100 sub panel to attached garage

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  #1  
Old 02-28-14, 10:23 AM
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100 sub panel to attached garage

Hi,
I am sure this has been posted but so far I just keep seeing variations to my particular situation so I thought I would just ask.

I have an attached garage which is about 60 feet from my main 200 amp box
I would like to run 70 amp or more to sub panel or to a straight plug[/U][/B] to my garage for an electric car charger and possibly 2 in the long run.
I need to run the wire in my crawl space so I believe it needs to be outdoor/wet rated.

We are doing it ourselves so more money on materials is ok if it makes the whole process easier so I was thinking of getting THWN Cable with 3 hots and a ground all in one. I do not want to deal with Conduit given the tight space under the house

I have found the following options both rated to 75 degrees from Wire and Cable to Go
#6-3C THHN-PVC Tray Cable with #8 Ground - max amps 65
#4-3C THHN-PVC Tray Cable with #8 Ground - max amps 85
#2-3C THHN-PVC Tray Cable with # 6 Ground - max amp 100

I have read, not sure if its true that cable makes the amp rating lower since the wires are close to each other for heat issue
Can you confirm the that the max amps are correct and does it make a difference in terms of wire choice if I do a plug or a sub-panel. Lastly, there is no brand on the wire, should I be concerned or look for a "brand" of wire?

Thanks for the help
 
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  #2  
Old 02-28-14, 10:36 AM
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I was thinking of getting THWN Cable with 3 hots and a ground all in one.
THWN is not a cable, but a single individual conductor. I would not recommend tray cable for this project, but would recommend UF-B cable if your AHJ requires a wet rated cable in a crawl space. The tray cables you listed are for 3-phase, 3 hots and a ground. All you need is 2 insulated conductors and 1 ground for 240 volts. I'd ask the AHJ if they would allow Type NM-B (aka romex) cable for this project.
 
  #3  
Old 02-28-14, 10:44 AM
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Conduit reduces rodent damage. Do you need 120/240 or just 240 for the charger? If 240 only you need 3 wires. With conduit at a later time you can pull two more wires (ground shared) for the second charger. No subpanel needed. Explain in detail the problem with running conduit. Generally with conduit you do not have to get under the house except at the beginning and end. Just push it from point A to Point B adding conduit as you push. It could be buried around the outer perimeter of the house also.

Does a single charger require 70 amps or was that for two chargers? #6 THWN should be okay for 70 amps if all connectors are rated 75. The receptacle may not be so figure on #4. 1" conduit should be big enough but guessing at details so may not.
 
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Old 02-28-14, 11:23 AM
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In addition you may want to talk to your power company to see if any upgrades are needed to their infrastructure. You may be looking at a service increase for your house.
 
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Old 02-28-14, 11:47 AM
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I only need 240v - I already have other 120v lines wired for the garage from the main panel

Thanks for the reply - the Conduit is an issue based on how my foundation is run, its would be a pain to get PVC or any straight non bending material into the space. Could I possibly use Metal Cable ?

Foundation in my house runs like connecting U bends, so the only space is where the brackets lie above the footing but below the house, its also not a straight shot, we would need to bend the conduit 90 degrees or so to get it into the garage, I would guess its about a 10 ft offset for the box and the garage

I was trying to run large amps so I don't have to do this again, sign!! but might be better of just going with 60amps - can I just use UF-B wire for that??

The charger I am getting is suppose to be 60amps, but my car will only pull 40amps (limit of car)
The units uses a 14-50 plug - what breaker would you use 50amps or 60amps, I am a bit confused by the receptacle/breaker
 
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Old 02-28-14, 11:50 AM
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I forgot, in case this makes a difference, I am in California - LA County - City of Hawthorne
What does AHJ stand for ?
 
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Old 02-28-14, 12:38 PM
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but might be better of just going with 60amps - can I just use UF-B wire for that?
Yes.
The units uses a 14-50 plug -
So it is 120/240 not 240. You will need 3-conductor +ground. A 50 or 60 amp breaker will be okay but if you plan to eventually use two then you need a 100 amp feed to a subpanel (3-2 or 2-2).
 
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Old 02-28-14, 07:17 PM
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What does AHJ stand for ?
Authority Having Jurisdiction, usually that would be your local building department.

the Conduit is an issue based on how my foundation is run, its would be a pain to get PVC or any straight non bending material into the space.
It would be a rare conduit installation to not have any bends. A conduit installation would be the best, but not usually necessary in residential work. Considering that what you need is 120/240 volts, I'd use 6-3 UF-B cable (it has a ground wire in it).
 
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Old 02-28-14, 07:22 PM
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You could use a mixture of non metallic Seal-Tite flexible conduit and PVC conduit.
 
  #10  
Old 03-02-14, 08:31 AM
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SDT or Tray cable

THWN is not a cable, but a single individual conductor. I would not recommend tray cable for this project, but would recommend UF-B cable if your AHJ requires a wet rated cable in a crawl space. The tray cables you listed are for 3-phase, 3 hots and a ground. All you need is 2 insulated conductors and 1 ground for 240 volts. I'd ask the AHJ if they would allow Type NM-B (aka romex) cable for this project.

Read more: http://www.doityourself.com/forum/el...#ixzz2uoqzSE2F

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Nothing wrong with using SDT cable / tray cable .

Around here , I can buy it by the foot & not have to buy a roll , if I do not need that much .

But if you have rodents , conduit or armored cable is not a bad idea .

If moisture is a problem , SDT cable is rated direct burial , so is water proof ( or as water proof as anything ever is ) .

I would use cable with 3 insulated conductors and an earth ground . The insulated conductors should be identified as 1 , 2 , 3 or A , B , C . Use white or grey tale at on each end of one of the conductors to mark it as the neutral . I would mark the # 3 or the C . I would also mark the # 2 or B as the red phase & let black remain black .

I am guessing you are originating at a residential 120/240 VAC single phase loadcenter ?

God bless
Wyr
 
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