Sub panel wiring

[Varczar]

I am relatively new to electrical contracting and I am doing my first residential basement finishing project installing a 100A sub panel to feed the load. I am wanting to install SE wire from the main to the sub panel. I have looked in 338.10 for installation requirements. In 338.10(A)(4)(a) it points me back to part II of 334.

My total load is only 51A. My questions are:

1) Is #4 SE cable overkill for this installation? It is 70' of wire and voltage drop looks good.
2) 334.10 seems to say I do not have to install it in conduit. Is that correct?

I appreciate any responses because I just want to make sure I get this to code with no issues.

Varczar

 

[infinity]

You can use SE cable but it must be sized according to 310.16, 60? C column for ampacity. Also you would need SER cable which will give you 4 conductors. You said you have a 100 amp subpanel, what ampacity feeder are you trying to use?

 

[pete m.]

1. 4awg aluminum SE cable is not overkill.
2. SE cable is not required to be installed in a raceway.
3. You probably want to use SER cable though so you have an equipment ground.

Pete

 

[Varczar]

Infinity,

Thanks for the reply. It is a 200A main with 1/0-1/0-2 AL feeding the main. I have a total load on the sub panel of 51A. The sub panel is a 100A main lug

Using the two conductor with ground SER AL cable, would I not use either the 75 or 90 degree column?

Again, thanks for the clarifications, I just want to get it right.

Varczar

 

[jumper]

Infinity,

Thanks for the reply. It is a 200A main with 1/0-1/0-2 AL feeding the main. I have a total load on the sub panel of 51A. The sub panel is a 100A main lug

Using the two conductor with ground SER AL cable, would I not use either the 75 or 90 degree column?

Again, thanks for the clarifications, I just want to get it right.

Varczar

If you are 2008 NEC, then the 60 degree column.

 

[raider1]

Infinity,

Thanks for the reply. It is a 200A main with 1/0-1/0-2 AL feeding the main. I have a total load on the sub panel of 51A. The sub panel is a 100A main lug

Using the two conductor with ground SER AL cable, would I not use either the 75 or 90 degree column?

Again, thanks for the clarifications, I just want to get it right.

Varczar

If you are working under the 2008 NEC you must use the 60 degree column of 310.16 for the ampacity of the SER cable. (See 338.10(B)(4)(a) which requires us to follow all of part II of Article 334 including 334.80 which limits the ampacity of SER cable to the 60 degree column of 310.16)

Under the 2005 NEC you could use the 75 degree column if the conductors within the SER cable were listed at 75 degrees C.

You could not use the 90 degree column except of ampacity adjustments. (See 110.14(C))

Chris

 

[jumper]

Infinity,

Thanks for the reply. It is a 200A main with 1/0-1/0-2 AL feeding the main. I have a total load on the sub panel of 51A. The sub panel is a 100A main lug

Using the two conductor with ground SER AL cable, would I not use either the 75 or 90 degree column?

Again, thanks for the clarifications, I just want to get it right.

Varczar

ER, what? typo? 4/0 maybe?

 

[SEO]

Infinity,

Using the two conductor with ground SER AL cable,


Varczar

SER cable has 3 insulated conductors and an uninsulated ground. Are you referring to SEU cable for your sub panel which has two insulated conductors and one uninsulated conductor?

 

[sparks2000]

I don't understand why you would use the 60 degree column

 

[jumper]

I don't understand why you would use the 60 degree column

'Cause the NEC tells you to. Want to clarify on what point you do not understand. Derating? Final ampacity?

 

[sparks2000]

If the terminals were rated for 75 degrees wouldnt you use the 75 and not the 60 ???

 

[SEO]

Section 338.10(B) (4) (a) for SE cable says the installation shall comply with the requirements of Part II of Article 334. Section 334.80 states the ampacity shall be in accordance with the 60 degree conductor temperature rating.

 

[sparks2000]

Ok I see that now, so if it was in conduit then you can use the 75 degree column ?

 

[Dennis Alwon]

Ok I see that now, so if it was in conduit then you can use the 75 degree column ?

Yes that is correct unless you install the se cable in the conduit.

 

[augie47]

Ok I see that now, so if it was in conduit then you can use the 75 degree column ?

Provided you are using a 75? or 90? wire (no TW, UF, NM, or SE) and your terminations are rated 75?.

 

[SEO]

If you mean installing the seu cable in conduit it would be ok to use the 75 degree table for the ampacity the answer is no. If you install a conduit system and use a conductor rated for 75 degrees you could provided all terminations are rated at least 75 degree C.

 

[SEO]

Sorry Gus you beat me to the draw.

 

[sparks2000]

Thanks, you guys cleared it up for me. I'm not use to running NM. Sorry if I was a PITA!

 

[Jim W in Tampa]

??????????? why if your load is only 51 amps are you doing all of this ?
are you saying 51 at 120 or 51 at 240. Are you out of spaces in main panel ? Why not put sub panel next to main ? Your spending way to much on a little load

 

[infinity]

Your #4 Al SER would have an ampacity of 55 amps. Next size up rule would allow you to use a 60 amp OCPD with the calculated load of 51 amps. IMO if you have a 100 amp panel and a 51 amp calculated load you should run a bigger feeder, but the NEC does not require it.