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Kevin
Kevin, Licensed Electrician
Category: Electrical
Satisfied Customers: 2944
Experience:  29 years as a Licensed Electrical Contractor in Illinois, 5 year college Electrical Instructor, Former Electrical Inspector, Diploma in Digital Electronics, Former Illinois Licensed Home Inspector
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I am adding a 100 amp subpanel next to my 200 amp main

Customer Question

i am adding a 100 amp subpanel next to my 200 amp main panel. what size breaker and wire do I use from my main panel to the subpanel?
JA: Thanks. Can you give me any more details about your issue?
Customer: I am installing an electric car charger 32 A. my plan is to add a subpanel and connect the car charger to the subpanel. to make room in the main panel I am routing the refrigerator and garage outlets to the subpanel.
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Submitted: 9 months ago.
Category: Electrical
Expert:  Kevin replied 9 months ago.

Hello Mike and welcome to Just Answer. My name is ***** ***** I will be happy to assist you with your electrical question.

1) Based on the sub-panel loads that you want to connect, I recommend a minimum of a 70 amp double pole feeder breaker will be required. The 70 amp sub-panel feeder circuit will require a 4 wire circuit comprised of 2 hots, 1 neutral and 1 equipment ground. A quantity of (3) three 4 AWG copper wires (type THHN insulated) will be required for the 2 hots and 1 neutral. An 8 AWG copper can be used for the equipment grounding conductor.

2) If the existing 200 amp main panel can sustain a 100 amp feeder circuit, I recommend installing a 100 amp double pole breaker in the main panel as this will obviously take care of the 3 sub-panel loads as well as providing for some future circuits. If using a 100 amp feeder breaker, the 2 hots and 1 neutral will require 4 AWG Copper (type THHN insulated) and an 8 AWG Copper for the equipment ground wire.

3) If connecting the 200 amp main panel to the sub-panel by EMT metal conduit, then the equipment grounding conductor can be eliminated since the EMT metal conduit will act as the equipment grounding conductor.

4) Since the sub-panel will be installed directly next to the main panel, a main lug sub-panel can be installed.

5) At the sub-panel, DO NOT install the green main bonding screw or a main bonding jumper strap to the neutral bus bar. On any sub-panel, the neutral feeder must always be isolated from the sub-panel metal enclosure cabinet. By not installing the main bonding screw or jumper, this is how the neutral remains isolated.

6) At the sub-panel neutral bus bar, only white neutral conductors will land there. Never inter-mix bare copper or green insulated ground wires onto the neutral bus bar. The sub-panel will require a separately installed equipment grounding bar to land any equipment grounding conductors.

If you have any additional questions, just let me know and I’ll be glad to answer them for you.

Otherwise, don’t forget to rate me before you log Off.

Thanks................Kevin:)

Expert:  Kevin replied 9 months ago.

If you have any additional questions, just let me know and I’ll be glad to answer them for you.

Otherwise, don’t forget to rate me before you log Off.

Thanks................Kevin:)

Expert:  Kevin replied 9 months ago.

If you have any additional questions, just let me know and I’ll be glad to answer them for you.

Otherwise, don’t forget to rate me before you log Off.

Thanks..............Kevin:)

Expert:  Kevin replied 9 months ago.

If you have any additional questions, just let me know and I’ll be glad to answer them for you.

Otherwise, don’t forget to rate me before you log Off.

Thanks...............Kevin:)

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