Feeder size to comply with NEC voltage drop recommendations

[tncjhb]

Hi,

I am wondering what size of feeder cable (either copper or aluminum) I would need to comply with the NEC recommendations of a 5% voltage drop from the main to the end receptacle in a branch circuit (going through a subpanel.)

If I put in a 50 amp breaker into my 200 amp main panel and run the feeder ~75-85' (85' as worst case scenario distance) to the attic to install a sub panel, what size feeder cable would give me a 2% voltage drop, so that I can use a 3% drop for the branch circuits? I will have three 20-amp, 240 volt in-wall heaters in the panel as well as a bunch of 15 amp 120V receptacle circuits, three 120V light circuits and two 120V 20-amp gfci bathroom circuits.

I am assuming that for 85' I would need either a 4-3 copper cable with ground or a 2-2-2-4 aluminum ser cable.

 

[George Stolz]

I am closing this thread, in accordance with the Forum Rules.

This site is designed for:

• Contractors
• Electricians
• Engineers
• Inspectors
• Instructors
• Other electrically related individuals

* This NEC? Forum is for those in the electrical and related industries. Questions of a "How-To" nature by persons not involved in the electrical industry will be removed without notice.

If you feel this action to be in error, feel free to contact me via PM to explain.

A reminder to all members, if you see a questionable post, feel free to report it by clicking the

button at the bottom left corner of the post.