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Old 04-23-2010, 04:02 PM   #1
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Wire size for 100A panel


I am going to install a 100A panel in my garage, I am debating running a cable (easy) or running EMT.

If I run cable, what type should I use? What size for 100A?

If I run EMT, what size conductors do I have to use?

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Old 04-23-2010, 05:48 PM   #2
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Wire size for 100A panel


is it an attached garage and how far from the main panel would the sub-panel be?

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Old 04-23-2010, 07:15 PM   #3
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Wire size for 100A panel


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is it an attached garage and how far from the main panel would the sub-panel be?
Yes. Within 50 feet or so.
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Old 04-23-2010, 07:54 PM   #4
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Wire size for 100A panel


For a cable I think you can use #2 provided that the load does not exceed 95a
For conduit you can drop to #3
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Old 04-23-2010, 09:25 PM   #5
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Wire size for 100A panel


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Originally Posted by Scuba_Dave View Post
For a cable I think you can use #2 provided that the load does not exceed 95a
It could be on a 100A breaker? How do you know if the load will go over 95A? Who knows what they are going to end up running in a garage, ya know what I mean?

Also, what type of cable is that for? I know that SER usually takes a higher amperage than Romex.

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For conduit you can drop to #3
Thanks!
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Old 04-25-2010, 08:07 PM   #6
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Wire size for 100A panel


Bump please
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Old 04-25-2010, 09:24 PM   #7
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Wire size for 100A panel


1/0-1/0-1/0-2 Al SER = 100 amp, cable

2-2-2-4 Cu SER = 95 amp, cable

1-1-1-3 Cu SER = 110 amps, cable

#3 Cu THHN in pipe = 100 amps

#1 Al THWN, XHWN in pipe= 100 amps
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Old 04-25-2010, 11:32 PM   #8
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Wire size for 100A panel


alright brric, help an old guy out. I cannot find the rule for using the next standard size breaker. If applicable, shrute would be able to use the #2 cu SER rather than needing the #1 cu SER.
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Old 04-25-2010, 11:50 PM   #9
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Wire size for 100A panel


Quote:
Originally Posted by nap View Post
alright brric, help an old guy out. I cannot find the rule for using the next standard size breaker. If applicable, shrute would be able to use the #2 cu SER rather than needing the #1 cu SER.
NEC 240.4 (B)

Devices Rated 800 Amperes or Less. The next higher
standard overcurrent device rating (above the ampacity of
the conductors being protected) shall be permitted to be
used, provided all of the following conditions are met:
(1) The conductors being protected are not part of a multioutlet
branch circuit supplying receptacles for cordand-
plug-connected portable loads.
(2) The ampacity of the conductors does not correspond
with the standard ampere rating of a fuse or a circuit
breaker without overload trip adjustments above its rating
(but that shall be permitted to have other trip or
rating adjustments).
(3) The next higher standard rating selected does not exceed
800 amperes.

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Old 04-26-2010, 01:15 AM   #10
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Wire size for 100A panel


thank you sir.
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Old 04-26-2010, 10:06 PM   #11
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Wire size for 100A panel


Thanks for the help guys. So I guess the best way is to run cable. SER is my best bet? They don't make Romex in this size?


ETA: Out of curiosity, why do you use the 60 degree column for SER? I thought that you normally use the 75 degree column, no? For example, I thought 8 gauge Romex could take 40 amps while 8 gauge SER could take 50 amps.

Last edited by Shrute; 04-26-2010 at 10:10 PM.
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Old 04-26-2010, 11:10 PM   #12
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Wire size for 100A panel


Quote:
Originally Posted by brric View Post
1/0-1/0-1/0-2 Al SER = 100 amp, cable

2-2-2-4 Cu SER = 95 amp, cable

1-1-1-3 Cu SER = 110 amps, cable

#3 Cu THHN in pipe = 100 amps *

#1 Al THWN, XHWN in pipe= 100 amps*
Quote:
Originally Posted by Shrute View Post
Thanks for the help guys. So I guess the best way is to run cable. SER is my best bet? They don't make Romex in this size?


ETA: Out of curiosity, why do you use the 60 degree column for SER? I thought that you normally use the 75 degree column, no? For example, I thought 8 gauge Romex could take 40 amps while 8 gauge SER could take 50 amps.
Shrute.,

Let me highlight with a dot {} that is for 60C rated conductor or cables and the star {*} is for 75C btw I will make it bold so you can not miss this.

The SER rating is the same as Romex cables I know they are listed for 90C but give you a head up the Romex and SER cables you must use 60C tables not the 75C tables { the 90C is used for derating only }

Merci,Marc
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Old 04-27-2010, 07:39 AM   #13
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Wire size for 100A panel


Ohh, I didn't know that. I thought that if you ran 8 gauge SER that you can put 50 amps thru that opposed to romex in which you can only run 40 amps thru it.

Thanks!
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Old 04-27-2010, 02:58 PM   #14
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Wire size for 100A panel


Are you on 2008 or 2005 NEC?
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Old 04-27-2010, 07:03 PM   #15
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Wire size for 100A panel


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Originally Posted by Code05 View Post
Are you on 2008 or 2005 NEC?
2008.

What would the difference be?

Thanks!

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