Is #8 wire overkill for a sub panel with 15 amp breakers

Reply

  #1  
Old 03-26-13, 07:14 AM
Member
Thread Starter
Join Date: Mar 2013
Location: USA
Posts: 41
Received 0 Votes on 0 Posts
Is #8 wire overkill for a sub panel with 15 amp breakers

I am installing two sub panels. One for the garage so I can cut the current to my electrical tools and one in my basement for a recording studio. Max draw on either panel is about 35 amps. I have two 50 amp breakers in the main panel to feed the sub panels.
1. Do I need a disconnect between the main and sub panel?
2. Is #8 wire overkill for a panel with estimated 35 amp draw

I know that I have to run wire with two feeds (Black and Red), a neutral, and a ground. I also know that there has to be a ground bar in the sub panel and that the neutral bar can not be bonded to the sub panel.

The garage is attached.
 
Sponsored Links
  #2  
Old 03-26-13, 07:26 AM
Member
Join Date: Dec 2010
Location: usa
Posts: 243
Received 0 Votes on 0 Posts
If you plan on using 50 amp breakers to feed them then it is too SMALL....You should use 6 gauge wire on those panels. The breaker in your main panel is your disconnect.
 
  #3  
Old 03-26-13, 09:35 AM
Member
Join Date: Dec 2010
Location: usa
Posts: 243
Received 0 Votes on 0 Posts
Were you planning on using Romex, service cable, or are you running conduit?
 
  #4  
Old 03-26-13, 02:28 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Received 1 Vote on 1 Post
You can install a subpanel that has a main breaker to use as a disconnect. The actual overcurrent protection is the feed breaker in your main panel, as Jim said.
 
  #5  
Old 03-26-13, 07:04 PM
Member
Thread Starter
Join Date: Mar 2013
Location: USA
Posts: 41
Received 0 Votes on 0 Posts
I purchased SE Style R XHHW-2. 600V 3 CDRS #6 AWG

It should meet the requirements of the Inspector since it is being used inside the house.
 
  #6  
Old 03-27-13, 06:51 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 10,042
Received 26 Votes on 20 Posts
I purchased SE Style R XHHW-2. 600V 3 CDRS #6 AWG
Is that aluminum? If it is, protect it with a 40 amp breaker.
 
  #7  
Old 03-27-13, 08:02 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,965
Received 59 Votes on 52 Posts
Is that aluminum? It's XHHW.

SE cable is required to be rated at the 60 degree table regardless of the wire type inside the cable. Joe is correct, you may only use a 40 amp breaker.

You also need to use a 4 conductor cable if you are planning on using a two pole breaker at 240 volts. You need a separate ground wire to connect to a separate ground bar in the sub panel. Your neutral bar will float, and is not connected to the grounds, or the case of the sub panel.
 
  #8  
Old 03-28-13, 10:04 AM
Member
Thread Starter
Join Date: Mar 2013
Location: USA
Posts: 41
Received 0 Votes on 0 Posts
Yep, its Aluminum...... I am fully aware of the need to keep the Neutral separate from the ground and I have it wired in that manor. The grounding screw is in my tool box and it is green with envy. The only 220 circuit that will be utilized is at 15 amps for a air compressor the rest are all 120. I can yank the 50's and replace them with 40's. I have no aspirations of connecting any kind of equipment that requires more than 15 amps to run. I recently replaced the G.E. panel with a Square D to gain 12 more circuits. The electric company asked if I was interested in upgrading my service to 200 amps. I also had to replace the mast head which was too close to the roof and not in code. I replaced the meter can as well. I have the capability of upgrading to 200 amps with the equipment I have installed now but I really don't see a need for it unless I go ahead and by a lathe in which case I would want the 200 amps. My issue is to feel confident that the inspector finds nothing wrong with any of my work. I purchased the house last October and it was built in 1977. Needless to say the house does not meet todays code. I have lots of work to bring this house up to date and with the remodeling I will be required to bring everything up to code. It has taken me 5 months to remove all the previouse owners wireing and construction and putting the house back to its original condition. So thanks for all the help, and suggestions, Guys. I was only an Electricans apperentice in the 70's and a lot has changed since then. After 4 years they still hadn't brought me to the point of taking the certification tests so I went into automotive. There are some 70 houses in Hilton Head South Carolina that have services in them that I installed. I wrote my name on the back of each and every panel I installed too.
 
  #9  
Old 03-28-13, 10:23 AM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
But the cable you posted is 3-conductor. You need 4-conductor.

P.S. Your paragraph button is broken and making your posts hard to read.
 
  #10  
Old 03-28-13, 11:33 AM
Member
Join Date: Dec 2010
Location: usa
Posts: 243
Received 0 Votes on 0 Posts
I think he is OK as his desription read 6-3 Se type R (Round) so that SHOULD be 4 conductors....(3 conductors with a separate ground) however he needs to confirm this... I apologize but in my first post I meant 6 guage copper not aluminum. I should have clarified that. Nothing wrong with aluminum but it does have to be derated a bit....Should be fine though
 
  #11  
Old 03-28-13, 12:33 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
I think he is OK as his desription read 6-3 Se type R (Round) so that SHOULD be 4 conductors.
Agree. Never used SE and the 3 CDRS was being misread by me.
 
  #12  
Old 03-28-13, 02:15 PM
Member
Thread Starter
Join Date: Mar 2013
Location: USA
Posts: 41
Received 0 Votes on 0 Posts
Yes that is correct. 3 conductors and a ground. The 40 amp breakers are now in the main panel.
 
  #13  
Old 03-28-13, 03:28 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Received 1 Vote on 1 Post
The 40 amp breakers are now in the main panel.
You should only need one 40A circuit breaker to protect the cable feeding your subpanel.
 
  #14  
Old 03-28-13, 07:26 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 10,042
Received 26 Votes on 20 Posts
Is that aluminum? It's XHHW.
But, copper conductors are available as XHHW-2 or THHN/THWN

Cable shall be UL-listed Type SE, Style U, suitable for operation at 600 volts or less in
all installations as specified in the National Electrical Code. Conductors shall be annealed
copper, Type XHHW-2 or Type THHN/THWN, weather resistant PVC jacketed, as
manufactured by Southwire Company or approved equal.

http://www.southwire.com/ProductCata...odcatsheetOEM8

That being said, Type XHHW conductors are not commonly seen at the supply houses.
 
  #15  
Old 03-28-13, 08:14 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,965
Received 59 Votes on 52 Posts
I stand corrected. I have never seen XHHW copper wire, and all the XHHW wire we buy from the supply house is aluminum. I am pretty sure it is all manufactured by Southwire.

Thanks Joe! I never knew that!
 
  #16  
Old 03-28-13, 08:31 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Received 1 Vote on 1 Post
I didn't know that either. But sure enough, they're included in the copper section of my go-to ampacity reference. I just never noticed.

ARTICLE 310: Conductors for General Wiring
 
  #17  
Old 03-29-13, 08:03 AM
Member
Join Date: Dec 2010
Location: usa
Posts: 243
Received 0 Votes on 0 Posts
He has TWO sub panels he is feeding that is why he bought two breakers. Yes, XHHW is available in copper too, but rarely used anywhere except where specified or in copper seu/ser cables. We used to stock 2-2-2-4 se(r) copper at one time but very expensive. We still stock some seu type cables in copper but sell less and less each year....Heating guys still like to use them from time to time.
 
  #18  
Old 03-29-13, 09:45 AM
Member
Thread Starter
Join Date: Mar 2013
Location: USA
Posts: 41
Received 0 Votes on 0 Posts
I have two runs for sub panels. One to my garage and into a lockable panel. This will allow me to shut off the power to power tools so that I don't have any grandchildren with missing arms or fingers. The other will be for my recording equipment and will be mounted in the console so that amps, lighting, and mixing equipment can be shut off at the main panel or the control console. Having the panel mounted at the console also will help me to diagnose humming from the 60hz power supply should someone want to use their own amplifiers or equipment.

I have another concern though. I have made sure that the ground and neutral bars are not connected at the sub panel. But what about the main panel? Does it have to be separated as well? The contractor put the bonding screw in the main panel and ran ALL of the ground and common wires to the neutral bar. All of the circuits I installed in the panel have the grounds running to the ground bar and all the neutrals running to the neutral bar. Why do I have this sinking feeling that I am in trouble here.
 
  #19  
Old 03-29-13, 10:35 AM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
But what about the main panel? Does it [neutral and ground] have to be separated as well? The contractor put the bonding screw in the main panel
Main panel isn't a NEC term but here it is used for convenience to refer to the panel with the first over current protection device (OCPD). Grounds and neutral by code are connected at the panel with the first OCPD but nowhere else.
 
  #20  
Old 03-29-13, 10:35 AM
Member
Join Date: Dec 2010
Location: usa
Posts: 243
Received 0 Votes on 0 Posts
On the main service panel the neutral is bonded and grounds and neutrals can share the neutral bar. A lot of main panels don't even come with a ground bar in fact for this very reason. On sub feed panels you isolate them both....grounds only to the ground bar and neutral to neutral bar. You do not bond the neutral bars in the sub panels. And of course the ground bars bolt straight to the box. Sounds like you are OK.
 
  #21  
Old 03-29-13, 03:06 PM
Member
Thread Starter
Join Date: Mar 2013
Location: USA
Posts: 41
Received 0 Votes on 0 Posts
Pictures

Name:  Close up main panel with sub panel wiring.jpg
Views: 56866
Size:  50.6 KBName:  Sub panel close up.jpg
Views: 40812
Size:  43.2 KB

This is where I am at. I added the custom wiring job just to illustrate what kind of electrical work I am finding in this house.
 
Attached Images  
  #22  
Old 03-29-13, 06:03 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 10,042
Received 26 Votes on 20 Posts
I stand corrected. I have never seen XHHW copper wire, and all the XHHW wire we buy from the supply house is aluminum. I am pretty sure it is all manufactured by Southwire.

Thanks Joe! I never knew that!
Just to be fair, I have never seen a roll of #10 or #12 copper XHHW either, but I have bid plans with copper XHHW spec'd for branch circuits run in both underground conduits and conduits under a concrete slab. You are right, typically all XHHW wire at a supply house is aluminum.
 
  #23  
Old 03-30-13, 03:53 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Received 1 Vote on 1 Post
He has TWO sub panels he is feeding that is why he bought two breakers.
Du'oh! Got it. Temporary brain freeze.
 
  #24  
Old 04-01-13, 12:19 PM
Member
Join Date: Dec 2010
Location: usa
Posts: 243
Received 0 Votes on 0 Posts
Hey, quick question.......I can't tell for sure but on your sub panels....You didn't use the green bond screws and bond the neutrals did you? On sub feed panels they do not get bonded. They "float" while the ground bars are of course bolted directly to the box. It looks like a green bonding screw in on that picture there on the sub panel. If I saw wrong, then my mistake.
 
  #25  
Old 04-01-13, 12:51 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Received 1 Vote on 1 Post
I only see a green bonding screw in the main panel - unless I'm not looking at it right.
 
  #26  
Old 04-01-13, 01:24 PM
Member
Join Date: Dec 2010
Location: usa
Posts: 243
Received 0 Votes on 0 Posts
Probably right, but look at the screw next to the lug at the top/RH on the sub panel...where the neutral is. it kind of look off green to me but not for sure. Looks out of place to me also. Could just be me. The wiring jobs looks great, just wanting to d/c that screw. It's probably a hold down screw for the interior......
 
  #27  
Old 04-01-13, 02:01 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Received 1 Vote on 1 Post
look at the screw next to the lug at the top/RH on the sub panel...where the neutral is. it kind of look off green to me but not for sure. Looks out of place to me also.
I think you may have spotted something the rest of us were overlooking. Good catch.

Certainly worth checking out.
 
  #28  
Old 04-02-13, 07:55 AM
Member
Thread Starter
Join Date: Mar 2013
Location: USA
Posts: 41
Received 0 Votes on 0 Posts
If you look just to the left of the Neutral wire and just above the first screw on the Neutral bar you can see where the bonding screw goes. The green screw is a trick of the light being cast on it. It is really silver in color and holds the plastic insulator to the case.

I appreciate the compliment on the wiring job. I guess the old fart, that taught me, did a good job of teaching after all. Some of you may remember the copper collars they used to bond ground wires together. I must have gone through 100 of them before the old fart finally said I did it correctly. I still use them today.
 
  #29  
Old 04-12-13, 09:32 AM
Member
Thread Starter
Join Date: Mar 2013
Location: USA
Posts: 41
Received 0 Votes on 0 Posts
Compleated Sub Panel Project

I wanted to show what the completed sub panel looked like. I see so many questions and answers but very few pictures of what the owner finally did with the project. In any case here is mine:Name:  Insidepanelfaceinstalled.jpg
Views: 17908
Size:  35.7 KBName:  Outerdoorclosedsubpanel.jpg
Views: 5829
Size:  25.2 KB
 
Attached Images  
  #30  
Old 04-12-13, 10:15 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,941
Received 30 Votes on 26 Posts
The connector at the top of the panel is not listed for use with that many or size cables.

If you had used an indoor rated box you would have had knockouts you could have secured the cables in using the correct clamps.
 
Reply

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


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: