0
This is a voltage drop question. To answer this question a voltage must be stated.
This is because the NEC (National Electrical Code) suggests that a feeder have no more than 3% voltage drop. So in order to answer the question, we must ask 3% of what supply voltage?
For instance, suppose the subpanel in question is a 120/240V single-phase panel supplying 120V branch circuits (common in the US). According to NEC (2011) 215.2 (A) informational note #2, we should limit the voltage drop to 3.6V (0.03 X 120).
Now NEC Table 310.15 (B)(7) says that copper #4 conductors are the minimum size we can use for a 100A feeder, but this would result in a voltage drop greater than 3% for our 100 foot run.
The formula for voltage drop is E (voltage) = I (current) X R (resistance).
#4 copper wire has a resistance of 0.308 ohms per 1000 feet, or 0.0616 ohms per 200 feet (remember that our 100 foot run includes two conductors for the round trip). So the voltage drop at full load would be E = 100 X 0.0616 or 6.16 volts, higher than the 3.6 volts maximum we are looking for.
In order to find the wire that will meet our needs, we need to calculate the maximum resistance we can tolerate. We can rearrange the formula for voltage drop to solve for resistance. Rearranging E = I X R we get R = E/I, so:
R = E / I
R = 3.6 / 100
R = 0.036
Our 200 feet of wire can have no more than 0.036 ohms resistance, but the tables list resistance for 1000 feet of wire, so we can say our wire can have no more than 0.18 ohms per 1000 feet (1000 / 200 X 0.036 = 0.18)
Consulting chapter 9 table 8, we find that #1 copper wire has a resistance of 0.154 ohms per 1000 feet, it is the smallest conductor that will limit our voltage drop to less than 3% worst-case.
You can follow the same steps to figure wire sizes for other supply voltages using the same method. Of course the NEC may not be adopted in your part of the world (and the informational note is not mandatory, but just a suggestion), but limiting voltage drop is a good idea no matter where you live, just be sure to follow your local laws if they are more stringent.
For a 100 amp subpanel, you would typically need to use #3 AWG copper wires for the hot conductors and a #8 AWG copper wire for the ground conductor. The size of the neutral wire would depend on whether the subpanel will be used for 120 volts or 240 volts.
#3 R90 or RW 90 degree copper wire. Its amperage rating is 105 amps.
A #3 copper conductor with an insulation factor of 75 degrees C is rated at 100 amps also, with an insulation factor of 90 degrees C a #3 conducor is rated at 105 amps.
A #3 copper wire with an insulation rating of 75 or 90 degrees C is rated at 100 and 110 amps consecutively.
Add your answer:
Earn +20 pts
What size wire should be used for ground wire from main to subpanel?
The size of the ground wire should be based on the amperage of the subpanel. A common recommendation is to use a copper wire of at least #8 gauge for a 100-amp subpanel, and a #6 gauge for a 200-amp subpanel. Always consult local electrical codes and regulations for specific requirements in your area.
What size wire is needed for carrying 100 amps under ground?
For carrying 100 amps underground, typically a 2-gauge copper wire or a 1/0-gauge aluminum wire would be suitable. It's important to consult with a licensed electrician to ensure the correct wire size based on distance, voltage drop, and local electrical codes.
What size feeder wire for 100 amps?
For a 100 amp service, a common feeder wire size would be 2 AWG (American Wire Gauge) copper or 1/0 AWG aluminum. These sizes are appropriate for handling the current capacity needed for a 100 amp electrical service. It is important to consult with a licensed electrician or local building code requirements to ensure the proper wire size for your specific installation.
What is the maximum amps for a sub panel?
The maximum amperage for a subpanel is typically determined by the size of the wire feeding it and the rating of the main panel. It is common for residential subpanels to be 100 or 200 amps, but it can vary depending on the specific installation and electrical code requirements. It's important to consult with a qualified electrician to determine the appropriate ampacity for your subpanel.
Can you use a 200 amp subpanel on a 100 amp branch circuit?
No, it is not recommended to use a 200 amp subpanel on a 100 amp branch circuit. The subpanel rating should not exceed the capacity of the branch circuit to prevent overloading and potential safety hazards. It is important to match the subpanel rating with the branch circuit capacity to ensure proper electrical function.
What size wire should be used for ground wire from main to subpanel?
The size of the ground wire should be based on the amperage of the subpanel. A common recommendation is to use a copper wire of at least #8 gauge for a 100-amp subpanel, and a #6 gauge for a 200-amp subpanel. Always consult local electrical codes and regulations for specific requirements in your area.
What size wire is needed for carrying 100 amps under ground?
For carrying 100 amps underground, typically a 2-gauge copper wire or a 1/0-gauge aluminum wire would be suitable. It's important to consult with a licensed electrician to ensure the correct wire size based on distance, voltage drop, and local electrical codes.
100 amp subpanel from 200amp service what size wire do you use?
A #4 copper conductor with an insulation factor of 75 or 90 degrees C is rated at 85 amps.
What size feeder wire for 100 amps?
For a 100 amp service, a common feeder wire size would be 2 AWG (American Wire Gauge) copper or 1/0 AWG aluminum. These sizes are appropriate for handling the current capacity needed for a 100 amp electrical service. It is important to consult with a licensed electrician or local building code requirements to ensure the proper wire size for your specific installation.
How is wire pulled into a conduit of 100 feet?
A 100 foot fish tape and wire lubrication will be needed to make this wire pull.
What is the maximum amps for a sub panel?
The maximum amperage for a subpanel is typically determined by the size of the wire feeding it and the rating of the main panel. It is common for residential subpanels to be 100 or 200 amps, but it can vary depending on the specific installation and electrical code requirements. It's important to consult with a qualified electrician to determine the appropriate ampacity for your subpanel.
What size wiring is needed to run 100 ft of direct burial wire to a shed for a light and 1 plug?
12/3 will work.
Can you use a 200 amp subpanel on a 100 amp branch circuit?
No, it is not recommended to use a 200 amp subpanel on a 100 amp branch circuit. The subpanel rating should not exceed the capacity of the branch circuit to prevent overloading and potential safety hazards. It is important to match the subpanel rating with the branch circuit capacity to ensure proper electrical function.
What is the required wire size for 100?
A 100 amp service requires that you use AWG 4 copper wire or AWG 2 aluminum wire.
What wire size is good for 100 amps?
# 4 copper wire short distance.
What size tech cable for 480 feet 100 amp?
This is a voltage drop to establish wire size question. For a correct answer to this question two values are needed. One value needed is the voltage and the other is whether it is three phase or a single phase installation.
What size wire for 2 100 amp meters?
1awg
