New garage and sub-panel requirements.

[chrisb]

Is it a requirement that a sub-panel located in a detached garage have a main circuit breaker, or does a 50 amp branch circuit breaker in the house pass as a disconnect means? (It's 80 feet away) The sub-panel in question has 4 circuit breakers installed but space for 12 1" wide circuit breakers.

Also, is it permissible to use #6 wire with a 50 amp circuit breaker for a sub-panel rated for 100 amps?

I have an existing 1" conduit under a large driveway that we're trying to utilize for this sub-panel and it's size is limiting the selection of wire gauge.

 

[iwire]

Chris you need to go to 225.30 through 225.40 and read them all along with 250.32.

Is it a requirement that a sub-panel located in a detached garage have a main circuit breaker,

No, not exactly but there must be a disconnecting means at the separate building.

or does a 50 amp branch circuit breaker in the house pass as a disconnect means? (It's 80 feet away)

No

Also, is it permissible to use #6 wire with a 50 amp circuit breaker

Yes, but I would use a 60.

for a sub-panel rated for 100 amps?

Yes.

 

[jwelectric]

Also, is it permissible to use #6 wire with a 50 amp circuit breaker for a sub-panel rated for 100 amps?

I disagree with Bob here because

225.39
(A) One-Circuit Installation. For installations to supply only limited loads of a single branch circuit, the branch circuit disconnecting means shall have a rating of not less than 15 amperes.
(B) Two-Circuit Installations. For installations consisting of not more than two 2-wire branch circuits, the feeder or branch-circuit disconnecting means shall have a rating of not less than 30 amperes.
(C) One-Family Dwelling. For a one-family dwelling, the feeder disconnecting means shall have a rating of not less than 100 amperes, 3-wire.
(D) All Others. For all other installations, the feeder or branch-circuit disconnecting means shall have a rating of not less than 60 amperes.

 

[iwire]

I disagree with Bob here because.....

(D) All Others. For all other installations, the feeder or branch-circuit disconnecting means shall have a rating of not less than 60 amperes.

Cool.....I have some time to fill this morning.

The '50' in question here is at the house and IMO is not the disconnecting means referenced in Part II of 225.

IMO the overcurrent protection at the house could be 15 amps, the conductors 14 AWG and the disconnecting means at the garage rated 60 amps.

 

[chrisb]

Finished reading section 225. Changes to be made:

1. Install 60 amp Circuit breaker as main disconnect in sub-panel.
2. Remove 50 amp circuit breaker in home and install 60 amp c/b.

Did I forget anything else?

 

[M. D.]

Finished reading section 225. Changes to be made:

1. Install 60 amp Circuit breaker as main disconnect in sub-panel.
2. Remove 50 amp circuit breaker in home and install 60 amp c/b.

Did I forget anything else?

You don't have to replace the 50 amp at the house.

 

[iwire]

I am guessing you plan on pulling three 6 AWG and a 10 AWG?

Have you looked at 250.32?

You need grounding electrodes out at the garage.

 

[iwire]

You don't have to replace the 50 amp at the house.

I agree.

The only reason I said I would use a 60 is that the wire size allows the use of a 60.

I also will point out that you could max this 1" PVC out with Two 3 AWG CU THWN 'hots' and one 6 AWG CU THWN neutral and provide a true 100 amps of capacity at the garage utilizing the 1" PVC. (Actually three 3 AWGs will fit but the neutral does not have to be full size.)

If you do the above there is no room for an EGC but that is currently allowed by 250.32(B)(2) as you would use the 6 AWG neutral as the grounding means.

 

[Energize]

I am guessing you plan on pulling three 6 AWG and a 10 AWG?

Have you looked at 250.32?

You need grounding electrodes out at the garage.

(Just woke up and trying to get my brain going)
Edit Note: Got my brain engaged and and realized what a ignorant post I had just created so I deleted it.

 

[chrisb]

I am guessing you plan on pulling three 6 AWG and a 10 AWG?

Yes

Have you looked at 250.32?

Yes

You need grounding electrodes out at the garage.

Yes - the GC left us exposed, concrete encased rebar.

 

[Dennis Alwon]

(Just woke up and trying to get my brain going)
Edit Note: Got my brain engaged and and realized what a ignorant post I had just created so I deleted it.

Wow. I just hit reply to your so called "Ignorant post" to respond to it and your changed statement above showed up.

 

[Energize]

Wow. I just hit reply to your so called "Ignorant post" to respond to it and your changed statement above showed up.

Sorry about that. We took a vote, and 3 out of the 5 voices in my head said to trash it, so we did!

 

[Dennis Alwon]

225.39
(A) One-Circuit Installation. For installations to supply only limited loads of a single branch circuit, the branch circuit disconnecting means shall have a rating of not less than 15 amperes.
(B) Two-Circuit Installations. For installations consisting of not more than two 2-wire branch circuits, the feeder or branch-circuit disconnecting means shall have a rating of not less than 30 amperes.
(C) One-Family Dwelling. For a one-family dwelling, the feeder disconnecting means shall have a rating of not less than 100 amperes, 3-wire.
(D) All Others. For all other installations, the feeder or branch-circuit disconnecting means shall have a rating of not less than 60 amperes.

I am curious why part (B) would not be applicable. It states feeders or branch circuits not less than 30 amps if there are 2 or more branch circuits. Could that not mean that there is one feeder to a panel with more than 2 branch circuits? I have always interpreted it that way. Am I wrong?

 

[M. D.]

Good question Dennis I agree .The inspector will want to see a two circuit only can though

Dennis it says not more than 2 - 2 wire circuits

 

[iwire]

Dennis it says not more than 2 - 2 wire circuits

Yes and the OP mentioned four breakers at the garage.

 

[Dennis Alwon]

Good question Dennis I agree .The inspector will want to see a two circuit only can though

Dennis it says not more than 2 - 2 wire circuits

I misread it-- I read more than 2- 2 wire circuits. Thanks

 

[M. D.]

AAAHHH , "the old read the post stupid" response . 60 it is

 

[romeo]

New garage and sub-panel requirements.

I am guessing you plan on pulling three 6 AWG and a 10 AWG?

Have you looked at 250.32?

You need grounding electrodes out at the garage.

Bob if ground rods are used for the grounding electrodes, does 250.56 apply or is 1 rod OK? I am told that 1 rod is OK but don't understand why.

romeo

 

[M. D.]

Bob if ground rods are used for the grounding electrodes, does 250.56 apply or is 1 rod OK? I am told that 1 rod is OK but don't understand why.

romeo

I'm not Bob ,but I would say 250.32 sends us directly to 250.50 ,if there are no electrodes present then we in stall one or more from the list in 250.52 starting at (A)4 up to (A)7 it does not send us to 250.56. so why would I go there ?? Habit I guess, I always install 2

 

[George Stolz]

All electrodes present at the structure must be used (250.50). So we can't ignore electrodes and just install a rod or two and walk away.

Mike Whitt submitted a proposal and had it accepted for the 2008, that 250.32(A) send you to "Part III of Article 250" instead of prior codes that have you assume that all of Part III applied. Their intent was for the grounding electrode system of a detached structure be to the same standard as the originating structure's system.