SUB PANEL QUESTION

[Youngfd]

My shop currently has a stand alone 200 amp panel located in the left side rear of shop. I have remodeled the 3 bays on the right and want to add a sub panel on that side. Thinking a Square D 100 amp panel (Not the Homeline) I have a couple of light circuits, 3 outlet circuits and will want a 50 AMP welder plug and room for expansion. Does the sub panel require a different panel than the main panel? Thoughts on my plan???

 

[sparky 1971]

A sub panel is fine, but you need to re-word your question. A sub panel is separate from the main panel, therefor it has to be a different panel than the main.

My shop currently has a stand alone 200 amp panel located in the left side rear of shop. I have remodeled the 3 bays on the right and want to add a sub panel on that side. Thinking a Square D 100 amp panel (Not the Homeline) I have a couple of light circuits, 3 outlet circuits and will want a 50 AMP welder plug and room for expansion. Does the sub panel require a different panel than the main panel? Thoughts on my plan???

 

[u2slow]

A sub panel can have its own main breaker or not.

If shopping at the big-box stores, usually the main breaker type is a better value. Other times the non-main type is on clearance.

 

[pattenp]

The panel you use as a subpanel can be a main breaker panel or a main lug panel.

 

[Youngfd]

Correction. My 200 amp panel will stay in place and I want to add a second panel (sub panel) 100 amp ?? in the remodeled section to service power needs in those 3 bays.

 

[ipgenie]

Feed the sub from a 90 amp breaker in the main and use aluminum wire. Best bang for the buck and the sub can have a 100a breaker or not, won't really matter because the conductor is protected by the 90a breaker in the main.

 

[mike93lx]

The brand doesn't need to match.

I'd probably do a main breaker panel and feed it with a 90a breaker and either #2 AL SER or conduit with 2-2-2-4 AL Xhhw. That sub can be any size, so go big enough (physical spaces) to do what you want. The main breaker size doesn't matter as long as it is at least as big as the breaker feeding it

 

[Junkman]

Just keep in mind that the sub-panel has to have the grounds and neutrals separated, and its own grounding rod.

 

[mike93lx]

Just keep in mind that the sub-panel has to have the grounds and neutrals separated, and its own grounding rod.

It's attached, so no ground rods. If it was detached, you would need two.

 

[sparky 1971]

Mike is right on. You can usually buy a 100 amp main breaker panel for less than a main lug. If you can run SER cable, that's going to be the less expensive route. As already stated, code says you have to use a 90 amp breaker for a sub when using #2 AL, you won't find them at a box store, but they can be ordered or purchased at an electrical supply house. I have #2 AL feeding my garage panel and sub in the house. I plead the 5th when asked if they are fed from a 100 amp breaker.

You will probably also have to buy the ground bar separately. There are a few that come with them, but not very often

 

[sparky 1971]

Just keep in mind that the sub-panel has to have the grounds and neutrals separated, and its own grounding rod.

Not if it's in the same building

 

[Innovate1]

A sub panel can have its own main breaker or not.

If shopping at the big-box stores, usually the main breaker type is a better value. Other times the non-main type is on clearance.

Don't think that's true in all cases. In this case it's in the same building so that is ok. If in a separate building I think it needs a main.

 

[sparky 1971]

Don't think that's true in all cases. In this case it's in the same building so that is ok. If in a separate building I think it needs a main.

If it's a separate structure, it has to have a disconnect. The most economical way is with a main breaker.

 

[u2slow]

Don't think that's true in all cases. In this case it's in the same building so that is ok. If in a separate building I think it needs a main.

It is true you can get them either way.

Which you're allowed to use in which situation is a Code issue.

 

[mike93lx]

Don't think that's true in all cases. In this case it's in the same building so that is ok. If in a separate building I think it needs a main.

You only need the main in a detached structure if it takes more than 6 handle throws to turn everything off. So a small sub could be main lug. That's what was done with the sub for my pool equipment.

I believe this exception is going away with the 2020 code

 

[FrancisJ]

No rqmt for type of manufacturer at sub, but NEC does have specific GND, neutral arrangements at sub panels. I’d also strongly consider GFCI — All my eight welders (all processes) are GFCI’d

 

[billconner]

You only need the main in a detached structure if it takes more than 6 handle throws to turn everything off. So a small sub could be main lug. That's what was done with the sub for my pool equipment.

I believe this exception is going away with the 2020 code

My electrical inspector said the six handle exception was deleted in 2017, but maybe that was NY amendment. Clearly 2020. Some history: https://www.ecmag.com/section/codes...020-nec-revision-has-major-impacts-electrical

Anyway I can't use it so have to have main in my detached accessory structure. Which is way off topic.

 

[Norcal]

You only need the main in a detached structure if it takes more than 6 handle throws to turn everything off. So a small sub could be main lug. That's what was done with the sub for my pool equipment.

I believe this exception is going away with the 2020 code

Not going away, just each disconnect has to be separate.

 

[mike93lx]

each disconnect has to be separate.

What do you mean by that?

 

[sparky 1971]

What do you mean by that?

It's one of the most brilliant things the CMP has come up with. Each disconnect needs to have separate access. The best example is a 400 amp meter main with two 200 amp breakers. If one door opens up to access both breakers, that's a no no. But if each breaker has its own door it's compliant. I've honestly never thought about the six throws in a single panel before now since I've never done it, but now I probably never will.

 

[mike93lx]

It's one of the most brilliant things the CMP has come up with. Each disconnect needs to have separate access. The best example is a 400 amp meter main with two 200 amp breakers. If one door opens up to access both breakers, that's a no no. But if each breaker has its own door it's compliant. I've honestly never thought about the six throws in a single panel before now since I've never done it, but now I probably never will.

Interesting.

The only panel I have that doesn't have a main is my pool equipment and it was just installed. I think VA is 2017. 5 throws to shut it all off and the panel is full. I was a little surprised they didn't use a main breaker panel, but I wasn't going to push back on it since it passed inspection and the breaker feeding it is about 15 feet away.