I would like to determine correct wire size for a 100 amp 240 volt single phase sub panel 300 ft from the main panel. Any one have a calculator for the voltage drop/ wire size? If I ran (3) #2 THHN's and (1) #6 in 2" SCH 80 PVC 300' what would the conductors ampacity be derated to?
Wire size
- Thread starter 70ramair
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peter d
Senior Member
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- New England
Re: Wire size
What is the calculated load?
What is the calculated load?
- Location
- New Jersey
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- Journeyman Electrician
Re: Wire size
If your calculated load is 61 amps or less than you would have a voltage drop of 3% or less. As Peter mentioned you'll need to know the calculated load since this is one component of the voltage drop formula. Take a look at this voltage drop calculator:
http://www.electrician.com/vd_calculator.html
If your calculated load is 61 amps or less than you would have a voltage drop of 3% or less. As Peter mentioned you'll need to know the calculated load since this is one component of the voltage drop formula. Take a look at this voltage drop calculator:
http://www.electrician.com/vd_calculator.html
- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: Wire size
If you choose to use a larger wire than is needed to support the current drawn by the load, and if that choice is based on voltage drop considerations, you are not changing the ampacity of any conductor. Rather, you are choosing a conductor with lower resistance. As a side benefit, but an unrelated benefit, you get a conductor with a higher ampacity.
They would not be "derated." The ampacity is first determined from the size of the conductor, its material of construction (copper versus aluminum), and its insulation type. That ampacity would be derated if you installed more than three current-carrying conductors in the same raceway, or if the ambient temperature exceeded 30C.
If you choose to use a larger wire than is needed to support the current drawn by the load, and if that choice is based on voltage drop considerations, you are not changing the ampacity of any conductor. Rather, you are choosing a conductor with lower resistance. As a side benefit, but an unrelated benefit, you get a conductor with a higher ampacity.
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