100a service

[Harley1209]

Hey guys! I'm new to this site but the threads I've been reading are extremely helpful. My question is about a 100a service from my house to a detached garage I'm building. I'm running 2-2-2-4 from my house through 2" conduit to a sub panel in the garage. The total length of the service wire is about 75'. 40' is underground in conduit. Do I need an additional ground rod out at the garage for the sub panel?

 

[Zeke]

Yes.

 

[Aceman]

If you're building a garage you should be using a ufer ground, it's required on new buildings. Verify with your inspector to be sure of local requirements.

 

[CNGsaves]

No, you don't need A ground rod . . . . . you need 2 ground rods or ufer ground in the concrete !!!

A detached building needs 2 ground rods connected with continuous copper wire at least 6 gauge to the subpanel. Also, detached building must be 4 wires from the main panel.

Inside the detached garage subpanel, Neutral and ground cannot be bonded (thus a separate ground bar).

You'll also see by reading prior threads below that you'll be limited to 90A in subpanel in the detached garage (ie wire limit of the Al 2-2-2-4 MHF).

Read previous threads in GJ on this same subject by using Google . . . .
. . . . ground rods detached site:garagejournal.com

 

[Charles (in GA)]

Note that the ufer ground system is only allowed by the code if the slab is in direct contact with the earth. If you put down plastic, insulation, etc, you will still need rods.

Charles

 

[wyliesdiesels]

No, you don't need A ground rod . . . . . you need 2 ground rods or ufer ground in the concrete !!!

A detached building needs 2 ground rods connected with continuous copper wire at least 6 gauge to the subpanel. Also, detached building must be 4 wires from the main panel.

Inside the detached garage subpanel, Neutral and ground cannot be bonded (thus a separate ground bar).

You'll also see by reading prior threads below that you'll be limited to 90A in subpanel in the detached garage (ie wire limit of the Al 2-2-2-4 MHF).

Read previous threads in GJ on this same subject by using Google . . . .
. . . . ground rods detached site:garagejournal.com

Not exactly. 2 rods is only required if u cant show that u have 25ohms or less of resistance to earth. The equipment to do so is expensive so most just put in 2 rods....

 

[CNGsaves]

^^ Thanks Wylie for correcting with specifics for sparky code !! Just was giving OP basics that A single ground was not going to cut it.

OP lots of great electrical advice in those prior threads and sure that Wylie and others will answer any other open questions you might have. Good luck.

 

[Harley1209]

Thanks for all the replies! Although, I'm confused about the amp rating on the 2-2-2-4 wire. I have the same wire running a 100a sub from the main panel inside the house and it was approved.

 

[Harley1209]

Thanks for all the replies! Although, I'm confused about the amp rating on the 2-2-2-4 wire. I have the same wire running a 100a sub from the main panel inside the house and it was approved.

 

[Harley1209]

Thanks for all the replies! Although, I'm confused about the amp rating on the 2-2-2-4 wire. I have the same wire running a 100a sub from the main panel inside the house and it was approved.

 

[pattenp]

Thanks for all the replies! Although, I'm confused about the amp rating on the 2-2-2-4 wire. I have the same wire running a 100a sub from the main panel inside the house and it was approved.

Technically #2 aluminum can be used to supply 100A when it's a service and is supplying the total power to the house. But as a branch feeder supplying power from the main service panel #2 Al is to be overcurrent protected to no more than 90A. Sometimes inspectors don't enforce it right to the letter of the NEC.

Edit: What is the type of 2-2-2-4 that you are going to use? Is it MHF, URD, etc.?

 

[Shadowdog500]

Hey guys! I'm new to this site but the threads I've been reading are extremely helpful. My question is about a 100a service from my house to a detached garage I'm building. I'm running 2-2-2-4 from my house through 2" conduit to a sub panel in the garage. The total length of the service wire is about 75'. 40' is underground in conduit. Do I need an additional ground rod out at the garage for the sub panel?

No, you don't need A ground rod . . . . . you need 2 ground rods or ufer ground in the concrete !!!

A detached building needs 2 ground rods connected with continuous copper wire at least 6 gauge to the subpanel. Also, detached building must be 4 wires from the main panel.

Inside the detached garage subpanel, Neutral and ground cannot be bonded (thus a separate ground bar).

You'll also see by reading prior threads below that you'll be limited to 90A in subpanel in the detached garage (ie wire limit of the Al 2-2-2-4 MHF).

Read previous threads in GJ on this same subject by using Google . . . .
. . . . ground rods detached site:garagejournal.com

I did the same thing when I built my shop and the pro that did my electric ran multiple ground rods, at least two, maybe three.

Chris

 

[Harley1209]

I'm using 2-2-2-4 mhf