14_2_NMB_electrical wire (C) D FriedmanElectrical Wire Size Required for Receptacles
How to choose the proper wire size for an electrical plug outlet or wall plug
     


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What size electrical wire should you use when hooking up an electrical receptacle (wall plug or electrical outlet)?

Here we explain the choice of No. 14 or No. 12 copper wire for 15A and 20A electrical circuits where receptacles are being wired.

This article series describes how to choose, locate, and wire an electrical receptacle in a home. Electrical receptacles (also called electrical outlets or "plugs" or "sockets") are simple devices that are easy to install, but there are details to get right if you want to be safe.

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What Size Electrical Wire Should I Use When Wiring an Electrical Outlet (Receptacle)?

The electrical wire used for the receptacle circuit must be the proper type in size (thickness or gauge) and number of conductors for the ampacity of the electrical circuit

Common house electrical wiring sizes (C) Carson Dunlop Associates

  • The electrical circuit must be properly protected by the right fuse or circuit breaker
  • For a 15-Amp circuit use #14 copper wire. The fuse or circuit breaker feeding this circuit is rated for 15 amps.
  • For a 20-Amp circuit use #12 copper wire.The fuse or circuit breaker feeding this circuit is rated for 20 amps.

Note: it's safe and ok to use a smaller fuse or circuit breaker, such as a 15-amp fuse protecting a circuit wired with #12 copper wire.

But in complex circuits that have many connections within a single junction box you could get into trouble: the number of connections that are allowed within an individual junction box depends on the wire size and the size of the box itself. Sketch courtesy of Carson Dunlop Associates.

Electrical Conductors: 2-Wire? 3-Wire? 2-Wire with Ground?

14_2_NMB_electrical wire (C) D Friedman

The electrical wire must have the proper number of conductors. In modern electrical circuits used to wire receptacles (electrical outlets).

Typically an electrical receptacle is wired with two insulated wires and a bare ground wire, all three of which are encased in a plastic (NMC) or metal (BX) jacket.

You'll see this wire labeled as 14/2 Type NM B with ground (photo at left) or 14/2 Type NM C with ground.

These wires are color coded black, white, and bare (photo below right). Sketch at left showing the number of conductors in types of electrical wire is provided by of Carson Dunlop Associates.

Details are at NUMBER of WIRE CONDUCTORS needed

Also see ELECTRICAL CODE BASICS and also SAFETY for ELECTRICAL INSPECTORS.

Our photo at page top is not an example of a proper electrical outlet installation.

This website provides information about a variety of electrical hazards in buildings, with articles focused on the inspection, detection, and reporting of electrical hazards and on proper electrical repair methods for unsafe electrical conditions. Critique and content suggestions are invited. Credit is given to content editors and contributors.

Question: how many electrical receptacles are allowed on a 20-amp circuit? How many receptacles on a 15-amp circuit?

How many receptacles can be wired To one 20 amp circuit No. 12. Wire - John K.

Reply:

20 Amp electrical outlet (C) D FriedmanJohn K:

Our photo (left) shows a 20-Amp electrical receptacle - you can recognize it by that horizontal opening that makes the left-hand slot look like the letter "T" on its side.

In general, the Electrical Code [NEC] allows

  • 10 electrical receptacles to be wired on a 15-Amp (#14 copper) wire circuit, and the Electrical Code [NEC] allows
  • 13 receptacles on a 20-amp (#12 copper) wire circuit.

    Watch out: When purchasing the receptacles to use on a 20A circuit, be sure to also buy receptacles that are themselves rated for 20Amp use.

    You'll see that those least-costly receptacles found in a big pile at building supply stores are more likely intended only for 15-Amp use.

Our photo (left) illustrates an electrical receptacle intended for use on a 20-Amp circuit.

Notice that extra horizontal slot? You won't see that on a 15-Amp electrical receptacle.

 

 

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Or see NUMBER of WIRE CONDUCTORS needed

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SIZE of WIRE REQUIRED at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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