redzev
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pulling wire; what gauge?

Thu Sep 01, 2011 7:13 pm

Just came home with a cayenne red Leaf and have been loving it so far.

We need to pull wires to make a dedicated circuit for charging. The 110V trickle charger is adequate for our driving needs now, but we want to future-proof the electrical installation in the event that we upgrade to a 220/240V EVSE later.

The panel is at least 50 feet from where the outlet will be.

AFAICT, for 110V charging we need:
- 20A breaker
- 12 gauge wire preferred (rather than 14), to reduce voltage loss
- standard polarized, grounded outlet (NEMA 5-15)

If we mod or buy a 220/240V EVSE, we would need:
- 40A breaker
- 8 gauge wire?
- whatever outlet the EVSE needs

First question: is any of the above incorrect?

Second: is there any harm in pulling 8-gauge wire now, to run at 110V?

Third: Can we get away with 10-gauge? I'm sure it's fine for 110V, but would it be safe for 220V?

smkettner
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Re: pulling wire; what gauge?

Thu Sep 01, 2011 7:39 pm

20a breaker requires #12 minimum and #8 is fine.
Ampacity and length determine the wire size not voltage.

The marginal cost of larger wire is negligable.
1 bar lost at 21,451 miles, 16 months.
2 bar lost at 35,339 miles, 25 months.
LEAF traded at 45,400 miles for a RAV4-EV
RAV4 traded in for I-Pace Dec 2018

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ttweed
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Re: pulling wire; what gauge?

Thu Sep 01, 2011 7:47 pm

Lots of info in this earlier thread.

TT
Tom Tweed
La Jolla, CA
Plowshare Media
2011 SLe #1317 del. 4/1/11
1st bar lost at 31,953 miles
2nd bar lost at 38,685 miles
3rd bar lost at 50,711 miles
4th bar lost at 59,758 miles after 64 months
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davewill
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Re: pulling wire; what gauge?

Fri Sep 02, 2011 10:15 am

redzev wrote:Second: is there any harm in pulling 8-gauge wire now, to run at 110V?
Here's what I would do in your shoes.
Pull the 8 gauge, but pull 4 wires (hot, hot, neutral, and ground). Use a double 20a breaker and wire both a 240v and a 120v (5-20R) receptacle. Use the 5-20R for 120v 12a charging now, later upgrade your EVSE (use an L6-20R) or buy the SPX PowerXpress (can be set for 12/16/24/32a, use a 6-30R), and use the 240v receptacle for 240v 16a charging. In the future, you can remove the 5-20R and convert the circuit to to 40a 240v if and when you get a car that can utilize the higher capacity.

OR (what I'd really do)

Forget about 120v charging and run the 40a 240v circuit now. Buy the SPX, set it for 32a, and wire it up. All done and future proofed for a reasonable cost.
2014 Rav4 EV, Blizzard Pearl White
2011 LEAF SL w/QC, Blue Ocean, returned at end of lease

amtoro
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Re: pulling wire; what gauge?

Fri Sep 02, 2011 11:50 am

davewill wrote:
redzev wrote:Second: is there any harm in pulling 8-gauge wire now, to run at 110V?
Here's what I would do in your shoes.
Pull the 8 gauge, but pull 4 wires (hot, hot, neutral, and ground). Use a double 20a breaker and wire both a 240v and a 120v (5-20R) receptacle. Use the 5-20R for 120v 12a charging now, later upgrade your EVSE (use an L6-20R) or buy the SPX PowerXpress (can be set for 12/16/24/32a, use a 6-30R), and use the 240v receptacle for 240v 16a charging. In the future, you can remove the 5-20R and convert the circuit to to 40a 240v if and when you get a car that can utilize the higher capacity.

OR (what I'd really do)

Forget about 120v charging and run the 40a 240v circuit now. Buy the SPX, set it for 32a, and wire it up. All done and future proofed for a reasonable cost.
Agree, but even in option 1, it is not recommended to install a receptacle for a higher current (6-30R) in a circuit rated for less (20A) even if you set the EVSE to 16A; it may lead to confusions and if an inspector is called in (which you should in any case, just to get the peace of mind and to have proof for your home insurance that the circuit is up to code) he/she will reject it.

Use #8 wire (#10 is still ok, but you get less voltage drop with #8) and a 30A two-pole breaker (or 40A if you want.

I just installer my SPX, consider buying it, it is a very nice unit.
---
2012 Nissan LEAF SL - Brilliant Silver
Delivery: Dec-5/11
Mods: Horn, XPEL paint protection film, AEGIS window film and VSP-off switch

tps
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Re: pulling wire; what gauge?

Fri Sep 02, 2011 7:14 pm

davewill wrote: Pull the 8 gauge, but pull 4 wires (hot, hot, neutral, and ground). Use a double 20a breaker and wire both a 240v and a 120v (5-20R) receptacle.
Does code allow the 240V and the 120V outlet on the same circuit??? I'm guessing you have to pull 5 wires: hot & neutral for the 120V outlet, 2 hots for the 240V outlet, and they can share the ground, so long as it can handle the full fault current from either circuit.

smkettner
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Re: pulling wire; what gauge?

Fri Sep 02, 2011 7:44 pm

tps wrote:
davewill wrote: Pull the 8 gauge, but pull 4 wires (hot, hot, neutral, and ground). Use a double 20a breaker and wire both a 240v and a 120v (5-20R) receptacle.
Does code allow the 240V and the 120V outlet on the same circuit??? I'm guessing you have to pull 5 wires: hot & neutral for the 120V outlet, 2 hots for the 240V outlet, and they can share the ground, so long as it can handle the full fault current from either circuit.
I think you would need to go to a subpanel and branch as needed.
1 bar lost at 21,451 miles, 16 months.
2 bar lost at 35,339 miles, 25 months.
LEAF traded at 45,400 miles for a RAV4-EV
RAV4 traded in for I-Pace Dec 2018

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planet4ever
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Re: pulling wire; what gauge?

Fri Sep 02, 2011 7:53 pm

redzev wrote:If we mod or buy a 220/240V EVSE, we would need:
- 40A breaker
- 8 gauge wire?
- whatever outlet the EVSE needs

First question: is any of the above incorrect?
Some of the responses addressed this implicitly, but it might be well to state explicitly that this isn't exactly correct. Only certain 240v EVSEs need a 40A breaker, and the current LEAF never uses more than 16A, so anything larger than 20A is only useful if you are planning for the future. (That includes the case of getting a 30A or 32A EVSE now.) And of course you don't need #8, or even #10, wire for a 20A breaker, though it never hurts to have heavier wire.

What you do need, though, is two breakers, at least 20A each, ganged together.

Ray
End of April 2013: Traded my 2011 SL for a 2013 S with charge pkg.

wwhitney
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Re: pulling wire; what gauge?

Fri Sep 02, 2011 8:46 pm

amtoro wrote:Agree, but even in option 1, it is not recommended to install a receptacle for a higher current (6-30R) in a circuit rated for less (20A) even if you set the EVSE to 16A; it may lead to confusions and if an inspector is called in (which you should in any case, just to get the peace of mind and to have proof for your home insurance that the circuit is up to code) he/she will reject it.
If you have a single receptacle on a circuit, then the rating can be anything equal to or greater than the breaker. If you have multiple receptacles on a circuit, then all their ratings should match the breaker rating. [Exceptions: 50A receptacles on a 40A breaker, and 15A receptacles on a 20A breaker.]
amtoro wrote: Use #8 wire (#10 is still ok, but you get less voltage drop with #8) and a 30A two-pole breaker (or 40A if you want).
If you use #10 wire, your breaker must be at most 30A [for almost all circuits, including EVSEs].

Cheers, Wayne

wwhitney
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Re: pulling wire; what gauge?

Fri Sep 02, 2011 8:49 pm

tps wrote:Does code allow the 240V and the 120V outlet on the same circuit???
Yes, I believe that you can do this, although since it is a multi-receptacle circuit, their ratings will have to match the breaker, e.g. 20A 240V and 20A 120V receptacles on a 20A breaker. Since the current on one of the hot legs will be additive, you couldn't use a full 20A on each receptacle simultaneouly, but this is no different than any other multi-receptacle circuit.

Cheers, Wayne

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