Hello,
I want to put a subpanel in my shop, and was wondering if a main service panel that they sell at say Home Depot is the same thing as a subpanel? I have a 200 amp service to my house, and want to put a 100 amp subpanel in my shop. Does the term "subpanel" just mean that it is wired off the main panel, or is the hardware actually different than a main panel? Also, what size wire would be recommended for this 100 amp panel? It is about 125' away.
Thanks

The short answer is, the "hardware" is the same. For the subpanel at the shop you can use a panel with or without a main breaker (called a Main Lug Only panel)since at the "main" panel you need to install a breaker to feed the new panel.

The important thing is how the neutral and ground are connected at an added panel.

The neutral and ground are "bonded', or connected ONLY at where the first disconnect for the entire service is located, which is typically, the "Main Panel". But not always, since many times the Main Service Disconnect is located outdoors at the meter.

In your case, the subpanel for the shop, if your run 4 wires, 2 hot, 1 neutral, and 1 equipment ground, you will need to purchase a separate equipment ground bar, bolt it directly into the new panel using machine thread screws, and use this for all equipment ground wires. DO NOT connect (bond), the neutral bar to the panel board box.

This may come as a surprise to some, but since you bring it up, there is no legal definition in the electric code for "Main panel" and "Subpanel".

The term "Sub"- panel implies that it takes it's feed from another panel.

And a Main Panel typically means just what is implies, the main, first, initial, only. Since your interested in adding a subpanel, let me work backwards. Any panel added, since it will not contain the Main Service Disconnect, the neutral bar must be kept insulated and isolated from the metal box and any equipment grounds.

If the Main Service Disconnect is located outdoors at the meter, then even at the "- panel implies that it takes it's feed from another panel.

And a Main Panel typically means just what is implies, the main, first, initial, only. Since your interested in adding a subpanel, let me work backwards. Any panel added, since it will not contain the Main Service Disconnect, the neutral bar must be kept insulated and isolated from the metal box and any equipment grounds.

If the Main Service Disconnect is located outdoors at the meter, then even at the " panel the neutral must be isolated and insulated from equipment grounds.

The key is where the Main Service Disconnect is located, and how the neutral and equipment ground is wired.

Not to confuse you, but you can buy a panel with a main breaker for the shop, but you still need a breaker back at your " panel the neutral must be isolated and insulated from equipment grounds.

The key is where the Main Service Disconnect is located, and how the neutral and equipment ground is wired.

Not to confuse you, but you can buy a panel with a main breaker for the shop, but you still need a breaker back at your " panel, and you still must not connect the neutral and equipment ground at this new panel.

For the wire size I would use #2 copper, because of the length and the purpose, to reduce voltage drop.

I hope this helped you more that confused you.

Thanks for the explanation tkrussell. You suggest using "#2 copper, because of the length and the purpose". Isn't aluminum wiring cheaper, and just as good? If I were to use aluminum, what would the size recommendation be? What is the Amperage rating for #2 copper?
Thanks.

Amp rating for #2 THHN is 115 Amps at 75Deg C,which is what rating will apply, and which is a bit more than you need, but I was suggesting #2 copper because of the 125 foot length, and the purpose being a shop, assuming there would be a substantial motor load.

For a residential feeder, you could get away with #4 copper or #2 aluminum, but this shop feeder I thought would serve better at #2, due to voltage drop. Motors do not start well or operate well with reduced voltage.

Yes copper is expensive, so if cost is a factor, and I am sure it is, then you could use #1 Aluminum XHHW, which will also help to reduce voltage drop and will work just fine.

The only issue with aluminum conductors is to be sure the terminations are treated properly, by wire brushing the bare wire, applying anti-oxidant compound on the bare wire at the connection, and torquing the connection properly.

Also, if this shop is not just related to a residential dwelling and can be considered as a commercial shop, the smaller wire sizes I mentioned will not apply, and you will end up with either #2 copper or #1 Al anyway.

Hi,

I'm doing a major renovation on my house and what I have had here is a 40 position 200 amp main panel. An electrician told me I need to have a sub panel next to that to deal with all the circuits I'm adding. Its not that any of them will have anything big here or there, but for convenience I have made many little circuits (for example, a separate one for microwave in kitchen, etc)

I want to put a subpanel next to the main one and have hopefully 40 more circuits to be able to cover everything in the house...

The electrician told me to get a MLO for this... and so I'm assuming to put something like a 100-125-150 or so amp breaker in the main panel and feed to the subpanel next to that... that part makes sense... but what I'm confused by is this part where I have to isolate the neutral bar from the ground bar... could you explain that to me a little bit? Basically I have a murry 200 amp main panel right now... if I purchase a 40 position murry mlo box, how should I connect the two? Then can I just have a bunch of 20 amp circuits on that?

-Dave