Minimum AWG wire that can feed a sub panel

[david]

I am saying that you calculate the min load to the garage

Than decide if you want one branch circuit. (Min of 15 amp 14 awg, not 16 or 18 gage

Two branch circuits (min of 30 amp min of 10awg)

More than two branch circuits( 60 amp a min of 6 awg)

It's the min of the calculated load and the min of a 15, 30 or 60 amp supply conductor

The scope of article 225 is the supply conductors and the electrical equipment associated with protecting the supply conductors.

 

[don_resqcapt19]

I am saying that you calculate the min load to the garage

Than decide if you want one branch circuit. (Min of 15 amp 14 awg, not 16 or 18 gage

Two branch circuits (min of 30 amp min of 10awg)

More than two branch circuits( 60 amp a min of 6 awg)

It's the min of the calculated load and the min of a 15, 30 or 60 amp supply conductor

The scope of article 225 is the supply conductors and the electrical equipment associated with protecting the supply conductors.

The rules in 225.39 only specify the minimum size of the building disconnect and do not specify the minimum size of the feeder circuit that supplies the disconnect. The feeder circuit is sized by the load.

 

[LarryFine]

Than decide if you want one branch circuit. (Min of 15 amp 14 awg, not 16 or 18 gage

Two branch circuits (min of 30 amp min of 10awg)

More than two branch circuits( 60 amp a min of 6 awg)

I don't see those amperage minimums, unless they're just your preferences.

 

[suemarkp]

Two branch circuits (min of 30 amp min of 10awg).

Two branch circuits could be a multiwire branch circuit, so a 2 pole 15A could provide that.

 

[david]

The rules in 225.39 only specify the minimum size of the building disconnect and do not specify the minimum size of the feeder circuit that supplies the disconnect. The feeder circuit is sized by the load.

It dosnt only do that, it addresses also min requirements of supply conductors associated with those disconnect ratings.
225.39(C) 3-wire is addressing the supply conductors not the rating of the disconnect.
225.39 (C) inadvertently is also telling us that other than (C) can have a min of 2- wire supply conductors

The calculated load is modified in this section by how the load is distributed.
One branch circuit, two branch circuits. more than two branch circuits, what other section in the code does that.
It's being said that modifying the calculated load by the way its being distributed only address the disconnect rating while the whole article is about outside supply conductors and protecting them dosnt make any sense

 

[david]

I know what the concensus here is in regards to the rating of the disconnects

30 amp single pole breaker supplies my shed with my electric fence, a few lights, and a rec I chose to distribute that load with three breakers I have to modify my rating to a min of 60 amps that my diatrubution is not capable of exceeding 30 amps again makes no sense

This has been discussed here before so I'll leave it at that

 

[infinity]

I am saying that you calculate the min load to the garage

Than decide if you want one branch circuit. (Min of 15 amp 14 awg, not 16 or 18 gage

I don't see how you can have a 15 amp branch circuit for a garage. You would need at least one 20 amp circuit.

 

[ramsy]

I am saying that you calculate the min load to the garage

Are you making the point that an Art. 220 load calc may exceed branch circuit minimums in 210.11(C)(4), also requiring a feeder?

If you're asking other questions, you should start a new thread, so people can follow the new topic.

If you avoid clicking the reply feature, people who rely on forum notification may not get your request.

Also, if you persist in leaving your occupation a mystery in your forum profile, people may ignore you.

 

[david]

I don't see how you can have a 15 amp branch circuit for a garage. You would need at least one 20 amp circuit.

You of course are right.

Disconnect Rating
15 amp min rating for a branch circuit

the calculated load of a single branch circuit supplying a rec in a detached garage.
I80 volt amps
load at the outlet for a duplex 15 amp rec up to 30 amps limited by a 20 amp overcurrent devicen8
Load at the outlet for a duplex 20 amp rec up to 40 amps limited by a 20 amp overcurrent device

This all becomes a rabbit trail away from what the op presented. I know what the general consensus is on this.
And again you are correct that a garage would have to have a 20 amp branch circuit

 

[david]

Are you making the point that an Art. 220 load calc may exceed branch circuit minimums in 210.11(C)(4), also requiring a feeder?

If you're asking other questions, you should start a new thread, so people can follow the new topic.

If you avoid clicking the reply feature, people who rely on forum notification may not get your request.

Also, if you persist in leaving your occupation a mystery in your forum profile, people may ignore you.

It was

Is there a NEC requirement for what size wiring has to be ran to a sub panel? If the homeowner wants to run power to a detached garage and only really wants a small sub panel with with a few breakers for lights and outlets, does it have to have a minimum AWG wire feeding a sub panel? Does it have to have both red and black hots if he doesn’t want/need 208/240 for anything in the garage? I was told by an electrician that a minimum 4AWG needed to be ran to the sub panel and that a black and red had to be ran. The homeowner had already ran a 10/2 Romex through underground conduit from his main to the sub panel and now had asked me whether he has done it to code. Also, I have informed him about the grounding for the sub panel but was unclear about if there is a NEC code about how far the grounding electrode can be from the sub panel. Is only one grounding electrode needing to connect to the sub panel because I was told I needed 2 spaced 8 feet apart. To avoid cutting/drilling into his concrete slab, can the electrode be driven in outside the building and then ran through the side into the sub panel? The ground wire from the electrode would be about a 15 feet run.

Is there a NEC requirement for what size wiring has to be ran to a sub panel?

Requirement would be based on a load calculation

If the homeowner wants to run power to a detached garage and only really wants a small sub panel with with a few breakers for lights and outlets, does it have to have a minimum AWG wire feeding a sub panel?

Does it have to have both red and black hots if he doesn’t want/need 208/240 for
anything in the garage

225.39 (C) only Requires a 3-wire supply ( two ungrounded conductors and one grounded conductor) (the equipment grounding is addressed in artle 250) for a one family dwelling. (For a one family dwelling that term does not include individual units of multi family dwellings)
In 225.39 a three wire supply is not required for (A,B and D)
So yes you could supply a garage panel with a 120 volt supply

 

[david]

I was told by an electrician that a minimum 4AWG needed to be ran to the sub panel and that a black and red had to be ran.

225.39 rating of disconnects tells you the min disconnect rating is first based on the calculated load. Than the min disconnect rating is further modified by how the load is distributed in (A,B,C and D)
Under (D) if you have three or more branch circuits you're min rating for the disconnect would have to be 60 amps.

I am unsure of the reason you would care how the load is distributed when the foundational principal is always based on the calculated load.

The general concensus here is no requiring a min of a 60 amp rated disconnect does not require a supply conductor that meets or exceeds that rating

 

[don_resqcapt19]

It dosnt only do that, it addresses also min requirements of supply conductors associated with those disconnect ratings.
225.39(C) 3-wire is addressing the supply conductors not the rating of the disconnect.
225.39 (C) inadvertently is also telling us that other than (C) can have a min of 2- wire supply conductors

The calculated load is modified in this section by how the load is distributed.
One branch circuit, two branch circuits. more than two branch circuits, what other section in the code does that.
It's being said that modifying the calculated load by the way its being distributed only address the disconnect rating while the whole article is about outside supply conductors and protecting them dosnt make any sense

Once again we are not going to agree. The rules in 225.39 and 230.79 have nothing to do with conductor size.
From the panel statement in rejecting Public Input 1809 for the 2020 code.

Section 225.39 only applies to the rating of the required disconnect. The proposed revisions do not add clarity.

For the 2023 code, there was a proposal, 1846, that would have changed the title of section 225.29 to

225.39 Rating of Conductors and Disconnecting Means.

That was rejected by Code Making Panel with the following statement:

The requirement for conductors to be sized per the calculated load is already referenced in Articles 210, and 215. There's no need to add the proposed language to 225.39.

 

[david]

Also, if you persist in leaving your occupation a mystery in your forum profile, people may ignore you.

I submitted all that information years ago resubmitted it not that long ago.
From astudent of the NEC starting back in 1978. Accociate degree in electrical technology, master electrician ( ohio Virginia, north Carolina and Kentucky to building official

Currently semi retired electrical inspector being ask to come out of retirement to do the electrical inspections on a large industrial site estimated to take two years

I can try again updating my profile

 

[david]

Once again we are not going to agree. The rules in 225.39 and 230.79 have nothing to do with conductor size.
From the panel statement in rejecting Public Input 1809 for the 2020 code.

Section 225.39 only applies to the rating of the required disconnect. The proposed revisions do not add clarity.

For the 2023 code, there was a proposal, 1846, that would have changed the title of section 225.29 to

That was rejected by Code Making Panel with the following statement:

Yes if I was to inspect what was ask by the OP it would be in accordance with post #51

 

[don_resqcapt19]

Yes if I was to inspect what was ask by the OP it would be in accordance with post #51

I was addressing your comment in post 45.

It dosnt only do that, it addresses also min requirements of supply conductors associated with those disconnect ratings.

I am reading that as you are saying a 60 amp disconnect requires feeder conductors rated at least 60 amps.

 

[david]

I was addressing your comment in post 45.

I am reading that as you are saying a 60 amp disconnect requires feeder conductors rated at least 60 amps.

I'm saying that taking a strick view point that the only subject matter addressed in 225.39 is the rating of the disconnects does not address the OP concerns about the supply conductors having to include both line one and line two supply to the garage. I'm saying those concerns about the supply conductors were also addressed in 225.39

I also believe the NEC has a purpose when it makes requiremenst as found in (A-D)

The min disconnect rating is already addressed by ensuring it has a rating that meets or exceeds the calculated load

So what is the reason to modify that rating by the way the calculated load is distributed?
It nit just to make you install disconnect with a larger rating than calculated

When you walk into a building and it has a 60 amp disconnect (single disconnect) your being led to believe the supply can Handel a 60 amp supply

The same way as when a three prong receptacle replaces a two prong rec. Your being led to believe an equipment grounding requirement has been met

So what is the reason for modifying the rating based on the distrubution?

 

[infinity]

When you walk into a building and it has a 60 amp disconnect your being led to believe the supply can Handel a 60 amp supply

Why would someone assume that? I've seen several garage/shed panels with 100 amp main breakers and 60 amp or smaller feeders.

 

[david]

Why would someone assume that? I've seen several garage/shed panels with 100 amp main breakers and 60 amp or smaller feeders.

Yes that would be by a choice but I'm talking about when it is a NEC requirement

 

[david]

Why would someone assume that? I've seen several garage/shed panels with 100 amp main breakers and 60 amp or smaller feeders.

When the NEC makes a requirement there is usually a reason it makes sence

 

[augie47]

Although rarely enforced here, I am of the opinion the 210.119C)(4) along with 210.70(A)(2)(2) requires a minimum of a MWBC.