Liebert AC4 用户手册

The Liebert AC4 is ideal for coordinated control of systems with redundant equipment, such as 

multiple environmental units or pumps. When the AC4 controller detects an alarm in an operating 

device, the AC4 enables a standby device and controls the device in alarm as configured, either 

leaving that device operating or disabling it. 
The AC4 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 AC4 can perform routine testing of standby devices and alert 

personnel if a standby device fails an operating test and requires attention.
Another capability of the AC4 is monitoring the status of connected devices and keeping personnel 

apprised through local alarming. 
The AC4 controller can interface with anything that closes an electrical contact. To improve process 

efficiency and troubleshooting, the controller tracks data in two types of logs: alarm and event. The 

AC4 has a local LCD interface and an RS232 interface.
When an alarm condition arises, the AC4 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. See 1.5 - Typical Configuration for a more detailed example.

The AC4 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 a computer connected directly to an RS232 port

These interfaces permit easy access and configuration of the AC4, allowing users to view data, silence 

alarms and have full access to information stored in the controller, including logs of alarms and 

events.

The two types of data logs—alarm history and event history—can be viewed on the LCD on the front 

of the AC4 or the Service Terminal Interface. The logs may also be downloaded to a computer through 

the Service Terminal Interface.

The alarms available with the AC4 are:

• Discrete input alarm (for each digital input)
• Loss of power
• No standby available
• Standby device failed
• No restart available