Car charger wire sizing

[mbrooke]

Yes. We don't derate NM to 60? if it's marked 75? or 90?. They've made some recent changes to bring things closer to the NEC, but nothing crazy:

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Note that even with the 90? rating on the cable, you'd probably have a 75? rating on the breaker termination and thus use the 75? column

Its things like that which really make me question our NEC, which IMO is overly conservative to the point of no return in investment. Then again it might have to do with our NM having paper in it, but who knows.

 

[mlnk]

Why not just follow the Tesla instructions...which say to use a 100 amp breaker with minimum of #3 wire. So I think using #2 would be more than adequate unless you encounter high ambient temp., or excessive conduit fill. I do not think this the Tesla engineers consider this charger to be a 3 hour continuous load at FLA.

 

[mbrooke]

Why not just follow the Tesla instructions...which say to use a 100 amp breaker with minimum of #3 wire. So I think using #2 would be more than adequate unless you encounter high ambient temp., or excessive conduit fill. I do not think this the Tesla engineers consider this charger to be a 3 hour continuous load at FLA.

I am tempted to just violate the NEC and use #2 NM-B. If Canada can get away with #3 NM for something like this I don't see why we cant either.

 

[mlnk]

Following the manufacturer's instructions is following the NEC.

 

[YourElectricianOC]

Silly Americans...

Worst case scenario you can decrease the charger's load via the DIP switches in 10A increments. The "90A breaker" setting should limit the charge current to 72 amps.

I had a home owner wanted to do this to skirt the panel upgrade the 100A circuit was going to buy him into. When I verified with the local inspector that this was not allowed, he followed up by verifying that I was licensed .

I would advise to do the installation the way the code requires, which is the way the manufacturer specifies as well.

There seems to be a lot of threads recently where guys are asking a group of professionals for permission/encouragement to willfully violate the standards of our profession. I'm amazed they are met so kindly.:happysad:

 

[petersonra]

There seems to be a lot of threads recently where guys are asking a group of professionals for permission/encouragement to willfully violate the standards of our profession. I'm amazed they are met so kindly.:happysad:

There is a fair amount of stuff in the code that has been arbitrarily made far more conservative than mere safety would dictate.

It is not surprising that people in the trade would question why it is necessary, or even how such things came about in the first place.

No excuse though for just ignoring the rules, even though it is an attractive and safe option at times.

 

[Rampage_Rick]

I had a home owner wanted to do this to skirt the panel upgrade the 100A circuit was going to buy him into. When I verified with the local inspector that this was not allowed, he followed up by verifying that I was licensed .

I don't see how your scenario is in any way relevant to what I posted. Go read the Tesla HPWC installation instructions. The unit allows you to configure the maximum load according to the allowable circuit ampacity.

 

[mbrooke]

I had a home owner wanted to do this to skirt the panel upgrade the 100A circuit was going to buy him into. When I verified with the local inspector that this was not allowed, he followed up by verifying that I was licensed .

I would advise to do the installation the way the code requires, which is the way the manufacturer specifies as well.

There seems to be a lot of threads recently where guys are asking a group of professionals for permission/encouragement to willfully violate the standards of our profession. I'm amazed they are met so kindly.:happysad:

Because the NEC rules are criminally unreasonable. There is no country on earth with such a convoluted electrical code. For the exact same scenario the CEC would allow 3-2 MD90 while our NEC forces us to run #3 in conduit or #1 SER for a load that will never come close to the NEC's own conservative ampacity tables.



People will argue the wire must be upsized 125% when the load is continuous so the breaker can dissipate heat into the wire but that is untrue. Under the 2012 CEC I can load #12 NMD90 to 25 amps and put in a 30amp breaker for an electric heat circuit. Homes aren't burning down in Canada nor in the rest of the world. All these safety factors exist to protect untrained personnel, they have nothing to do with professionals or safety.

 

[kwired]

Because the NEC rules are criminally unreasonable. There is no country on earth with such a convoluted electrical code. For the exact same scenario the CEC would allow 3-2 MD90 while our NEC forces us to run #3 in conduit or #1 SER for a load that will never come close to the NEC's own conservative ampacity tables.



People will argue the wire must be upsized 125% when the load is continuous so the breaker can dissipate heat into the wire but that is untrue. Under the 2012 CEC I can load #12 NMD90 to 25 amps and put in a 30amp breaker for an electric heat circuit. Homes aren't burning down in Canada nor in the rest of the world. All these safety factors exist to protect untrained personnel, they have nothing to do with professionals or safety.

You may be right to some extent.

One more question - How many other countries have non professionals doing as much wiring as non professionals in the US do?

 

[mbrooke]

You may be right to some extent.

One more question - How many other countries have non professionals doing as much wiring as non professionals in the US do?

About a dozen others, Russia is a big one. However the major difference: if a person burns down a home or kills someone the none professional will be the one charged with manslaughter. If the NEC had to consider everything unqualified professionals might do we might as well run 12 volts DC with #2 cu over to ever device or ban electricity all together in homes. Or as Iwire said it shut down the power grid because idiots will screw up a 2 wire lamp cord.

 

[GoldDigger]

You may be right to some extent.

One more question - How many other countries have non professionals doing as much wiring as non professionals in the US do?

A member of another forum who lives in Turkey noted that "You can tell who is an electrician because he has a screwdriver."
Professional? You be the judge.

 

[kwired]

A member of another forum who lives in Turkey noted that "You can tell who is an electrician because he has a screwdriver."
Professional? You be the judge.

Well I once was in a city and saw a truck (nice looking truck BTW) that had signage that said something like "NAME NAME Professional Handyman Service".

I had to think about that one because I didn't know handymen were considered professionals - I guess I was wrong.:huh:

 

[mbrooke]

I hate handyman just as much as the rest, but I still stand behind the NEC not catering to them.

 

[mlnk]

"professional" means that the activity is the dominant job done to earn a living. It is not a pastime, hobby, or secondary source of income.

 

[kwired]

"professional" means that the activity is the dominant job done to earn a living. It is not a pastime, hobby, or secondary source of income.

But "handyman" usually means someone that doesn't really specialize in one particular trade or area of expertise, so a "professional handyman" must be someone that is good a many things, or thinks he is anyway

I admit to being that myself, but do limit what I do for hire to mostly electrical work