Cable gauge feedback

[xcyber]

I have a 40ft run from panel to garage. My electrician says 6/3 wire and a 60A breaker is good enough for the wall charger (48A max draw)
From what I have read, He should be using a 4/3 wire, with a 60A breaker.
The wire would terminate in a sub-panel in the garage.

What is the consensus? 6/3 is good enough for a 60 A breaker?

 

[jmaddr]

The answer is it could be but there are a lot of interdependencies (distance, insulation, CU/AL, conduit, romex, etc). Look up wire gauge calculator and you will see plenty of them based on NEMA (for the US). Be sure to put in 60 amps even though you’ll never pull more than 48A.

If he/she is a reputable electrician, they will take care of all this for you. If your location requires a permit, then they will specify that in the permit and you can be confident it’s to code.

 

[DC5R]

I believe your electrician is basing the awg of the wire on the current draw, which would be maxed out at 48A and not the actual breaker. At 48A, 6 awg would be sufficient. However, if you ever decide to go above the 48A draw, then a 4 awg wire is needed.

 

[X.l.r.8]

6/3 or a 4/3 for a 240v, why?

 

[DC5R]

The determining awg of the wire in this situation is not about the voltage, but the amp draw. In @xcyber's situation, the max amp draw due to the wall charger is 48A so a 6/3 would suffice. However, if a wall charger wasn't being used and the car could actually utilize the full 60A allowed by the breaker, then 4/3 is required.

 

[X.l.r.8]

What’s the white cable do?

 

[Stirfry]

I have a 40ft run from panel to garage. My electrician says 6/3 wire and a 60A breaker is good enough for the wall charger (48A max draw)
From what I have read, He should be using a 4/3 wire, with a 60A breaker.
The wire would terminate in a sub-panel in the garage.

What is the consensus? 6/3 is good enough for a 60 A breaker?

I think it depends on the type of wire being installed. I do not believe bundled/Romex 6/3 is acceptable for a 60A line. However individual 6gauge wires (THNN?) are acceptable. It has to do with the heat capacity and ampacity rating of the wires.

Check over in the model Y/charging subforum. There are a few posters over there that are very knowledgeable with great posts that lay it all out (RockyH and JCanoe). They post links to codes and ampacity tables.

 

[Stirfry]

SNIP..... (THNN?) ......SNIP

Too late to edit my reply.

That should read THHN, but I believe that may be an American designation.

The Canadian version that would work would be either TW75 or T90 #6 gauge conductors (red and black) with a #10 T90 bonding conductor (green).

 

[ATPMSD]

In the United States, #6 romex is NOT acceptable on a 60-amp circuit, period! The wire is rated at 55-amps, not 60-amps. Also, if we look at the 80% rule the 55-amp wire will support 44-amps continuous whereas the wall connector will draw 48-amps, so #6 romex fails on two counts. If you use #6 romex the wall connector must be set to 50-amps.

HOWEVER, as it looks like you are in Canada, #6 romex may have a different rating. Ask you electrician what #6 romex is rated at in Canada. If it is 60-amps or more you are OK.

 

[Stirfry]

HOWEVER, as it looks like you are in Canada, #6 romex may have a different rating. Ask you electrician what #6 romex is rated at in Canada. If it is 60-amps or more you are OK.

Agree with what you said; my installer also noted that Romex #6 and equivalent was not to code (I'm in Canada).

 

[pb2000]

To sum up what a lot of people have already said:
6awg romex is not sufficient for 60A according to NEC/CEC (it really comes down to your local inspector though)
6awg in conduit is acceptable
The wall connector doesn't use a neutral wire, so unless you want the option of adding a sub panel later, it's not required (I don't think 4awg romex is available without a neutral, so you may not have a choice unless you go conduit).

 

[xcyber]

4/3 wire would also help to have future capability to use the line to charge 2 cars at a high Amp rate. With one car, Wall charger will take 48 A, so 6/3 is fine.
I finally decided to go 6/3, and if I need to charge 2 cars in future, I will throttle the currents so my total draw stays at 50 A.

The reason for not going 4/3 now is because it will cost me about CAD1500 more than 6/3. (4/3 wire + Sub panel and Breakers)

 

[ATPMSD]

6/3 is fine

Just curious, what kind of 6/3 wire will you be using?

 

[xcyber]

Just curious, what kind of 6/3 wire will you be using?

No idea. Will have to ask the electrician. Can you tell me what to ask? How many types are there?

 

[ATPMSD]

No idea. Will have to ask the electrician. Can you tell me what to ask? How many types are there?

The issue is that in the United States Romex 6/3 wire is not a 60-amp wire and cannot be used with the Tesla Wall Connector (at least not at the full 60-amp rating). The fact that it only draws 48-amps is irrelevant (the wire used must be rated at 125% of the continuous load so 48A * 125% = 60A). Other wires, such as THHN, are rated at 65-amps or more and are suitable. So the wire type makes a difference.

Without going into the wire’s type, one way to verify if the wire is suitable is to ask these questions:

1. Is the wire rated at 60-amps or greater e.g. can it support a load of 60-amps?
2. What is the wire rated at for an 80% continuous load (60A * 80% = 48A)? If it is truly a 60-amp wire he should tell you it is 48-amps (or greater)

 

[xcyber]

Thanks. My electrician says he will use 6/3 BX cable and it is rated for 60 A in Ontario (Canada) Electrical Safety code.

The book is nearly $300 so I cannot verify this. Can someone here verify the above claim?

 

[X.l.r.8]

BX is like saying I’m buying a car. Can you verify how fast it goes. At some point you have to trust your certified technician, unless you found him on Kijiji. No one needs 3 core, unless you are installing a second panel. Just like no one needs a 14-50 unless they are needing a 40A 120v power supply. That being said BX is probably the highest markup for a supplier to make money from, we used to call it a PUWYBS supplement. I wonder if people spend as long reading about temperature ratings on cables and connections as they do on tires or accessories.

 

[Tz00]

Thanks. My electrician says he will use 6/3 BX cable and it is rated for 60 A in Ontario (Canada) Electrical Safety code.

The book is nearly $300 so I cannot verify this. Can someone here verify the above claim?

6 gauge wire is rated for 55A only at 60°C. If the equipment is rated 75°C or 90°C, it is fine for 60A. The Tesla gen 3 wall connector is rated for 90°C. So as long as the breaker is rated 75°C or higher, you are fine.

 

[pb2000]

Romex is de-rated to it's 60C rating regardless of the breaker or equipment rating. Armored cable is good for it's 75C rating, so is fine for this application.

 

[Stirfry]

6 gauge wire is rated for 55A only at 60°C. If the equipment is rated 75°C or 90°C, it is fine for 60A. The Tesla gen 3 wall connector is rated for 90°C. So as long as the breaker is rated 75°C or higher, you are fine.

I think this is correct is some cases, but not all.

6 Gauge NMD90 is rated for 65A at 90C; it all depends on the insulation of the wire. THWN is rated at 75C, and there are others (T90, NM-B).