Questions re: Installing 6 AWG Wiring for Tesla Charging

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Old 11-18-18, 02:39 PM
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Questions re: Installing 6 AWG Wiring for Tesla Charging

Hi All,
My house was built in 1981. I'm getting a Tesla and will want to improve the charging capability available in my home. I currently have two NEMA 10-30 240-volt receptacles in my garage that have 10-gauge wiring, and are connected to separate 20-amp breakers. Although these receptacles use only (3) 10-gauge wires, it looks like the cable coming to them has 5 10-gauge wires (i.e., 2 wires are not used). My circuit breaker box's biggest breaker says 70 amps, probably for the furnace or AC, which tells me that I should have at least 60 amps available.

1. Can I change one of the 20-amp breakers to a 30-amp breaker, since the wiring is 10 gauge? The actual plug receptacles have a "30" on their fronts, and that implies to me that they can handle 30 amps. Each 240-V receptacle is on its own breaker.

2. At some point, I would like to run heavier cable from the breaker box to a better location in my garage, for the Tesla. I already have 3 x 50' of 6-gauge THHN/THWN-2 and 1 x 50' of 8-gauge, and am wondering if I could run these wires through my attic , dropping them down at the circuit breaker box and at the garage receptacle location. I would leave the wires un-connected on both ends and have a licensed electrician complete the work. Basically, I'm trying to reduce the electrician's effort by running the wiring through difficult-to-reach areas of my attic myself. Of course, it would also greatly reduce the cost of the electrician, and his/her pain as well, since I doubt most electricians would be keen on crawling 80+ feet on their hands and knees to reach the garage area of my attic.

3. Is THHN/THWN-2 adequate for up to 60 amps "within walls"?

4. Assuming an electrician would be ok with my running the 4 cables (three 6-gauge and one 8-gauge) myself so they don't have to, what conduit do I need to use? I assume I need to use conduit, but the type of conduit, and diameter, I'm not sure about.

Any advice will be greatly appreciated!
Thank You!
 
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Old 11-18-18, 02:51 PM
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1 - yes
2 - see #4
3 - #8 will handle 60A ok.
4 - THHN are individual conductors and need to be inside a conduit. 3/4" would be adequate for this application.
 
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Old 11-18-18, 03:21 PM
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Thank you, Pjmax!

Would most electricians be ok with my running the wiring through the attic myself?
And, do you mean that each THHN wire has to have its own individual 3/4" conduit, or that all the wiring can be in one 3/4" conduit? I don't think they'll fit. Is there a table somewhere showing what size conduit will handle 3x6 and 1x8? Also, is gray PVC adequate?

Thx again!
 
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Old 11-18-18, 03:41 PM
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Code requires all current carrying wires for a circuit must be in the same conduit.
"Gray PVC" is conduit and suitable for your purposes.
" conduit is rated for four #6 but 1" will be an easier pull.
 
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Old 11-18-18, 04:50 PM
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A little excerpt for you......

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Old 11-18-18, 05:29 PM
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4. Don't assume anything. Contact the electrician before you do any work. Many pros do not like coming in behind a home owner to finish the job.
 
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Old 11-18-18, 06:51 PM
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My circuit breaker box's biggest breaker says 70 amps, probably for the furnace or AC, which tells me that I should have at least 60 amps available.


Yes, most likely you do have 60 amps available for sure when the furnace or A-C is not running. But, what about when it is running? I'd start by checking on the size of the service entrance to the house.
 
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Old 11-25-18, 08:48 AM
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I got sidetracked by the holiday....
Good advice and the table was just what I was looking for. I will find an electrician, have him come out & take look, and go from there.
I hadn't thought about the A/C sucking up all the power...
The conduit coming into the house looks like about 4" diameter, but I didn't actually measure it.
Thanks!
 
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