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Tesla wall charger users. What size wire is your charger using?

ozziegn

Member
Jul 31, 2019
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26
Orlando
I have a Tesla wall charger that's being fed by 6AWG wire with a run of 50 feet or less to my main breaker panel. The wire is attached to a 60A breaker. I did the research and according to some sites, 6AWG wire should be able to carry 50A at 50 feet or less. I had my wall charger set to charge at 44A but the 60A breaker was getting a little too warm for my comfort level. So I'm wondering if my breaker getting pretty warm is normal or not? I have toned the charging level down to 33A until I figure things out.

What size wire are other Tesla wall chargers using at what charging rate?

This site shows 6AWG should carry 50A over a 50 foot run.

wiresize.png
 
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ucmndd

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Mar 10, 2016
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There’s no ambiguity on this topic in the electric code, which makes it easy for an accurate, concise answer.

6awg type NM wire (commonly called “Romex“) - bundled wire with a nonmetallic insulation on the outside, usually used inside finished walls - can be used on circuits up to 55 amps.

Other types of individual 6awg conductors such as THHN or THWN, RUN IN CONDUIT, can be used in circuits up to 65 or 75 amps, depending on the temperature rating you are allowed to use by code or local restrictions.

So the answer is, it depends on the type of 6awg wire you’re using.

Warm breakers are normal. HOT breakers are not.
 

mswlogo

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Aug 27, 2018
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There’s no ambiguity on this topic in the electric code, which makes it easy for an accurate, concise answer.

6awg type NM wire (commonly called “Romex“) - bundled wire with a nonmetallic insulation on the outside, usually used inside finished walls - can be used on circuits up to 55 amps.

Other types of individual 6awg conductors such as THHN or THWN, RUN IN CONDUIT, can be used in circuits up to 65 or 75 amps, depending on the temperature rating you are allowed to use by code or local restrictions.

So the answer is, it depends on the type of 6awg wire you’re using.

Warm breakers are normal. HOT breakers are not.

And you are allowed to use a 60A breaker because they don’t make a 55A.

As far as I know the Wall Connector doesn’t have a 44A setting. It has 40A and 48A, you must set it to 40A (NOT 48A). There is no 33A setting either.

You have to round DOWN from 55A * 80% = 44A. So round down to 40A.
 
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ucmndd

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As far as I know the Wall Connector doesn’t have a 44A setting. It has 40A and 48A, you must set it to 40A (NOT 48A).

It’s much less confusing to use the “circuit breaker” column in the installation manual for the rotary setting.

In this case, if OP is using 6awg romex, he should use rotary setting 8 AND replace his 60A breaker with a 50A breaker, which will deliver 40A max to the car.

If 6awg THHN or THWN in conduit. Rotary setting 9 with a 60 amp breaker, delivering 48A max to the car, is allowed/optimal.

61A696C4-5B3F-4DBC-9E52-DC5FFBD89F35.jpeg
 
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brkaus

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Jul 8, 2014
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Re: breaker temp. I’m pretty sure I’ve measured my 50a breaker (40a load) at about 115 F.

Posted it and a thermal image here somewhere.
 
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mswlogo

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I don’t believe that’s true. On the contrary you MUST downsize to 50A in the case of 6awg romex, not upsize to 60.

Google it. You’ll see several threads on this site about it, as well as others. For this application since you need to round down to 40A load anyway, a 50A breaker is a good idea. But it’s not required. Nor would either breaker itself cause the high temp in the breaker the OP is worried about with the wall connector set to 40A (charging).

But there are applications that can use the 44A load and would need a 55A breaker and you are allowed to round up (for circuit protection) to a 60A breaker. But It is still a 55A circuit.
 
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ajdelange

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Dec 10, 2018
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Virginia/Quebec
I believe I have No. 1. It's a long story having to do with a long run, choosing to use SE rather than run conduit and ultimately that that is what the warehouse had in stock. It is total overkill, even for a 100 A circuit but it runs nice and cool and maintains load voltage over 240 even when the car is drawing 72 A. It also cost me a bunch.
 

ucmndd

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Mar 10, 2016
7,037
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California
Google it. You’ll see several threads on this site about it, as well as others. For this application since you need to round down to 40A load anyway, a 50A breaker is a good idea. But it’s not required. Nor would either breaker itself cause the high temp in the breaker the OP is worried about with the wall connector set to 40A (charging).

But there are applications that can use the 44A load and would need a 55A breaker and you are allowed to round up (for circuit protection) to a 60A breaker. But It is still a 55A circuit.

I understand what you’re saying but it seems ambiguous at best, which is a bummer given my first post in this thread says the NEC is unambiguous on this topic. ;)

This thread seems to be a good representation of thoughts on the topic and is specific to the use case of EVs.

Next size up: conductor size, too? - Mike Holt's Forum

The last post on that thread is salient. I’m 99% positive my local inspector would fail a 60 amp breaker on 6awg NM.

Completely agree RE your point that none of this makes a hill of beans difference with respect to the breaker itself heating up.
 
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ozziegn

Member
Jul 31, 2019
47
26
Orlando
So the answer is, it depends on the type of 6awg wire you’re using.

Warm breakers are normal. HOT breakers are not.

I believe I'm using normal Romex, 6AWG wire that's not inside conduit except in the actual garage where the line comes down from the ceiling to the sub panel I installed for the wall charger.

Re: breaker temp. I’m pretty sure I’ve measured my 50a breaker (40a load) at about 115 F.

Posted it and a thermal image here somewhere.

I set my rotary dial to #7 which toned the charge rate down to 9kwh from #9 which was charging at 12kwh. I will use my infrared thermometer and take some temp readings.

I will also add this. On top of pretty warm breaker temps while the charger was set @The #9 setting, my breaker would also have a slight buzzing/humming sound at the breaker for the first 15 minutes or so after I'd plug the charger in my Model 3. The buzzing/humming sound would go away after 15 minutes or so but that still alarms me why it does that.
 

mswlogo

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Aug 27, 2018
6,178
5,336
MA, NH
I understand what you’re saying but it seems ambiguous at best, which is a bummer given my first post in this thread says the NEC is unambiguous on this topic. ;)

This thread seems to be a good representation of thoughts on the topic and is specific to the use case of EVs.

Next size up: conductor size, too? - Mike Holt's Forum

The last post on that thread is salient. I’m 99% positive my local inspector would fail a 60 amp breaker on 6awg NM.

Completely agree RE your point that none of this makes a hill of beans difference with respect to the breaker itself heating up.

It is a confusing topic especially where Tesla Table references “Circuit Breaker Rating”.

OP’s post has a few holes in it.
 

mswlogo

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Aug 27, 2018
6,178
5,336
MA, NH
I believe I'm using normal Romex, 6AWG wire that's not inside conduit except in the actual garage where the line comes down from the ceiling to the sub panel I installed for the wall charger.



I set my rotary dial to #7 which toned the charge rate down to 9kwh from #9 which was charging at 12kwh. I will use my infrared thermometer and take some temp readings.

I will also add this. On top of pretty warm breaker temps while the charger was set @The #9 setting, my breaker would also have a slight buzzing/humming sound at the breaker for the first 15 minutes or so after I'd plug the charger in my Model 3. The buzzing/humming sound would go away after 15 minutes or so but that still alarms me why it does that.

If it was on #9 that would be wrong.
#8 is the correct setting (based on what was posted).
 
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ucmndd

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Mar 10, 2016
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If it was on #9 that would be wrong.
#8 is the correct setting (based on what was posted).

Agree.

OP, by code you can’t exceed 80% of the rated ampacity of your conductors for “continuous loads” like EV charging. In the case of 6/3 romex this is (55 x 0.8) 44 amps. Since there’s no 44 amp output setting on the wall connector you need to round down to the 40 amp setting (dial setting 8). Ideally you’d downsize your breaker to 50A to match, providing extra overcurrent protection for the conductors, but it seems that isn’t technically required strictly speaking.

This setup will give you 40A charging at the car.

As mentioned though, none of this really speaks to why you might be seeing higher than normal temperatures at the breaker. To diagnose that I’d pull it and verify the terminations. Are the lugs properly torqued? Are you certain you have no insulation pinched in them?
 
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ozziegn

Member
Jul 31, 2019
47
26
Orlando
I'll change my charger dial from #7 to #8 and see if the breaker heats up like before when I had it set to #9. I don't see any harm by using a 60A breaker for now. I will change it to a 50A if need be.
 

brkaus

Well-Known Member
Jul 8, 2014
8,095
6,649
Austin, TX
I believe I'm using normal Romex, 6AWG wire that's not inside conduit except in the actual garage where the line comes down from the ceiling to the sub panel I installed for the wall charger.



I set my rotary dial to #7 which toned the charge rate down to 9kwh from #9 which was charging at 12kwh. I will use my infrared thermometer and take some temp readings.

I will also add this. On top of pretty warm breaker temps while the charger was set @The #9 setting, my breaker would also have a slight buzzing/humming sound at the breaker for the first 15 minutes or so after I'd plug the charger in my Model 3. The buzzing/humming sound would go away after 15 minutes or so but that still alarms me why it does that.
My first brand new 50a breaker got pretty darn hot and had a slight buzzing sound. Tightening the wire lugs didn't help. Replaced the breaker with a new one and it was fine.
 
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eprosenx

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May 30, 2018
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Other types of individual 6awg conductors such as THHN or THWN, RUN IN CONDUIT, can be used in circuits up to 65 or 75 amps, depending on the temperature rating you are allowed to use by code or local restrictions.

Other types of wire that can be used at 75c include SE wire and MC cable. Also, for the most part you can't use the 90c rating of wire since I don't know of any residential breakers that are rated at over 75c terminals so the fact that the wire can do more does not really help.

I don’t believe that’s true. On the contrary you MUST downsize to 50A in the case of 6awg romex, not upsize to 60.

So NM wire is limited to the 60c rating which is 55 amps. As mentioned elsewhere in the thread, the Wall Connector only has certain steppings. 40 amps or 48 amps are the relevant ones here. They would require 50 amps or 60 amps of conductor AND breaker ampacity respectively. So you are forced to set the Wall Connector to 40 amps with 6 AWG NM cable.

Now the question is if you can still use a 60 amp breaker even though at the 40 amp setting you only NEED a 50 amp breaker (which is a standard size breaker). 2017 NEC (NFPA 70) 240.4(B) is what defines the "next size up rule". I don't see anything in the rule that says you can only make use of that rule if you NEED it for the intended load.

Screen Shot 2019-10-16 at 10.35.13 PM.png


So while it may be allowed technically, I would not do it normally. I see zero reason to oversize the breaker even more than the 125% rule requires.

It’s much less confusing to use the “circuit breaker” column in the installation manual for the rotary setting.

Yeah, that is probably poorly labeled. It should be labeled as "circuit ampacity" or something like that. "Circuit Breaker" is actually technically WRONG and could be dangerous if someone had sized it using the "next size up" rule.

I understand what you’re saying but it seems ambiguous at best, which is a bummer given my first post in this thread says the NEC is unambiguous on this topic. ;)

This thread seems to be a good representation of thoughts on the topic and is specific to the use case of EVs.

Next size up: conductor size, too? - Mike Holt's Forum

The last post on that thread is salient. I’m 99% positive my local inspector would fail a 60 amp breaker on 6awg NM.

Completely agree RE your point that none of this makes a hill of beans difference with respect to the breaker itself heating up.

Yeah, I actually do think technically a 60a breaker on 6 AWG NM cable is allowed as long as the Wall Connector is set to a 40a max charge rate, but you are right, an inspector might give you a hard time for it. Honestly though, I generally find the inspectors just don't look that closely or know the code well enough to get to that level of detail. Never have I had them look that deeply. EV charging has a lot of very detailed gotcha's with some EVSE's being settable load wise, the 80 / 125% continuous load rule (the fact that they ARE always continuous loads), the next size up breaker rule, derating for ambient temp or number of current carrying conductors, terminal ratings, Article 625.54 GFCI rules, etc... are all very complex and perhaps beyond your average residential inspector.

I believe I'm using normal Romex, 6AWG wire that's not inside conduit except in the actual garage where the line comes down from the ceiling to the sub panel I installed for the wall charger.

I set my rotary dial to #7 which toned the charge rate down to 9kwh from #9 which was charging at 12kwh. I will use my infrared thermometer and take some temp readings.

I will also add this. On top of pretty warm breaker temps while the charger was set @The #9 setting, my breaker would also have a slight buzzing/humming sound at the breaker for the first 15 minutes or so after I'd plug the charger in my Model 3. The buzzing/humming sound would go away after 15 minutes or so but that still alarms me why it does that.

So warm breakers are OK, hot is not OK. (warm is generally over your body temp to begin with, so I am not sure 115 degrees is actually outside the allowable range?) Note that "standard test conditions" in which they test breakers in (to 100% of their limit) is 40c (104f) in "free air" (so no other breakers up against them). Because they know other breakers will be around them and the temp of the breaker may exceed that, this is the reason the 80% rule comes into play (they only allow you to use 80% of the capacity for continuous loads so that when you go over 104f at the breaker you don't trip it).

Now, optimally though, it would run as cool as possible, that does sound a bit warmer than I would expect. And I don't like the buzzing. Buzzing is common in 60 cycle electrical systems, but it is not super common in residential breaker panels. I would probably inspect the breaker panel carefully (including removing the breaker with the panel powered down) and inspecting the bus bar behind it. I then would likely replace the breaker as they are only $10 or so. It is a cheap attempt at a fix for several issues you have (breaker size, breaker temp, and buzzing).
 
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eprosenx

Active Member
May 30, 2018
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Beaverton, OR
I ran 6 awg THHN the 12-ish feet through 1" metal conduit to the wall connector. Using a 40 amp breaker for 32 amp charging. Everything I can hit w/ the IR thermometer stays equal to ambient, even in 115+ temps.

I am not surprised! That is way overbuilt. :)

You could use a 60a breaker and get 48a charging on that exact same wire (with the right car that can make use of 48a).

But hey, you should never have to worry about the wire being insufficient with your current setup!
 

ajdelange

Active Member
Dec 10, 2018
1,077
638
Virginia/Quebec
Other types of wire that can be used at 75c include SE wire and MC cable. Also, for the most part you can't use the 90c rating of wire since I don't know of any residential breakers that are rated at over 75c terminals so the fact that the wire can do more does not really help.
This is an important point. Breakers have temperature ratings too.


Yeah, I actually do think technically a 60a breaker on 6 AWG NM cable is allowed as long as the Wall Connector is set to a 40a max charge rate
As W.C. Fields would say "Think again". The required breaker is there to protect the wire and is determined by the type of wire irrespective of the actual load. You can put a string of 20 A receptacles on a 20 A breaker and plug toaster ovens into all of them thus tripping the breaker as long as the wire is 12 (NM). But you can't put a single 15 A receptacle on a 20 A breaker if you have run No. 14 even if it's going to a night light. The reasons are pretty plain. You do an installation with No. 6 and a 60 A breaker, I buy your house, see the HPWC wonder why my car only reads 40/40 when there's a 60 amp breaker in the panel, open the box and reset it 40 a 68 breaker.
 

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