Why no neutral in the HPWC?

[EVer Hopeful]

I woke up in the middle if the night last night and, as you do, I went going over the installation instructions for the Wall Connector in my mind and it occurred to me that, there's no neutral connection. Just two energized conductors and a ground (which is probably only there as a fault protection)

So I wondered why this was

It also bother's me that I'm going to have this on a 30A 10 gauge THHN circuit coming from a Sub Panel, but that the Sub Panel is fed by 6/3+Ground NM-B from a 50A breaker ... AND ... the ground in that 6 gauge is a lot narrower than 6 gauge




and more importantly, why do I keep typing "groung" ?????

 

[mongo]

I woke up in the middle if the night last night and, as you do, I went going over the installation instructions for the Wall Connector in my mind and it occurred to me that, there's no neutral connection. Just two energized conductors and a ground (which is probably only there as a fault protection)

So I wondered why this was

It also bother's me that I'm going to have this on a 30A 10 gauge THHN circuit coming from a Sub Panel, but that the Sub Panel is fed by 6/3+Ground NM-B from a 50A breaker ... AND ... the ground in that 6 gauge is a lot narrower than 6 gauge




and more importantly, why do I keep typing "groung" ?????

Everything in the wall connector and vehicle charger can runs off 240V, so there is no need for a neutral line to get 120V.

The ground wire on 6/3 NM-B is 10 gauge which matches your 30A branch to the wall connector.

 

[Sophias_dad]

In a 120V circuit, the hot and neutral are used, hot being hot, and neutral being return.

In a 240V circuit, there are two 120V legs which are 180 degrees out of phase with each other. Each of the hots is really acting as a return for the other, in a way. In this case even if you had a neutral there should be zero current going across it.

The ground is indeed only in the HPWC for fault protection. The reason for only requiring a smaller ground conductor is that its only expected to be energized for a very short time like when someone drives a nail through the wire, before the breaker cuts the power. I'd wager #10 is good for 75+ amps for 10+ seconds before it overheats to the point where insulation starts melting. I'm sure someone has done the math. I just did, and 100 amps through 10 gauge will generate 10w/ft.

 

[EVer Hopeful]

lol - thanks the two of you

Went for a walk this morning in the Arboretum and came to the same conclusion. I guess I got confused with the 10-30 outlet, because whilst that's 240, it also has a neutral. I suppose that's incase part of your washer or dryer needs 120v


A nail through the wire . . . Now that reminds me of the time I remodeled the kitchen and was just about finished. One of the last jobs to do was to mount a panel of Smart Siding on the outside under the window, which I did, then I glanced down and noticed I had a lone nail sitting on the ground (you can see where this one is going right?) Rather than take it back to the tool shed, or even just chuck it away, I figured I'd use it. So I hammered it in only to immediately hear an unfortunate hissing sound. THAT unfortunate hissing sound. Yes, I'd hit the cold feed to the kitchen sink square on with this nail - and in a really awkward place to fix

 

[wws]

Went for a walk this morning in the Arboretum and came to the same conclusion. I guess I got confused with the 10-30 outlet, because whilst that's 240, it also has a neutral. I suppose that's incase part of your washer or dryer needs 120v

The 10-30 is not used in new construction for a reason - no safety ground. Code now requires a 14-30, which has both neutral and safety ground, instead.

 

[watsongrg]

It also bother's me that I'm going to have this on a 30A 10 gauge THHN circuit coming from a Sub Panel, but that the Sub Panel is fed by 6/3+Ground NM-B from a 50A breaker ... AND ... the ground in that 6 gauge is a lot narrower than 6 gauge

That is a shame, because your charging rate is going to be limited below what the Tesla Wall Connector and your Tesla charger are capable of (48A) (Unless you have a standard range (SR)Model, which is limited to 32A.)
And if you paid someone for a new circuit, they should have maximized the installation.

Although it sounds like you went with a plug-in install, instead of a hardwire install? If so that explains the step down.

 

[mongo]

That is a shame, because your charging rate is going to be limited below what the Tesla Wall Connector and your Tesla charger are capable of (48A) (Unless you have a standard range (SR)Model, which is limited to 32A.)
And if you paid someone for a new circuit, they should have maximized the installation.

Shame seems a bit strong. 24A continuous is enough to recharge 60kWh in a 12 hour overnight session (22,17,14 miles per hour for older 3,S,X)
Plus, we don't know anything about the rest of the house loads or preexisting panels.

 

[EVer Hopeful]

I had a load calculation done and 30A seemed to be the maximum a prudent person would install. The Main Panel is only 150A and is full. It even has a few tandem breakers in there. Like I said the feed going to the Sub Panel is 6 gauge, so I could possibly have stepped it up to 40A but I'm ok with it as it is. If I need more, three's a supercharger near me

And no, it's hardwired

 

[watsongrg]

I had a load calculation done and 30A seemed to be the maximum a prudent person would install. The Main Panel is only 150A and is full. It even has a few tandem breakers in there. Like I said the feed going to the Sub Panel is 6 gauge, so I could possibly have stepped it up to 40A but I'm ok with it as it is. If I need more, three's a supercharger near me

And no, it's hardwired

Sounds like the right install. When you said it bothered you, I was just sympathizing If it didn’t t meet your expectation. But I realize you may have been referring to the ground wire.

 

[EVer Hopeful]

no problem. And yes I would have liked the full 60A, but maybe the next house (where we'll also have solar panels)

Mind you, having said all that, what I really want is to take delivery of the freaking car!

 

[sleepydoc]

I'm sure someone has done the math

Yes, the people at the National Fire Protection Association, (the organization that publishes the National Electric Code) have done the math. More than once, I'd wager.

This is why the code exists and why electricians study and understand it, so we don't have to worry about the safety of an installation that has followed code.