Frequently Asked Questions

Any Questions?

We’ve compiled some of our most frequently asked questions below. If you still have a question you need answered, you can contact us here.

What connectors are used for 400 Hz Power Distribution Panels?

AC General offers a 400 Hz three phase and single phase PDU rated at 20A service. The power input connector is Non-NEMA Hubbell Twist-Lock, commonly referred to as a “Variload TwistLock®” connector. The connector is UL498 Listed, and marked for 20A, 120/208V, 3PH, 400Hz service.

Note the single phase PDU also utilizes the same three phase connector, however only X-Phase, neutral, and ground wire are utilized.

For custom panels requiring more than 20A service, AC General will generally use a Amphenol MIL-5015 Type Standard Cylindrical Connector for the input and, oftentimes for the outputs.

Can I use a remote control PDU without a remote control panel

A PDU equipped with a remote control option can be used without a remote control panel by connecting an AC General Bypass Plug into the REMOTE connector on the PDU rear panel.

Regardless of the PDU remote control configuration “R1” (momentary On and momentary Off switches) or “R” (single maintained On/Off switch), use Bypass Plug, P/N 400-029


When a Bypass Plug is used, all contactor-switched outputs are enabled whenever the main breaker is On.

See more information here.

Don’t hesitate to contact AC General with any questions in this area. There’s always a solution!

I see a PDU or control panel that almost meets my needs. Can I modify it?

Absolutely. AC General specializes in adapting any of our products to meet your needs. Over the years, we’ve tailored our standard PDU, Lockout Panels, and Control Panels in hundreds of different ways. Most of the time, we can tailor a product with little or no cost to you.

What is an Utility Outlet?

A Utility outlet (or Convenience outlet) is an output that provides power independent of the PDU control scheme. Generally, they are activated whenever the main breaker is switched ON. Utility outlets are used to power devices equipment that needs to remain ON such as computers, monitors, etc.

What is a Switched vs an Unswitched Branch?

A branch is an electrical circuit taken from the AC Mains and controlled by one of two switching schemes.

A “Switched” branch is controlled by a contactor or power relay. Usually, the switching is controlled via a  Remote Control Panel or other built-in means of opening/closing the branch.

An “Unswitched” branch is a circuit that remains ‘live’ whenever the main circuit breaker is active. It is indpendent of the contactor controlled switching scheme mentioned above. Typically, computers or other keep-alive equipment is plugged into an unswitched branch circuit.

Each circuit type is marked “Switcched” or “Unswitchedd” on all PDU outputs.

How do I Return a Product to AC General?

Contact AC General via web, phone, or email and request a Return Material Authorization (RMA). The following items are needed before an RMA is granted:

  1. Reason for return
  2. Product Serial Number
Where is the Product Serial Number?

Generally, the serial number is located on the product side panel of the PDU. Cables, Lockout Panels, and Control Panels don’t usually have a serial number.

Do PDUs Need to be Cooled?

PDUs generally consume very little power and don’t need any special cooling. See PDU Specifications

Can 60Hz PDUs be operated at 50Hz?

60Hz PDUs can be operated at 50Hz provided the PDU doesn’t have a phase monitor. Also, if the PDU is used outside North America, the connectors may not be compatible with host country connector standards.

What is phase rotation and what causes an AC Line Fault?

Phase rotation is the sequence of voltage or current phasors in a multiphase electrical system. AC General PDUs assume an ABC phase rotation, whereby the B-phase voltage lags the A-phase voltage by 120°, and the C-phase voltage lags B-phase voltage by 120°.  If the PDU is newly installed and AC Line Fault indicator is illuminated, consider swapping the B-phase wire with the C-phase wire in the facility power input connector. If that does not resolve the problem, there may be a sustained phase under-voltage (V phase-to-phase < 15% of nominal) or missing phase voltage. If the problem persists, contact AC General.

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