Got Electrician - What do I need to know?

[Semibruce]

FWIW: My licensed electrician used the wrong cable type to support a sustained 48A charge. Specifically, he installed 6/2 Romex NM-B cable, which is only rated for 55A. Because EV charging is considered a continuous load, that cable can safely support 40A max, not 48A.

I had my Rivian EVSE DIP switch set to 48A, which over time (a year+) resulted in “warm plug” warning and derating issues. Thankfully, Rivian replaced it under warranty, even after they pointed out the wiring issues from photos they requested as part of a warranty claim.

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[babock]

FWIW: My licensed electrician used the wrong cable type to support a sustained 48A charge. Specifically, he installed 6/2 Romex NM-B cable, which is only rated for 55A. Because EV charging is considered a continuous load, that cable can safely support 40A max, not 48A.

I have that same cable. I use 44A which is 80% of 55A.

 

[Semibruce]

I have that same cable. I use 44A which is 80% of 55A.

I'm not sure I understand. In my case, I had to adjust the dip switches to 40A to prevent overheating again.

 

[dj200]

Appreciate the feedback. It sounds like I could get away with a 100 amp panel, but it’s safer to go 200 amp.

I‘m running a 60 amp breaker in a 100 amp panel with no problems.
The charger is pulling 48 amps over 6 gauge wire with a length of 3 feet (Hard-wired). Never had any overheating problems.
If you are going to use a NEMA 14-50, then the max breaker size is 50 amps with the charger pulling 40.
Bottom line - the 100 amp panel should be fine. (Assuming your overall usage has “room”)

 

[babock]

I'm not sure I understand. In my case, I had to adjust the dip switches to 40A to prevent overheating again.

Thae max crrent that the AWG 6 Romex will support is 55A...as you stated. 80% of 55A is 44A.

With my Wallbox, I can set it from my app. Not that I am promoting wallbox, I hate it.

From the car's control panel, you can also limit it to 44A.

 

[Semibruce]

With my Wallbox, I can set it from my app. Not that I am promoting wallbox, I hate it.

Gotcha... Missed that. Unfortunately, my options are 40 or 48.

 

[Time2Roll]

Beacuse romex is in a tight sheath The NEC derates it and it is not acceptle for 48 amps. 6awg in a conduit sheds more heat and is code complient. Despite this many electricians will use 6awg romex on a 60 A breaker to a 48 v charger.

50A outlet should have the EVSE set to 40A max.

Also 40A circuit is fine on 50A outlet with the EVSE limited to 32A. This may also reduce the load to avoid upgrading the main panel. 32A is about 13 - 15 miles per hour range on the Rivian.

Is this not a rental? Good luck with $3K to upgrade a main panel.

 

[CampfireWisdom]

I‘m running a 60 amp breaker in a 100 amp panel with no problems.
The charger is pulling 48 amps over 6 gauge wire with a length of 3 feet (Hard-wired). Never had any overheating problems.
If you are going to use a NEMA 14-50, then the max breaker size is 50 amps with the charger pulling 40.
Bottom line - the 100 amp panel should be fine. (Assuming your overall usage has “room”)

Excellent! I got room and was told about $4K for a new panel. As a renter, hell no. So, I’m going to do as you all recommended.

Hubbell 9450a
Metal conduit
6 ga THHN
50amp (I’m fine with 9.6)
$525 - I provide outlet & breakers

 

[Kaiju]

Edit: Nevermind. If you're renting it makes no sense to pay yourself for the ugprade.

My house had a 200A service coming in but from the meter to the panel was only sized for around 150 and the panel itself was too small to accommodate the extra breaker (which was a code violation but hey). I did the math on my actual demand with certain things running and found out that yeah, I could trip the main if I was charging and certain other automatic things were running, particularly electric heat and the hot water boiler. I didn't want to have to manually manage that and didn't want to set the charger to only run at 20A.

There's also a point where if you make changes you'll have to bring everything up to current codes, which is a thing that can bite you if you're doing any sort of electrical work. I used the opportunity to not only match the 200A service coming in but completely replace the panel with a bigger one. Had to eat some extras to make everything compliant to the latest code, but it's not only futureproofing but avoids issues with either homeowners insurance demanding upgrades and potential issues with home inspections and quibbling if you sell.

I also used a Hubbell 9450A and put wire one gauge better than necessary in the wall, though it was actually a bit of a bear making the plug fit in the box because the wire was actually a bit too large/stiff to fit conveniently. I can't fault people for wanting to hardwire it, though personally I'm cool with charging at 40 amps and using the 50A plug/breaker combo. The plug has some extra utility and if I ever have problems with the charger it's just a matter of unplugging it and either using the portable one or getting another one. Or I can just take it with me places, though how convenient that is depends on which one you have.

 

[babock]

Gotcha... Missed that. Unfortunately, my options are 40 or 48.

You can set your charger to 48 and just set the car to 44 and you will charge at 44

 

[HaveBlue]

To the OP, step one will be a load calculation by the electrician. He should be able to give you a print out. Step two will be to evaluate the panel whether it can support that load calculation as just the main breaker of 100A means little if it's a legacy panel. There are a lot of things to consider beyond wire. You might get lucky and have a nice empty panel that can support a 60A circuit. You might have some Zinsco burned bus where maybe a 14-30A is what should have gone in. For code reasons, many mobile 14-50 chargers only draw 32A and that is often pretty safe.

 

[Rivian Owner]

To the OP, step one will be a load calculation by the electrician. He should be able to give you a print out. Step two will be to evaluate the panel whether it can support that load calculation as just the main breaker of 100A means little if it's a legacy panel. There are a lot of things to consider beyond wire. You might get lucky and have a nice empty panel that can support a 60A circuit. You might have some Zinsco burned bus where maybe a 14-30A is what should have gone in. For code reasons, many mobile 14-50 chargers only draw 32A and that is often pretty safe.

Yeah I've seen the Zinsco burned bus on more than one panel. Without doing the load calcs, by code you can't put more load in a 100 amp box than 100 amps. I guess you can do it if you want to gamble on things like an insurance claim being denied, just like you can drive your Rivian without insurance and hope you don't get in an accident.

As a renter modifying the electrical without permitting, inspections, and work done by a licensed electrician, and approval from the landlord could expose you to a lifetime of debt or worse if things go wrong. Because someone on the web says it's ok, doesn't make it ok. If the work is permitted and signed off by the city you will be covered, anything short of city approval leaves you exposed, including after you move out.

 

[HaveBlue]

Excellent! I got room and was told about $4K for a new panel. As a renter, hell no. So, I’m going to do as you all recommended.

Hubbell 9450a
Metal conduit
6 ga THHN
50amp (I’m fine with 9.6)
$525 - I provide outlet & breakers

That's the most reasonable way to go. Your code area may mandate a GFCI breaker for that outlet. You should consider looking for one that matches the panel. Two panel spaces will be needed for that otherwise the electrician will need some duplex or quad Plex replacements as well to make space. You'll need a deep outlet box that fits the 14-50; either a retrofit or surface mount. Several companies are making ev considered receptacles now as well.

 

[Rade]

I gave the Rivian charger specs to my electrician, and he took it from there.

 

[Oldsmobile_Mike]

use metal conduit

When I did mine, I didn't use conduit / armored cable. Granted, my install is only this far away from the garage sub-panel:

But now you've got me wanting to pull my wall board down and add it, LOL.

One of these days!

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