Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 04-15-2008, 09:49 PM   #1
Master Of Nothing
 
mr500's Avatar
 
Join Date: Mar 2008
Location: Alabama
Posts: 141
Share |
Default

Sizing Wire


Im running a new 100amp sub about 40 ft from house. In you guys' opinion, should I go with THWN #2 or #3 for my hots. As well, What about the neutral and EG? I'm kinda confused about the 90/75 degrees that rate this type wire. Also I understand about having to conduit this in from panel to panel underground. Asking this because I was going with 2-2-4-6 al mobile home feeder but the place I was going to buy it from went out of business and I WONT listen to the guys at HD and Lowes. TIA.

May have answered my own question with the NEC Table 310.15.B.6
Posted it up as well. Says I can use up to #4 for 100amp. Whats your guys' opinion on that?? So If I use #4 does that not mean I can use #8 for the EQ ground??

So in a nutshell I will run 2 #4 for hot, 1 #4 for Neutral and 1 #8 for equipment gnd. out to sub. Does this all compute OR am I way off base?


Mike

__________________
Im Not An Electrician...But I Did Stay At A Holiday Inn Express Last Night!!

Last edited by mr500; 04-15-2008 at 11:00 PM.
mr500 is offline   Reply With Quote
Old 04-15-2008, 10:49 PM   #2
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 4,851
Default

Sizing Wire


Can't use that table it is for main service entrance conductors or main power feeders that supply an entire dwellings electrical. Sub panels do not qualify.

You must use 310.16 for you wire ampacity.

No voltage drop concerns require #3 awg copper but #2 is easier to find for a DIYer.

Wrong table for the equipment ground you need to use T250.122.

Stubbie is offline   Reply With Quote
Old 04-15-2008, 11:04 PM   #3
Master Of Nothing
 
mr500's Avatar
 
Join Date: Mar 2008
Location: Alabama
Posts: 141
Default

Sizing Wire


OK are these correct ?? So if i can find #3 I can use that if not use #2 OK.. On the neutrals I was going to go with same size as my HOTS.

The gnd will have to be #8 no matter what I feed with ??

So 2 #3's for hots, one #6 for Neutral and one #8 for eq gnd. Would this do me and let me have power. I luv power lol

All of which will be THWN buried 2' in conduit!! Correct? One last thing, what is the temp rating all about? IS that the ground temp or what? just like to be informed????
Attached Thumbnails
Sizing Wire-250.122.jpg   Sizing Wire-310.6.jpg  
__________________
Im Not An Electrician...But I Did Stay At A Holiday Inn Express Last Night!!

Last edited by mr500; 04-15-2008 at 11:27 PM.
mr500 is offline   Reply With Quote
Old 04-16-2008, 09:45 AM   #4
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 4,851
Default

Sizing Wire


S
Quote:
o 2 #3's for hots, one #6 for Neutral and one #8 for eq gnd. Would this do me and let me have power. I luv power lol
Neutral should be full sized...same as your hots. For over 60 to 100 amp overcurrent protection a #8 copper for your equipment ground.

Last edited by Stubbie; 04-16-2008 at 09:56 AM.
Stubbie is offline   Reply With Quote
Old 04-16-2008, 09:46 AM   #5
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Default

Sizing Wire


The temperature listing you see in the ampacity tables is the rating of the insulation. Most lugs and terminals have a maximum 75 degree rating, so that is the column to use for conductor types listed in the 90 or 75 degree column. The 90 degree column is used as a starting point for any required derating such as in table 310.15 B 2 a, for the wire types listed in that column. Make sure you use the correct side for either copper or aluminum.

Many jurisdictions (including mine) will make you show your load calculations to justify reducing the neutral conductor size on feeders. I would check that before pulling it in.

The equipment ground is sized per the size of the over current protection devise on the circuit. 100 amps requires a #8 minimum. As Stubbie said, see table 250.122.

See table 300.5 for burial depths. You mentioned conduit. 18" for PVC or 6" for rigid or intermediate metal.
jrclen is offline   Reply With Quote
Old 04-16-2008, 01:07 PM   #6
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 4,851
Default

Sizing Wire


Quote:
Many jurisdictions (including mine) will make you show your load calculations to justify reducing the neutral conductor size on feeders. I would check that before pulling it in
.

John

Thats exactly why I don't like homeowners fooling with reducing neutrals. There is no guarantee that the calculation will be verified.
Stubbie is offline   Reply With Quote
Old 04-16-2008, 04:19 PM   #7
Master Of Nothing
 
mr500's Avatar
 
Join Date: Mar 2008
Location: Alabama
Posts: 141
Default

Sizing Wire


OK Thanks guys. I will keep the Neutrals same size as my main hots. In this case #3 IF I can find it. Also #8 for equipment ground.

One last thing I have #6 bare, will that be OK to run out my panel down to the ground electrode outside ????
__________________
Im Not An Electrician...But I Did Stay At A Holiday Inn Express Last Night!!
mr500 is offline   Reply With Quote
Old 04-16-2008, 08:31 PM   #8
Newbie
 
Join Date: Mar 2008
Posts: 4
Default

Sizing Wire


Quote:
Originally Posted by mr500 View Post
OK Thanks guys. I will keep the Neutrals same size as my main hots. In this case #3 IF I can find it. Also #8 for equipment ground.

One last thing I have #6 bare, will that be OK to run out my panel down to the ground electrode outside ????
Yes #6 will be fine.
TexasSparky is offline   Reply With Quote
Old 04-16-2008, 08:58 PM   #9
Cow
Member
 
Join Date: Jan 2008
Location: Oregon
Posts: 116
Default

Sizing Wire


Quote:
Originally Posted by Stubbie View Post
SNeutral should be full sized...same as your hots. For over 60 to 100 amp overcurrent protection a #8 copper for your equipment ground.
What about 250.122(B)? Honestly, I never really thought about it until now, since #2 is so common for 100 amp circuits. I actually ran one today, two #2's, #4 neutral, and a #8 ground. Hope the inspector doesn't catch it...
Cow is offline   Reply With Quote
Old 04-16-2008, 09:40 PM   #10
Master Of Nothing
 
mr500's Avatar
 
Join Date: Mar 2008
Location: Alabama
Posts: 141
Default

Sizing Wire


I just found a place that has the 2-2-4-6 direct burial mobile home feeder. Its a little cheaper being its aluminum. Is there a preference among you pros out there?
__________________
Im Not An Electrician...But I Did Stay At A Holiday Inn Express Last Night!!
mr500 is offline   Reply With Quote
Old 04-16-2008, 09:45 PM   #11
Newbie
 
Join Date: Mar 2008
Posts: 4
Default

Sizing Wire


I don't like any direct burial. If anything ever happens to it your S O L.

Last edited by TexasSparky; 04-16-2008 at 10:43 PM.
TexasSparky is offline   Reply With Quote
Old 04-16-2008, 10:12 PM   #12
Master Of Nothing
 
mr500's Avatar
 
Join Date: Mar 2008
Location: Alabama
Posts: 141
Default

Sizing Wire


Happens to it? Such as? Just curious is all.
__________________
Im Not An Electrician...But I Did Stay At A Holiday Inn Express Last Night!!
mr500 is offline   Reply With Quote
Old 04-16-2008, 10:12 PM   #13
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Default

Sizing Wire


Quote:
Originally Posted by mr500 View Post
I just found a place that has the 2-2-4-6 direct burial mobile home feeder. Its a little cheaper being its aluminum. Is there a preference among you pros out there?
I was hoping you weren't going to do that. For aluminum you will need a #1 wire.
jrclen is offline   Reply With Quote
Old 04-16-2008, 10:22 PM   #14
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Default

Sizing Wire


Quote:
Originally Posted by Cow View Post
What about 250.122(B)? Honestly, I never really thought about it until now, since #2 is so common for 100 amp circuits. I actually ran one today, two #2's, #4 neutral, and a #8 ground. Hope the inspector doesn't catch it...
The conductors aren't being upsized due to voltage drop or any reason related to proper circuit operation. So I wouldn't apply that here. Good point though. Are you talking about a service with aluminum 2-2-4-8? We are talking about a copper feeder with 2-2-2-8. I doubt the inspector will even blink at your wire size if it is a service. That is very common.
jrclen is offline   Reply With Quote
Old 04-16-2008, 10:24 PM   #15
Licensed Electrician
 
jrclen's Avatar
 
Join Date: Feb 2008
Location: central wisconsin
Posts: 982
Default

Sizing Wire


Quote:
Originally Posted by mr500 View Post
Happens to it? Such as? Just curious is all.
There are probably a million miles of direct burial wire in use right this minute. Some guys just don't like it. Some guys don't like Miller Lite either.

jrclen is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Dryer Grounding??? Traci_howdyadothat Electrical 7 05-27-2008 01:14 PM
Installing Fluorescents in Garage rzrbkpk Electrical 26 04-08-2008 09:00 PM
Stranded wire on screw connections BigJimmy Electrical 7 01-19-2008 02:42 PM
Old house, new light fixture, too many wires Persephonee Electrical 3 01-15-2007 08:58 AM
Help with wire sizing pdxoregon Electrical 2 08-17-2006 07:15 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.