Your Outlet Has a Story to Tell

You probably don’t give a second thought when you plug in an appliance to a wall outlet. And that’s a good thing because it means outlets in the US are mostly standardized and safe. But not always and not everywhere. Let’s take a look.

The National Electrical Manufacturers Association (NEMA) and Building Codes

The National Electrical Manufacturers Association (NEMA) is a North American trade organization that represents electrical equipment and medical imaging manufacturers. It helps develop technical standards for safety and efficiency and advocates for their adoption. Its standards are in use in most of North and Central America and have been incorporated in both national and international electrical codes. These codes have been adopted by most local building codes, including the types of outlets permitted. US electrical plugs and receptacles (outlets) are identified as “NEMA-type” with other numbers and letters designating their specific use.

110-125 Volt Connections

US household voltage is either 120 or 240 volts. The normal household appliance voltage is 120 volts, 15 amps, which is what is present at most of your regular wall outlets. Those outlets can be either grounded or ungrounded, and the receptacle tells the story.

Ungrounded (NEMA-1) outlets have two parallel rectangular slots to receive a two-prong plug. NEMA-1-15 outlets have one slot is longer than the other so a matching plug can only be inserted one way, preserving the polarized current flow from feed (hot) to return (neutral). NEMA-1-15 outlets are no longer permitted in new construction but can be found in older building.

Grounded Outlets

NEMA-5-15 outlets have the same polarized slots but add a third, round receptacle that’s deeper than the slots and makes a positive grounding connection as well as enforcing polarity. They’re the standard in the US, Canada, Mexico, and Panama and are used in other countries as well. The grounding slot has typically been oriented at the bottom of a vertical installation, but now positioning it to the top is recommended. Receptacles can also be mounted horizontally without affecting their function. The National Electrical Code specifies the neutral (long) slot on top and the ground hole on the left in that case.

Some appliance circuits may be rated for 20 amps instead of 15 in order to supply heavier loads in places like kitchens and laundry rooms. These are designated NEMA-5-20 and have a small notch added into the left-side prong opening to identify them.

Tamper-Proof and GFCI Outlets

Ground-fault circuit interrupter (GFCI) protection is required on receptacles in wet locations including kitchen appliance outlets, bathrooms, basements and most outdoor outlets.

All of Canada and 46 US states now require tamper-resistant outlets in new construction. Both GFCI and tamper-resistant outlets accept NEMA-5-15 style plugs.

High-Voltage Outlets (220-240 volts)

Heavy appliances like ovens, stoves, dryers, and electric water heaters, furnaces, and air conditioners are typically served by 240 volts. They also carry more current than 15-amp appliance circuits, typically 30-50 amps and each amperage has its own type of outlet.

240-volt outlets are larger, rounded, and have three or four slots depending on the age of the outlet. Since electricity is supplied to your home at 240 volts and separated into two 120-volt wires, early ungrounded 240-volt outlets had three slots, two at 120 volts for feed and a neutral. Modern outlets are grounded, adding a fourth hole for the ground wire.

Standard 30-amp outlets usually have two rectangular slots set at angles, a return (often L-shaped) and a grounding hole. 50-amp circuits have four slots, too, but the slots are usually parallel. But there are several types of outlets, including locking styles, so be sure your plug matches your outlet.

Confused? Call a Pro!

It’s important that outlets and connections be wired right and the variety can be confusing. Remodeling, renovations, and additions need top-notch electrical work, and Allstar Electrical Services delivers the safe, quality results you expect and deserve.

Whatever your electrical needs, call Allstar Electrical at (303) 399-7420 or visit our website. Then use our handy on-line forms to request an estimate or set up an appointment. We’ve served the Front Range for over 15 years and are top-rated by the BBB and Angie’s List.

Allstar also offers 24/7 radio-dispatched emergency service throughout our Front Range service area.