Overload Standard

In our data center, each rack has an A & B circuit.  The circuits are either 20 or 30 AMP depending on the requirement of the rack.

Each piece of equipment in the racks has dual power supplies.    When the equipment runs on a single power supply, the AMP load required by the power supply will increase.  With this in mind our standard rating for a maximum normal PDU load is based on the following formula:  

80% of the circuit rating / 2  

For example: 30 AMP circuit * .8 divided by 2 would indicate that a single PDU would be considered overloaded if it exceed 12 AMPs.  This standard helps us avoid tripping a circuit breaker when running on a single circuit.