Last Updated on October 22, 2023 by Kevin Chen
Image source DIY.stackexchange
Wire size: A very important factor that you should consider when buying and installing a circuit breaker. Do you want to install a 40 amps circuit breaker? You should choose the perfect wire size for it. To help you make the right choice, we are going to discuss the essentials of choosing the right wire for your 40 amps breaker.
So which is the perfect wire size?
Wire size in the field of electronics are usually defined by Gauge. The American Wire Gauge(AWG) provides the defined standards for measuring the diameter of the wires. So, whichever size you choose, it should be based on the AWG.
80% NEC rule
Another way in which we have arrived at the 8 gauge wire size for the 40 amps circuit breaker is by using the 80% NEC rule. Here, the 80% refers to the 80% of the current that your circuit breaker can handle. So, if you choose an 8 gauge wire size for your 40 amps breaker, then it will be able to carry 20 amps out of the 40 amps that the circuit breaker can handle.
The other factor that you must consider is how much voltage will be lost when running a certain amount of current through a certain thickness of wire? For example, if you are using 8 gauge wire, then there will be 1.7 volts lost in every 100 feet of wire. If you are using 10 gauge wire then there will be 1.4 volts lost in every 100 feet of wire and so on.
The type of wire matters
Even as you pay attention to the thickness of the wire, you should also check out the type of wire that you are going to connect to your circuit breaker.
Copper and aluminum are the two most common wires used for electrical installations. So, what happens to their sizes?
Copper wires have a maximum current of 20 amps and a voltage of 120 volts. Aluminum wires have a maximum current of 40 amps and a voltage of 240 volts. So, if you are going to use copper wire you will need to make sure that your circuit breaker can handle the amount of current that it is being asked to carry at the same time.
On the other hand, if you are going to use aluminum wire then you should size your circuit breaker accordingly.
The thicker the wire is, the more voltage it loses as it travels through it. That is why 10 gauge wire can carry 40 amps while 8 gauge wire can only carry 20 amps. If you are using 10 gauge wire and want to run 40 amps through it then you should make sure that your circuit breaker has enough amperage rating for the job.
The ideal length of the wire
Is there a fixed length for the 40 amps circuit breaker? What you should know is there is no minimum wire length for this circuit breaker, especially if the circuit is positioned below 100 meter.
However, for the longer distance, you will have t reconsider the size of the wires. For instance, if the circuit breaker distance is more than 100 meters away, you will have to reduce the wire size to 6 gauge.
Why should the length of the wire matter?
The longer the wire is, the higher the voltage will be at its center. So if you have a circuit that is positioned more than 100 meters away then reducing the size of the wires will help to reduce any voltage drop at its center.
If you are using aluminum wire then this circuit breaker should be used for indoor use only. It is not recommended to use it for outdoor works. It can be used as long as it does not get in contact with water or electrical shock hazards. You should also make sure that your circuit breaker has a rating of 30 amps and above.
Can you use 6 wire on a 40 amp breaker?
While this wire size may work, it is not the recommended size for the wire. A size 6AWG will reduce the resistance on the circuit and this can lead to an increase in the current flow.
This can damage your circuit breaker and this will not be good for the safety of your home.
How many amps can 8 AWG wire carry?
Under normal conditions, size 8 wires are designed to accommodate up to 55 amps continuously. How have we arrived at this value?
The current carrying capacity is determined by the cross-sectional area of the wire and the voltage drop across the wire.
The larger the cross-sectional area, the higher current that can be carried by a given size circuit wire.
The equation for current flow is:
A = Area of the conductor through which voltage will be spread
V= Voltage drop across conductor
C = Constant between 0 and 1, where 1 means no voltage drop (wire is perfect). If you use 8 AWG wire, then you should not exceed 40 amps continuously. In other words, you should not exceed 40 amps for 10 seconds or more at a time. If you want to test your circuit breaker with this size of wire then make sure that it has a rating of 30 amps or above. You do not want your circuit breaker to fail while using this size of wires. If your circuit breaker fails while using 8 AWG wires then it may lead to an electrical fire in your home or even a house explosion
What are some uses for 8 AWG Wire?
This type of wiring is commonly used in CCTV cameras due to its high resistance ability and its ability to carry high amperage continuously without creating any sparking at all which can cause danger in case there is a short circuit in your home’s electrical system. The 8 AWG wires are also used in data transmission. They are able to carry high amount of data through them without creating any electrical sparks.
Now you know the right wire size for the 40 amp circuit breaker. If you know what wire size to use for your circuit breaker then you need not worry about it. If you are still confused, then don’t hesitate and ask the electricians in your area or search online and find out the right wire size for your 40 amp circuit breaker.
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