Home Charger Wiring, Does This Work?

[Ladiver]

I stand corrected but I would of asked him the follow up question of how fits that affect my up stream main breaker? At some point, you have the issue the sum being greater than the feeder breaker. No way to avoid it.

I will follow up with the inspector tomorrow

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[jphillips97]

I completely agree with you. If the house only has 200A service, then I am “dedicating” 62.5% of the usable power to a circuit for EV charging. I bet there is more than 80A worth of breakers in the current panel. I know there are 2 garbage disposals (which should be on dedicated 20A) and a steam oven with a dedicated 30A. There’s 70A, guess I need to go buy some candles because I can’t put in a 15A for lights.

honestly, I think you city inspector is wrong. But not for me to say. I’d consider a second opinion

 

[Zoidz]

Honestly, if your goal is to future-proof, have the electrician:
- Run conduit from your panel to a 4-square box in the car bay
- Pull 2x 6AWG hots and an 8AWG ground through the conduit
- Terminate it on a 14-50R with a 50-amp breaker

Now you can use it immediately with the portable charger at 32A or with a specifically purchased 40A charger equipped with a 14-50P.

Then, if you want to hardwire a 48A-amp charger down the line, all you have to do is replace the receptacle face of the 4-square with a whip that goes to your hardwire charger, spliced right there in the existing box and swap the 50A breaker for a 60A one.

Agree. The only thing I would do differently for full future proofing would be to also run a neutral. Some new fangled EVSE or other vehicle/charge technology could require a neutral because the device needs 120 VAC for whatever reason, and they don't provide a 240/120 control transformer. Or at a minimum, if you run conduit, size the conduit for the neutral, install a pull line, and pull the neutral later if needed. This is a case where "never say never" applies.

Edit:
I also noticed something possibly overlooked in this thread - GFCI.

NEC 625.54 Ground-Fault Circuit-Interrupter Protection for Personnel
In addition to the requirements in 210.8, all receptacles installed for the connection of electric vehicle charging shall have ground-fault circuit-interrupter protection for personnel.

 

[timesinks]

Agree. The only thing I would do differently for full future proofing would be to also run a neutral. Some new fangled EVSE or other vehicle/charge technology could require a neutral because the device needs 120 VAC for whatever reason, and they don't provide a 240/120 control transformer. Or at a minimum, if you run conduit, size the conduit for the neutral, install a pull line, and pull the neutral later if needed. This is a case where "never say never" applies.

That's why I suggest conduit (1" minimum). Easy to pull the neutral in the future if you need it without buying wire today you may never use.

 

[ajdelange]

OK, I spoke with a City Inspector and he said if both circuits are going to be used for EV charging (even if not at same time), the sub-panel (50A and 60A) should be supplied with a 125A breaker.

honestly, I think you city inspector is wrong. But not for me to say. I’d consider a second opinion

The inspector may not always be right but he is always the inspector. In this case we have an EVSE load of 48 A and a receptacle into which a second 40 A EVSE can be plugged for a continuous load of 88 A. The pane/wiring must support 1.25 times that equal to 110A. This is for NEC compliance. Your JHA may have additional requirements. Or he may not have inderstood your question or forgotten that there are 110A breakres available (I did) or done the calculation wrong. When the moment of truth comes if he wants to see 125A you will want to have 125 in there or the code book in your hand.

 

[Dirty_B]

Yes, breakers can fail closed and the code deals with this by not allowing you do put more than the intended load on a wire. In this way, you'd have to have two failures instead of just one to be in a really bad state (a short circuit and a failed breaker at the same time).

By definition in the code, the receptacle intended for an EVSE and the circuit for a hardwire EVSE would both be continuous loads. It's not an either-or thing unless there is some additional equipment to ensure it's operated either-or. The code doesn't care what you intend to do in terms of not using both at the same time. That's in large part because what you intend to do may not be what your house guest or future owner will do.



Your proposed subpanel with two EVSE circuits (one for a hardwire outlet and one for a receptacle) without an interlock or load management system, requires that you size the feeders to 125% of the maximum load of the equipment. That's all the equipment. That's the code.



Most people have at least marginal awareness that it's not a great idea to run multiple "power hungry" things on one circuit. That awareness is the first line of defense. This is also only something we do for relatively low amperage circuits (15A and 20A). Most things at higher amperages require dedicated circuits.

People also mistakenly think if you run 16A on a 15A breaker that it'll pop right away. In reality, for a breaker to trip right away, you typically need around 5-6x the handle rating -- that would be 75-90A on a 15A breaker. The further over 15A, the faster it should trip. If you're only an amp or two over, it may well not trip at all.

Thanks, interesting - never knew that about tripping it. But to be honest I bet 99% of people don't know what outlet is on what breaker and what other outlets are on same breaker...me to a large extent as well. They just buy the house and plug stuff in.

I've found some double throws for $400 up to $X,000, I think that would work for OP...vs just using an A/B rotary switch made in China, sold on Amazon, and certified by no one (horrible idea).

 

[ajdelange]

I stand corrected but I would of asked him the follow up question of how fits that affect my up stream main breaker? At some point, you have the issue the sum being greater than the feeder breaker. No way to avoid it.

Your main panel breaker is determined in the same way as sub panel breakers. It must cover all the loads connected to it but as I have pointed out a couple of times already in this thread not all loads are treated the same. Code requires a certain allowance for lighting per square foot but knowing that not all the lights in you house are on all the time assigns some percentage of the lighting requirement as the lighting load. Something similar is done for 120V outlets (per foot of wall IIRC) and then there are rating for washers, driers, electric ovens, heat pumps etc. To work up a robust load calculation really requires software though there are forms you can find in books. It is because, before the advent of BEV, there were few if any continuous loads in a normal residece, that one would often find a 200A (400 pole amp) panel with 800 pole amps of branch circuits.

 

[Zoidz]

OK, I spoke with a City Inspector and he said if both circuits are going to be used for EV charging (even if not at same time), the sub-panel (50A and 60A) should be supplied with a 125A breaker.

I suspect that the inspector is basing his statement on the NEC section below and the fact that EVSE is considered continuous load (defined as operating for more than 3 or more hours continuous). Trying to compare/justify to residential panels with regular 120v, 15A outlets is irrelevant since they are considered non-continuous loads.

Just because they are an inspector does not mean they are correct. I've been there more than once. You have to be able to prove they are wrong by showing them in the code why they are wrong. Some will admit it and professionally move on, others will reluctantly admit it, get pissed off, and they will double their efforts to "show you who is boss". Sometimes it's better to suck it up and do what they want (when it's in excess of code requirements) if it doesn't cost you much.

210.19 Conductors — Minimum Ampacity and Size
(A) Branch Circuits Not More Than 600 Volts
(1) General

Branch-circuit conductors shall have an ampacity not less than the larger of 210.19(A)(1)(a) or (A)(1)(b) and comply with 110.14(C) for equipment terminations.

(a) Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch-circuit conductor size shall have an ampacity not less than the noncontinuous load plus 125 percent of the continuous load in accordance with 310.14.

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