Tesla gen 3 (Help me understand)

[nietzj]

I have watched several Youtube install video's and even one from Tesla's own website on installing the gen3 Tesla wall charger. It seems like everyone is using a #6 THHN for the EGC. My calculation is with this charger on a 2pole 60 amp breaker using #6 THHN for the CCC a #10 EGC is all that's required. Am I missing something? Maybe the install specs call for a #6 EGC or something, I'm confused. BTW, I'm talking about conductors in a conduit.

 

[ptonsparky]

I've never installed one, but if installation specs call for a #6 EG, that is what it should get.
Doesn't matter what you are installing. RTFM.

 

[ramsy]

have watched several Youtube install video's

My daughter grew up doing the same thing, and remains unimpressed with other sources of information.

At 21yrs old with no need to consult me, social-media, anecdotal testimony, and YouTube led her right into an unsecure digital wallet, where she lost $2000 investing in a crypto currency scheme.

Chase bank fraud department just giggled that she was SOL.

Had to change my bank & retirement beneficiary to "Poor Peoples Trust", with a spendthrift clause to shackle my adult kid's financial vulnerability.

All we can do is lead your horse to water, in your case NFPA-70 Table 250.122, but we can't force you to drink.

 

[jaggedben]

As I read it, while badly worded, the manual does not specify a 6awg ground and you should follow 250.122.

https://www.tesla.com/sites/default/files/support/charging/Gen3_WallConnector_Installation_Manual.pdf

 

[ptonsparky]

Nothing says you cannot use a #6 EG. I wouldn't spend 2 hours on a road trip if I had 6 or 8 easily available. Might indicate PPP on my part, but it happens.

 

[infinity]

According to that manual the EGC is sized according to the NEC.

 

[ramsy]

Nothing says you cannot use a #6 EG.

Yes, since NEC is a minimum standard, nothing wrong with better than minimum.

Also forgot NEC 110.3(B), which subjects installers to listed instructions. So, if written manual requires #6; however poorly written, or if installers feel more comfortable interpreting instructions that way, rather than using 250.122 minimums, then a better listed minimum is correct.

My earlier rant should have included more alternatives to YouTube.

Especially NEC 110.3(B), listed instructions, and rough-in inspections by AHJ's freely available with the required building permit.

 

[NYC_NY]

isnt #10 is good up to 60 amps for grounding?

 

[ramsy]

According to that manual the EGC is sized according to the NEC.

Pg.12 of that manual describes "injecting a small amount of current into the ground conductor in order to measure the impedance" on TN grids, which if excessive locks out with fault code 38.

What happens if code 38 may be calibrated for impedance of #6cu per Pg.6, as that Equipment Grounding per Pg.7 travels back thru the Ground (PE) main-bonding noodle?

Also while other wall charger MFG's may use built in RDC-DD with Type A GFCI, Pg.2 of Tesla's wall connector features a 3-Phase Type B RCD, which may need Ground (PE) to check for 6mA, from a #6cu impedance path, as described on Pg.6, "If installing for maximum power, use minimum 6 AWG, 90° C-rated copper wire for conductors."

So if YouTube knuckleheads ever get it right, its only because they didn't follow the NEC, or assumed instructions that also don't follow NEC.

 

[jaggedben]

No, the manual is just written sloppily. Fails to clarify that the instruction about needing 6awg for full power doesn't apply to the EGC. I will bet lunch on it.

 

[infinity]

Just size the EGC to T250.122 like any other branch circuit and call it a day.

 

[ActionDave]

Pg.12 of that manual describes "injecting a small amount of current into the ground conductor in order to measure the impedance" on TN grids, which if excessive locks out with fault code 38.

What happens if code 38 may be calibrated for impedance of #6cu per Pg.6, as that Equipment Grounding per Pg.7 travels back thru the Ground (PE) main-bonding noodle?.....

How does that work? Unless every circuit is identical for every Tesla charger installed in the world there is going to be a different impedance back to the main bond jumper. Code 38 be damned.

 

[ramsy]

Code 38 be damned.

Looks like that impedance can be fudge factored for knuckelheads.

Pg.12 Wall Connector ground assurance may be adjusted in countries with TT or IT grid configurations and can be disabled in the commissioning procedure

 

[jaggedben]

Yeah, the ground assurance measures the impedance. It might get the same reading for 20ft of 6awg as it does for 31 feet of 8awg. It can't know. So it's threshold for the error code must therefore be equivalent to a few hundred feet of 250.122 sized EGC, or else they'd get far more bad product reviews than they could possibly tolerate.

 

[ActionDave]

Looks like that impedance can be fudge factored for knuckelheads.

Pg.12 Wall Connector ground assurance may be adjusted in countries with TT or IT grid configurations and can be disabled in the commissioning procedure

Or there is a reasonable design engineering built into the charger and a 6AWG equipment ground changes nothing about the operation compared to the NEC required size.

 

[jaggedben]

Looks like that impedance can be fudge factored for knuckelheads.

Pg.12 Wall Connector ground assurance may be adjusted in countries with TT or IT grid configurations and can be disabled in the commissioning procedure

I guess by 'knuckleheads' you mean the Japanese and Norwegians?

 

[acrwc10]

I have seen dozens of them connected with 6-3 NM and there has not been any issues.

 

[ramsy]

Or there is a reasonable design engineering built into the charger and a 6AWG equipment ground changes nothing about the operation compared to the NEC required size.

Are you sure thats true for all ambient conditions, and has no bearing on High Temperature Detect/Disable, or Class B RCD function?

Regardless, your point is well taken: the reasons why instructions may deviate from the NEC is not required, and just debatable speculation.

No, the manual is just written sloppily. Fails to clarify that the instruction about needing 6awg for full power doesn't apply to the EGC. I will bet lunch on it.

With no good reason for listed instructions to require #6 for all wires, is knucklehead installer the authority having jurisdiction (AHJ) to overrule 110.3(B), by speculating the instructions must be in error?

 

[jaggedben]

...

With no good reason for listed instructions to require #6 for all wires, is knucklehead installer the authority having jurisdiction (AHJ) to overrule 110.3(B), by speculating the instructions must be in error?

Nobody has speculated the instructions are in error. We have asserted they are badly worded and we are doing our best to interpret them.

You're the one engaging in (very unconvincing) speculation as to why a 6awg EGC might be necessary, even though the instructions unambiguously state you can follow local code for less than full power.