Server and rack power connector guide
Every common plug and socket you meet in a rack, with ratings and where it is used. Printable version: one-page PDF cheat sheet.
IEC 60320 equipment connectors
These are the cords between equipment and the PDU or wall cord. The pair names always go odd (female) to even (male).
| Pair | Rating | How it mates | Typical use |
|---|---|---|---|
| C5 / C6 | 2.5 A | C5 coupler into C6 inlet | Laptop power bricks ("cloverleaf") |
| C7 / C8 | 2.5 A | C7 coupler into C8 inlet | Small devices, some mini PCs and set-top boxes ("figure 8") |
| C13 / C14 | 10 A IEC, 15 A UL | C13 coupler into C14 inlet | Most 1U/2U servers, switches, storage, PCs, monitors. Most PDU outlets are C13 |
| C15 / C16 | 10 A, 120 °C | C15 fits C16 and C14 inlets; C13 does not fit C16 | Hot-running gear, some network switches and kettles |
| C19 / C20 | 16 A IEC, 20 A UL | C19 coupler into C20 inlet | High-watt server PSUs (about 2000 W and up), GPU servers, PDU and UPS inputs |
| C21 / C22 | 16 A, 155 °C | C21 fits C22 and C20 inlets | High-temperature version of C19/C20 |
Wall and PDU input plugs
| Plug | Rating | Region | Typical use |
|---|---|---|---|
| NEMA 5-15 | 15 A, 125 V | North America | Standard US/Canada wall outlet |
| NEMA 5-20 | 20 A, 125 V | North America | 20 A outlet with a T-shaped neutral slot |
| NEMA L5-30 | 30 A, 125 V, locking | North America | Some 120 V rack PDUs and UPS inputs |
| NEMA L6-20 | 20 A, 250 V, locking | North America | 208/240 V rack PDUs |
| NEMA L6-30 | 30 A, 250 V, locking | North America | Common 208/240 V single-phase rack PDU input |
| NEMA L21-30 | 30 A, 120/208 V 3-phase, locking | North America | Three-phase rack PDUs |
| IEC 60309 blue 2P+E | 16 A or 32 A, 200-250 V | Europe, Africa, Asia | Single-phase rack PDU inputs (e.g. 32 A, 7.4 kW at 230 V) |
| IEC 60309 red 3P+N+E | 16 A or 32 A, 380-415 V | Europe, Africa, Asia | Three-phase rack PDU inputs |
| CEE 7/7 (Schuko) | 16 A, 250 V | Most of Europe | Wall outlet |
| BS 1363 | 13 A fused, 250 V | UK, Ireland, parts of Africa/Asia | Wall outlet |
| SANS 164-1 (Type M) | 15 A, 250 V | South Africa | Large round-pin wall outlet |
| SANS 164-2 (Type N) | 16 A, 250 V | South Africa, Brazil | Newer compact wall outlet |
Rules that prevent wrong orders
- The inlet on the installed PSU decides the cord, not the server model. Read the PSU label.
- Odd numbers are the female end (coupler/outlet), even numbers the male end (inlet/plug): C13 goes into C14, C19 into C20.
- A C13 cord does not fit a C20 inlet. A C19 cord does not fit a C14 inlet.
- Cord current rating is set by its weakest end. A C13-to-C20 cord is still a 10 A cord.
- North America: load circuits to 80% of the breaker for continuous load (30 A circuit = 24 A usable).
- A/B feeds: plug each PSU into a different PDU on a different circuit. One PDU must carry the whole load alone.
- High-watt PSUs often give full power only on 200-240 V. On 120 V they are derated.
Next steps
Find the cord for one server and one PDU on the home page matcher. Size a PDU with the PDU calculator. Estimate running cost with the power cost calculator. Detail pages: C13 vs C14, C19 vs C20, C13 vs C19.
Cabling a whole rack? Build the full cord list and get a free quote.
How much power each connector carries
Theoretical maximum = volts × amps. North American circuits are limited to 80% for continuous load. Real PSUs should run well below these numbers.
| Connector | Rating | at 120 V | at 208 V | at 230 V |
|---|---|---|---|---|
| C13 / C14 | 10 A IEC, 15 A UL | 1.8 kW (15 A) | 3.1 kW (15 A) | 2.3 kW (10 A) |
| C19 / C20 | 16 A IEC, 20 A UL | 2.4 kW (20 A) | 4.2 kW (20 A) | 3.7 kW (16 A) |
| NEMA L6-30 input | 30 A, 250 V | — | 6.2 kW (5.0 kW continuous) | — |
| IEC 60309 blue 32 A input | 32 A, 230 V | — | — | 7.4 kW |
Locking connectors
Locking C13 and C19 cords stop a cord from being pulled out by accident in a dense rack. Some lock with a latch on the cord, others need a PDU with locking outlets. Vendors use different systems, so check that the locking cord and the PDU outlet are made to work together. A normal cord still fits a locking outlet; it just does not lock.
Reading cord markings
- IEC cords: a code like H05VV-F 3G1.0 means a harmonised flexible cord with 3 conductors of 1.0 mm². 16 A C19 cords use 1.5 mm².
- UL cords: SJT 14AWG/3C means a 3-conductor 14 AWG jacketed cord. 20 A C19 cords normally use 12 AWG.
- The connector body is stamped with its rating, for example 10 A 250 V or 16 A 250 V. The lowest rating on the cord is the cord's rating.
Frequently asked questions
Which numbers are male and which are female?
In IEC 60320 the odd number is the female end (coupler or outlet) and the even number is the male end (inlet or plug). C13 mates with C14, C19 with C20.
What is the most common rack connector?
C13/C14. Most PDU outlets are C13 and most 1U/2U server PSUs have C14 inlets.
What plug does a 208 V rack PDU use in the US?
Often NEMA L6-30 (30 A, 250 V, locking) for single-phase, or L21-30 for three-phase.
What plug does a 32 A PDU use in Europe or Africa?
Usually an IEC 60309 blue 2P+E 32 A plug for single-phase, or red 3P+N+E for three-phase.