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Section 4: Glossary of Control Functions
If a zone includes more than 1 Standby unit, the same actions occur. At
the end of each Interval, one unit is started and one is stopped. For
example, if two Standby units are used, the First is started after the First
Interval. The unit that had been running the longest becomes the
Standby unit. After the second Interval, the second Standby unit is
started, and the Running unit with the longest operating time becomes
the Standby unit.
C key
The Clear key <C> at the local control panel serves two functions:
• Remove incorrectly entered data.
• Return to the previous display page.
Clear Alarms
All alarms are latching and must be manually cleared from the control
panel or from a terminal. Be sure to review alarms before clearing them
because recent alarm history is your best indication of system
performance. When alarms are cleared, units that are running because
of an Autochangeover will change back to their programmed status.
Common Alarm—Inputs
Each environmental control unit has a Common Alarm contact closure
output. The RAC2-8 receives the Common Alarm from each unit as a
control input. These alarms are annunciated only if the programmed
Delays (Hold and/or Alarm) are exceeded. A Common Alarm from a
Running unit causes a Standby unit to be turned ON, and turns OFF the
Running unit if shutdown is selected. A Common Alarm from a Standby
unit causes the unit to be unavailable.
Common Alarm—Output
A Form C contact labeled Common Alarm is available for customer
use. This relay is energized during the following conditions:
• A Common Alarm input from one of the units
• A Temp/Hum Alarm
• Manual Override ALL ON internal switch
• Emergency Power Operation mode
• Emergency Power OFF
The Common Alarm is de-energized by the Silence pushbutton if DIP
switch 1-7 is ON.
Control Lockout
A Form C contact labeled (optional) Control Lockout is available for
customer use. This relay is energized during the following conditions:
• Manual Override internal switch (all units on)
• Emergency Power Operation mode
30 • User Manual (9/97)