Article 225.39

[Dennis Alwon]

I have a learning disability and English is my first language. What more can I say. I read it as Colorado enforced it as not needing the feeder conductor to be increased but he got flagged on it. Sorry-- chemo brain-- I like to blame it on that anyway

 

[gaelectric]

Yes. My forum quoting skills are not top notch. But that was a quote from the OP

The inspector did require that the OCPD at the dwelling be 60 amps and that the conductor to the garage be of matching amperage.

 

[don_resqcapt19]

(2008 ROP) 4-26 Log #2194 NEC-P04 Final Action: Reject
(225.39, FPN )
______________________________________________________________
Submitter: David Williams, Lansing, MI
Recommendation: Revise as follows:
The rating feeder or branch-circuit disconnecting means shall have a rating of not less than the load to be supplied, determined in accordance with Parts I and II of Article 220 for branch circuits. Parts III or IV of Article 220 for feeders, or Part V of Article 220 for farm loads. In no case shall the rating be lower than specified in 225.39(A), (B), (C), or (D). FPN: The rating of the overcurrent device protecting the feeder does not need to be rated to the minimum rating in this section.

Substantiation: The code section specifies the minimum rating of the disconnect and is not clear that the feeder or branch circuit needs to be rated for this minimum rating. As an inspector, I am not positive if this section only applies to the rating of the disconnect or does this mean that the minimum size of a feeder to a building should be 60 amperes. Just trying to clear up a concern.

Panel Meeting Action: Reject
Panel Statement: An additional FPN is not necessary. The title of 225.39 defines the requirement as solely being the rating of the disconnect.
Number Eligible to Vote: 10
Ballot Results: Affirmative: 10

 

[Smart $]

(2008 ROP) 4-26 Log #2194 NEC-P04 Final Action: Reject
(225.39, FPN )
...

Along with this one, I have seen many good proposals rejected IMO because they are poorly written, lacking a concise description of the problem and remedy. It seems the CMP's do not waste any of their precious time trying to interpret the submitter's intent.

 

[Dennis Alwon]

Panel Meeting Action: Reject
Panel Statement: An additional FPN is not necessary. The title of 225.39 defines the requirement as solely being the rating of the disconnect.
Number Eligible to Vote: 10
Ballot Results: Affirmative: 10

I wish they would explain that thinking

 

[don_resqcapt19]

I wish they would explain that thinking

It seems clear to me that their thinking is the same as mine...the rule in 225.39 applies to the rating of the building disconnect, and not to the rating of the circuit or OCPD that supplies the building disconnect.
The proposal was to add a fine print note to make it clear that the rule in 225.39 has nothing to do with the rating or OCPD of the circuit that supplies second building. The proposal was rejected with the panel saying that is already clear in the existing code wording and there was no need for the FPN.

 

[Dennis Alwon]

It seems clear to me that their thinking is the same as mine...the rule in 225.39 applies to the rating of the building disconnect, and not to the rating of the circuit or OCPD that supplies the building disconnect.
The proposal was to add a fine print note to make it clear that the rule in 225.39 has nothing to do with the rating or OCPD of the circuit that supplies second building. The proposal was rejected with the panel saying that is already clear in the existing code wording and there was no need for the FPN.

My point is why would they require a 60 amp disconnect if I can run a 30 amp wire with 30 amp overcurrent protective device as the feeder. Why enforce the disconnect to a higher rating.

 

[trojans4]

Even if the article meant that you need 60A circuit conductors and 60A OCP that would be ridiculous for the situation where I have an unattached one car garage or small shed and just want to put in some lights and one receptacle. I would need to run #6 AWG conductors for what could have been a 15A or 20A circuit? Now, I would have probably run #10 AWG and had a 30A circuit for that example but having a 60A circuit for that small of load seems way out of line.

 

[don_resqcapt19]

My point is why would they require a 60 amp disconnect if I can run a 30 amp wire with 30 amp overcurrent protective device as the feeder. Why enforce the disconnect to a higher rating.

I have no idea why the rule is there. I just don't see the rule in 225.39 having anything to do with the rating of the circuit that feeds the second building.

 

[Dennis Alwon]

Even if the article meant that you need 60A circuit conductors and 60A OCP that would be ridiculous for the situation where I have an unattached one car garage or small shed and just want to put in some lights and one receptacle. I would need to run #6 AWG conductors for what could have been a 15A or 20A circuit? Now, I would have probably run #10 AWG and had a 30A circuit for that example but having a 60A circuit for that small of load seems way out of line.

Agreed, but requiring even the 60 amp disconnect is strange. In most case the disconnect will be 60 amps as there aren't too many 30 amp discos around but the spelling it out as 60 amps for the disconnect only makes no sense.

They did the same for services in 230.79 however with art. 230.41(B) that changes it so the conductors must be rated the same as the req. of 230.79

 

[Smart $]

Even if the article meant that you need 60A circuit conductors and 60A OCP that would be ridiculous for the situation where I have an unattached one car garage or small shed and just want to put in some lights and one receptacle. I would need to run #6 AWG conductors for what could have been a 15A or 20A circuit? Now, I would have probably run #10 AWG and had a 30A circuit for that example but having a 60A circuit for that small of load seems way out of line.

Your forgetting about 225.29(A) and (B), which only require 15A (one circuit) and 30A (two circuit) disconnect ratings respectively. 60A would only be required for three or more circuits, which I believe is a bit overkill in some scenarios where a 30A disconnect for a three-wire supply would suffice for three or more circuits. The biggest problem with this section is it being a word for word copy of 230.79(A) through (D).

 

[don_resqcapt19]

Part B was added to Article 225 for the 99 code based on proposal 4-46 and comment 4-36. The following is from comment 4-36 from the commenter.

225-38. Size and Rating of Supply Conductors and Disconnects.
(a) General. Disconnects for and conductors supplying buildings or structures shall be of sufficient size to carry the loads
as computed in Article 220.
(b) Ungrounded Conductors and Disconnects. The rating for a building or structure disconnecting means, and the ampadty of ungrounded supply conductors shall be not less than:
(1) One-Circuit Installation. For installations to supply only limited loads of a single branch circuit, 15 amperes.
(2) Multiple-Circuit Supply. For installations where the building or structure is supplied by multiple branch circuits or feeders originating ahead of that building or structure, 15 amperes for each provided the combined capacity is not less than as required by this section.
(FPN): An example would be a detached garage fed with two branch circuits.
(3) Two-Circuit Installations. For installations consisting of not more than two 2-wire branch circuits, 60 amperes.
(4) One-Family Dwelling. For a one-family dwelling, 100 amperes, 3-wire.
(5) All Others. For all other installations, 60 amperes.

The following is from the panel action on comment 4-36. The panel action changed the section from 225-38 to 225-39 and took out the reference to the rating of the conductors that was in the original comment. The panel statement gives no guidance as to their reasoning.

225-39. Rating of Disconnect. The feeder or branch circuit disconnecting means shall have a rating not less than the load to be carried, determined in accordance with Article 220. In no case shall the rating be lower than specified in (a), (b), (c), or (d) below.
(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.

 

[Smart $]

Here's what I think it should be or in effect...

225.39 Rating of Disconnect. The feeder or branch-circuit
disconnecting means shall have a rating of not less than the
calculated load to be supplied, determined in accordance
with Parts I and II of Article 220 for branch circuits, Part III
or IV of Article 220 for feeders, or Part V of Article 220 for
farm loads. Where the circuit supplies one or more dwelling
units, the supply circuit and disconnecting means ratings
shall be not less than required for an identical service per
Article 230.