wrong commercial service conductor size

Status
Not open for further replies.

sgreany

Member
Location
massachusetts
I am constantly running into 200a commercial services that the original installer used 4/0 aluminum as the service conductor. I am not going to quote the code here but we all should know that we can not install wiring tthat is supplied by wiring that contains code violations as we become liable for the existing wiring we attached to. Therefore the way I see it I can not do any wiring on the premise if the service is in violation. Do you agree? Also I would like to know why the electrical inspectors are passing these 200a commercial services using 4/0 al. When the required wire size is 250mcm al. I certainly am not the smartest guy in the trade and I am open to being factually corrected (that includes my bad spelling and grammer skills)


I forgot I posted this a wile back and never followed it up.


ART. 230.90(a)


Un-grounded conductors of a service "shall be provided by an over current protective device in series with each un-grounded service conductor that has a rating or setting not higher than the allowable ampacity of the conductor"


If your using aluminum conductors its 250 MCM for single phase. If you go three phase and apply the de-rating table for more than 3 current carrying conductors you need 350 MCM
 

iwire

Moderator
Staff member
Location
Massachusetts
Un-grounded conductors of a service "shall be provided by an over current protective device in series with each un-grounded service conductor that has a rating or setting not higher than the allowable ampacity of the conductor"

You are ignoring the exception that allows us to use 2404(B).
 

retire09

Senior Member
Everywhere I have worked; the underground service lateral is owned, sized and installed by the utility company per their standards rather than the NEC. They are always smaller than what the NEC would require. It's not my problem.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
........
I forgot I posted this a wile back and never followed it up.


ART. 230.90(a)


Un-grounded conductors of a service "shall be provided by an over current protective device in series with each un-grounded service conductor that has a rating or setting not higher than the allowable ampacity of the conductor"

As I-wire pointed out, the section you quoted has those pesky little things called exceptions.
Note exception No. 2

So often it falls back to the basic rule: Calculate the load, size the conductor, select the protective device.

A commercial with a 200 amp main and a 180 amp (or less) calculated load may well meet the Code. The reason you are"constantly running into" that situation may be because the calculated loads may be 180 amps or less.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
...Therefore the way I see it I can not do any wiring on the premise if the service is in violation. Do you agree? ...
I don't agree that just because there is an existing code violation, that you can't do any electrical work.
 

Canton

Senior Member
Location
Virginia
Occupation
Electrician
I am constantly running into 200a commercial services that the original installer used 4/0 aluminum as the service conductor. I am not going to quote the code here but we all should know that we can not install wiring tthat is supplied by wiring that contains code violations as we become liable for the existing wiring we attached to. Therefore the way I see it I can not do any wiring on the premise if the service is in violation. Do you agree? Also I would like to know why the electrical inspectors are passing these 200a commercial services using 4/0 al. When the required wire size is 250mcm al. I certainly am not the smartest guy in the trade and I am open to being factually corrected (that includes my bad spelling and grammer skills)


I forgot I posted this a wile back and never followed it up.


ART. 230.90(a)


Un-grounded conductors of a service "shall be provided by an over current protective device in series with each un-grounded service conductor that has a rating or setting not higher than the allowable ampacity of the conductor"


If your using aluminum conductors its 250 MCM for single phase. If you go three phase and apply the de-rating table for more than 3 current carrying conductors you need 350 MCM


I install 4/0 aluminum conductors for 200 amp services all day, every day.....except Sundays and Federal Holidays:D.
A 180 amp breaker is not a standard size...so using the next size up rule takes you to a permitted 200 amp breaker for a service (as long as the calculated load is below 180 amps).

Also, derating is not always required with a four wire circuit. Depends if your counting the neutral as a CCC, and looking at non-linear loads. In regards to a 200 amp service I have never counted the neutral as a CCC.....so those 350 MCM you would put in would probably be 4/0 aluminium if I were installing them.
 

iwire

Moderator
Staff member
Location
Massachusetts
we all should know that we can not install wiring tthat is supplied by wiring that contains code violations as we become liable for the existing wiring we attached to. Therefore the way I see it I can not do any wiring on the premise if the service is in violation. Do you agree?

No I do not agree and just noticed you are from Mass. Take a look at our Mass rules found ahead of the Mass amendments and you will see rules 3 and 4.

Rule 3 tells us not only can we do work with existing violations we do not even have to correct the violations.


Rule3-4.jpg
 

JRW 70

Senior Member
Location
Eastern Central Missouri
Occupation
Testing and Engineer
As said above, unless you have an adjustable
circuit breaker that can be set at 180 Amps
(assuming 75*C 4/0 cable) then the round up
permission is given for CB's in this size range.
I have seen many installations such as
described and the temperature of the wire was
no where near 75*C. If the load calculations are
not pushing the limit (over 180), then if there is
a catastrophic internal panel failure and the CB is
in good condition, it would probably enter the
magnetic trip rather than the thermal range.
But there is no reason you can't go big on the wire,
it just isn't required in most of the places I have been.
If your load calcs. show 190+ then you are absolutely
right to move up to the appropriate size. And in some
situations with plans (Engineering, etc.) that call out
over size for some future purpose, but if not save your
client the cost of oversized equipment.

JR
 
Last edited:

kwired

Electron manager
Location
NE Nebraska
Quote Originally Posted by sgreany View Post
...Therefore the way I see it I can not do any wiring on the premise if the service is in violation. Do you agree? ...

I don't agree that just because there is an existing code violation, that you can't do any electrical work.

If OP doesn't want to work in those places - he very easily limits himself to only new construction projects. Even a newly finished project likely has some relatively minor violations that get missed or even ignored.
 

sgreany

Member
Location
massachusetts
As I-wire pointed out, the section you quoted has those pesky little things called exceptions.
Note exception No. 2

So often it falls back to the basic rule: Calculate the load, size the conductor, select the protective device.

A commercial with a 200 amp main and a 180 amp (or less) calculated load may well meet the Code. The reason you are"constantly running into" that situation may be because the calculated loads may be 180 amps or less.


I agree with you on the exception however I would like to point out that they do make a 180A circuit breaker so you cant fuse 4/0 al. with 200A
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
I would like to point out that they do make 180A circuit breakers

That may be true, but for purposes of this discussion, refer to section 240.6 and you will see 180 is NOT a standard breaker size, 175 is, so 4/0 aluminum at 75 degrees is rated 80 and the next standard size breaker is 200 amps.
 

JRW 70

Senior Member
Location
Eastern Central Missouri
Occupation
Testing and Engineer
What is the quote that goes something like: Don't let
the perfect stand in the way of possible.

At my job we would never be able to do any repairs.
Document the part you did, take note or better yet
pictures of the violations and state they were beyond
the scope of the project. We refer to this as practicing
defensive procdures. We know what we did and can
prove it if need be ( we have countless DVD's of pictures
of unsafe equipment on the customer's side and also where
the marking companies flag or paint the underground pipes,
phone lines/fiber optic, etc. so when the crews dig we have
a legal standing for it being their error when our trackhoe
pulls up who knows what that wasn't marked.

Just do the best work you can and consider some of the
defensive measures that may be appropriate for your
line of work.

JR
 

sgreany

Member
Location
massachusetts
No I do not agree and just noticed you are from Mass. Take a look at our Mass rules found ahead of the Mass amendments and you will see rules 3 and 4.

Rule 3 tells us not only can we do work with existing violations we do not even have to correct the violations.


Rule3-4.jpg


Too lazy to look it up right now but I dose say that we are not allowed to increase the magnitude of an existing violation. So wouldn't you consider adding load to an undersized conductor increasing the magnitude of the problem. i would say yes. I usually just point the violation out to my customer and do the job job anyway. Honestly ive gotten a few service changes out of it.
 

sgreany

Member
Location
massachusetts
I would like to point out to the people who hopefully are enjoying this conversation as much as I am, For 3 phase services dont forget to apply 310.15(b)(3)(a) for more than 3 current carying conductors
 

pete m.

Senior Member
Location
Ohio
Too lazy to look it up right now but I dose say that we are not allowed to increase the magnitude of an existing violation. So wouldn't you consider adding load to an undersized conductor increasing the magnitude of the problem. i would say yes. I usually just point the violation out to my customer and do the job job anyway. Honestly ive gotten a few service changes out of it.

How have you determined that a violation even exists? On the ones that you believe are in violation have you performed a load calculation to prove this to your customer?

You ever had a mechanic offer to change the "stale" air in your tires?

Pete
 

iwire

Moderator
Staff member
Location
Massachusetts
I would like to point out to the people who hopefully are enjoying this conversation as much as I am, For 3 phase services dont forget to apply 310.15(b)(3)(a) for more than 3 current carying conductors

Very few 3 phase 4 wire services have more than three current carrying conductors.

You rarely have to count the neutral as a current carraying conductor.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Summary, 180 amps is not a standard size, almost all 3? services have 3 CCC's and the exception #2 is pretty specific:

VII. Service Equipment ? Overcurrent Protection
230.90 Where Required. Each ungrounded service con-
ductor shall have overload protection.
(A) Ungrounded Conductor. Such protection shall be
provided by an overcurrent device in series with each un-
grounded service conductor that has a rating or setting not
higher than the allowable ampacity of the conductor. A set
of fuses shall be considered all the fuses required to protect
all the ungrounded conductors of a circuit. Single-pole cir-
cuit breakers, grouped in accordance with 230.71(B), shall
be considered as one protective device.
Exception No. 1: For motor-starting currents, ratings that
comply with 430.52, 430.62, and 430.63 shall be permitted.
Exception No. 2: Fuses and circuit breakers with a rating
or setting that complies with 240.4(B) or (C) and 240.6
shall be permitted.
 
Status
Not open for further replies.
Top