Anyone use this Romex 6/3 cable during install?

[MY-Y]

Before the wire gets potentially hot enough to start a fire, wouldn't the car notice a voltage drop and automatically lower the amps? I have to think Tesla thought of this and if not, there would be a lot of fires.

I agree 100% with following the code and being safe and I would never trust voltage drop sensing vs. proper wiring, but I'm curious if anyone here knows whether the car does this or not.

Keep in mind that we are mixing "code" and "safe." Code covers many scenarios (wire in a well insulated wall, house in a very hot climate, etc.) There is margin built in for safety. A 60 amp draw on a 6 gauge romex is 9% over its rating. This means ~19% more heat in the wire. Is this to code? No. Is this safe? That's a different debate. Since the vast majority of the members here aren't qualified to judge electrical safety, I think it's best to keep to code.

As far as the car preventing a fire by noting the voltage drop, that is not something I'd rely on. It will happily charge at 48 amps with a 5 volt drop. That's 240 watts being dissipated in the system. If that heat is spread out across a long wire, no big deal. If that heat is in a small area, it is more than enough to light a fire. A 30 watt soldering iron can easily start a fire.

Edit: I just noticed that Johnny Vector covered some of this while I was typing my reply.

 

[Midnightsun]

Don't assume those are the same. I was talking a bit in private messaging with an electrician who is in Canada, and NMD90 is just something different that Canada has, and it must be a little bit different in why it's allowed some different amp ratings at different temperatures.

NMD90 is simply Non Metallic Dry locations rated for 90 degrees C
NM-B is simply Non Metallic and the b stands for a rating of 90 degrees C, NM-B is designed for Dry locations

Both have the same type jacket and insulation and 6 gauge copper is 6 gauge copper so what is the difference if they are not the same? Personally I cannot see any difference in the specs except that the NM-B is not CSA certified therefor not acceptable in Canada and visa versa for the NMD90

 

[MY-Y]

NMD90 is simply Non Metallic Dry locations rated for 90 degrees C
NM-B is simply Non Metallic and the b stands for a rating of 90 degrees C, NM-B is designed for Dry locations

Both have the same type jacket and insulation and 6 gauge copper is 6 gauge copper so what is the difference if they are not the same? Personally I cannot see any difference in the specs except that the NM-B is not CSA certified therefor not acceptable in Canada and visa versa for the NMD90

NM-B is rated for 60C in the USA, not 90C.
Although it is rated at a 90C conductor temp, its ampacity is limited to 60°C according to the NEC. From what I read, the 90C is for derating calculations, fixture terminations, etc. Regardless of that, when all of the calculations are done, you cannot exceed the 60C ampacity rating.

For our Tesla HPWC to operate at its 48 amp max, it's simple. 60A breaker on a 4 gauge 60C wire (e.g. NM-B) or 6 gauge 90C wire (e.g. THHN in conduit, MC). No need to over complicate it or push the limits with a high current circuit.

 

[sleepydoc]

A couple of observations -
First, if the wire is exposed you may be required to protect it in conduit. Code requires it to be protected ‘where subject to damage.’ This is a bit open to interpretation by the inspector.
Second - if you have questions, call your local electrical inspector and pull a permit. It’s a small price to help ensure you’re wiring things correctly.
Finally, if you really have to ask this many questions, you probably shouldn’t be doing the wiring yourself anyway.

 

[Magnetic Flux]

NMD90 is simply Non Metallic Dry locations rated for 90 degrees C
NM-B is simply Non Metallic and the b stands for a rating of 90 degrees C, NM-B is designed for Dry locations

Both have the same type jacket and insulation and 6 gauge copper is 6 gauge copper so what is the difference if they are not the same? Personally I cannot see any difference in the specs except that the NM-B is not CSA certified therefor not acceptable in Canada and visa versa for the NMD90

If I were a betting man I would bet that Southwire (manufacturer of Romex) likely makes the exact same cable for CSA certified NMD90 and NEC listed NM-B due to the simplicity of manufacturing massive quantities of these cables. Simply having to print a different lettering on the outer jacket is much simpler from a manufacturing perspective.

In the end, we have the follow the code requirements in the regions we live, so in the US we need to follow the requirement that all NM cable is only rated for 60 deg C.

I would also venture to say that most people installing these feeds into their garage probably aren't following the temperature derating of the conductors to begin with and probably are not checking the limitation and listing on the terminations in the panelboard or at the wiring device. With that, I would err on larger size conductors (or better rated ones).

The other thing to remember in the US is that the National Electrical Code (NEC, also known as NFPA 70) is part of the National Fire Protection Association books of standards and codes. It isn't a standalone code like the Mechanical Code and Plumbing codes, etc. The NFPA documents focus on life safety and human protection. I was taught years ago to think of the NEC as being developed for life safety, above all else. It helps explain a lot of the requirements and decisions made.

 

[Midnightsun]

Not saying one should not follow code to the contrary as originally stated and obey the laws where one may live after all the code is kind of like the electrical law. Just curious as to why the rather large acceptable ampacity of the 2 standards differ so much yet seem to be identical in fabrication.

My brother lives in NH, and I have a condo in Florida. Oddly enough I can go to any of these locations and ride my motorcycle with no helmet. Heck in NH an adult is not even required to wear a seatbelt. Safety first, LOL. There are quite a few items in Canada that are not to code yet are in the states and in fact you cannot even buy them here such as those plastic remodelling boxes which I personally think are the best thing since sliced bread. Considered unsafe here yet not in the US, go figure.

 

[JeffnReno]

Thanks for all the input.

I'm a little confused, it's true that the wire I linked to only has a max 55 amp rating, but the Tesla wall charger data shows the
Maximum output (amps) of 48 amps on a 60 amp breaker. If the max output is only 48amps for the charger, can't I use the 55amp cable?

Now that I think about it, it's probably a bad idea because a future owner of this house might add a different charger and calculate it off the breaker and not the cable which might not end well.

Since the garage has unfinished walls I would rather not run conduit but use a jacketed cable for easier install.

Just use a 50amp breaker. I ran mine to a 14-50 outlet which is rated for 50amps anyway and I use my mobile charger that came with my car which only charges at 32amps and is plenty for overnight charging.

 

[dn325ci]

I understood all this, and found it informative as a newbie. A question I didn't really see brought up here: what role does the length of the conductor play? Seems like long runs would make this problem worse. When talking about 6/3 or any other conductor, it made me curious what length of line was assumed in the standards setting.

 

[Rocky_H]

I understood all this, and found it informative as a newbie. A question I didn't really see brought up here: what role does the length of the conductor play? Seems like long runs would make this problem worse. When talking about 6/3 or any other conductor, it made me curious what length of line was assumed in the standards setting.

Ah, that's a good question. Extra length in the line mainly causes an issue with voltage drop by the time you get to the end of the line. That's generally not a danger issue as much as an effectiveness issue. Some kinds of devices have problems if they are not getting voltage as high as they are expecting. Fortunately with charging an electric car, that's not really much of an issue. They usually have really wide tolerance to detect and use whatever lower levels they are getting, so some sagging by several volts isn't going to matter.

Electric code doesn't have strict rules on that either; they have more of recommendations of trying to keep the voltage drop to within reasonable % and upsize the wire thickness if necessary to compensate. For regular house installations, where the runs are usually less than 100 feet, it's probably not an issue you need to consider. It's more of commercial settings, where they might have to run something a few hundred feet out to some charging stations in the parking lot that they would need to take that into account.

If you want to experiment with this some, here is a voltage drop calculator tool. You can either see what wire requirements you need to stay tight within a certain % drop, or you can loosen up the drop % and just see how much drop there is over that length. And you can play around with the variables to see what it gives for different lengths and wire gauges.

Voltage Drop Calculator | Southwire

www.southwire.com

And one other thing. Tesla did build in a little software check into the car that will compare the voltage before charging to after it ramps up and pulls heavy current, and if that shows a sizeable drop, it will show a warning and try a lower current level. So if there is a really long run or with undersized wire, the car may detect that. But those usually don't flag there, because it's looking for the change, and a long circuit is probably already a bit low voltage to start with. But it's more as a safety check, because if there is a loose connection, even on a very short run, that weak spot is very resistive and will have a big voltage drop when current tries to go through it, which can be a hot spot and dangerous.

 

[LEBSD]

I assume that your going to buy the Power Wall Charger? Remember, the normal mobile charger will only go up to 32 Amps/240V (learned that after installing a 50Amp breaker/wiring). As others stated above, you need #4 NMB (rated max 70Amp). Also, NMB can not be exposed and it cannot be in a conduit. I recommend using PVC Electrical pipe and run 2 #4 (240V), your gnd does not need to be a #4, can be smaller.

 

[DonaldBecker]

I assume that your going to buy the Power Wall Charger? Remember, the normal mobile charger will only go up to 32 Amps/240V (learned that after installing a 50Amp breaker/wiring). As others stated above, you need #4 NMB (rated max 70Amp). Also, NMB can not be exposed and it cannot be in a conduit. I recommend using PVC Electrical pipe and run 2 #4 (240V), your gnd does not need to be a #4, can be smaller.

A reminder to readers that "cannot be in a conduit" isn't as simple as it sounds.
NM-B can be "sleeved" for protection. Which means running the exposed part in a conduit, and not calling it a conduit.

There are extensive discussions elsewhere on the rules and interpretation. The take-away is that NM-B in 'conduit' isn't always a code violation. The most common place to see it is in a garage, just where you would find an EVSE connection.

 

[LEBSD]

A reminder to readers that "cannot be in a conduit" isn't as simple as it sounds.
NM-B can be "sleeved" for protection. Which means running the exposed part in a conduit, and not calling it a conduit.

There are extensive discussions elsewhere on the rules and interpretation. The take-away is that NM-B in 'conduit' isn't always a code violation. The most common place to see it is in a garage, just where you would find an EVSE connection.

You are right in that it can be in conduit. The NEC says

 

[LEBSD]

You are right in that it can be in conduit. The NEC says

I was trying to not go in details and not making it an electrical discussion but since we are talking installation, it is important to be per code. NMB cannot be in a conduit if it goes through a wet area (ex: coming from a wall and under a slab in a pipe). Also, if it is exposed, it needs to be protected for damage. So yes, you can run it inside a conduit in dry areas. Now practically, I use NM inside walls or over the ceiling ending in a junction box. If I need to go beyond that junction box, I just use a flex conduit with individual conductors ending in junction boxes. If I need to run outside the wall, I just run a conduit with multi-conductors ending in junction boxes (it is cheaper, easier to work with). Keep in mind that the NMB jacket does not slide very well in a conduit and bending a bundled set of coppers is not easy compared to individual conductors. If you plan running NM in a conduit over 6 to 8' with some type of bend, do yourself a favor and increase the conduit inside cross-area.

 

[LEBSD]

I am getting tired of having to repeatedly correct your misinformation and lying.


And here's the lying. This is a thread about people's home installations for EV charging, and you have been telling people here in this thread that they can use 6 gauge Romex with a 60A breaker. Stop. The wall connector doesn't have a way to set for 44A continuous, so that is not a valid answer.

No, that is not wrong. That would be the only correct way to do this if it were possible. The 6 gauge Romex has a max rating of a 55A circuit, but the wall connector does not have a 55A circuit setting. End. Of.

I am definitely not at all missing the point. The point in why we keep talking here is your stubbornness and obstinance in continuing to repeat things that are misleading to people and dangerous instead of accepting correction.

I am fully well aware of that.

I am not wrong. I have said repeatedly, agreeing with you, that it is possible to physically take your hands and hook those two things together. That is a thing that can literally be done. What I have been correcting you on (for the benefit of people who have to read this thread) is making sure people know that it is NOT something that can result in a valid code compliant circuit for charging their electric vehicle, because there would be nothing valid that they could use on the other end of it. And that is why it is not "irrelevant"; it is actually vitally relevant. People need to know that trying to use a 60A breaker is not a way to get to the goal they are trying to accomplish.

You earlier accused me of saying things that are wrong. Cite them and explain why you think that.

Thought I provide what I think are the applicable NEC code requirements:

210.3 Rating. Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device. The rating for other than individual branch circuits shall be 15, 20, 30, 40, and 50 amperes. Where conductors of higher ampacity are used for any reason, the ampere rating or setting of the specified overcurrent device shall determine the circuit rating.

210.21 Outlet Devices. Outlet devices shall have an ampere rating that is not less than the load to be served and shall comply with 210.21(A) and (B)...

Table 21O.21(B)(3) Receptacle Ratings for Various Size Circuits
Circuit Rating / Receptacle Rating (Amperes)
15 / Not over 15
20 / 15 or 20
30 / 30
40 / 40 or 50
50 / 50

Table B.310.15(B)(2)(1) Ampacities of Two or Three Insulated Conductors, Rated 0 Through 2000 Volts, Within an Overall
Covering (Multiconductor Cable), in Raceway in Free Air Based on Ambient Air Temperature of 30°C (86°F)*

 

[LEBSD]

Thought I provide what I think are the applicable NEC code requirements:

210.3 Rating. Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device. The rating for other than individual branch circuits shall be 15, 20, 30, 40, and 50 amperes. Where conductors of higher ampacity are used for any reason, the ampere rating or setting of the specified overcurrent device shall determine the circuit rating.

210.21 Outlet Devices. Outlet devices shall have an ampere rating that is not less than the load to be served and shall comply with 210.21(A) and (B)...

Table 21O.21(B)(3) Receptacle Ratings for Various Size Circuits
Circuit Rating / Receptacle Rating (Amperes)
15 / Not over 15
20 / 15 or 20
30 / 30
40 / 40 or 50
50 / 50

Table B.310.15(B)(2)(1) Ampacities of Two or Three Insulated Conductors, Rated 0 Through 2000 Volts, Within an Overall
Covering (Multiconductor Cable), in Raceway in Free Air Based on Ambient Air Temperature of 30°C (86°F)*

View attachment 644644

View attachment 644647

210.20 Overcurrent Protection. Branch-circuit conductors and equipment shall be protected by overcurrent protective devices that have a rating or setting that complies with 210.20(A) through (D).

(A) Continuous and Noncontinuous Loads. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load.
Exception: Where the assembly, including the overcurrent devices protecting the branch circuit(s), is listed for operation at 100 percent of its rating, the ampere rating of the overcurrent device shall be permitted to be not less than the Sum of the continuous load plus the noncontinuous load.

 

[TBrownTX]

4/3 Romex or go home.

Tim

 

[MY-Y]

4-2 NM-B is OK as well. I have 4-3, and it is difficult to route - especially through studs on a wall with drywall.. The supply house had 4-2, but I wanted the neutral just in case I put a 14-50 there later (I have an RV). Regarding the note above about 4-3 being difficult for a novice to install... I strongly discourage a novice from installing a high current circuit like the HPWC.

 

[TBrownTX]

now that is terrible advice. There is no need for a neutral. Installing 4/3 Romex, if you can find it, will be much more difficult to install for the novice that 6 thhn.....

I installed 4/3 Romex that I purchased at Lowes. I left the neutral capped. Should I ever move, I’ll use the neutral wire for a NEMA 14-50. And the 4/3 was totally manageable FWIW.

Tim

 

[ohmman]

Moderator Note: Removed some bickering and misleading (if technically accurate) information to snippiness. If you'd like to engage with another member on the possibilities for marginal installations, feel free to take it to PM. Otherwise, let's try to keep this thread informative and not argumentative. Thanks!

 

[Pictreed]

Ooof, this topic got thick. New Tesla coming soon. Just want to know if I can run 60 amp breaker with this wire 6/2 Copper MC Cable w/ Ground to the new Tesla charger and get the most out of the charger or do I need something else?