Subpanel with 2 DP breakers for 2x240 outlets

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  #1  
Old 03-13-14, 01:41 PM
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Subpanel with 2 DP breakers for 2x240 outlets

I just bought a Nissan Leaf and I want to put a level 2 EVCE into my garage. For the sake of flexibility, I'd like to put in a NEMA 14-50R outlet in and then plug the charger into that (the charger comes with the plug pre-installed; see it at HCS-40P, 30A, 240V Charging, 25′ Cord, NEMA 14-50 Plug | Clipper Creek Vehicle Charging Station). The car has the 6.6 kW "quick-charge" package, so it will be pulling 27.5A at 240V. In addition, I have an electric dryer (pulls 22A) that plugs into an outlet that was not properly wired (I just bought this house), and I would like to put in an outlet that is to code for that for safety reasons. I don't have space on my current main panel to put in 2 double-pole breakers, so I need to install a sub-panel. To save on money, I'd like to get all the equipment and rough-in the wiring myself, and then have an electrician come in and finish the job. Does anyone see any flaws in the plan below?

Note: this is an indoor job.

70A DP breaker in the main panel
1/0-1/0-1/0-2 Aluminimum SER to subpanel
Sub-panel = 100A rated with 6 slots (just in case I want to add a couple small circuits in the future)

To the outlet for the EVCE to plug into:
50A DP breaker
Copper 6-3 NM-B W/G cable to outlet
terminating at a surface-mounted 14-50R NEMA outlet

To the outlet for the electric dryer:
30A DP breaker
Copper 10-3 NM-B W/G cable to outlet
terminating at a surface-mounted 14-30R NEMA outlet

I should mention I was planning on the wiring for the EVCE to plug into to be 50A, (not the minimum required 40A) because I'd like to leave some leeway for possible upgrades in the future, not to mention that the charger I listed above says it needs a 50A supply circuit (although I'm not entirely sure why, as it's listed charging amperage is 30A). I would assume as long as I use the appropriate outlet, cable, and breaker, this should be OK.

Any comments or suggestions are much appreciated.

Edit: my service panel is rated at 200A
 

Last edited by Snoogans; 03-13-14 at 02:25 PM.
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  #2  
Old 03-13-14, 02:00 PM
Tolyn Ironhand's Avatar
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You did not post how many amps your service is now to handle the new loads you will be installing.

My only suggestion would be to install a larger sub panel then one that only has space for 6 circuits as 4 will be taken up by the charger and dryer. A larger panel will only run you about $50 compared to $30 for the smaller panel.
 
  #3  
Old 03-13-14, 02:23 PM
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The service panel is rated at 200A.

Since I could conceivably be using ~50A at one time through that panel (if the car was charging and the dryer was running at the same time), isn't it a good idea to limit the number of slots to ensure that the panel was not overloaded?
 
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Old 03-13-14, 02:29 PM
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200 amps should be fine.

If it was me doing it, I would install the subpanel right next to the existing panel and connect them together with conduit, or large offset nipple. You could then use smaller wire for 70 amps as you could use THHN or XHHW instead of cable, or install a 100 amp breaker and use #3 THHN or #1 XHHW. A 100 amp breaker might be close to the cost of a 70 amp.

I would then relocate some smaller loads from the main panel to the subpanel and put the dryer and charger in the main panel.
 
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Old 03-13-14, 02:30 PM
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I'd put the EV charger circuit in the main panel and put some lighter breakers in the subpanel.
 
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Old 03-13-14, 02:46 PM
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@ Tolyn - Interesting you say that, because I was planning on putting the subpanel on the opposite side of the wall from the service panel (back-to-back) and run a nipple between them for the wiring. What guage would you use for the THHN or XHHW, #2 copper?

@ both Tolyn and Justin - you both said to put the EV breaker and the dryer breaker in the main panel rather than the sub, and move the lighter stuff to the sub - Could you tell me why you would do it that way? I thought it would be safer to have the EV breaker in the sub right next to where the charger was just in case I need to shut it off in a hurry (i.e., it's just more accessible).
 
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Old 03-13-14, 04:29 PM
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It keeps the heavy loads in the main instead of the smaller sub panel.
 
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Old 03-13-14, 04:46 PM
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Back to back is a good plan. I would still use conduit to relocate the loads as I mentioned. (PC covered why. )

If you keep the larger loads in the main panel your sub panel could also be fed with a smaller feeder if you wish. Here is what wire size you would need for different amps: (Assumes THHN copper or XHHW aluminum individual wires. Numbers shown are maximums)
60 amps #6 Al
70 amps #6 Cu #4 Al
80 amps #3 Al
90 amps #4 Cu #2 Al
100 amps #3 Cu #1 Al

Remember to install a bushing on the conduit ends if you use wire #4 or larger.
 
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