Cable gauge larger than the breaker terminal, what to do?

A very common problem in the electrical service is to come across a cable that has a larger gauge than the connector terminal! Changing the gauge of the cable is out of the question because this will cause the dimensioning to be incorrect, so what to do? In this article, the World of Electrical will show you the best options to solve this problem, come on guys!

Cable gauge
In some cases, the electric cable comes from a long distance, and to avoid a voltage drop it needs to be thicker. However, this can cause another problem, which is that the electric cable has a larger gauge than the circuit breaker terminal, which is also popularly called the circuit breaker nut!

When we researched the solutions to this problem in the photo below, some people indicated the use of the terminal on the end of the cable, others indicated the replacement of the circuit breaker terminal, and there were also people who said that the right thing was to change the circuit breaker or even use the bus waiting.

Increase the gauge of the circuit breaker terminal
Cable gauge larger than the circuit breaker terminal, how to solve?

Dimensioning of cables and circuit breakers
It is essential to respect the dimensioning of the electrical cables mentioned above! That is why it is so important to analyze the voltage drop, as we know that the longer the cable, the greater the voltage drop. Understand that the problem in the photo above does not have only one solution, and to answer this question we will use as an example this CM12 that appears below, which is a measuring box from CEMIG here in Minas Gerais. It is possible to see that all the cables of this CM12 have terminals at the circuit breaker poles.

Cable gauge larger than the circuit breaker terminal
CM12 measuring box with all components installed.

When researching the topic, one of the most cited solutions was precisely the use of the eyelet terminal, aiming to group the cables to enter the circuit breaker terminal. In case you don’t know, there are eyelet terminals for several gauges, up to the 250mm² gauge.

Circuit breaker, busbar and connection terminal
Eyelet terminals can be a solution for connecting cables to circuit breakers!

Although this option is excellent for joining the cable wires, this will not solve the problem of our first photo, because the action to correct this problem must be done directly at the circuit breaker terminal. Following the article, we will show you 3 possible solutions.

Change the circuit breaker nut
Various types of circuit breakers allow the terminal to be changed or even removed. Then, the first option would be to change the terminal to a larger one that accepts the correct wire gauge, as shown in the image below.

Circuit breaker, busbar and connection terminal
Change the circuit breaker nut to change the gauge!

And do not think that this is exclusive to industrial circuit breakers only! See in this other image that even on mini circuit breakers it is possible to place a terminal on the terminal, that is, residential circuit breakers can also receive thicker cables using this feature.

Cable gauge larger than the circuit breaker terminal
Larger gauge terminal on the residential mini circuit breaker terminal.

A circuit breaker with eye terminal
The next image shows the second option, which would be to remove the terminal from the terminal and connect the cable directly with an eye terminal. However, this option is only possible if the terminal hole accepts a screw that guarantees adequate pressure to the eye terminal.

Cable gauge larger than the circuit breaker terminal
Ends eye on the circuit breaker terminal

Use standby bus
Our third option is to remove the nut from the breaker pole and use a waiting bus. It is important to emphasize that this busbar must have the appropriate hole for the eye terminal and also for the screw.

Circuit breaker, busbar and connection terminal
Waiting for bus at the circuit breaker terminal

In the image below, we can highlight the use of the waiting bus in the input cables. Note that the main circuit breaker is 450A and the input cables are 3 per phase. That is why a waiting bus with 3 holes is used in each phase, in addition to two smaller holes for measuring cables.

Cable gauge larger than the circuit breaker terminal
Details of the CM12 box main circuit breaker and standby bus

Do not confuse with a branch bus! It is important to remember that this is the breaker input and not the output. Remember that tap is the name given to the output bus of the general circuit breaker that supplies the partial circuit breakers.

You may not know it, but some circuit breakers already have all of these factory options. Then you will be able to choose whether to use the terminals for varying cable sizes, or to use the busbars.

With all these options available to solve the problem, what cannot be accepted is the use of the wired cable outside the terminal, and the cable gauge should never be changed, leaving the dimensioning incorrect!

Currently, companies are using questions like this in their selection process, that is, instead of asking for bills, it asks you to present the solution to the problem. Therefore, knowledge in the area becomes essential.

This kind of trick is not taught in traditional courses, and the World of Electrical strives to bring this content to help all of you. Speaking of mallets, in the video below we teach a quick way to read your energy meter, it is very worth watching!

What are the subjects that most take your sleep? Leave your doubts in the comments, that we will prepare the contents to solve this problem. Keep accessing the site, because there are hundreds of articles that can further increase your training in the area.