Double-lugged circuit breakers are one of the most common electrical defects that I see as a home inspector. (There are two terms that are commonly used for this: double-lugged and double-tapped. I will use both terms interchangeably in this post, and they both mean the same thing.) In this post, I am going to answer the following questions. What is a double-lugged circuit breaker? Are double-lugged circuit breakers ever allowed? Why is a double-lugged circuit breaker dangerous? How to repair a double-lugged circuit breaker? (The two photos below show examples of double lugging.)
What is Double-Lugging or Double-Tapping?
Double lugging is when two wires are placed under the same screw on a circuit breaker or on the neutral bus in an electrical panel. Double-tapping is normally done by a homeowner or a handyman who knows just the basics of electrical work, but is not familiar with codes or other safety requirements. I don’t think that any licensed electrician would ever create a double-tapped breaker. Occasionally, I have even seen more than two wires under the same screw, and this is just as dangerous if not more so. However, in this article, I will refer only to double lugging. Just keep in mind that more than two wires under the same screw is dangerous also. (See the photo to the right.)
Why are Double-Lugged Circuit Breakers Dangerous?
One of the main causes of electrical fires in the home is arcing. Arcing is when electricity “jumps” from an energized wire to another wire or piece of metal at a lower voltage – (essentially a spark). When this occurs, the air is turned into plasma, a very hot gas. This is the same thing that occurs with lightning. A principal cause of arcing on an electrical wire in homes is a loose electrical connection
When a wire is installed under a screw in an electrical panel, that screw is tightened down onto the wire to hold it securely. (The photo on the right shows wires properly installed on circuit breakers.) When two wires are placed under the same screw, those wires are not normally exactly the same size so it is almost impossible for that screw to hold both wires at the same tightness. One wire will almost always be looser than the other wire. If one of the two wires is loose enough, it is very likely that the loose wire will arc when it is carrying current. (If you are not familiar with electrical terms, check out this short blog post that explains some basic electrical terms such as current.) As I mentioned above, arcing produces heat so, if there is enough arcing, it is possible for a fire to result. This is why double tapping is dangerous. (The photo on the right shows the result of electrical arcing. Although it is not due to double tapping, it shows the dangerous result of arcing.)
It does not matter if the double-tapped screw is the screw on a breaker or if it is on the neutral busbar because the wire on the breaker (the hot wire), and the wire on the neutral busbar (the neutral wire) are both carrying the same amount of current. So double lugging in either place has the same potential to cause a fire.
Let me explain something that can make arcing resulting from double tapping even more likely. It is unlikely that both of the double-tapped wires will be carrying the same amount of electrical current. One will almost always carry more load/current than the other one. The wire that is carrying more current will be hotter than the other wire. The hotter wire will expand more, and will push against the screw. As it pushes against the screw, the other wire will become even looser, making the risk of arcing even greater.
Is Double-Lugging Ever Allowed?
Yes, there are some breakers that are designed to hold two wires. To my knowledge, the only two companies that make these breakers are Square D and Cutler-Hammer. Be aware that not all Square D and not all Cutler Hammer breakers are designed to hold two wires, but some of them are. This would be the only time that double lugging is allowed and does not create a dangerous situation. (In the photo to the right, you can see in the circled area that it shows a symbol representing two wires under one screw. This indicates that this breaker is allowed to be double lugged.
How to Repair a Double-Lugged or Double-Tapped Breaker
There are several methods to remedy a double-tapped breaker, and I would recommend that they all be performed by a licensed electrician.
- If there is room in the panel, another breaker can be added and then one of the wires on the double-lugged breaker can be moved over to the new breaker
- You can replace the existing double-lugged breaker with a breaker that allows for double lugging. Note: this can only be done if you have a Square D or Cutler Hammer panel that will accept the breakers that are designed for double tapping.
- You can install a pigtail. This basically consists of removing the two wires that are connected to the breaker, and using a wire nut to connect those two wires and a third short wire together. After connecting the ends of the three wires together, the free end of the short wire can then be attached to the breaker. In this way, there will now only be one wire attached to the breaker.
Double lugging or double-tapping is normally not allowed because it creates a potentially dangerous situation that could result in an electrical fire in your home. For this reason, it is important that electrical work is done by a licensed electrician. If you are in the process of purchasing a home, and your home inspector found one or more double-tapped breakers, I would highly advise that you have this condition corrected before you purchase the home. It is a potential fire hazard and it is fairly easy to correct this condition and eliminate the hazard. If you have any questions or comments, please leave a comment below.
© 2020 Mike Morgan
This article was written by Mike Morgan, the owner of Morgan Inspection Services. Morgan Inspection Services has been providing home, septic and well inspection services throughout the central Texas area since 2002. He can be reached at 325-998-4663 or at firstname.lastname@example.org. No article, or portion thereof, may be reproduced or copied without prior written consent of Mike Morgan.