I'm wiring 100 amp subpanel to detached Garage with 2/2/2/4 copper. I'm hoping to replace the subpanel to my detached garage which was previously wired to run on a 40 or 60 amp subpanel with like 6 spaces powered by a tandem 15A/20A breaker with 10/2 cable. So far, I have already disconnected any and all breakers and sub panels that were going to my detached garage in an effort to streamline the new installation and eliminate any confusion as to what(if any) electrical wiring/circuits (is/are) going from the detached garage from the main panel.
Now that I removed the original wiring used for the detached garage,
I am hoping to run a 125 amp subpanel on a 2-pole 100 amp breaker that will be placed inside of the garage where the conduit elbow comes up through the slab.
(((Just FYI If you're looking at my main panel and wondering why I have them there, there is a 2-pole 60 amp breaker on the top right and a 2-pole 30 amp breaker on the bottom left, I point those out because they are both disconnected. the 60 amp one was from my original garage subpanel. )))
The distance is approximately 94' plus the height going from the trenched conduit to the main panel and the subpanel.
I ran copper with 2/2/2/4 and now for due diligence, I am hoping to verify from a 3rd party where I connect the Neutral line and the ground lines on the main and subpanel before I attempt it.
My understanding is that on the subpanel, the two hot wires go to the left leg and right leg and on the other end, go into the breaker itself which then goes on the Main panel.
(Here is Where I'm hoping to get some clarification)
I'm guessing (But Not Sure) the Set Screw on the top center of the subpanel that is connected to both neutral bars is for the Neutral wire. Please let me know if I'm wrong.
There was an included plastic baggy that had a roughly 5" ground bar with a Set Screw on it and I'm not sure but I'm guessing but not sure that is where I connect the ground wire. Please let me know if I'm wrong.
On the Main panel, I see there is a flat Bar on the left side with (2) Set Screws, One of those on the bottom is being used to hold the Copper Ground Wire which is connected to the (2) posts that are buried and sticking out of the ground a couple of inches. I'm guessing But Not Sure, that the empty Set Screw is where I connect the #4 copper subpanel ground wire. Please let me know if I'm wrong.
Feel Free to Roast me or Educate me. Thanks in advance.
I've had maybe 3 or 4 legitimate electricians come out over the last 6 months and they all are booked up with work and I've ran out of time. I know a half dozen other "amateur" electricians but I don't have the confidence that they have so much as heard the term NEC or comprehend safety standards/measures. I feel more comfortable checking on sites like this one so I can try to get the process personally/firsthand.
Best Answer
Since you are connecting the feed from the sub-panel to the main panel, it really doesn't make any difference where you connect the neutral and ground, since they are bonded (connected) in the main panel. Still I like to separate the neutral from the ground, just in case the main panel becomes a sub-panel at some point (Like installation of a generator transfer switch between the meter and the panel). In your case, I see the neutrals and grounds are combined on a couple of bus bars, not a big deal, common practice.
You'll need some lug adapters to accommodate your wire sizes to connect the neutral and ground to the bus bars.
In your sub-panel, you'll need to "float the neutral" meaning isolate the neutral from the ground. Usually that just means not installing the bonding screw that comes with the panel. Also, because it's a separate building, you'll need ground rods connected to the grounding bus bar in the sub-panel. Yeah, it feels kinda redundant to have a ground wire to the main panel and still have to install ground rods at the out-building, but that's code.
Lastly, and this "opinion based". You might consider returning the new sub-panel for one that has PON (Plug on Neutral) capability. That way you don't need to get breakers with those curly pig tails. I recently installed a PON panel in my son's house and it made for a very clean install.