclosure.
Units
Each environmental control system connected to the RAC2-8 is called a
Unit. Each Unit is located in a Zone, is assigned a Label, and a status
(Running or Standby). All of these selections are made from the display
(for 2 to 8 units). The RAC2-8 monitors Unit Common Alarms and
turns Units ON or OFF from the automatic control program or from
manual inputs.
Liebert RAC2-8 • 35