Emerson Autochangeover Controllers AC8 - Manual (Page 9)

Introduction
1
1.0 I
NTRODUCTION
The Liebert AC8 is ideal for coordinated control of systems with redundant equipment, such as
multiple environmental units or pumps. When the AC8 controller detects an alarm in an operating
device, the AC8 enables a standby device and controls the device in alarm as configured, either
leaving that device operating or disabling it.
The AC8 controller can also balance usage of devices by rotating units through Operating and
Standby modes according to a user-defined schedule. This helps keep redundant equipment operating
efficiently and only when needed. The AC8 can perform routine testing of standby devices and alert
personnel if a standby device fails an operating test and requires attention.
The staging feature permits standby devices to be turned on or off when a sensor detects specified
levels. For example, the AC8 might be configured to turn on a fan when the temperature reaches
75°F, then turn on a second fan at 80°F. When the temperature falls below 80°F, the second fan is
turned off; when it drops below 75°F, the first fan is turned off.
Another capability of the AC8 is monitoring the status of connected devices and keeping personnel
apprised through local alarming. The AC8 employs local alarming and remote paging services to keep
personnel on-site and at remote locations apprised of the status of equipment.
The AC8 controller can interface with anything that closes an electrical contact. To improve process
efficiency and troubleshooting, the controller tracks data in three types of logs: alarm, event and trend.
The AC8 has a local LCD interface and a remote dial-up interface.
When an alarm condition arises, the AC8 displays alarm information, sounds an audible alarm,
changes the state of the common alarm relay and turns connected devices on or off according to user
configuration. If configured, the controller also sends pager notifications. See 1.6 - Typical Configu-
ration for a more detailed example.
1.1 Methods of Viewing and Configuring the AC8
The AC8 features access through two interfaces that allow users to configure the unit, silence alarms,
back up logs, and perform many other functions to keep a large or small operation running smoothly
and safely.
• LCD—liquid crystal display on the front of the panel
• Service Terminal Interface—accessible via computer connected directly through an RS232
port or remotely through the AC8’s onboard modem
These interfaces permit easy access and configuration of the AC8, allowing users to view data, silence
alarms and have full access to information stored in the controller, including logs of alarms and events.
One more interface—Liebert’s SiteScan Web enterprise monitoring system—is primarily for monitor-
ing, though SiteScan also provides some configuration functions.
1.2 Data Logs
The three types of data logs—alarm history, event history and trend data of analog sensor readings—
can be viewed on the LCD on the front of the AC8 and downloaded through onboard communications
ports.
1.3 Transformer Module
A Transformer Module converts 115VAC or 230VAC to 24VAC.
1.4 Available Alarms
The alarms available with the AC8 are:
• Discrete input alarm
(for each digital input)
• High setpoint
• Low setpoint
• Loss of power
• Low battery
• Check battery
• Battery unplugged • Internal modem fault
• No standby available
• Standby device
failed
• No restart available
• Emergency power
alarm