50 amp vs 40 amp vs 30 amp

[Joe schmoe]

If you are only overnight charging, speed won't matter as much, but for those times you need it NOW, speed matters. I am firmly entrenched in Camp Prepare For The Worst. As my dad likes to say, "always better to have it and not need it, than need it and not have it."

All things being equal, get the 60A circuit.

Another (probably cheaper) even more versatile option to cover the "once or twice a year" scenario is to buy a portable generator capable of maxing out the plug-in EVSE so you can charge one of the vehicles with the generator, and not have to load share for the other. I bought a 9.5kw Generac that can put out 120/240 and charge the Rivian in a pinch. It also has much greater capacity than the Rivian's 1500w inverter for maintaining critical house loads in the event of a power failure. You do have to make sure that the generator has a NEMA 14-50 and can output enough wattage continuously. Mine only has a 30 amp 240 outlet, but it was less than $900 delivered and is a well respected brand with good reviews.

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[Electrified Outdoors]

Depends on how much you drain the battery. If your only going from 70% to 40% no problem with 30amp (24 amp charging) overnight. The question is if you have to put in a new line why not go for the max charge rate (48 amps on a 60 amp breaker)? That way if you need to charge faster you can. 24 amps is relatively slow for a large battery like what is in the Rivian.

At 24amps on 240v its going to take you 12 hours to charge a Rivian from 20% to 70%.

 

[Monkey]

2023 NEC 625.42(B) does allow for if the EVSE has "restricted access to an ampere adjusting means". I do not have a Rivian charger (I have OpenEVSE which is software configurable), but I believe the dip switches qualify as restricted access.

That must be new for 2023. And how does that apply to other restrictions on wiring multiple devices to 240V circuits?

I'm not sure what would qualify as restricted access... If software controls would be adequate.

 

[Grabs10]

Longer you keep the vehicle awake and charging the less efficient the charging will be via the losses and energy lost keeping the vehicle awake and the charger running. Take it to the max capability and get the charging done and let the vehicle sleep. 6 hours of charging is going to have more losses then 3 hours of charging.

 

[ThisIsMyHandle]

So with 50 amps direct wired you are only going to deliver 48. The same with 60 and a plug.

I went 50 direct and get 26-27 miles per hour while charging at 48 amps. Charging at 24 amps prior when I was using my 30 amp dryer outlet was 11 miles an hour.

This page I found very helpful.

https://evadept.com/calc/ev-charging-time-calculator

 

[Monkey]

So with 50 amps direct wired you are only going to deliver 48. The same with 60 and a plug.

With 50 Amp direct wired, you get 40 Amp if you have it set up properly. Same as if you connect with a 50 Amp plug like a NEMA 14-50. Does not matter if the device is direct-wired on the circuit or not, the maximum sustained draw allowed is 80% of the limit. So a 60A circuit charges at 48A, 50 at 40, 40 at 32, etc..

I went 50 direct and get 26-27 miles per hour while charging at 48 amps. Charging at 24 amps prior when I was using my 30 amp dryer outlet was 11 miles an hour.

If you're charging at 48A on a 50A breaker, you're doing it wrong.

 

[ThisIsMyHandle]

With 50 Amp direct wired, you get 40 Amp if you have it set up properly. Same as if you connect with a 50 Amp plug like a NEMA 14-50. Does not matter if the device is direct-wired on the circuit or not, the maximum sustained draw allowed is 80% of the limit. So a 60A circuit charges at 48A, 50 at 40, 40 at 32, etc..



If you're charging at 48A on a 50A breaker, you're doing it wrong.

I don't know how my 50 AMP direct wired circuit works, and I won't pretend I'm an electrician.

They way the charger install manual and my electrician explained is you lose the 20% if you use a plug. That was the original plan actually, but then he cut out the plug, wired direct to the circuit breaker, and I have up to 50 AMPS I can deliver because there is no plug. Both MY EVs charge at 48 and I get the charging times you would expect from 11.5 KWH.

That's all I know.

 

[jjswan33]

I don't know how my 50 AMP direct wired circuit works, and I won't pretend I'm an electrician.

They way the charger install manual and my electrician explained is you lose the 20% if you use a plug. That was the original plan actually, but then he cut out the plug, wired direct to the circuit breaker, and I have up to 50 AMPS I can deliver because there is no plug. Both MY EVs charge at 48 and I get the charging times you would expect from 11.5 KWH.

That's all I know.

@Monkey is right. This is not to code and potentially dangerous depending on the wiring used, if the wiring is only rated for a 50A circuit then you risk overheating the wires and causing a fire. The codes have a safety margin for a reason.

The fix is to open the charger and change the dip switches to the correct setting for a 50A circuit.

Page 17 - https://assets.rivian.com/2md5qhoea...wall-charger-install-guide-en-us-20230525.pdf

 

[ThisIsMyHandle]

@Monkey is right. This is not to code and potentially dangerous depending on the wiring used, if the wiring is only rated for a 50A circuit then you risk overheating the wires and causing a fire. The codes have a safety margin for a reason.

The fix is to open the charger and change the dip switches to the correct setting for a 50A circuit.

Page 17 - https://assets.rivian.com/2md5qhoea...wall-charger-install-guide-en-us-20230525.pdf

I have the Charge Point Flex and I know he used 6 gauge wire... No dip switches, it just asked me if I was direct wired and what the breaker was.

 

[jjswan33]

I have the Charge Point Flex and I know he used 6 gauge wire... No dip switches, it just asked me if I was direct wired and what the breaker was.

Same applies. Just instead of dip switches it's a software setting in either the installer app or the chargepoint home app.

https://chargepoint.ent.box.com/v/Flex-Install-EN-US

6 gauge wire would depend on the type, most likely your electrician used Romex 6-3 which is not rated to 48A continuous.

 

[Monkey]

I have the Charge Point Flex and I know he used 6 gauge wire... No dip switches, it just asked me if I was direct wired and what the breaker was.

I've installed several ChargePoint Home Flex chargers. The manual does not in any way imply that you only lose the 20% from using the plug. Your electrician should automatically know that any SUSTAINED loads are to not exceed (in nominal operation) 80% of circuit capacity. The Charge Point manual does point out the maximum circuit setting usable with the plug is 50A, because you can order it with a 14-50 or 6-50 plug, or direct wire it.

6 AWG wire... Yes, that is the appropriate size, but hopefully he used the correct rated wire. When you configure the charger, it asks you what size breaker you are running. If you're direct wired on a 50A breaker, you would choose 50A circuit size on setup and it will operate properly. If that is how you're set up, you're charging at 40A and not 48A. And all is well.

 

[ThisIsMyHandle]

 

[Thedude]

How much more range will I get in a pinch over a 50 amp line vs a 30 amp line?

The math is simple. A 50 amp circuit will give you a 60% charge rate increase assuming you’re utilizing the circuit at 80% with an appropriate charger.

 

[Zoidz]

That must be new for 2023. And how does that apply to other restrictions on wiring multiple devices to 240V circuits?

I'm not sure what would qualify as restricted access... If software controls would be adequate.

For restricted access 2023 NEC references "Energy Management Systems" Article 750.30(C)(3) which specifies "at least one of the following":
- Located behid removable and sealable covers over the adjustment means
- Located behind a cover or door that requires a tool to remove
- Password protected with password provided only to qualified personnel
- Software that has password protection access provided only to qualified personnel

I interpret this as that the Rivian EVSE dip switches would qualify, but my OpenEVSE woud not qualify, because I can change the charge rate from the front panel or via the app.

 

[emoore]

Another (probably cheaper) even more versatile option to cover the "once or twice a year" scenario is to buy a portable generator capable of maxing out the plug-in EVSE so you can charge one of the vehicles with the generator, and not have to load share for the other. I bought a 9.5kw Generac that can put out 120/240 and charge the Rivian in a pinch. It also has much greater capacity than the Rivian's 1500w inverter for maintaining critical house loads in the event of a power failure. You do have to make sure that the generator has a NEMA 14-50 and can output enough wattage continuously. Mine only has a 30 amp 240 outlet, but it was less than $900 delivered and is a well respected brand with good reviews.

Why in the world would you charge an EV with a portable generator at home? Defeats the purpose of an EV.

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