Rackmount PDUs: Basic, Metered and Switched

Metering and switching: what do you need to see or control?

A basic PDU is a rack-mounted outlet bar: it feeds power to servers and switches and does nothing else. A metered unit adds a display or network reading of current, so you can see how close a circuit is to its limit before adding another server. Switched PDUs go further and let you turn individual outlets on and off remotely, which makes rebooting a frozen device possible without a trip to the rack.

Pay for the features you will actually use. In a small closet a basic unit is enough, while a larger room benefits from metering to balance load across circuits. Remote switching needs a network connection and a secure management setup, so check the access methods the unit supports. Vertical bars save rack height, whereas 1U and 2U horizontal units take rack space.

Input plug, amps and outlet types

Start at the wall. The input plug and its amp rating must match the receptacle that feeds the rack: a 15 A unit with a NEMA 5-15P plug fits a standard outlet, while 30 A models often use a locking L6-30P plug on a 208 V circuit. Supply voltage listed as 200 to 240 V will not work on a 120 V outlet. Planners usually load a PDU to around 80 percent of its rating for continuous use.

Then count the outlets by type. C13 outlets feed most servers, switches and monitors using standard IEC cords, while C19 outlets carry heavier loads such as large servers and blade enclosures. Mixed units offer both. Cord length, such as 10 to 15 feet, decides whether the unit reaches the wall without an extension, and rack depth decides whether a long bar fits behind your equipment.

Questions about Rackmount PDUs: Basic, Metered and Switched

What is the difference between a PDU and a power strip?

A PDU is built for racks, with higher current ratings, rack mounting, IEC outlets and often metering or remote control. A power strip suits a desk and usually offers none of those features.

What do C13 and C19 mean?

They are IEC outlet shapes. C13 serves typical servers, switches and displays, while C19 handles higher currents for large servers. Cords must match the shape, so check the connector on each device's power supply.

Can I use a 120 V PDU on a 208 V circuit?

Only if the unit is rated for that voltage. A unit rated for 120 V only can be damaged or become unsafe, so check the supply voltage range in the listing before connecting.