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Sub panel Installation

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In this how-to install a sub-panel installation I will guide you through the complete installation of a subpanel step by step.

The first question is why are you installing a subpanel. There are either one or two reasons to do this. One because you need more room in your existing panel and in that case if your existing panel is old this would be a great time to just upgrade your current service. Newer 200 amp main panels hold a lot more circuits/breakers.

Two, because you need to bring more power somewhere else like a garage you just built or addition or even in some cases a finished basement. Either way, you want to install a subpanel. Ok. So let’s get going.

First: Where do you plan on placing the new sub-panel? If it’s right next to your main panel that’s one thing, but further away like in that new garage you just built 100 feet away you will certainly want to figure in voltage drop.  I can’t get too much into that because every setup would be different.

Second: How many amps are you needing for the new sub-panel. So let’s say you need 50 amps. Well, it’s not brain surgery, 50 amp sub panel, 50 amp wire, 50 amp breaker in the existing main panel. See wasn’t that easy.

bonding screw
bonding screw

Neutral Bonding Jumper: 

This is very very important. This is also known as a bonding screw. It may even be green. This screw is used to bond the neutral coming in the main panel to the case “panel” itself. however, in a sub panel, the neutral bus bar must be totally isolated from the ground. The very first thing the electrical inspector is going to look for is if the sub-panel is bonded or not.

Now as far as wiring the panel. You would wire it just like any other panel. Hot leads to the breakers, grounds to the ground bus bar, and neutrals to the neutral bus bar.

But Why Do You Need To Remove The Green Screw?

Because the neutral only gets bonded at 1st means of disconnect so any unbalanced load only has one true path to the ground and that’s at the power source.

You would install a 220-volt two-pole breaker in the main existing panel. Whatever the amperage is that you’re using. That breaker gets installed in the main panel of course. This is now the main breaker to your sub-panel. By turning this breaker on or off will control the entire subpanel.

Always remember safety first. Turn the main power off before removing panel covers or touching any wires.

You will need a 4 wire, wire between each panel. No matter how the panel is, this part will always stay the same. You will have two hots, one neutral and one ground. Two hots will go from the new breaker you just installed in the main panel to the sub-panel. A neutral will go from the neutral bus bar in the main panel to the NON bonded bus bar in the sub-panel and ground from the ground bus bar in the main panel to the bus bar in the new sub-panel.

wire size


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  1. have a 200 amp main panel. I’m going to install a 50 amp sub panel with # 6 wire in the next stud bay over. I’ll connect the two with a 2” pvc nipple. I need to move 4 circuits out of main panel into sub panel. Can I run the 4 circuits through the pvc nipple or do I disconnect all 4 circuits out of main panel then install them in sub panel. I’m in Washington state.
    Thanks Bill

    • By code 20″ but I always always go deeper. Go at least 24″ But if you can do 48″ This way you don’t have to worry about where you plant a tree or something like that.

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Written by Dominick Amorosso

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