Subpanel/stranded wire

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  #1  
Old 07-06-05, 07:58 PM
DanG
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Subpanel/stranded wire

I am going to install a 125 Amp 20 slot Square D subpanel to the existing 200 Amp Main service Panel. The Breaker will be 100 Amps double pole. I have to use stranded wire to run through conduit of ~50 feet. I have not used stranded wire before. The electrical runs will be 12 Gauge/20amp for 6 dedicated locations of 120/240 volt outlets/switches. I have normally used romex and Uf wire previously. 1)Could someone give me an idea what stranded wire I need to run thru the conduit? A hot, neutral, ground or an additional hot for this particular setup? Please give me some background on stranded wire types and cost? 2)What size feed line do I need to connect the 100 Amp breaker to the MLO subpanel? 2 or 4 Copper 3) What size conduit should I use 3/4"or 1" and also metal or plastic conduit? Any advice would be appreciated. Thank you.
 
  #2  
Old 07-06-05, 08:43 PM
R
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Sounds like you're mounting the subpanel next to the main panel and then running 6 circuits somewhere else 50 ft away? Can you mount the subpanel close to where you want these 6 circuits?

What are you wiring? Something inside the house? A detached building?
 
  #3  
Old 07-06-05, 09:41 PM
W
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I respectfully suggest that you need to do quite a bit more reading on your own prior to starting this project. Your questions indicate that you don't know the basics of multi-wire circuits (which are not recommended as branch circuits, but which are almost universally used for feeders to sub panels), ampacity of conductors, sizing of conduit, etc.

The problem with electrical installations is that there are many, many details that you must get right, and there is no way that a few internet postings can give you all of the information that you need. The best way to use this forum is to first read the books, and then ask questions about things that you don't understand.

I'd suggest the book 'Wiring Simplified' and anything by Rex Cauldwell. I am sure that there will be other suggestions.

Regards
Jon
 
  #4  
Old 07-07-05, 11:14 AM
P
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Apparantly , you need to run a raceway for a 100-amp Feeder across and on "finished" wall & ceiling surfaces such as sheetrock and masonary, approx lenth of 60 ft.

Use 1" PVC conduit for the raceway, and three #3 THHN conductors, one of them White, for the Feeder, and a Green #8 stranded wire for the required Equiptment Grounding Conductor.

Good Luck & Enjoy the Experience!!!!!!!!!
 
  #5  
Old 07-07-05, 05:22 PM
DanG
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Followup-subpanel

I appreciate all your feedback. To clarify the project, I will be mounting the subpanel right next to the main panel. I will be running conduit out the back of the building and over ~10 feet then re-enter the building for the last 40 feet. This is located in my garage where it is attached to my house but has a flat roof. This route is easier to access the needed outlets for the run. I checked the NEC for the feeder line and it states to use either #4 Cu or #2. Which do you gentleman prefer? I know the stranded wire (12 gauge) is easier to run through the conduit than romex or UF. The advantages of metal conduit is the grounding capability but I like PVC because of its ease of use. What do you recommend? These 6 dedicated lines/runs are to feed 6 different 20amp /250 volt outlets. Primarily their use will involve an air compressor and vacuum system. Also and air conditioner/heating system. I put a generator/transfer panel in ~5 years ago but it had a 60 amp breaker and I used a #6 Cu feeder line at that time. I just wanted some advice from the experts before tackling this job.
 
  #6  
Old 07-07-05, 09:25 PM
W
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Dan,

I repeat my suggestion above. You need to pick up more background prior to running this project. Here are the issues that jump out at me:

If you are running 6 240V circuits in a single conduit, then you will need 12 conductors; if any of these are 120/240V circuits, then you have even more conductors. When you have that many conductors in a single conduit, you need to consider _derating_, and use larger conductors. For a 20A circuit you may be required to use 10ga or even 8ga conductors.

The feeder conductors between the main panel and the sub panel must be at least 3ga copper or 1ga aluminium. The #4/#2 information that you have is incorrect, either from misusing the 90C column of 310.16 or from misusing 310.15.

If you are running a conduit both inside and outside of a heated space, then you have to consider issues of temperature difference and condensation. Warm, moist air from inside could condense moisture in the code portion of the conduit on the outside.

For your application, I would probably want to use PVC conduit. I would use stranded THHN/THWN for the run in the PVC, #10 (or #8 depending upon the exact number of conductors and the derating required). I would use #3Cu between the panels. I would try to place the subpanel closer to the loads, rather than near the main panel. I am certain that a careful design review would result in other changes.

-Jon
 
 

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