Best plug type for EV charger?

[hmcgregoraz]

Still cannot figure out why all our houses are not burning down in Canada. I used Romex 6/2 for both my wall connectors, rated at 75amps. Have searched and cannot find the physical difference between NMD90 Canadian spec and NM-B90 US spec. 6 gauge copper is 6 gauge copper and will easily support over 60 amps however there must be something with the insulation that sets them apart. Regardless, not acceptable to use this in the US.

If you live in Canada, yes Romex 6 gauge is more than adequate as it is rated at 75A. NMD90 6/2 Cu G Rd 492R | Southwire

I suspect it is based on expected ambient temps. Canada, even in the summer, at least used to not get to the temps that most of the southern US gets to.

The primary reason NM-B is derated to 60C is due to the expected ambient temp in attic and crawl spaces, etc.

-Harry

 

[hmcgregoraz]

A good many of us Tesla owners have been charging on 220v 50-amp circuits for years, from an outlet, and have never experienced any problems with that setup. An EVSE is a waste of money, and higher charge rates are unnecessary since we charge overnight. I bought and wired my own outlet in my garage. The outlet cost me (ten years ago) about $10, the wire not a whole lot more for #6 romex. I cannot understand why people need some fancy junk on the wall just to charge their car, when this set up has done the job for me since 2012.

Remember, Tesla has decided to stop shipping the mobile connector with newly sold vehicles.

Personally if you don't have an EV yet, put in a 14-50 (yes, with the unnecessary neutral wire), on NM-B 6/3 with 50 amp breakers, with a mobile connector this may be limited to 32amp charging, depending on the version of mobile connector). You can always change it to a wall connector with 40amp charging later.

If you do have a Tesla already or will soon, put in a wall connector with NM-B 6/3 with 50 amp breaker (max 40amp charging). If you need to run conduit, use #6 THHN without the neutral, and a 60amp breaker. The difference between 40amp charging and 48 amp charging is minimal and IMHO not worth the cost in most cases.

We did install conduit and THHN, and 100 amp breakers, but will most likely have to swap out one of them for a 60amp breaker when we install our powerwalls to be able to keep it on the backup load side of the panel. We also have a 14-50 on the outside wall next to the inside wall connector, and I am planning to put a second wall connector in and use the power sharing function (Gen2, with a wire) between the two. Already have it stubbed out to do it.

-Harry

 

[wwhitney]

If you do have a Tesla already or will soon, put in a wall connector with NM-B 6/3 with 50 amp breaker (max 40amp charging).

If you are hardwiring a wall connector, you can omit the unnecessary neutral and use 6/2 NM.

If you can locate 6-6-6 copper SEU (harder to find than NM cable), then you could use that on a 60A breaker, and you end up with an oversized EGC. Unless you are subject to the 2014 NEC and it would run through thermal insulation, then you'd be limited to 50A like NM cable is.

Cheers, Wayne

 

[STS-134]

If you do have a Tesla already or will soon, put in a wall connector with NM-B 6/3 with 50 amp breaker (max 40amp charging). If you need to run conduit, use #6 THHN without the neutral, and a 60amp breaker. The difference between 40amp charging and 48 amp charging is minimal and IMHO not worth the cost in most cases.

If you're doing a new install, why not? It's only materials costs and the labor is exactly the same. If it's already installed then yeah, you can continue using that wiring until it no longer meets your needs, but I don't think it makes sense to use smaller wiring on a new install, ever.

 

[h2ofun]

If you're doing a new install, why not? It's only materials costs and the labor is exactly the same. If it's already installed then yeah, you can continue using that wiring until it no longer meets your needs, but I don't think it makes sense to use smaller wiring on a new install, ever.

I thought specs I read on NM-b 6/3 says 60 amps?

 

[wwhitney]

I thought specs I read on NM-b 6/3 says 60 amps?

Negative. 55A.

Cheers, Wayne

 

[STS-134]

Negative. 55A.

Cheers, Wayne

That's probably why my electrician used 4/3.

 

[h2ofun]

Negative. 55A.

Cheers, Wayne

So, the engineering approved drawings say thhn/thwn-2 #6, 3/4 inch emt conduit

They used nm-B 6/3. About 100 feet. 60 amp breaker. Have they no done this to code, and the drawings? If not, should I try to get them to fix?

 

[wwhitney]

So, the engineering approved drawings say thhn/thwn-2 #6, 3/4 inch emt conduit

They used nm-B 6/3. About 100 feet. 60 amp breaker. Have they no done this to code, and the drawings? If not, should I try to get them to fix?

Yes, #6 Cu THHN in conduit has an ampacity of 65A, while #6 NM has an ampacity of 55A. So it's a code violation. And it's arguably a less robust installation, and doesn't match the plans. That's the argument for redoing. The letter of the requirements is clearly on your side.

The argument against redoing is that (a) if it's supplying a 48A continuous load (an EVSE), there's really no good justification for the NEC to require a 60A ampacity circuit, a 51A ampacity circuit would both be sufficient for protecting by a 60A breaker and sufficient for the load. This is not a widely held view, more my opinion of this corner case. (b) And perhaps that penalizing NM cable by reducing its ampacity isn't technically justified.

Up to you.

Cheers, Wayne

 

[h2ofun]

Yes, #6 Cu THHN in conduit has an ampacity of 65A, while #6 NM has an ampacity of 55A. So it's a code violation. And it's arguably a less robust installation, and doesn't match the plans. That's the argument for redoing. The letter of the requirements is clearly on your side.

The argument against redoing is that (a) if it's supplying a 48A continuous load (an EVSE), there's really no good justification for the NEC to require a 60A ampacity circuit, a 51A ampacity circuit would both be sufficient for protecting by a 60A breaker and sufficient for the load. This is not a widely held view, more my opinion of this corner case. (b) And perhaps that penalizing NM cable by reducing its ampacity isn't technically justified.

Up to you.

Cheers, Wayne

This wiring is from my inverters to generation panel, so nothing to do with evse.

I am assuming the inverter, when it is now running at 11.6kw is at full power? But if I read the spec, the max is 48 amps, so would not matter?

But for an EV, this does not work unless 4/2 but they do not make, and 4/3 nm is 10 bucks a foot

If this was your house, what would you do?

But, clearly its not what the engineer approved. Of course the inspector missed. Now, on line was nm-b 4/3, but they removed when they messed it up.
This is good I believe up to 75amps, or at least that is what the first installer company did?

 

[wwhitney]

This wiring is from my inverters to generation panel.

OK, I was wondering why there would be engineered drawings.

In that case I would certainly get it replaced if it was my house. A 48A continuous output inverter clearly requires conductors with a 60A ampacity, per NEC 690.8. So they could use #6 Cu with a 75C rating (not NM); #4 Cu with a 60C rating (NM); or #4 Al with a 75C rating.

BTW, #4 Cu with a 60C rating (NM) has an ampacity of 70A.

Cheers, Wayne

PS I do see now that my position is apparently inconsistent, in that I seem to think that a 48A continuous load should be OK with 51A ampacity conductor and a 60A OCPD (although the NEC clearly requires a 60A ampacity), but don't feel that way about a 48A continuous source. I'll need to think about that.

 

[h2ofun]

OK, I was wondering why there would be engineered drawings.

In that case I would certainly get it replaced if it was my house. A 48A continuous output inverter clearly requires conductors with a 60A ampacity, per NEC 690.8. So they could use #6 Cu with a 75C rating (not NM); #4 Cu with a 60C rating (NM); or #4 Al with a 75C rating.

BTW, #4 Cu with a 60C rating (NM) has an ampacity of 70A.

Cheers, Wayne

PS I do see now that my position is apparently inconsistent, in that I seem to think that a 48A continuous load should be OK with 51A ampacity conductor and a 60A OCPD (although the NEC clearly requires a 60A ampacity), but don't feel that way about a 48A continuous source. I'll need to think about that.

I wrote the installer this morning, pointed out the issue, and hope this will be fixed without having to take other actions. I have learned so much about this stuff. Glad I knew this before I installed EV charging. I would have assume NM 6/2 would have worked on a 60 amp breaker. Nope.

 

[holeydonut]

I've never understood why people advise something like "just plug in with the lower amperage, you'll fill up just fine to recharge overnight".

The reason you get the max charge rate available is to deal with the outlier-edge cases where you need as many suds as possible as fast as possible.

My household rarely remembers to plug in the car when they park. Like they're always busy trying to get the kids or groceries... and don't want to lug a dusty cable over to the car and plug it in. So, it usually ends up we're like "crap the car isn't charged" when we're getting ready to head out to drive across the Bay.

You want to be able to sneak in a charge at max amperage for an hour or so, that's why you want the highest possible charge rate. It's not like you'll be charging at 48A each day for funsies.

Oh, and when you host that mega charge party to soak up your NEM credits, we'll want 48A at each charge station. K-thx.

 

[STS-134]

I've never understood why people advise something like "just plug in with the lower amperage, you'll fill up just fine to recharge overnight".

The reason you get the max charge rate available is to deal with the outlier-edge cases where you need as many suds as possible as fast as possible.

My household rarely remembers to plug in the car when they park. Like they're always busy trying to get the kids or groceries... and don't want to lug a dusty cable over to the car and plug it in. So, it usually ends up we're like "crap the car isn't charged" when we're getting ready to head out to drive across the Bay.

You want to be able to sneak in a charge at max amperage for an hour or so, that's why you want the highest possible charge rate. It's not like you'll be charging at 48A each day for funsies.

Oh, and when you host that mega charge party to soak up your NEM credits, we'll want 48A at each charge station. K-thx.

Yeah, there are zero scenarios where being able to charge faster hurts you. There are scenarios where not being able to do it would be a problem. If you want to charge slower, you can always dial back the current level on your vehicle or at the EVSE, despite having wiring that can handle faster charging. But you cannot increase the current level beyond what your wiring can handle. And if you're doing a new install, it's just materials costs and labor is the same. It makes zero sense to skimp on materials because in the event that it's not enough, you'll be paying all of the labor costs twice, whether it is your own labor or someone else's, on top of the materials cost for twice the wiring (the wiring you should have bought in the first place plus the now useless lower capacity wiring that you now need to get rid of). Set things up to handle the maximum current your EVSE can supply and just wire a neutral, even if you don't need one. Do it right the first time so that you don't have to do it over.

 

[wwhitney]

And if you're doing a new install, it's just materials costs and labor is the same.

That, of course, assumes that the closest source (panel) has sufficient capacity. If it's a choice between a smaller circuit from nearby, or a larger circuit back from the main panel, then the price difference could be significant.

Cheers, Wayne

 

[STS-134]

That, of course, assumes that the closest source (panel) has sufficient capacity. If it's a choice between a smaller circuit from nearby, or a larger circuit back from the main panel, then the price difference could be significant.

Cheers, Wayne

In that case, I'd wire for at least 48A, but downsize the breaker and set the EVSE to charge at a lower current. Then when the panel is upgraded in the future, you just replace the breaker with a bigger one and don't need to run new wiring, and only need to purchase wiring and do the labor once.

If PG&E had let me do so, I would have upgraded my service to 200A on a 400A-capable service line. But due to the way PG&E's rules work, I had to go all the way to 400A even though I don't really need that much capacity (with everything in the house on, I'm not sure I even hit 200A, and if I do, it's in some artificial scenario that is likely to never occur, such as all stove burners on high, both ovens running, all AC units running, and all EVSEs charging at maximum rate, simultaneously). But it's really better to make sure you don't have to do something over because you underestimated your needs.

 

[wwhitney]

In that case, I'd wire for at least 48A, but downsize the breaker and set the EVSE to charge at a lower current.

That makes sense, although it runs into a technical violation if wired with NM cable. Namely when you upsize the ungrounded conductors you are supposed to upsize the EGC. But the EGC in larger NM cable (above #10) is sized for largest breaker the cable can handle. So when you downsize the breaker, you end up with an undersized EGC. Arguably a silly rule in this context, the intent is for long runs when you upsize for voltage drop.

Anyway if you can side step that issue, and if upsizing the feeder is a future possibility, I agree upsizing the branch circuit is good futureproofing.

Cheers, Wayne

 

[h2ofun]

OK, I was wondering why there would be engineered drawings.

In that case I would certainly get it replaced if it was my house. A 48A continuous output inverter clearly requires conductors with a 60A ampacity, per NEC 690.8. So they could use #6 Cu with a 75C rating (not NM); #4 Cu with a 60C rating (NM); or #4 Al with a 75C rating.

BTW, #4 Cu with a 60C rating (NM) has an ampacity of 70A.

Cheers, Wayne

PS I do see now that my position is apparently inconsistent, in that I seem to think that a 48A continuous load should be OK with 51A ampacity conductor and a 60A OCPD (although the NEC clearly requires a 60A ampacity), but don't feel that way about a 48A continuous source. I'll need to think about that.

So, how did your thinking go on your PS?

I so far have had no luck in the last 2 weeks trying to have V3 electric call me back with their position.

I just got off the phone with the inspector who signed off the job. Clearly, this was over his head, so he is going to do some more research
and would get back to me. I just said what was on the signed drawings, what I see on the spec to buy new (NM), and your data.
Clearly, everyone wants to not have to deal with, but he said, bottom line, if it does not meet code, it will have to be dealt with. I asked since he signed off, can he get them to fix it if it does not meet code, since I told him I would rather not go to the contractors board. Boy did he quickly say we should not have to do that, which implies, the county would be brought into this if I have to file.

 

[wwhitney]

So, how did your thinking go on your PS?

I guess I've decided that for both a 48A continuous supply (inverter) or load (EVSE), the NEC should allow a 55A ampacity conductor with a 60A breaker.

But it doesn't currently, it requires a 60A ampacity conductor with a 60A breaker. So as long as your sure your #6 copper cable is type NM or UF, and not type SE, TC, AC, or MC, then it's a clear cut violation. [Those last two have metallic cladding, so that would be obvious.] Just not a very consequential one, in my opinion, although I think most may disagree and consider it consequential.

Cheers, Wayne

 

[h2ofun]

I guess I've decided that for both a 48A continuous supply (inverter) or load (EVSE), the NEC should allow a 55A ampacity conductor with a 60A breaker.

But it doesn't currently, it requires a 60A ampacity conductor with a 60A breaker. So as long as your sure your #6 copper cable is type NM or UF, and not type SE, TC, AC, or MC, then it's a clear cut violation. [Those last two have metallic cladding, so that would be obvious.] Just not a very consequential one, in my opinion, although I think most may disagree and consider it consequential.

Cheers, Wayne

cable is clearly marked nm-b

I just need what is code, not what will work.