IEC

Socket

vs

5-in-1

Combo

Socket:

Choosing

the

Right

PDU

Configuration

7 min read • Published: 6 November 2026 • Last updated: 6 November 2026

Selecting the right PDU socket configuration can improve compatibility, efficiency, and power distribution within your setup. This guide compares IEC sockets and 5-in-1 combo sockets to help you choose the best option for your application.

Every PDU in a data centre rack needs outlet sockets, and the type of socket fitted it determines what equipment can plug in, how flexibly the rack can be reconfigured, and how much physical space the outlets consume on the PDU strip. For most of the history of rack power distribution, that meant choosing a fixed mix of single-type IEC sockets, typically a set number of C13S and C19S, and living with that configuration for the life of the PDU. The emergence of combo sockets, which accept multiple IEC connector types in a single outlet position, changes that equation. But understanding when a combo socket is genuinely the right choice, rather than a conventional fixed-outlet PDU, depends on the data centre’s actual operational demands.

This guide explains how standard IEC sockets and 5-in-1 combo sockets work, compares them on the parameters that matter for PDU configuration, and covers the broader input and output decisions involved in getting a PDU setup right.

How Standard IEC Sockets Work in a PDU 

Standard IEC 60320 sockets are single-type outlets. Each socket position on the PDU accepts one connector family:

• C13 accepts C14 plugs, rated at 10A, 250V AC, with a 70°C temperature rating. This is the standard outlet for servers, switches, and most rack-mounted IT equipment.

• C19 accepts C20 plugs, rated at 16A, 250V AC, at 70°C. Used for higher-draw equipment such as high-performance servers, storage arrays, and UPS-to-PDU links.

• C15 accepts C16 plugs, rated at 10A, 250V AC, at 120°C. Specified where the equipment or environment runs at elevated temperatures.

• C21 accepts C22 plugs, rated at 16A, 250V AC, at 155°C. The highest temperature class in the IEC 60320 family, used in specialised high-thermal applications.

A conventional PDU is built with a fixed combination of these socket types, for example, 36 C13 outlets and 6 C19 outlets. That combination is set at the time of ordering. If the equipment in the rack changes and the outlet mix no longer matches the plug types needed, the PDU either has unused sockets or needs to be replaced entirely.

What a 5-in-1 Combo Socket Is 

A 5-in-1 combo socket is not a different connector standard. It is a single outlet position, built on the same IEC 60320 connector family, that is physically designed to accept five different plug types: C14, C16, C16A, C20, and C22. That means a single socket can serve as a C13, C15, C15A, C19, or C21 outlet, depending on which plug is inserted.

The practical effect is that every outlet on a combo-socket PDU is universal across all five IEC connector types. There’s no fixed ratio of C13 to C19 to decide at the time of purchase, no stranded sockets when equipment changes, and no need to replace the PDU when the rack’s power profile shifts.

It’s worth being precise here: the combo socket doesn’t change the electrical rating of the connected equipment. A device with a C14 plug still draws what it draws. What the combo socket changes is the PDU’s ability to accept that device in any outlet position, rather than only in the positions that happen to match its plug type.

Parameter	Standard IEC socket PDU	5-in-1 combo socket PDU
Connector types per outlet	One (C13 or C19 or C15 or C21)	Five (C13, C15, C15A, C19, C21)
Outlet mix	Fixed at time of order	Every outlet is universal
Reconfiguration when equipment changes	May require PDU replacement	No change needed
Temperature class coverage	Set per socket type (70°C, 120°C, or 155°C)	All temperature classes available at every position
Inventory complexity for operators	Multiple PDU configurations to stock	Fewer configurations needed
Primary use case	Stable, predictable rack loads	High-density, frequently reconfigured, or mixed-equipment racks

Both configurations use the same IEC 60320 connector standard. The difference is whether the outlet mix is locked at purchase or remains configurable throughout the PDU’s service life.

Choosing the Right PDU Outlet Configuration

A fixed-outlet PDU with a conventional C13/C19 mix is the right choice when the rack’s equipment profile is well established, unlikely to change significantly, and the outlet ratio can be confidently specified at order time. This covers a large portion of stable production environments where the server and network hardware stays consistent across refresh cycles.

A 5-in-1 combo socket PDU suits environments where one or more of the following apply: the equipment mix in a rack changes frequently, the ratio of low-power to high-power devices varies across racks, high-temperature connector types (C15, C21) are needed alongside standard ones, or the operator wants to standardise on a single PDU model rather than stocking multiple outlet configurations.

This last point is especially relevant for high-density AI data centre infrastructure, where per-rack power demands are climbing, and equipment generations turn over faster. A PDU that can absorb those changes without being replaced extends the useful life of the power distribution layer and reduces the downtime and cost associated with PDU swaps.

Getting the PDU Input Right: Where Industrial Power Connections Fit 

The outlet side is only half of the configuration. A PDU also needs the right input connection, and in higher-capacity installations, that means moving beyond a single-phase plug to a three-phase power infeed.

For data centres drawing 16A or 32A per rack at three-phase supply, the PDU’s input is typically an industrial plug and socket connection built to IEC 60309, the standard that governs industrial electrical sockets and plugs with keyed, colour-coded, round-pin connectors. A 3-phase industrial socket provides the high-current, three-phase feed that a rack of PDUs needs to distribute power across its outlets. The input plug configuration, whether 3P+N+E (three phases, neutral, and earth) or 3P+E, needs to match both the facility’s supply and the PDU’s internal distribution architecture.

Getting this wrong limits the PDU’s capacity regardless of how well the outlet side is configured. An undersized input connection, or a phase configuration that doesn’t match the supply, creates a bottleneck that no amount of outlet flexibility can overcome.

The Right PDU Configuration Matches Both the Rack and the Facility Supply 

Choosing between standard IEC sockets and a 5-in-1 combo socket comes down to how predictable the rack’s equipment mix is and how much operational flexibility the data centre needs from its power distribution layer. For stable, well-defined environments, a fixed-outlet PDU does the job reliably. For high-density, mixed-equipment, or rapidly evolving racks, a combo socket PDU removes the constraint of a locked outlet ratio and extends the PDU’s useful life across equipment changes.

Elcom International manufactures PDUs across both configurations. Our IEC power entry component range covers standard C13, C14, C19, C20, C21, and C22 inlets and outlets for conventional fixed-configuration PDUs, while our patented ELGO 5-in-1 combo socket PDUs accept C14, C16, C16A, C20, and C22 plugs in every outlet position, with hot-swappable connectors that can be reconfigured on-site using a finger-safe extraction tool conforming to IEC 61032. The ELGO range includes single-phase and three-phase models with IEC 60309 industrial plug and socket inputs, TFT display, CLASS 1 metering accuracy, circuit breaker trip detection, and outlet-level monitoring and switching. For facility-level power distribution, our industrial electrical sockets range covers 16A to 125A across IP44 and IP67 protection classes.

If you’re specifying PDU outlet configuration for a new data centre build or looking to standardise across mixed-equipment racks, we can help you work through outlet type, input configuration, and monitoring requirements.

Get in touch with our team to find the right PDU configuration for your application.