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Changing the Line VRMS (Nominal Line Voltage) on your 208/230VAC capable Rack Automatic Transfer Switch (ATS)


Certain Rack Automatic Transfer Switch (ATS) models can support both 208VAC and 230VAC operation, by design. Consequently, they are used in different parts of the world. The default configuration is 230VAC. For North America 208VAC environments, a configuration change must be made during initial setup for proper operation.

Product Line
  • Rack Automatic Transfer Switch (ATS)
    • AP7721
    • AP7723
    • AP7724

  • Most North America installations
  • 208VAC input voltage environments
  • All serial numbers
  • All firmware versions


The default Line VRMS (nominal voltage setting) for the AP7721, AP7723, and AP7724 is 230VAC.

Please note: In order to use this in majority of North American installations (which are typically 208VAC), a configuration change must be made or the ATS will not function properly. It also may report a fault prior to the required setting change.


Change the Line VRMS (nominal input voltage) setting via the web or Telnet/SSH/serial cable prior to attaching any equipment and completing the installation.

Using serial cable/local connection/terminal emulation:
  1. Using the included serial configuration cable (part number 940-0144) and connect at the default port settings using a terminal emulation program such as HyperTerminal, PuTTy, or similar:
    • 9600 baud rate
    • 8 data bits
    • parity none
    • 1 stop bits
Note: for more detailed setup instructions, view knowledge base article ID FA156064 which includes how to access the local serial console as well as configuring TCP/IP settings
  1. Press <enter> several times and wait for the username prompt.
  2. Enter apc for the username and apc for the password. Press <enter>.
  3. Go to 1-Device Manager menu, 3-ATS Configuration and configure item 8-Line VRMS to 208
  4. Important: Use 12-Accept Changes to save and apply the change.

Using Telnet/SSH:
  1. Connect to the device using a Telnet or SSH client (which assumes your ATS is configured with valid TCP/IP settings and is physically connected to the network).
  2. Use apc/apc for the username/password. 
  3. Go to 1-Device Manager menu, 3-ATS Configuration and configure item 8-Line VRMS to 208
  4. Important: Use 12-Accept Changes to save and apply the change. 

Using Web Interface:
  1. In the web interface, go to Unit menu->frequency/voltage, set Line VRMS to 208.
  2. Press Apply to save changes.

If you have any questions on this process, please contact your local technical support team.


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