EV Charger Risks: Home Charging Installation Risks and Advice - by Munro Live

[opnwide]

I'm not an electrician, but if the code for sizing says it can run 48A if the wire is rated for 90C I can't really see the difference. Again, I'm not an electrician but I did have a licensed electrician tell me it was fine.

In a nutshell, it’s the “continuous load” rule 215.2(A)(1) that trumps the “next size up” rule 240.4(B). The maximum ampacity of #6 Romex is 55amps. Since an EVSE is “continuous load”, rule says you must multiply 48A load by 125%=60amps, too much for 55ampacity #6 Romex.

At least that’s what my bartender told me. YBTMV (your bartender may vary).

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[SANZC02]

I'm not an electrician, but if the code for sizing says it can run 48A if the wire is rated for 90C I can't really see the difference. Again, I'm not an electrician but I did have a licensed electrician tell me it was fine.

Look at the specs, Romex 6/2 and 6/3 are not rated for 90c, the external sheathing is tight and not enough air to circulate so it is derated to 60c with a max draw of 55 amps. That is not enough to charge at 48 amps.

 

[Donald Stanfield]

Look at the specs, Romex 6/2 and 6/3 are not rated for 90c, the external sheathing is tight and not enough air to circulate so it is derated to 60c with a max draw of 55 amps. That is not enough to charge at 48 amps.

Then Why is it stamped with 90C rating right on the outer sheath?

 

[Riviot]

Then Why is it stamped with 90C rating right on the outer sheath?

Typo

 

[opnwide]

Then Why is it stamped with 90C rating right on the outer sheath?

"NMB cable is rated for 90 degree as per the manufactures and the listing of the cable.
HOWEVER,
NMB is LIMITED to 60 degree as far as the ampacity is concerned (by The National Electric Code)
One uses the 90 degree column in the NEC for derating and such BUT the 60 degree column for ampacity.
For example a # 8 awg NMB cable is rated for 55 amps at 90 degree BUT limited to 60 Degree which limits it to 40 amps. "

Again, what my bartender told me. YBTMV.

 

[fotoflux]

This is VERY IMPORTANT.

3 years ago, I had 2 240 drops in the garage off their own panel from a local and reputable electrician. They were plug-in 14-50s vs. hardwired so I could be flexible with the chargers we bought (since we figured they would improve dramatically over time).

Abut 15 months later, I smelled burning plastic while the i3 was charging.

Here is the result.

Welp, just bought the Hubbell 14-50 plug on Amazon to replace the Home Depot one I have in there currently. Better safe than sorry.

Well, looks like even the Hubbell brand can fail. There must be a specific version of the outlet that has a higher duty cycle. I wish the video was specific about which model numbers have the higher duty cycle rating.

 

[electruck]

I'm not an electrician, but if the code for sizing says it can run 48A if the wire is rated for 90C I can't really see the difference. Again, I'm not an electrician but I did have a licensed electrician tell me it was fine.

Unfortunately, licensed electricians don't always get this right. Many aren't familiar with or used to dealing with the continuous load considerations of an EVSE.

One also has to keep in mind that codes are often designed to address or prevent issues in common usage scenarios. For example, the heating considerations associated with a single conductor are more restrictive when conductors are bundled. Keep in mind that several runs of Romex are commonly in direct contact with each other when passing through the same small hole in a wall stud. Code has to account for this. Similar considerations exist for single conductors like THHN in conduit, there are requirements that limit the number/size of conductors within conduit based on the size of the conduit. So when you ask "why", you may just have to settle for an "it's complicated but that's just the way it is" kind of answer.

Regardless of temp ratings, and as already pointed out, code requires that for continuous loads such as presented by an EVSE, both the breaker and the conductor have to be sized for 125% overcurrent protection. For a 48A continuous load, that means a 60A rating. Regardless of the temp rating of the individual conductors, the insulation on those individual conductors, or the cable jacket, the #6 NMB end product has an amapcity of 55A (see manufacturer spec sheet here) which does not meet the 60A requirement for this use case.

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