Wire sizes vary for different reasons. Wire materials, temperature, amount of electricity to be carried, the distance of sub-panels, weight, etc. are the major determinants of wire sizes.
With the increasing electrical flow and distance, bigger size wires are suggested for safe flow.
Temperature also plays a major role. Increased temperature also creates resistance that restricts the electricity flow. So, wider wires are suggested that can supply electricity within minimum temperature increase.
Usually, 6AWG wires are suitable for 50 amps. But, if the wire length is bigger than 100 feet, 4AWG wires are suggested to avoid any unpleasant circumstances.
Ampacity refers to the maximum capacity of a conductor to flow electrical current continuously.
Wire ampacity is the maximum electrical current carrying capacity of a wire or cable. The term ampere ensures safe carrying capacity through a wire or cable throughout its life.
The flow of current should not exceed the temperature limit. Temperature plays a vital role in determining the ampacity of a conductor.
With the increasing temperature, the resistance of the conductor increases. So the capacity of carrying current gets limited.
However, ampacity is measured by ampere or amps and refers to a conductor’s maximum capacity of carrying current under normal usage conditions.
A wire gauge is used to measure the diameter of a wire. It refers to the physical size of the wire.
Gauge is rated with numbers that are opposite to its measurement. It means smaller sized gauge is characterized by larger numbers and vice versa.
The electrical current carrying capacity of a wire depends on its gauge size. The gauge determines the amount of current to be carried. It also determines the resistance and weight.
Common sizes of the gauge are 16-, 14-, 12-, 10-, 8-, 6-, 4-, 2-, etc.
50 amp sub panel wire size:
Wire sizes determine the amperage flow for sub-panels. A 6-gauge wire is best suited for 50 amps of electric flow. A 6-gauge wire can easily handle up to 55 amperages. It is perfectly suitable for 50 amps as well. Usually 50 amps are used to power different appliances and they use a 50 amps breaker.
NEC code for wire size:
National Electric Code (NEC) is a standard measurement that has been adopted regionally to ensure the safe installation of electric wires and equipment in the United States. NEC determines the wire size required for a particular electrical flow.
With the help of NEC code, anyone can determine the required wire size for a particular appliance and install it safely. Wire sizes are expressed by numerical values opposite to their diameter.
The smaller diameter of wires is expressed by large numbers such as 14 AWG is smaller than 12 AWG. So, smaller numbers are for bigger wires and bigger numbers are for smaller ones.
NEC suggests wire sizes for both copper-based and aluminum-based conductors within the range of 0-2000 volts. As different materials have different melting points, different ranges of current can flow through them.
Wire sizes are determined considering these issues. NEC follows the 80% rule in which wire sizes are determined keeping 20% extra carrying capacity. It means if 50 amps are to be supplied, wires should be selected for carrying 62.5 amps.
Wires should always be bigger than the required electric flow. According to this rule, the following chart has been given-
|Amperage||Wire size (Copper)||Wire size (Aluminum)|
|20||12 AWG||12 AWG|
|30||10 AWG||8 AWG|
|40||8 AWG||6 AWG|
|50||6 AWG||4 AWG|
|60||4 AWG||3 AWG|
|80||2 AWG||1 AWG|
|100||1 AWG||1/0 AWG|
|125||1/0 AWG||3/0 AWG|
|150||2/0 AWG||4/0 AWG|
Wire sizes also depend on the length of the wires. The voltage of electricity drops by 20% for every 100 feet. So, when your sub panel will be set far away, wire sizes should be determined based on the distance as well.
NEC suggests the following sizes for different distances. Usually, 50 amps require 6 AWG, but for a 100 feet-long cable or more, 4 AWG is considered safe for wiring. 2 AWG is recommended for more than 400 feet distance.
|Wire size for 50 amp sub panel||Distance/Length of wire|
|4 AWG||100 feet away|
|4 AWG||150 feet away|
|4 AWG||200 feet away|
|2 AWG||400 feet away|
How to determine a 50 amp sub panel wire size?
50 amps are one of the most common amperages we use regularly. 50 amps are usually used to power different appliances. So for the safe installation and wiring of your appliances, you need to know how to determine the wire size.
To determine the required wire size, you need the electricity flow and the distance of the sub-panel. However, you can take the following steps to determine the required wire size-
NEC 80% rules:
NEC recommends an 80% rule to determine the wire size. It means a wire should supply 80% electric flow of its capacity. 20% extra should be on top of the amperage.
So, for 50 amps, you should use a wire that has the capacity to flow 50/0.8= 62.5A. But there is no exact wire available. The closest available wire is 6AWG with 65 amp. We can easily use 6AWG for 50 amps sub panel following the NEC 80% rule.
In most cases, 6AWG is used for 50 amps. But you can also use 4AWG which is bigger than the previous one.
Remember that, you should never use smaller size wire. Always use wider wires, otherwise, there will be a short circuit resulting in a fire accident.
Another important rule is to measure the distance. Electric flow also depends on the distance passed.
There are chances of voltage drop if the way is too long. Usually, voltage drops by 20% for every 100 ft. so, you should consider the distance.
If the sub-panel is 100 feet away, you need to add 20% more to your amperage. So, 62.5X1.2= 75A cannot be covered by 6AWG. You will need 4AWG which can handle up to 85A. With the increasing distance, wire size also widens.
Some people mistakenly think that for different voltages, you will need different wire sizes. But, different voltages do not create different amperages, rather it creates different power (Watt).
So, your wire size will not depend on voltage. You can use the same wire for both 110V and 220V.
These are some mostly used rules followed by NEC to determine wire sizes. You need to follow the chart to determine the appropriate measure. Any carelessness may lead towards something unexpected and unacceptable.
Why is wire size important?
NEC suggest different wire sizes for the different conductor. It is mandatory to follow the code. Otherwise, any unwanted accident may occur. NEC code is suggested with the purpose of safe installation and wiring. The followings are some reasons behind using different wire sizes-
The major concern of using perfect size is safety and security. Different wire sizes are suggested for different amps because if smaller wires are used compared to the current flow, the insulation may melt due to the increased temperature of the cable.
On the other hand, an oversize cable might seem appropriate, but actually, it is nothing but a waste of money. You will not wear an oversized shirt or an undersized shirt for no reason. Similarly, wire sizes should be selected as per requirement.
Another important factor is resistance. A narrow wire is more resistant than a wide wire.
It means more electricity can pass through wider wires compared to wires of smaller diameters. Narrow wires are congested sometimes for higher electric flow.
But you will never want overflows of electricity to your appliance which might deteriorate it. So, you should choose wire size depending on your need.
Sub panel wire size & Amp rating chart:
|Amp rating||Aluminum wire gauge size (AWG)||Copper wire gauge size (AWG)|
|60 amp||3-gauge||4- gauge|
|50 amp||4-gauge||6- gauge|
|40 amp||6- gauge||8- gauge|
|30 amp||10- gauge||10- gauge|
|20 amp||12- gauge||12- gauge|
It is vital to know the wire size determination process as any wrong step may lead to unavoidable fire accidents. NEC provides a distinct chart to measure the appropriate wire size. Mostly 50 amps are used in different appliances in our day-to-day life which require 6 AWG and sometimes 4 AWG wire.