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:
- 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.
- Add another breaker in the panel, and connect one of the wires to the new breaker.
- 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.
• • • • • • • • • • • • • • • • • • • • • • • • • •
Here’s links to a collection of our other blog posts about ELECTRIC PANELS:
How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
for Links to Collections
of Blog Posts