Questions About Power to Garage

[BigBrian]

Good morning all,

I have some questions regarding the wiring for my new (20x20) garage.

I have a 200 amp service to my house. I have a 100 amp breaker feeding a 30x32 garage. I obviously have all the breakers required for a home as well (dryer, range, etc).

I ran 2-2-2-4 to my new 20x20 garage, i'm planning on putting that on a 100 amp breaker as well. The run is roughly 95 feet from the main panel to my 20x20 sub panel. The sub panel in my 30x32 has a disconnect (breaker) on the incoming power, in addition to the breaker on the main panel. My sub panel in my 20x20 does not.

My questions are;

-Am I required to add a knife switch or some other type of disconnect in my 20x20?

-Do I need to add a ground rod even though I am running a ground from the main panel to the garage?

Trying to make sense of all these electrical codes, don't want to cause any issues or dangerous situations.

Thanks!

 

[mike93lx]

90a is the max breaker you can use to feed with a #2 aluminum wire. If that wire is copper, 100a is fine.

Your sub needs to have a main breaker, or some other means of disconnect

Yes, two ground rods. They serve a different purpose than the egc wire. Your other shop needs to have them too.

In the subpanels, you have to make sure your neutral bar is isolated from the ground, and all neutrals must be kept separate from grounds.

There is a great sticky in this electrical subforum that you should read

 

[BigBrian]

90a is the max breaker you can use to feed with a #2 aluminum wire. If that wire is copper, 100a is fine.

Your sub needs to have a main breaker, or some other means of disconnect

Yes, two ground rods. They serve a different purpose than the egc wire. Your other shop needs to have them too.

In the subpanels, you have to make sure your neutral bar is isolated from the ground, and all neutrals must be kept separate from grounds.

There is a great sticky in this electrical subforum that you should read

Thank you! I will swap out the 100a breaker for my 30x32 with a 90a and use a 90a for my 20x20.

Thank you for the info on the grounding rods, I will be sure to put them in for both my garages.

I did know that the neutrals needed to be separate from the grounds, I appreciate the heads up though!

Once I get home, I will read the sticky.

Thank you!

 

[mike93lx]

Thank you! I will swap out the 100a breaker for my 30x32 with a 90a and use a 90a for my 20x20.

Thank you for the info on the grounding rods, I will be sure to put them in for both my garages.

I did know that the neutrals needed to be separate from the grounds, I appreciate the heads up though!

Once I get home, I will read the sticky.

Thank you!

Its the breaker feeding that needs to be 90a. The main in the shops can be any size you want they are are just a disconnect, not protection. I'd be putting in 200a 40 space panels for any new work.

 

[acer66]

I'd be putting in 200a 40 space panels for any new work.

Is that not a bit too small for such a big garage?

 

[PCustoms]

Is that not a bit too small for such a big garage?

Is this sarcasm?

 

[mike93lx]

Is that not a bit too small for such a big garage?

Good point, what was I thinking? Dual 40's with 320a service is the way to go

 

[PCustoms]

Is this sarcasm?

Good point, what was I thinking? Dual 40's with 320a service is the way to go

 

[acer66]

Good point, what was I thinking? Dual 40's with 320a service is the way to go

Now that sounds more like it and with a 3Phase drop we should be good for a minute.

 

[mike93lx]

Now that sounds more like it and with a 3Phase drop we should be good for a minute.

Gotta leave room for just in case. What if it turns into a 20 person repair shop?

 

[BigBrian]

Now that sounds more like it and with a 3Phase drop we should be good for a minute.

Ain't no kill like overkill!

 

[BigBrian]

A little update for you all.

There was an existing run of 4" PVC pipe which fed the power to the old garage. Unfortunately, it only ran to the corner of the concrete so I had to dig a trench to lengthen the PVC pipe that was already there so I could run my 2-2-2-4 to the garage.

I drove the grounding rods in, what a PITA!! I ended up having to use my air hammer to get them all the way in.

I have 6AWG bare copper wire to connect my grounding rods to each other and to the panel. My question is this, can I drill a small hole in my PVC run to feed the wire up to the panel? Everything I read says it is fine to run that in the same pathway as the main power.

As for the panel, i'm going with a 100A Square D main panel. That will satisfy the need for a disconnect and give me 20 spaces for any circuits I want to run.

Thanks!

 

[PCustoms]

A little update for you all.

There was an existing run of 4" PVC pipe which fed the power to the old garage.

What color is the PVC?

 

[BigBrian]

What color is the PVC?

It's the grey schedule 80 stuff.

 

[mike93lx]

It's the grey schedule 80 stuff.

Wow 4"? That's a special level of overkill

I would not drill a hole in it for ground. Run a separate small one

 

[PCustoms]

It's the grey schedule 80 stuff.

I was not expecting that.

Someone spent a lot of money putting that in.

Picture? I wouldn't drill for the ground either

 

[BigBrian]

Thanks guys! I'll add a length of small conduit just for the ground wire.

Yeah i'm not sure why they used 4" grey sch80 PVC either.

I'll snag a pic once I get home.

 

[mike93lx]

I didn't see it asked earlier... What kind of wire did you use for the 2-2-2-4?

 

[BigBrian]

I didn't see it asked earlier... What kind of wire did you use for the 2-2-2-4?

I believe it was list as "mobile home feeder cable" I was told it was safe to use underground. It is aluminum. Same stuff I ran to my 30x32

 

[mike93lx]

I believe it was list as "mobile home feeder cable" I was told it was safe to use underground. It is aluminum. Same stuff I ran to my 30x32

Mint. I was worried it was SER

MHF is perfect for this

 

[BigBrian]

Mint. I was worried it was SER

MHF is perfect for this

Out of curiosity, what's wrong with using SER?

 

[mike93lx]

Out of curiosity, what's wrong with using SER?

It can't go underground

 

[BigBrian]

It can't go underground

Fair enough

 

[Norcal]

Out of curiosity, what's wrong with using SER?

It has a bare aluminum grounding conductor that will degrade to a toothpaste like substance if used underground.

 

[BigBrian]

It has a bare aluminum grounding conductor that will degrade to a toothpaste like substance if used underground.

Appreciate the explanation

 

[Bert_]

What color is the PVC?

His wire is rated for direct bury. If you want to protect the underground portion of the wire, you do not need to use electrical conduit.

 

[PCustoms]

His wire is rated for direct bury. If you want to protect the underground portion of the wire, you do not need to use electrical conduit.

Direct bury must be in conduit above ground, right?

So white PVC end to end is OK?

 

[mike93lx]

Direct bury must be in conduit above ground, right?

So white PVC end to end is OK?

It'll function the same. I'm pretty sure electrical conduit just has uv stabilizers and no pressure rating

 

[Bert_]

Direct bury must be in conduit above ground, right?

So white PVC end to end is OK?

Yes

Anywhere conduit is required, it would need to be grey electrical PVC or some other form of conduit that meets the requirements.

I actually take advantage of this quite a bit. 2" foam core pvc drain pipe is about 70 cents a foot and works great for 4/0 urd if you need additional protection. I sleeve a lot more underground wire than I ever used to because it's so cheap