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FLIR pics and wall charger/breaker temps

mrprometheus

Member
Jul 21, 2021
14
48
New York
After a Gen3 wall charger install I was curious on temps so I took some FLIR pics. They are quite interesting to look at. Makes you appreciate what is going on that your eyes can not pick up.

Setup
100A subpanel in garage
60A breaker to wall charger
#6 romex of about 20 feet dedicated branch circuit
Gen3 Wall charger
Model S Plaid

Results
The wall charger was initially set to 48A for about an hour but dialed back to 44A in Model S location settings due to breaker temps being warm and realizing code really wants you to be at 20% of the rating for constant loads and #6 romex gets a hit at being rated 55A. Being right at the 48A limit made things feel warmer than maybe they should be. Needs more testing to see if setting the location limit to 44A made a difference. Until then will likely set the wall charger to 40A. It is not going to be that much of a noticeable addition of time for charging for my situation.
 

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Vines

Active Member
Jul 20, 2018
2,192
2,685
Silicon Valley, CA
Cool pics, are those the phone version or one of the larger ones?

I'd not have that 55A wire on a 60A breaker, if for no other reason than the NEC says so. If you own a FLIR you might know significantly what you are doing.

Your car will pull the amount it is set for, but guests might not, assuming those are a thing again. Better safe than sorry imo.
 

mrprometheus

Member
Jul 21, 2021
14
48
New York
Cool pics, are those the phone version or one of the larger ones?

I'd not have that 55A wire on a 60A breaker, if for no other reason than the NEC says so. If you own a FLIR you might know significantly what you are doing.

Your car will pull the amount it is set for, but guests might not, assuming those are a thing again. Better safe than sorry imo.
FLIR is the phone usb-c/Android version. I should have mentioned units on the color scale are Fahrenheit so within the temp specs of wire and breaker.

I *think* that with the round up breaker size allowance in NEC and the wall charger "appliance" being hard restricted to max of 48A that the 55A #6 romex just barely sneaks into within code territory. Splitting hairs though and agree that it would be safer to not worry that another car comes or worse a firmware update or something ups the wall charger beyond 48A rating.
 
  • Disagree
Reactions: Rocky_H

Rocky_H

Well-Known Member
Feb 19, 2015
7,111
8,735
Boise, ID
60A breaker to wall charger
#6 romex of about 20 feet dedicated branch circuit
Gosh, ^&$%ing dammit! How do people constantly end up with this code violation?!?!
I *think* that with the round up breaker size allowance in NEC
People get this wrong frequently. There is a provision for round up of the breaker, but NOT FOR THE WIRE! That's probably the most simple way to point this out. The wire is still limited at 55A rating, so it CANNOT be for a 60A circuit. There are hardly ever any real practical situations in which this round up provision can really be used.
and the wall charger "appliance" being hard restricted to max of 48A that the 55A #6 romex just barely sneaks into within code territory.
That's not how that works. That is full 100% usage of a 60A circuit. NEC specs the circuit requirements for intermittent versus constant loads. For constant loads, it says it must have a circuit rated for 125% of the constant current level. That is running at 48A, and must have a full 60A rated circuit. Using only 55A rated wire, you DON'T have a 60A rated circuit.

And before you say it's not constant current because it only runs for a few hours at a time, no. NEC now defines all electric car charging as always being treated as constant loads.

Since you used 6 gauge Romex, the way you can be code compliant without having to rerun the wire is to switch it to a 50A breaker and configure the wall connector for a 50A circuit.

In a way, I guess it's good that people keep posting threads on other unrelated things and just offhandedly mention that they are using #6 Romex on a 60A circuit. Because at least this way they can find out that they are doing something dangerous and get it fixed. If they never mentioned it, they might never know they have that problem.
 

Vines

Active Member
Jul 20, 2018
2,192
2,685
Silicon Valley, CA
FLIR is the phone usb-c/Android version. I should have mentioned units on the color scale are Fahrenheit so within the temp specs of wire and breaker.

I *think* that with the round up breaker size allowance in NEC and the wall charger "appliance" being hard restricted to max of 48A that the 55A #6 romex just barely sneaks into within code territory. Splitting hairs though and agree that it would be safer to not worry that another car comes or worse a firmware update or something ups the wall charger beyond 48A rating.

FLIR is Forward Looking Infra Red. FLIR One is the Phone version Handheld Thermal Cameras | FLIR Industrial | Teledyne FLIR

I guess this is a case where the proper knowledge wasn't passed along to you. I'd recommend setting that HPWC correctly for the 50A breaker that this installation should have.

As a PV and ESS electrical designer, who does this for a living I agree with everything @Rocky_H said above.
 

mrprometheus

Member
Jul 21, 2021
14
48
New York
Agreed with everything both of you mention. Already swapped out the 60A breaker with a 50A last night and wall unit reconfigured for 40A max on the 50A breaker.

I knew that initial setup setup was questionable hence the FLIR pics to confirm and hopefully show others that heat is certainly there and to be concerned with.

The gotchas that I think we see this setup keep coming up are the following:

1) The instruction manual Tesla provides for Gen 3 wall unit mentions using #6 for a 60 amp circuit. There is a brief "Upsize as required" statement that is likely intentionally vague. This gotcha ties to the next few.

2) #6 Romex/TW/UF is only rated to 55A however THHN is 75A when in a proper conduit. When people, and Tesla above, simplify and say use #6 without specifying the type and installation method of #6 this gotcha comes out. The experience of a licensed qualified electrician/installer is going to sort this out.

3) Seeing mention of the breaker round up rule is really a disservice. It makes you think the 55A to 60A works out but the gotcha is that these chargers are absolutely constant current AND the appliance limits are easily reconfigured. There are ways to force the charger to respect 44A as a max but this gets you in the position of individuals having to know the setup. If anything changes you are quickly in a very dangerous spot. Breakers are there to protect the wires so rounding up beyond the wire should raise flags. I am curious where this rounding up sits well with an installer regardless of appliance. Feels like one of those exception cases that has a very specific purpose that rarely is worth knowing about. Proper size your breakers for wires.

4) Running conduit is not always ideal. In the grab for Romex #6/2 and #6/3 being far more available than #4/2 and #4/3 makes the likelihood of coming back to the above gotchas larger.

Appreciate the feedback and hope the pics help show that being above/right at the limits is a risk. Also highlights the nuance in code and specs.
 
After a Gen3 wall charger install I was curious on temps so I took some FLIR pics. They are quite interesting to look at. Makes you appreciate what is going on that your eyes can not pick up.

Setup
100A subpanel in garage
60A breaker to wall charger
#6 romex of about 20 feet dedicated branch circuit
Gen3 Wall charger
Model S Plaid

Results
The wall charger was initially set to 48A for about an hour but dialed back to 44A in Model S location settings due to breaker temps being warm and realizing code really wants you to be at 20% of the rating for constant loads and #6 romex gets a hit at being rated 55A. Being right at the 48A limit made things feel warmer than maybe they should be. Needs more testing to see if setting the location limit to 44A made a difference. Until then will likely set the wall charger to 40A. It is not going to be that much of a noticeable addition of time for charging for my situation.
Cool photos. Not sure if what I am seeing is the wires leading in to the breaker, but it looks like the wire has a bend in a tighter angle. I maybe mistake, but having the wire bent like that can produce a lot more heat than a slight bend. Might be worth looking in to. Did you do this yourself or have an electrician do it?
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,111
8,735
Boise, ID
What is recommended wire for a full 60A?
Whatever complies with electric code. That's why I find this so shocking that it gets messed up so often. It is mostly pretty straightforward. Here is a table of wire types, and their allowed amp ratings:


Where your installation is going usually determines what type of wire or conduit or cable you will want to use, and then you just pick the gauge of that which shows that it's rated at least 60A.

Any vendor of CB (Square D?) recommend, or to avoid?
You don't usually get a lot of choice with circuit breakers, because you usually have to match the brand of your panel and can't mix and match most of the time. Some do have an alternate brand that is compatible, but I don't know what those are offhand.

This may be a good place to throw in this general warning: if you happen to have one of the old Federal Pacific brand panels, the breakers for those were horrible for defectivity rates and were a fire hazard, so if you have that, you should replace it now anyway.
 

MontyFloyd

Member
Aug 9, 2021
364
227
Houston
Where your installation is going usually determines what type of wire or conduit or cable you will want to use, and then you just pick the gauge of that which shows that it's rated at least 60A.
I see from chart lists various standards, which have no idea what they mean.

If I understand this correctly, #6 THW, THWN, SE, USE, XHHW they can be sustained 75°C (167°F) temp and good for 60A circuit.

But it looks like a #4/3 is better/safer option, caveat is if you can get it (as mentioned in above post).
Yes?
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,111
8,735
Boise, ID
If I understand this correctly, #6 THW, THWN, SE, USE, XHHW they can be sustained 75°C (167°F) temp and good for 60A circuit.
Yes, if you are doing individual wires in conduit, that's that middle column of stuff, and the #6 is good for up to 65A, so that's good. If you are having to run inside walls, so you are using that multi-wire bundled cable, that is called NM-B, and it's the first column. The #6 of that is only good up to 55A, so that won't work for a 60A circuit. You would need the #4 for that.
 
  • Informative
Reactions: MontyFloyd
Gosh, ^&$%ing dammit! How do people constantly end up with this code violation?!?!

People get this wrong frequently. There is a provision for round up of the breaker, but NOT FOR THE WIRE! That's probably the most simple way to point this out. The wire is still limited at 55A rating, so it CANNOT be for a 60A circuit. There are hardly ever any real practical situations in which this round up provision can really be used.

That's not how that works. That is full 100% usage of a 60A circuit. NEC specs the circuit requirements for intermittent versus constant loads. For constant loads, it says it must have a circuit rated for 125% of the constant current level. That is running at 48A, and must have a full 60A rated circuit. Using only 55A rated wire, you DON'T have a 60A rated circuit.

And before you say it's not constant current because it only runs for a few hours at a time, no. NEC now defines all electric car charging as always being treated as constant loads.

Since you used 6 gauge Romex, the way you can be code compliant without having to rerun the wire is to switch it to a 50A breaker and configure the wall connector for a 50A circuit.

In a way, I guess it's good that people keep posting threads on other unrelated things and just offhandedly mention that they are using #6 Romex on a 60A circuit. Because at least this way they can find out that they are doing something dangerous and get it fixed. If they never mentioned it, they might never know they have that problem.

I think the confusion may come from Canada. We have NMD90 wire up here that we call Romex.

The difference between our NMD90 and the US NM-B is that NMD90 is rated for 90C and NM-B is only rated for 60C.
 
  • Informative
Reactions: Rocky_H

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