# Ocp



## ceb58 (Feb 14, 2009)

Senerino: You have a regular 200amp back to back service. Now you want to install a service rated non fusible, R3 DT switch for a generator. You come out of the meter base with the conductors and land them on the top utility lugs. You bring the gen feeders to the bottom lugs. And you remove the conductors from the meter base to the panel and reroute them to the center lugs. All sounds simple. Even though the meter base and DT switch are outside the building something is telling me there should be an over-current devise installed between the meter and the switch for the utility service conductors. I am not concerned with any thing the gen. may or may not need just the utility conductors and any code reference as to it.
Thanks


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## manchestersparky (Mar 25, 2007)

Read 230.82 , 230.90 and 230.91

230.82 tells us what is allowed on the supply side of the service disconnecting means

230.90 tells us that we need overcurrent protection on the ungrounded service conductors

230.91 tells us that the service overcurrent device shall be an integral part of the service disconnect OR SHALL be located immediately adjacent to it.

So if you are installing a service rated DT disconnect between the meter and the main breaker you must either use a fused DT switch or set another service rated fusible switch or service rated enclosed breaker next to the DT switch to comply with 230.91.
This in turn would become the service and all the grounding electrode conductors would need to be extended to this point.( using irreversible connections of course) Then you will need to isolate all the grounded conductors from the grounding conductors in the panel as it became a sub-panel.


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## ceb58 (Feb 14, 2009)

manchestersparky said:


> Read 230.82 , 230.90 and 230.91


 
230.91 is what is throwing me. "immediately adjacent thereto"
We are allowed to do a back to back install using "the closest point of entry" with out OCP/disconnecting means between the meter and MDP. If you were to come directly out of the DT switch back to back with the MDP wouldn't it be the same?


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## manchestersparky (Mar 25, 2007)

immediately adjacent to equals NEXT to


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## jwjrw (Jan 14, 2010)

ceb58 said:


> 230.91 is what is throwing me. "immediately adjacent thereto"
> We are allowed to do a back to back install using "the closest point of entry" with out OCP/disconnecting means between the meter and MDP. If you were to come directly out of the DT switch back to back with the MDP wouldn't it be the same?



You should be fine coming out of the transfer switch back to back to your panel. Your AHJ sets the limit on how far your SEC can run unfused. Here we can get up to 10 ft in some instances.


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## ceb58 (Feb 14, 2009)

jwjrw said:


> You should be fine coming out of the transfer switch back to back to your panel. Your AHJ sets the limit on how far your SEC can run unfused. Here we can get up to 10 ft in some instances.


That's what I am thinking. 
I am from the same here as you are. Not county but state. Never had an inspector let me get 10'.
I had an informed inspector say the ruling from DOI was they would allow the length of the service conductors be twice the length of the panel. This allows you on a 400amp service to come into 1 panel back to back and set the 2nd panel in the next stud cavity and come in the bottom.


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## jwjrw (Jan 14, 2010)

ceb58 said:


> That's what I am thinking.
> I am from the same here as you are. Not county but state. Never had an inspector let me get 10'.
> I had an informed inspector say the ruling from DOI was they would allow the length of the service conductors be twice the length of the panel. This allows you on a 400amp service to come into 1 panel back to back and set the 2nd panel in the next stud cavity and come in the bottom.


That is what the state says. We used to have an exception for commercial buildings allowing 10ft but I can't find it now. It may have changed.
This is a link from my home county from the DOI.

http://charmeck.org/mecklenburg/county/CodeEnforcement/Electrical/Documents/SERVLENG.pdf


Found it. You can go up to 16ft in some cases.

http://charmeck.org/mecklenburg/county/CodeEnforcement/Electrical/Documents/UNFUSEDCONDUCTORS.pdf


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## manchestersparky (Mar 25, 2007)

ceb58 said:


> 230.91 is what is throwing me. "immediately adjacent thereto"
> We are allowed to do a back to back install using "the closest point of entry" with out OCP/disconnecting means between the meter and MDP. If you were to come directly out of the DT switch back to back with the MDP wouldn't it be the same?


No it is not the same.
230.91 tells us that the service over current device ( fuses or circuit breaker) *SHALL* be part of the service disconnecting means OR *SHALL* be located *IMMEDIATELY ADJACENT* hereto.
The use of the word SHALL tells us it must be. Article 230.91 does not tell us to locate the service overcurrent device in the service disconnecting means or nearest point of entrance of the service conductors.

Look up the definition of adjacent in the dictionary. The definition is :"Next to"
So to meet the code if you mount that DT switch outside then you will need to also install overcurrent device next to it.

You are talking about 2 different items in your posts.
The first item is the location of a DT switch and the need for overcurrent protection. 
The second item you started talking about is the length of unfused service entrance conductors allowed in a structure. 
Yes they are directly related but different items at the same time


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## ceb58 (Feb 14, 2009)

manchestersparky said:


> No it is not the same.
> 230.91 tells us that the service over current device ( fuses or circuit breaker) *SHALL* be part of the service disconnecting means OR *SHALL* be located *IMMEDIATELY ADJACENT* hereto.
> The use of the word SHALL tells us it must be. Article 230.91 does not tell us to locate the service overcurrent device in the service disconnecting means or nearest point of entrance of the service conductors.
> 
> ...


Manchester, I completely understand what you are saying and I am thankful for the input. But as always it boils down to what the inspector says and will allow. And that is the fun/headache of the code book.


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## NormW64 (Jan 19, 2011)

Just playing Devil's Advocate - but adjacent to doesn't mean there can't be a barrier between the two. If the exterior surface was a honeycomb pattern, each piece of service equipment would be permitted in it's own cell, as long as each cell were side-by-side or top-bottom. Why would back-to-back not be the same ruling?


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## manchestersparky (Mar 25, 2007)

I will say that in my opinion the reason for the immediately adjacent hereto is so the service disconnect means without overcurrent protection is next to and in sight of the overcurrent protection.


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## Shockdoc (Mar 4, 2010)

OCD about OCP


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