Safe Connections through NEMA and IEC Configurations

By Brian Earl, Contributor

NEMA – National Electrical Manufacturers Association developed standards for safe, non-interminable connections through their NEMA Wiring Device Configuration Chart. Similarly, IEC, The International Electrotechnical Commission, developed standards for all electrical, electronic, and related technologies to ensure safe connections.

We’ll start with NEMA Wiring Devices and their category definition – Wiring devices are current-carrying electrical or electronic products that serve primarily as a connection or control point for electrical circuits within a range of 0–400 amperes, 0–600 volts (AC and DC), and AC/DC (660 watts, 1,000 volts AC fluorescent) as well as certain non-current-carrying wiring devices and supplies.

NEMA wiring device categories include:

• Convenience plugs and power outlets (plugs and receptacles)
• Connector bodies and flanged outlets
• Cover plates
• General-use switches and dimmers
• Lampholders (incandescent, fluorescent, cold cathode, neon, quartz lamps, and others)
• Lighting control devices
• Motion sensing and timer switches
• Receptacles
• Switch, outlet, FM/TV, blank, and telephone plates
• Undercarpet premise wiring systems

Products include other safety devices like receptacle-type GFCI (ground fault circuit interrupters and recently arc-fault circuit interrupters (AFCIs), protection devices that can detect an unintended electrical arc and disconnect the power before the arc starts a fire. AFCI technology in residential and commercial buildings is an important electrical safety device.

We’ll focus our attention on NEMA wiring devices that are designed for commercial and industrial grade, locking and straight blade plugs, connectors, inlets, and outlets.

NEMA has established straight blade configurations, from 15-60A, 125-600V and locking configurations, from 15-60A, 125-600V. (Note NEMA 50 & 60A locking configurations, although established, are currently inactive. Most manufacturers use industry accepted, non-NEMA, configurations at those higher amperages). There are 26 different configurations for both straight blade and locking devices. The NEMA configuration configurations also include Canadian 347V (typically used as a lighting voltage, like 277V, however derived from 600V) and 415V (most often use in Data Center Applications). The intent of these configurations is to provide standard and guidance for safe electrical connections by amperage and voltage to prevent intermating various voltages and amperage configurations that would cause an unsafe condition. There are also locking configurations for Midget Locking, DC voltage, 400Hz, Marine Ship to Shore, and Travel Trailer (straight blade) connections for special applications.

How to read and select the proper configuration from a NEMA configuration chart – start by identifying the blade configuration and selecting the proper configuration from either the straight or locking charts.

What do wires and poles on the chart refer too? Wires are the total number of wires used in a configuration while poles relate to the number of current carrying poles. For example, a popular 2-pole, 3-wire device commonly seen in residential applications has three wires – hot, neutral, and ground. While a 4-pole, 4-wire, uses 3-phase conductors and a neutral, without a separate ground. This is true for both straight blade and locking configurations, which share the same NEMA Number. The only difference is that Locking Device configurations start with an L – for example a 5-15 and L5-15 have the same connection configurations.

Although these configurations are meant to be non-interchangeable, there are two straight blade configurations – NEMA 5-20 (20A, 125V) and NEMA 6-20 (20A 250V), often called T-Slot receptacles, that allow lower 15A devices to be plugged into higher 20 amperage receptacles and connectors. This is solved with NEMA 5ALT-20R and NEMA 6ALT-20R receptacles that only allow the proper 20A device plug to be connected. This ensures that a 15A device received the proper rated amperage.

Now let’s transition to IEC Pin and Sleeve devices that are offered in both North American and International Configurations. All IEC 60309-2 Configurations are non-interchangeable among IEC configurations and rely on a ground clock position, (when looking at a receptacle or connector with alignment keyway grove pointed down) which is determined by the numbers of wires and voltage. The devices have specific colors to denote voltage, so from a distance you can determine the voltage used in a particular application. The physical size of the device differs by the number of poles and amperage.

How to read and select the proper IEC Device – There are eight North American IEC 309-2 Clock Positions with ampere ratings from 20-100-Amp and 11 International Configurations ranging from 16-125-Amp. The difference is voltage and ampere ratings. The same rules apply with it comes to poles and wires.

From a safety perspective, some pin and sleeve devices, like Ericson, offer early make and late break features on the contacts. This means the pins sequentially engage when connected. The ground pin first, then neutral, followed by the power poles, which makes then inherently safer. In similar fashion, when disconnected the power poles disengage first then neutral and lastly ground to ensure a safe disconnection and always contact with ground. Most IEC pin and sleeve devices have high-impact nonmetallic external components, adding another level of safety.

Because of their pin and sleeve design, these devices offer greater surface area for the contacts to engage, especially at higher amperages.

When selecting a pin and sleeve product, or replacement, ensure you are dealing with IEC 60309 configurations. There are several legacy pin and sleeve products from various manufacturers that have proprietary configurations and do not intermate with other manufacturers, nor follow the IEC 309 standards. Although perhaps obvious, IEC Pin and Sleeve Devices will not intermate with NEMA style straight or locking devices configurations.

Brian Earl is VP of Sales and Marketing at Ericson. He has an extensive background in developing and leading a variety of marketing, sales, and technical teams serving customers nationally and internationally. To learn more about Ericson’s extensive line of products that comply with NEMA and IEC Configurations go to www.ericson.com.