Safety is always an issue when it comes to installing electrical wiring. There is the immediate concern of an electrical shock if the person who is doing the wiring makes a mistake. The ongoing danger is overloading 12-gauge wire capacity, possibly blowing out breakers or causing a fire. Safety should always be the primary concern when working on anything with electricity within the home. It is recommended to always get a professional to do any work with electricity.
The number of outlets that you can safely place on 12-gauge wire is partially dependent on the used circuit’s amperage. As a general rule, 12-gauge wire can safely employ 10 receptacles on a 20-amp circuit using copper wire. By comparison, 14-gauge wire can handle 15 amps and 8 receptacles.
There are many relevant considerations when it comes to installing electrical wiring. These include the quality of the materials, your intended use for the receptacles, and the various codes involved. This article will discuss the basic guidelines for safely installing proper 12-gauge wiring and outlets.
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Electrical Wiring Codes for 12-Gauge Wiring
Someone might ask, “Is there a national set of guidelines for installing electrical wiring?” The answer is both yes and no. Since 1897, a code has been published every three years that gives updated recommendations for all manner of electrical installations.
This is called the National Electrical Code (NEC), and it is published triannually by the National Fire Protection Association (NFPA). The most recent version of this was released in 2020. It is available from the NFPA in downloadable form on their website (source).
Is the NEC the law, and must all electricians and inspectors follow it? Yes and no. The NEC is just a recommendation when it comes out. Each individual state must decide whether to adopt the new NEC, adapt it with some changes, or stay with previous NEC recommendations (source).
Probably because the 2020 NEC is so new, only 9 states have adopted it officially so far, and there are 31 states still using the 2017 version of the NEC. The remaining states use codes that go back even further.
Once a state officially adopts the NEC, it becomes law and must be adhered to when installing or upgrading electrical wiring.
The issue of using 12-gauge wire to establish new links for outlets is interesting. It is relevant to know that the “gauge” of wire refers to its thickness, and the smaller the number associated with a wire gauge, the thicker the wire — 10-gauge wire is much thicker than 14-gauge wire.
The use of the term “gauge” is part of a standardized system called American Wiring Gauge (AWG) that goes back to 1857. Craftsmen produced electrical wire by pulling it through a series of dies or progressively smaller holes with 14-gauge wire pulled through 14 dies. That means 12-gauge wire went through only 12 and so on.
As you might expect, 12-gauge wire is capable of handling a stronger electric current than 15-gauge wire. Indeed, there is quite a difference between these two wire sizes. A 15-gauge wire, according to code, can handle a 15-amp circuit, while a 12-gauge wire can handle a 20-amp circuit.
The size of an electrical wire also determines the amount of amperage it can safely carry. Amperage is a way of measuring the flow of electric current. Every electrical wire and device is rated as to how many amps it can safely carry. For information on especially thick wire, read our article on what size wire you need for a 100-amp subpanel.
There is a significant step up in amperage between 12- and 14-gauge wire. While a 14-gauge wire can handle 15 amps, and thus 8 receptacles or outlets of 120 volts, 12-gauge wire can safely handle 20 amps, with a capacity of 10 outlets or receptacles.
Wiring and the Quality of the Materials You Use
The gauge of electrical wiring and the amperage it carries are only part of the picture when it comes to safely installing new electrical wiring. When speaking about electrical wire, the default type of wiring used is copper. However, copper is not the only material used for electrical wiring.
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Between 1965 and 1972, many American homebuilders used aluminum rather than copper when wiring new houses. Since the median building date of home construction in the US is 1977 — this means half the houses in America today were built in 1977 or before — that means a great many homes still have aluminum wiring.
Aluminum is a good conductor of electricity, but it is simply not as safe in residential and commercial electrical wiring applications as copper. Indeed, the US Consumer Product Safety Commission determined that aluminum wiring is 55 times more likely than copper to cause a home fire through overheating (source).
Whether a homeowner plans to add wiring, breakers, and receptacles or not, if that home was built in the aluminum wiring era, it is a good idea to determine if it is wired with aluminum wiring or copper.
Both copper and aluminum wiring are NM — non-metallic, also called “Romex” — coated, but the plastic coating on aluminum should say “AL” or “Alum.”
If a home is wired with aluminum and rewiring the entire house is unfeasible, the homeowner should decide whether it is safe to add new circuits and increase the ampere load.
Should a homeowner decide to proceed with installing new wiring, the potential hazards are mitigated to a degree by adding copper wire extensions to the ends of the aluminum wires at those points where connections will occur. This also implies that the new wiring is copper.
It is also important to mention another safety feature whose uses have been growing ever since it was first introduced in 1968: the ground fault circuit interrupter (GFCI) outlet. The GFCI came into being because, even if the homeowner used the proper type and wiring size, sometimes electrical shocks and overloaded circuits still occurred (source).
The GFCI circuit automatically senses an electrical charge that will overload an electric circuit, and it opens (disconnects) the electric current. If a GFCI trips and it cannot be reset, that means there is a dangerous short that needs to be discovered and repaired. Here are some circuits that require a GFCI:
- Underwater pool lights
- Outdoor receptacles
- Basements and crawl spaces
- Wet bar sinks
- Utility room sinks
Safely Installing Wiring
Once you have determined how many outlets and receptacles can safely be installed on new 12-gauge electrical wiring, what type of wiring you will use, and whether there should be a GFCI breaker on the wiring, one question remains. Who is going to install the new wiring and outlets?
In some states, homeowners themselves may legally install their own new electrical add-ons. Other states require licensed electricians to do this type of installation. Virtually all states, counties, and municipalities require new electrical work to be reviewed by electrical inspectors.
A homeowner who has added a new room or screened porch, or perhaps wants to electrify an outdoor recreation area, may be tempted to run the wiring and add the receptacles and outlets personally. To be sure, a small electrical project such as this is much more amenable to amateur electricians than a full-home rewiring.
Certain conditions should be in place before proceeding with such a project. The homeowner must know the following:
- The local codes and how those apply to the project.
- What advance inspection and follow-up inspection are necessary.
- Materials that must be used .
- How much the project will cost to avoid overruns and using inferior materials.
- What tools are necessary for the various aspects of the project.
- Which parts of the project will require additional help.
During the planning process, the homeowner may decide to involve professional electricians. This could be to take over and complete the work or to accomplish certain difficult elements of the project. Homeowners who decide to call in professional help for such work are demonstrating their wisdom.
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Licensed electricians must understand all elements of the NEC as well as local codes that apply to simple wiring projects. Additionally, experienced electricians often see potential safety issues or construction issues that a homeowner might not recognize.
Electricians are also able to determine the quickest, cheapest way to complete projects safely. In this way, electricians can sometimes actually save money for the homeowner. Above all, electricians are interested in the safety of the projects entrusted to them.
Consult An Electrician
An article such as this cannot cover all eventualities and codes that apply in all countries and all local municipalities.
For this reason, as well as for the safety of you, your family, and your home, it is best to consult with a local electrician before any type of electrical work.
When electricity is concerned, a little bit of knowledge can be deadly, and it is not worth taking the risk simply to save a little money.
Asking how many outlets you can run on 12-gauge wire is a deceptively simple question. A great deal goes into understanding safety issues, materials, amperage, and installation when discussing the addition of electrical wiring.
In the final analysis, the use of 12-gauge wiring allows the use of a 20-amp circuit and the safe installation of 10 combined receptacles or outlets.
As arcane and mysterious as the world of electrical wiring may be for many of us, it is worth noting that electrical installation codes date back to the 1890s. It behooves those who would install new wiring and outlets to first learn the old – and new – rules of electrical safety. Any type of electrical work should never be considered a DIY job with little basic knowledge of electrical work. Make sure to always get a professional to do the work with any type of electricity.