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 an 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 you 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 ever setup would be different.
Second: How many amps are you needing to 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.
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 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 buss 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 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 buss bar in the sub panel and a ground from the ground buss bar in the main panel to the buss bar in the new sub panel.