Emerson AC4 User Manual

The digital inputs and outputs are on the lower right side of the Liebert AC4 printed wiring assembly 

board. This section describes how to connect devices to the Liebert AC4’s inputs and outputs.
Each input is tied to an output with the same number:

• Input 1 is tied to Output 1 (default name: Device_1)
• Input 2 is tied to Output 2 (default name: Device_2)
• Input 3 is tied to Output 3 (default name: Device_3)
• Input 4 is tied to Output 4 (default name: Device_4)

Up to four devices may be connected to the Liebert AC4. Each device must be connected to an input 

and an output with the same number. 
To determine the proper wire size, see Table 4 Wiring specifications.

For Liebert Precision Cooling units, follow these steps (be sure to connect the same device to inputs 

and outputs with the same number (Input 1 and Output 1, Input 2 and Output 2, and so on): 

• Connect a digital input from the Liebert AC4 to the Common Alarm Relay of the environmental 

unit: terminals 75/76 or TB1-6,TB1-7. 

• Connect a digital output (numbered the same as the input) from the Liebert AC4 to the Remote 

Shutdown (Power Control) of the environmental unit: terminal 37/38 or TB1-4, TB1-5.

The four digital inputs are on the lower right side of the 

Liebert AC4, just below the output terminal blocks, as 

shown at right. These inputs are numbered 1 through 4.
To connect an input:
1. Turn Off electrical power to the Liebert AC4.
2. If necessary, remove a conduit knockout to permit wire 

entry into the Liebert AC4 enclosure.

3. Bring the wire(s) into the Liebert AC4 enclosure 

through a conduit knockout or access slot.

4. Loosen the appropriate screw and slip the stripped end 

of the wire into the terminal block.

5. Tighten the screw until it holds the wire snugly.

NOTE
Each terminal block is a removable assembly to permit easier connection of more than one