Code officials

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nizak

Senior Member
Had a final inspection completed today on a new residence.
I placed a sub panel at the opposite end of the house and fed it with #1 Al SER cable protected by a 100A breaker.

Inspector questioned the use of #1 cable and asked why #2 was not used.
I explained that the #2 was not rated for 100 amp in this
application.
He went on to say that he has always approved the use of #2 for sub feeds because the code allows it in residential applications.

He went on to tell me that there is no reason to use a more expensive cable if it's not required.

Am I missing something here?
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
No you are not missing anything.
That inspector is a idiot and even an aXX IMO.
#2 can only be used if it carries the entire load of a dwelling. Code changed several years ago. I think it was the 2008 NEC
 

tkb

Senior Member
Location
MA
310.15(B)(7) allows the feeder in a dwelling unit that has the total load to be derated to 83% of the circuit ampacity.
#2 AL @75°c is rated at 90amps which is more than 83% so it can be used on a 100amp breaker.

The SER cable would have to be rated at 60°c if it is run through insulation then #1 is the correct size based on its 85 amp rating @60°c per 338.10(B)(4).
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Either my brain has not awakened yet or I see a bunch of incorrect info.
IMO, first off, throw out the 83% rule (OR 310.15(B)(*) in earlier Codes).
This cable does not feed the entire load associated with the dwelling so you are back to 310l.15(B)(16) "standard" ratings.
Next you have to take into account your 338.10 rules which will vary depending on the Code cycle and the type install (in insulation, etc).
In the best case scenario #2 AL SE would have a rating of 90 amps which is a standard breaker size so the inspector is certainly incorrect.
Based on the Code cycle and details of your install, assuming 338.10 is being enforced, your #1 AL SE might have a rating of only 85 amps which would limit the OCP to 90 amps also.
If the install is such that the 75 degree rating is allowed you are fine with your 100 amp and your #1. In no situation would the #2 for a sub panel be compliant on the 100 amp breaker.
 

tkb

Senior Member
Location
MA
Either my brain has not awakened yet or I see a bunch of incorrect info.
IMO, first off, throw out the 83% rule (OR 310.15(B)(*) in earlier Codes).
This cable does not feed the entire load associated with the dwelling so you are back to 310l.15(B)(16) "standard" ratings.
Next you have to take into account your 338.10 rules which will vary depending on the Code cycle and the type install (in insulation, etc).
In the best case scenario #2 AL SE would have a rating of 90 amps which is a standard breaker size so the inspector is certainly incorrect.
Based on the Code cycle and details of your install, assuming 338.10 is being enforced, your #1 AL SE might have a rating of only 85 amps which would limit the OCP to 90 amps also.
If the install is such that the 75 degree rating is allowed you are fine with your 100 amp and your #1. In no situation would the #2 for a sub panel be compliant on the 100 amp breaker.

I assumed the total load of the dwelling was on this feeder. I see now that this is a sub panel so standard ratings apply and #1 in insulation can only be on a 90 amp breaker.

If the total load of the dwelling in on a panel, I stand by my my post.
 

growler

Senior Member
Location
Atlanta,GA
Inspector questioned the use of #1 cable and asked why #2 was not used.
He went on to tell me that there is no reason to use a more expensive cable if it's not required.


I don't like it when an inspector gets into design issues. I don't think that's his/her job or really any of their business. There was no code violation and that should have been the end of it.
 

kwired

Electron manager
Location
NE Nebraska
I don't like it when an inspector gets into design issues. I don't think that's his/her job or really any of their business. There was no code violation and that should have been the end of it.
And on top of that he actually had been missing something that is a violation
 

nizak

Senior Member
Fwiw.
The #1 SER I installed is run through bored holes in floor joists. It does not come in contact with insulation.
I believe I am correct in protecting this with a 100A breaker.
 

tkb

Senior Member
Location
MA
Fwiw.
The #1 SER I installed is run through bored holes in floor joists. It does not come in contact with insulation.
I believe I am correct in protecting this with a 100A breaker.

If the #1AL SER is not in contact with insulation then the 75°c column can be used for ampacity and a 100amp breaker is correct since this panel doesn't carry the full load of the dwelling.

If this feeder carried the full load of the dwelling then #2AL would be able to be used on a 100amp breaker if not in contact with insulation.

The inspector is incorrect.
 

mwm1752

Senior Member
Location
Aspen, Colo
I don't like it when an inspector gets into design issues. I don't think that's his/her job or really any of their business. There was no code violation and that should have been the end of it.


You must be a joy to be around -- inspector can't suggest or talk to you -- I see nothing in his actions that failed the inspection. bottom line is that 2# ser @ 75 deg is rated at 90 amps which is a standard breaker -- the 100 amp rating @ 90 deg can be used for derating. BTW I have great conversations with the contractors here & they appreciate the informality of the working conditions.
 

kwired

Electron manager
Location
NE Nebraska
You must be a joy to be around -- inspector can't suggest or talk to you -- I see nothing in his actions that failed the inspection. bottom line is that 2# ser @ 75 deg is rated at 90 amps which is a standard breaker -- the 100 amp rating @ 90 deg can be used for derating. BTW I have great conversations with the contractors here & they appreciate the informality of the working conditions.
But his comments on overdoing it are not justified, people over design certain aspects all the time - it is a design choice. There are guys out there that never run 1/2 raceway other then maybe really short runs or flex whips even though they never fill the raceway with more conductor then a 1/2 inch can take quite often.

RMC is often run in places where EMT or PVC would be sufficient.

Many homes get a 200 amp service even if 100 would have worked.

Some prefer QO or CH loadcenters even though Homeline or BR meet same listing requirements and will usually cost less.
 

JFletcher

Senior Member
Location
Williamsburg, VA
Had a final inspection completed today on a new residence.
I placed a sub panel at the opposite end of the house and fed it with #1 Al SER cable protected by a 100A breaker.

Inspector questioned the use of #1 cable and asked why #2 was not used.
I explained that the #2 was not rated for 100 amp in this
application.
He went on to say that he has always approved the use of #2 for sub feeds because the code allows it in residential applications.

He went on to tell me that there is no reason to use a more expensive cable if it's not required.

Am I missing something here?

:slaphead:

Odd statement: there are several reasons why one might use a better or higher capacity cable than required. I've had inspectors mention similar things to me (going above code) tho I believe their intent was to save me money/labor.
 

kwired

Electron manager
Location
NE Nebraska
:slaphead:

Odd statement: there are several reasons why one might use a better or higher capacity cable than required. I've had inspectors mention similar things to me (going above code) tho I believe their intent was to save me money/labor.
And it is too late to do that once it has already been done right?
 

JFletcher

Senior Member
Location
Williamsburg, VA
And it is too late to do that once it has already been done right?

Yeah, but could be good information for the next project. Since we worked in many different cities and states, rarely the same place twice, often far from home, it was generally more cost effective for us to build to the strictest specs we encountered than to do something, get red tagged, and hold us up, or have to travel 6+ hours one way to fix something minor, possibly (probably) interfering with another project.

Inspectors of all people should know the NEC is a minimum set of requirements. Most I encountered did know this, so instead of catching flack/questions if we secured RPVC every 4' instead of 5', ENT every 24-30" instead of 36", nail plating penetrations even if set back >1.25" from a stud/top or bottom plate face, using 4 hour rated firestop when 2 would do, etc, we usually got a thumbs up. What some would consider overkill, we considered cheap insurance for a passing inspection.
 

growler

Senior Member
Location
Atlanta,GA
Inspectors of all people should know the NEC is a minimum set of requirements.


The NEC is a minimum set of safety requirements. They state up front in the code book that it's not a design manual and that useing minimum standards may not be the best design.


The other day there was a topic where an engineer had speced metal boxes instead of plastic boxes for use on a job where NM was used. I think that is a reasonable design choice ( consider how they cut out those boxes in the sheetrock, less damage when useing the roto zip around the metal plaster ring). Sure it cost more but who gets to make that decision? The EC, the inspector or the guy writeing the check.
 
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