Derating Modular Buildings / Shelters Confused

[killer76]

I have been reading and reading and reading the Forum on this topic and I am now totally confused, perhaps I should just describe my application and see what exception if any may apply, or if I am on the right track, I have several questions and will separate them

The buildings / shelters manufactured all are built and shipped, all are OEM specific, so some may be mobile and some may become permanent after shipment. Some application are classified and some general purpose

I have this debate when routing the conduit throughout interior and exterior,

First of all we very rarely every have the final destination, so for a rule of thumb, should I use a standard temperature range

Q1) Temperature adjustment

Now the part I need the most help, derating

Example:
From my panel board or load center I have for this occurrence a single phase panel, I need help on sharing the neutral, to reduce the number of ccc from what I have been reading in a single phase application I can use the same neutral for several circuits, and more in a 3 phase application, most of the application require (1) HOT, (1) NEUT, & (1) GND per circuit,

I would like to reduce the number of wire fill, share the neutrals and reduce the number of grounds conductors and submit code to support this

Q2) Neutral & Ground

Were in the code can I study this

Now derating the conductors,
Example:
I have a 30 ckt panel and I have 20 ckt all too various components: receptacles, interior lights, exterior lights, exit signs, emergency lights, etc... wire size is typical #12 AWG THHN, and most of the circuits are on 20a circuit breakers I know now to reduce the breakers closer to the load required {i.e. exit sign on a 10a rather than a 20a} and allow for multiple ccc in one conduit based on table 310.15

From what I have been told the simple method is to run the circuits in individual conduits, this makes for an overwhelming amount of conduits however after reading I would like to know were in the code it will allow for anything outside this

Example:
I have (1) 1? EMT and 21 conductors (7) HOT, (7) NEUT, & (7) GND from what I have read this will be 14 ccc and the ampacity is now at 50% the #12 AWG conductors are now only rated for 10 amps so the breakers need to be 10 amp breakers,

During my reading I found that I can rate the wire by the load as well, now my confusion grows

Q3} Derating / Conduit fill what articles can I study this


Thank you all, I know that I need help in this area, and this is the place to find answers
Also if anyone can give me guidance to learning books or suggestion, I recently purchased the ?illustrated guide to the national electrical code? based on the 2005 code by Charles Miller
Any other reference books or sites in addition to the code book (I plan to get my own soon) would be great!!

Thanks again

 

[chevyx92]

I have been reading and reading and reading the Forum on this topic and I am now totally confused, perhaps I should just describe my application and see what exception if any may apply, or if I am on the right track, I have several questions and will separate them

The buildings / shelters manufactured all are built and shipped, all are OEM specific, so some may be mobile and some may become permanent after shipment. Some application are classified and some general purpose

I have this debate when routing the conduit throughout interior and exterior,

First of all we very rarely every have the final destination, so for a rule of thumb, should I use a standard temperature range

Q1) Temperature adjustment

Now the part I need the most help, derating

Example:
From my panel board or load center I have for this occurrence a single phase panel, I need help on sharing the neutral, to reduce the number of ccc from what I have been reading in a single phase application I can use the same neutral for several circuits, and more in a 3 phase application, most of the application require (1) HOT, (1) NEUT, & (1) GND per circuit,

I would like to reduce the number of wire fill, share the neutrals and reduce the number of grounds conductors and submit code to support this

Q2) Neutral & Ground

Were in the code can I study this

Now derating the conductors,
Example:
I have a 30 ckt panel and I have 20 ckt all too various components: receptacles, interior lights, exterior lights, exit signs, emergency lights, etc... wire size is typical #12 AWG THHN, and most of the circuits are on 20a circuit breakers I know now to reduce the breakers closer to the load required {i.e. exit sign on a 10a rather than a 20a} and allow for multiple ccc in one conduit based on table 310.15

From what I have been told the simple method is to run the circuits in individual conduits, this makes for an overwhelming amount of conduits however after reading I would like to know were in the code it will allow for anything outside this

Example:
I have (1) 1? EMT and 21 conductors (7) HOT, (7) NEUT, & (7) GND from what I have read this will be 14 ccc and the ampacity is now at 50% the #12 AWG conductors are now only rated for 10 amps so the breakers need to be 10 amp breakers,

During my reading I found that I can rate the wire by the load as well, now my confusion grows

Q3} Derating / Conduit fill what articles can I study this


Thank you all, I know that I need help in this area, and this is the place to find answers
Also if anyone can give me guidance to learning books or suggestion, I recently purchased the ?illustrated guide to the national electrical code? based on the 2005 code by Charles Miller
Any other reference books or sites in addition to the code book (I plan to get my own soon) would be great!!

Thanks again

I say hire a licensed electrician.

 

[coulter]

If stamped prints are required, you are going to need an engineer.

carl

 

[coulter]

...First of all we very rarely every have the final destination, so for a rule of thumb, should I use a standard temperature range...

Even if you ship to both Iraq and Greenland and the inside spaces are all temp controlled, you are likely okay, unless some is routed through a boiler room. If not temp controlled - maybe not. If you are designing marginal, you will need to know the ambient. The less information, the less marginal the design.

... 14 ccc and the ampacity is now at 50% the #12 AWG conductors are now only rated for 10 amps so the breakers need to be 10 amp breakers...

If you are using 90C wire, then the temp derate is from the 90C column

... I need help on sharing the neutral, to reduce the number of ccc ...

Multiwire branch circuits, Def Art 100, 210.4, hazards areas have different rules - 501.40

...Also if anyone can give me guidance to learning books or suggestion, ...

You really need a design class. An example is Stallcup's Design Guide and class. I'm not particularly a fan of Stallcup, but his Design Guide and class are a good start. Mike H likely has similar stuff, i'm just not familiar with his.

Yes you need to get a code book.

Keep in mind the NEC is not a design guide. If anyone is telling you different, have them read NEC, 90.1.B and 90.1.C.

...I know now to reduce the breakers closer to the load required {i.e. exit sign on a 10a rather than a 20a} ...

I don't recall ever using a 10ACB in a panel. I've used them for suplimentary protection, but not branch ckts in a panel. Didn't even know they were available. I learned a new thing today and that is good.


carl