How To Look At A House

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What is a double tap at a circuit breaker?

Tuesday, September 25, 2018

A double tap occurs when two wires are connected to a circuit breaker that is only designed to accept one wire. It’s considered a defect for most breakers because the two wires compressed under a one-wire connector may not be securely fastened. Some, but not all, circuit breakers manufactured by Square D and Cutler Hammer are rated to accept two wires. 

    We know of no other brands of 120-volt breakers that allow what is called “two poles” in the trade. When two wires are allowed, it is marked “2 Pole” in small lettering or with a tiny graphic of two wires at the front or side of the breaker. 

   In the photo below, two wires are connected to a breaker marked “1 POLE UNIT” on the front sticker.

And here’s a Square D breaker that is marked as double pole allowed, but only for copper (CU) wires #10 through #14 AWG. Single pole acceptable for aluminum (AL) and copper.

    This is another breaker that uses graphic wire symbols to indicate the same thing, but without a note about wire size limitation.

   Although double taps are a common defect, they is also easy to fix. There are several alternatives:

  1. Connect the two wires together to a third short piece of wire using a wire nut, then connect the other end of the new wire to the breaker. This is called a “pigtail,” and is by far the easiest remedy.
  2. Add another breaker in the panel, and connect one of the wires to the new breaker.
  3. If there is no space in the panel for an additional breaker, you can exchange the offending breaker for a “tandem,” basically two breakers that fit in the slot for one breaker. There are a number of restrictions on adding tandem breakers to a panel, and some panels are not rated to accept them. A licensed electrician can advise you as to whether your panel can accept tandem breakers—also called “half-high” or “duplex” breakers. 

   The two breakers below with the double red switches are examples of tandem breakers but, unfortunately, the top one also an example of two double taps.

   Another type of double tap can occur at the service lugs (connection of the electric utility’s power to the panel, typically at the top). The lugs are not rated for multiple wire connections and there is also a second safety concern because any wiring connected at this point has no circuit breaker for overcurrent protection. The fix for a double tap at service lugs is to add a breaker in the panel. In the photo below, the thin black and red wires at the left and right lugs should be connected a 240-volt breaker rated for the wire size and the white wire at the center lug connected to the neutral bus. 

    Also, see our blog posts Can you add circuit breakers by different manufacturers to an electric panel if they fit? and What is the maximum number of circuit breakers allowed in an electric panel?

• • • • • • • • • • • • • • • • • • • • • • • • • • 

Here’s links to a collection of our other blog posts about ELECTRIC PANELS:

What causes copper wires to turn green or black in an electric panel?  

When should a corroded or damaged electric panel cabinet or disconnect box be replaced? 

What is a tandem circuit breaker? 

When did arc fault circuit interrupter (AFCI) breakers first become required?

Can an electric panel be located in a closet? 

Can an electric panel be located in a bathroom? 

My circuit breaker won't reset. What's wrong?  

What is a split bus electric panel?

How do I identify a combination AFCI (CAFCI) circuit breaker? 

What does a circuit breaker with a yellow or white test button indicate? 

What is the maximum gap allowed between the front of a recessed electric panel box and the wall surface surrounding it? 

What are the requirements for NM-cables entering an electric panel box?

Why is a fuse box/panel an insurance problem for homebuyers? 

Why is bundled wiring in an electric panel a defect?

What is the difference between GFCI and AFCI circuit breakers? 

Why are old electrical components not always "grandfathered" as acceptable by home inspectors?

What happens when you press the "TEST" button on a circuit breaker in an electric panel?

What is a Dual Function Circuit Interrupter (DFCI)? 

What is the difference between a Combination Arc Fault Circuit Interrupter (CAFCI) and an Arc Fault Circuit Interrupter (AFCI) circuit breaker?  

What is the difference between "grounded" and "grounding" electrical conductors? 

What does it mean when a wire is "overstripped" at a circuit breaker?

Why is an old fuse panel dangerous?  

Who is the manufacturer of those "bad" electric panels?

Why is the circuit breaker stuck in the middle? 

What is the right electric wire size for a circuit breaker in an electric panel?

What is the life expectancy of a circuit breaker? 

My circuit breaker won't reset. What's wrong? 

Why do some breakers in my electric panel have a "TEST" button on them?

What is the right size electric panel for a house? 

• What do I need to know about buying a whole house surge protector? 

What is the maximum allowed height of a circuit breaker (OCPD) above the floor?

• What is the maximum height you can mount an electric panel above the floor? 

• What is the code required clearance in front of an electric panel?

What is the main bonding jumper and where do it find it in an electric panel? 

   Visit our ELECTRIC PANELS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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