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The electrician is well recommended and has done dozens of installations. The wire will be installed with a 60 A breaker and wiring will be inspected and certified.
Below is a screenshot he provided from Ontario safety code, so I guess it is okay to go with what he is recommending. He also said all breakers and terminals are rated at 75 degree C.
 

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The electrician is well-recommended and has done dozens of installations. Below is the screenshot he provided from Ontario code.
I guess it is OK to use the wire he is installing.
The wire will go with a 60 A breaker on panel and it will be inspected and certified. Not cutting corners on safety.

I'm not an electrician so huge grain of salt.

I don't quite understand the table and it is only a snip without the referring clause provided (which is important).

I would take this over to the Charging Forum (in the model Y sub forum) and get some advice from either JCanoe or RockyH.

As I mentioned before there are several different types of 6 gauge wire (meaning different insulation levels). My understanding is that some can only handle 55A at 75C while others can handle 65A at 90C. It is up to your electrician to pick the correct one.

So far I still don't know what type he is providing; just ask him to provide the type: THWN, NMD 90, T90, or whatever. Then you can look that up the spec on your own and confirm it can do 65A at 75C. In this case #6 NM-B would not work as it has an Ampacity of 55A at 60C.

*edit* Also; I believe the cable insulation rating must match or exceed the breaker rating which is the item you have circled in your snip.
 
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It's not a reference to ambient temperature, but rather how much the conductor heats up as you push additional amperage through it.

Almost all wire produced today is 90C rated, but romex is always limited to it's 60C rating and residential and light commercial breakers rarely exceed 75C rating.
 
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The book is nearly $300 so I cannot verify this.
The Ontario Electrical Safety Code (OESC) is available at some Toronto Public Library branches. This is reference only, so you have to visit the branch to read it. Currently, only the 2018 edition is available, not the 2021 edition which has now been adopted, but the differences are minor and likely won't affect cable gauge requirements.

OESC

Also, any changes between OESC 2018 and OESC 2021 will likely be found in the Canadian Electrical Code (CEC) that the OESC is based on. The CEC 2021 edition is also available for reference at some Toronto Public Library branches.

CEC

I referenced library copies of both for installing a 14-50 outlet in my garage myself and passed the Ontario Electrical Safety Authority inspection without any issues. (I used 6/3 NMD-90 even though I only used a 40 amp breaker.)
 
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A 14-50 is rated for 50 A max draw (40 A continuous) and the cable can certainly take it.
The question is, would he have passed you if you had a wall connector (Instead of 14-50) that is rated up to 48A continuous (60 A max)?

Though looking at the discussion here, it appears because switches, breakers etc are all rated at 75C, the wire can take 65 A max.
So all good!
 
Unless I missed it somewhere I don't think this has been confirmed.

Simply stating it is #6 gauge isn't enough as it depends on the insulation. Have you confirmed the type yet? E.g: NM-B, NMS, T90, etc?
All building wire for sale today is rated for 90C. It is only romex that is de-rated to 60C for additional safety factor in residential. You could slice the sheath off, shove the individual wires in a conduit and use them at their 90C rating (with 90C breaker and load).
 
All building wire for sale today is rated for 90C. It is only romex that is de-rated to 60C for additional safety factor in residential. You could slice the sheath off, shove the individual wires in a conduit and use them at their 90C rating (with 90C breaker and load).
Maybe; I suspect a strict inspector would fail that if they found out someone has sliced the sheath off (missing markings) due to possible damage.
 
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It's not a reference to ambient temperature, but rather how much the conductor heats up as you push additional amperage through it.
Just a small addition to this, as I didn't get it quite right:
The temperature rating is the maximum continuous temperature the cable jacket is designed to survive at over it's lifetime, so 75C and 90C jackets just have more buffer room for heat from additional current, but extreme ambient temperatures (attics) do need to be taken into account and de-rated as appropriate.
 
The question is, would he have passed you if you had a wall connector (Instead of 14-50) that is rated up to 48A continuous (60 A max)?
I meant to ask the inspector this question but forgot to. The Wall Connector can be provisioned to match and limit the maximum current to whatever your overall circuit is rated for. However, I've heard that some Canadian inspectors have failed circuits rated less than 60A with the Gen 3 Wall Connector because maximum current provisioning is done through software. Some inspectors interpret sections of the CEC to say that if provisioning can be changed though software then the circuit must be able to handle the maximum current that the Wall Connector can be set for.

This isn't a problem with the Gen 2 Wall Connector because its current limit is provisioned via physical switches inside the unit.

The possibility that I might fail inspection for the reason above is one minor reason why I chose not to use a Gen 3 Wall Connector. The main reason is that I got the Mobile Connector free with the car and so the overall cost, even with having to buy a 14-50 adapter and a Bryant outlet, was less. My house only has a 100A service and the load calculation came to 94.26A with the 32A load of the Mobile Connector, so taking advantage of the increased current capability of a Wall Connector (or even a Corded Mobile Connector) was not possible (which is why I also used a 40A breaker instead of 50A, besides it being cheaper). Another minor reason for going with a 14-50 outlet is that it's available for use with other high current 240V equipment, such as an electric welder.
 
Both my welders use a 6-50 plug. I have yet to see a good reason to have a 14-50. The adoption of 14-50 for a 240v power supply is a strange concept to me.
14-50 is a common plug at campgrounds that cater to large motorhomes, especially in the southern US. The cost of the extra conductor isn't much, especially if you have to buy both a 6-50 and 14-50 adapter for your mobile connector.

That being said, recent supply chain issues have hit 14-50 receptacles pretty hard, so a 6-50 may be a decent choice these days.
 
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Having driven the roadster across the US several times relying on campsites I know why that was the original choice for the 2010 UMC, but I don’t know if any level 2 charger that can take advantage of 40A 120v. It’s not 2010 anymore, Tesla has super chargers now and I don’t drive a motorhome that requires a 120 and 240 hookup, an adaptor is $50, what’s the extra conductor cost? I don’t know the answer. The only reason I would run a 3 core would to be able to put a panel or load center in place of the outlet at a later date. But to have a 14-50 solely for an exclusive 240v outlet makes no sense any more. The 6-50 is a much better outlet for that application.
Again at some point you have to trust the installer, if you keep questioning his decisions then don’t be upset if you see the costs of installation increasing. The issue annoys me because the information is out there, like many I did my own installation and pulled a permit. If you tell the installer you want a 14-50 don’t question what they do, try telling them you want a pure 240v 40a outlet and see what they suggest, it won’t be a 14-50.
 
8/3 is currently $13.95/m, 8/2 is 11.80/m and a 6-50 adapter is $60 (14-50 is $55). Break even is 27.9M assuming you want the 14-50 for travel. Above that distance probably means detached garage, so you'd be doing a sub panel anyways and need the neutral.

Also, for comparison, 8/3 was $6.24 in the fall of 2019.
 
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Today is installation day. This is the cable being used from panel to 14-50 socket.

Can the electrical experts weigh in on the cable quality etc?
 

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