Installing Level 2 at Home (SOOW vs. NM-B) Which one?

[goldbrick]

SOOW isn't rated for this application. While it would probably work, it won't be up to code.

If you want to use 1 piece of wire with no GFCI I'd use 8/2G UF cable. It is rated for indoor or outdoor use and it can be run inside conduit for protection. NM-B, even inside conduit, isn't rated for outdoor use.

With a 14-50 receptacle there will be 4 terminals. The L1 and L2 are obvious. I'd connect the bare ground wire to the ground terminal and leave the neutral terminal open. I'm not 100% sure that is the best way to do it though, so you might want to read up on that.

Actually, now that I think about it.....I'd run 8/3G UF and connect L1, L2, N and Ground at the receptacle and breaker box.

 

[pr0lab]

thank you again. This is very interesting as I love to learn and understand what and why I am doing.

re-read your reply again....

I assume you are talking about this cable https://www.homedepot.com/p/Southwire-50-ft-8-3-Gray-Stranded-CU-UF-B-W-G-Wire-14783522/300916642 Could you please confirm?

What you are saying that at the breaker I only need to connect the 2 Ls to the breaker and the ground and neutral will go to their respective buses. did I get it right?

Additionally, what would recommend using to secure the cable to the joist? it looks like it's a 1" cable, is there a specific requirement for how to secure there to the wood? Something like that would work? https://www.homedepot.com/p/Gardner...raps-for-6-SER-Cable-5-Pack-GSE-505/100123363

Also - as I am thinking of doing this once, is it worth connect the 50 amp breaker with #6 THWN cables in a conduit? Is there an issue having a 50 amp breaker and wire while I am using only 30 amps? (I get that it's only 80% of the 50 amps)

 

[jlv]

You meant 14-50 receptacle

Yes; fixed. I'm a bit zoned out today, having just gotten a booster shot last night.

 

[jlv]

but if you do use a 40, then clearly and permanently label the outlet "40 Amp Maximum."

Except that the label should be "32 Amp Maximum" when using a 40A breaker.

And then you might just forget and plug in something that takes a 14-50.... and have it pull 40A. E.g., a Tesla UMC selects the max amperage to tell the car based upon the adapter that is plugged into it. Use a UMC1 with the 14-50 pigtail and it will tell the car to pull 40A. You have to remember to manually override this in the car (which a Tesla car lets you do; other cars might not).

It's far better long run to just wire it for the chosen receptacle.

 

[jlv]

Also - as I am thinking of doing this once, is it worth connect the 50 amp breaker with #6 THWN cables in a conduit? Is there an issue having a 50 amp breaker and wire while I am using only 30 amps? (I get that it's only 80% of the 50 amps)

Yes, if you have a 50A breaker, appropriate wiring, and a 14-50 outlet, then there is no issue just pulling 30A from it (or 27.5A if using a LEAF).

What you are saying that at the breaker I only need to connect the 2 Ls to the breaker and the ground and neutral will go to their respective buses. did I get it right?

You are asking for advice on the Internet on wiring something that can/has caused fires when wired incorrectly. If you don't know exactly what you are doing, you might instead consider hiring an electrician to do this for you.

 

[goldbrick]

I assume you are talking about this cable https://www.homedepot.com/p/Southwire-50-ft-8-3-Gray-Stranded-CU-UF-B-W-G-Wire-14783522/300916642 Could you please confirm?

What you are saying that at the breaker I only need to connect the 2 Ls to the breaker and the ground and neutral will go to their respective buses. did I get it right?

yes and yes

Additionally, what would recommend using to secure the cable to the joist? it looks like it's a 1" cable, is there a specific requirement for how to secure there to the wood? Something like that would work? https://www.homedepot.com/p/Gardner...raps-for-6-SER-Cable-5-Pack-GSE-505/100123363

This is the kind of thing your inspector will check. In general you need to use staples that are designed for this type of cable, and use one within 12" of each junction box and spaced 4' or less otherwise (I think, please check this). Don't bend the cable too tightly and don't run the cable on the bottom of floor joists. I know that last part is vague but once again, that's why you do an inspection - so someone who knows all these little details can make sure it is done properly.

Also - as I am thinking of doing this once, is it worth connect the 50 amp breaker with #6 THWN cables in a conduit?

That's a lot of extra work and it will only be useful if you get an EVSE in the future that requires 40A (continuous) instead of 32A (continuous). That could happen but it wouldn't be worth the extra trouble to me for that difference.

 

[SageBrush]

You are asking for advice on the Internet on wiring something that can/has caused fires when wired incorrectly. If you don't know exactly what you are doing, you might instead consider hiring an electrician to do this for you.

OP has since deleted a question whether to buy a single pole or two-pole breaker. That is a red flag that he is over his head.

 

[SageBrush]

That's a lot of extra work and it will only be useful if you get an EVSE in the future that requires 40A (continuous) instead of 32A (continuous). That could happen but it wouldn't be worth the extra trouble to me for that difference.

I'm of fan of 50 Amp circuits for 40 Amp continuous because I like plugs, but EVs seem to be heading towards 48 Amps Max OBC as a quasi standard. Admittedly that requires a hard wired EVSE but it would be one reason to use #6G wire. The other reason, if the run is a long one, is to reduce voltage sag. The Nissan EVSE, e.g. is known to be picky.

As for why strive for 48 Amp charging, that is an age old question . Overnight much lower Amp ratings are fine; the advantage pops up when one forgets to plug in the night before.

OP has still not figured out what his electrical panel can handle, so this comment is entirely general.

 

[pr0lab]

Thank you all. I have much better clarity.

From my understanding running the #6 THHN wires more work since you need a conduit but it's probably better for the long run, anyhow the car will only use 27 amps, even if I have a 50 amps breaker (double pole, previous q was deleted as it doesn't make sense for 240).

If anything, my understanding and pls correct me here, is that having a larger wire capacity and breaker will be safer since the cable is not going to overhead on a low load.

additionally, the THHN is rated for outdoor use if used in conduit so I think this is also more appropriate with the code? What I am not sure if what size conduit do I need for these 4 cables 3/4 or 1".
OR even just getting the UF cable https://www.homedepot.com/p/Southwi...O2mBIGS6GrDwhoN0K4saAo86EALw_wcB&gclsrc=aw.ds and installing it instead of the 8/3 with a 50 amp

Again not sure if there is a drawback installing 50 amp (40 in reality based on 80% rule) for a leaf. Thinking that in the future I may upgrade to a nicer charger or get another EV car down the road.

 

[LeftieBiker]

Again not sure if there is a drawback installing 50 amp (40 in reality based on 80% rule) for a leaf.

If it were me, I would go with the 50 amp capable cable, and a 40 amp breaker, with a 14-50 outlet labeled 40A. The reason is that I think a 50A breaker might be a little slower to trip if a 27.5 amp load was beginning to short. I may just be over-cautious on this.

 

[jjeff]

Again not sure if there is a drawback installing 50 amp (40 in reality based on 80% rule) for a leaf.

If it were me, I would go with the 50 amp capable cable, and a 40 amp breaker, with a 14-50 outlet labeled 40A. The reason is that I think a 50A breaker might be a little slower to trip if a 27.5 amp load was beginning to short. I may just be over-cautious on this.

That's not a bad idea, I also like to match the load more closely to the breaker but then again it would require possibly purchasing another 2 pole breaker in the future(<$50). It would also require opening up the breaker panel and hooking up the new breaker, and #6 wire is very stiff and hard to work with. That said if you'd already had a 14-50 outlet with a 50a breaker or were to plug into an outlet in the wild, you wouldn't have the luxury of changing the breaker so you might just want to use a 50a breaker and call it good. Not sure on your conduit size question, maybe someone else will know. I'm glad you are planning on running a neutral, while an EVSE doesn't need it, again it would be nice for future proofing in case you ever want to plug something else in, like an RV, which would require the neutral.

 

[SageBrush]

I'm about 98% sure that my 3/4" EMT holds three #6G THHN conductors and a bare ground wire. A Google search will tell you the cross-sectional area of each conductor, the cross-sectional area of the conduit, and how much of the cross-sectional area of the conduit may be used.

By the way OP, you have to ground the EMT. My way is to use a connector lock-nut with a ground lug. The grounding wire goes from ground lug to ground electrode.

 

[pr0lab]

Thank you everyone for your help!

I am looking at the sizing and wondering is there a reason why #8 THHN wire https://www.homedepot.com/p/Southwi...anded-CU-SIMpull-THHN-Wire-20490999/204632886 would not work? it's rated for 55 amps https://www.cerrowire.com/products/resources/tables-calculators/ampacity-charts/ looking at the ampacity chart

 

[wwhitney]

Calling @wwhitney for the real answer.

Apparently this forum doesn't implement that feature, I didn't get any notification and don't see a notification option for it. Anyway, let me address various incorrect information:

- I suggest the OP hire an electrician to do this job; don't do the job if you don't have a torque screwdriver and know when to use it.
- Cord (such as SOOW) is not to be used in place of the fixed building wiring. (NEC 400.12(1)) So not appropriate for this job.
- NM cable (Romex) is not to be used outside, even in conduit (334.12(B)(4) and 300.5(B))
- UF is the wet location version of NM and would be fine to use if not exposed to damage (a subjective call). UF can be used for the whole run to avoid a splice.
- It's fine to use a 50A receptacle on a dedicated 40A circuit (210.21(B)(1)). Labeling the receptacle is a nice, optional touch ("40A circuit"; 32A max only would apply to continuous loads, like an EVSE).
- An EVSE only needs a 240V circuit, so if it is has a 6-xx plug on it, or is to be hardwired, the circuit only requires 2 circuit conductors (plus EGC). But if it has a 14-xx plug on it, then a 14-xx receptacle is a 120/240V receptacle, and requires 3 circuit conductors.
- The 2020 NEC, in addition to expanding the GFCI requirements for outdoor receptacles, requires GFCI protection for any receptacle used for an EVSE (625.54). I believe this was added as a TIA (amendment) to the 2017 NEC, so it applies to jurisdictions under the 2017 NEC that have adopted the TIA, as well.
- NM, UF, and LFNC are 60C wiring methods, so ampacities should be taken from the 60C column. Most other wiring methods are 75C, so the 75C column can be used, if the equipment terminations at both ends are so marked. Most insulation is actually 90C rated, which is primarily useful for derating purposes
- A properly made up EMT connector between a metal enclosure and the EMT provides the necessary bonding. The EMT can be used as the EGC itself, in lieu of a wire-type EGC, although that has fallen out of favor, not necessarily for any good reason.

Cheers, Wayne

 

[SageBrush]

Thanks Wayne !

- The 2020 NEC, in addition to expanding the GFCI requirements for outdoor receptacles, requires GFCI protection for any receptacle used for an EVSE (625.54). I believe this was added as a TIA (amendment) to the 2017 NEC, so it applies to jurisdictions under the 2017 NEC that have adopted the TIA, as well.

Is this requirement waived if the EVSE has GFCI built-in ?

 

[LeftieBiker]

I was about to ask something similar. You don't want to piggyback GFCI on GFCI. Is there such a thing as a GFCI that can be switched off? I can see why you'd want GFCI on a general use or RV circuit, but it could cause problems with an EVSE. The way around that would probably be to omit the GFCI and hardwire the EVSE and label it...?

 

[pr0lab]

Calling @wwhitney for the real answer.

Apparently this forum doesn't implement that feature, I didn't get any notification and don't see a notification option for it. Anyway, let me address various incorrect information:

- I suggest the OP hire an electrician to do this job; don't do the job if you don't have a torque screwdriver and know when to use it.
- Cord (such as SOOW) is not to be used in place of the fixed building wiring. (NEC 400.12(1)) So not appropriate for this job.
- NM cable (Romex) is not to be used outside, even in conduit (334.12(B)(4) and 300.5(B))
- UF is the wet location version of NM and would be fine to use if not exposed to damage (a subjective call). UF can be used for the whole run to avoid a splice.
- It's fine to use a 50A receptacle on a dedicated 40A circuit (210.21(B)(1)). Labeling the receptacle is a nice, optional touch ("40A circuit"; 32A max only would apply to continuous loads, like an EVSE).
- An EVSE only needs a 240V circuit, so if it is has a 6-xx plug on it, or is to be hardwired, the circuit only requires 2 circuit conductors (plus EGC). But if it has a 14-xx plug on it, then a 14-xx receptacle is a 120/240V receptacle, and requires 3 circuit conductors.
- The 2020 NEC, in addition to expanding the GFCI requirements for outdoor receptacles, requires GFCI protection for any receptacle used for an EVSE (625.54). I believe this was added as a TIA (amendment) to the 2017 NEC, so it applies to jurisdictions under the 2017 NEC that have adopted the TIA, as well.
- NM, UF, and LFNC are 60C wiring methods, so ampacities should be taken from the 60C column. Most other wiring methods are 75C, so the 75C column can be used, if the equipment terminations at both ends are so marked. Most insulation is actually 90C rated, which is primarily useful for derating purposes
- A properly made up EMT connector between a metal enclosure and the EMT provides the necessary bonding. The EMT can be used as the EGC itself, in lieu of a wire-type EGC, although that has fallen out of favor, not necessarily for any good reason.

Cheers, Wayne

Thank you. To summarize, I am thinking of actually putting a 50 amp breaker and doing the 50 amp wiring so either #8 cable with rubber conduit or using the UF cable without conduit to the 14-50 outdoor receptacle. which would you recommend? which is the easier to work with? I like not having to deal with conduit in the UF 6/3 cable but it's very think too.

 

[wwhitney]

Is this requirement waived if the EVSE has GFCI built-in ?

Nope, to avoid it you need to hardwire your EVSE. The EVSE also has something GFCI-like built-in (without specifying if the trip characteristics exactly match that of a GFCI), and there is an older requirement that that functionality has to be within 12" of the plug for cord-and-plug connected EVSEs (so only a 12" cord, or built into the plug or cord). Both requirements are in force.

You don't want to piggyback GFCI on GFCI. . . . it could cause problems with an EVSE.

No problems with GFCIs in series, other than that if you get an actual ground fault, it is indeterminate which one (or both) will trip. Not a problem for the EVSE.

Cheers, Wayne

 

[wwhitney]

Thank you. To summarize, I am thinking of actually putting a 50 amp breaker and doing the 50 amp wiring so either #8 cable with rubber conduit or using the UF cable without conduit to the 14-50 outdoor receptacle. which would you recommend? which is the easier to work with? I like not having to deal with conduit in the UF 6/3 cable but it's very think too.

See my advice about hiring a professional. Or at least get a knowledgeable friend to help. Do you have a torque screwdriver?

A cable is an assembly of multiple wires. With conduit, you'd typically use individual wires.

Conduit is not made of rubber.

6/3 UF and a 50 amp GFCI double pole breaker would allow you to install an outdoor 14-50 receptacle without any need for a changeover in wiring method or splice. Or 8/3 UF and a 40 amp GFCI, with the optional but good idea label.

Cheers, Wayne

 

[SageBrush]

Is this requirement waived if the EVSE has GFCI built-in ?

Nope, to avoid it you need to hardwire your EVSE. The EVSE also has something GFCI-like built-in (without specifying if the trip characteristics exactly match that of a GFCI), and there is an older requirement that that functionality has to be within 12" of the plug for cord-and-plug connected EVSEs (so only a 12" cord, or built into the plug or cord). Both requirements are in force.

I'm a bit dense today. Am I reading you correctly that a hard-wired EVSE with a short cord and with GFCI built-in does not require a GFCI breaker according to 2020 NEC ?

Your other sentence about older requirements has me confused. Are you talking about pre NEC 2020 which is now deprecated for those jurisdictions that require NEC 2020, or can an EVSE with a short cord to the receptacle still pass NEC 2020 without a GFCI breaker ?