Is there a 40 amp charging solution for home?

[FlasherZ]

The OP said 40 amp wire, so I assume it is a 40 amp breaker. If so, DO NOT terminate it with a NEMA 14-50, that is dangerous, against code, etc.

Terminating it with a NEMA 14-50 is not against NEC -- the code allows for it, but plugging the Tesla into it then violates code because it's considered a 50A load (with 125% continuous load provision). Technicality, but hey.

If only three wires were run, then the best you could do would be to use a NEMA 10-30 receptacle, but now you would really be pushing it since the 10-30 neutral connection would have to be connected to the (presumably) bare ground wire, and if the 10-30 receptacle were used as a 10-30 in the future for something other than Tesla charging, you'd potentially have current running over than bare wire. Not good.

You may NEVER connect a 10-30's neutral pin to the bare copper wire. The neutral *must* be insulated and it is a serious safety issue and code violation.

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Ah nuts. The convenient availability of a large number of such outlets for purchase online made me think it had to be legal.

You may only replace an existing 10-series receptacle with another one. They were in wide use prior to 1996, so that's why you still find them plentiful on the shelves. All new circuits (and subpanel feeders, for that matter) must be 4-wire.

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I'm not so sure about that. A 14-50 outlet is an advertisement of a 50A circuit. The assumption is the wire gauge and breaker behind it are all rated for 50A. However, if you go above 80% of the breaker's rating (40A) for more than 1 hour, it should trip the breaker. You should be able to use all 50A of it, but not for over 1 hour.

Not quite. NEC permits a 50A receptacle to be fed with a 40A conductor and OCPD (breaker), provided the load to be connected is rated for a 40A circuit. Connecting a 50A load to that is what violates the NEC.

If you want to switch back and forth between charging the car and running the sauna, put a 14-50 plug on the end of the sauna's hardwires and switch them when you want to use them. You might be able to put a switch in the middle between the sauna and the car, just make sure it's properly rated for the amperage. Go over a bit to be on the safe side, too.

NEC section 110 requires all manufacturer's instructions to be followed; some appliances are marked for hardwire only. While not a safety issue, technically it's a code violation to attach a plug to a device whose instructions specify hardware only.

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Replacement of an existing outlet may be OK, but I'm not sure. Where's FlasherZ when you need him?

FlasherZ needed a bit of a break to deal with holidays and business travel and a bunch of other crap.

I haven't seen one in person, but anecdotally, I've heard of newer homes with 14-50's for electric ranges, wired with a 40A breaker and 8 Ga wiring. Mine (built in '04) has a 50A breaker and 6Ga.

Many kitchen range outlets are configured as such because most electric ranges fall in the 30-40A range. It's not really a matter of saving a buck, it's a matter of sizing the circuits for the appliances the developer installs.

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If and only if the wire is rated to 50A, you would terminate it with a NEMA 14-50 receptacle as posted. The rating is for transient loads. For continuous loads, it is derated to 80%, so you'd run it at 40 A for routine charging.

Technical point - you don't de-rate for continuous loads, you size the conductors and OCPD's (breakers) for 125% of the offered load. The result ends up the same in most cases, but for certain sections of the code it affects calculations (stacking de-ratings e.g., temperature, etc.).

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You can't install a 30a receptacle unless you downgrade the breaker to 30a to match it...which probably isn't enough for the Sauna. I'd do the HPWC, set to charge at 32a to match the 40a breaker. It would be hard wired so you don't have to worry about the receptacle.

This is correct - two choices... either install an HPWC/EVSE set for 40A branch circuit, or place a 30A breaker & 14-30 receptacle on that circuit.

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And be careful of dryer 14-30's with Romex 12-3 on a 20A 2-pole too.

Big difference: a 30A receptacle may not be installed on a 20A circuit, while a 50A receptacle on a 40A circuit is permitted under the NEC. If you see a 30A receptacle on a 20A circuit, smack the installer/electrician over the head and hand them a copy of the code.

(NOTE: all my previous responses in this thread are per NEC, not CEC which the OP falls under... they're close but not equivalent.)

 

[linkster]

OMG!!! He's back to set us straight. :smile: Got worried there for a bit.

 

[tga]

FlasherZ needed a bit of a break to deal with holidays and business travel and a bunch of other crap.

I guess that's OK...:smile:

This is correct - two choices... either install an HPWC/EVSE set for 40A branch circuit, or place a 30A breaker & 14-30 receptacle on that circuit.

The 14-30 option assumes a neutral - if no neutral is present, then the OP's only real option is an EVSE/HPWC, correct?

Big difference: a 30A receptacle may not be installed on a 20A circuit, while a 50A receptacle on a 40A circuit is permitted under the NEC. If you see a 30A receptacle on a 20A circuit, smack the installer/electrician over the head and hand them a copy of the code.

This one confuses me - aren't they the same case? Sizing the wire and breaker for the expected load, and using a larger outlet rated to handle the current, ie, 20A wire/breaker & 30 A outlet vs 40A wire/breaker & 50 A outlet? I guess the right thing to do on a 20A dryer circuit would be to install a 14-20 (good luck finding that at Home Depot).

Does the difference settle around the existence of a 14-20 outlet, but the lack of a "14-40" outlet, or is there an explicit exemption in the code for the 40A/14-50 case?

 

[davewill]

This one confuses me - aren't they the same case? Sizing the wire and breaker for the expected load, and using a larger outlet rated to handle the current, ie, 20A wire/breaker & 30 A outlet vs 40A wire/breaker & 50 A outlet? I guess the right thing to do on a 20A dryer circuit would be to install a 14-20 (good luck finding that at Home Depot).

Does the difference settle around the existence of a 14-20 outlet, but the lack of a "14-40" outlet, or is there an explicit exemption in the code for the 40A/14-50 case?

Yes, because there are NEMA 20a receptacles to choose for this duty, you can't use a 30a receptacle. If you have a 25a circuit, then I think you can use a 30a receptacle...but I'm not an electrician and I'm not 100% sure of that one.

The 14-30 option assumes a neutral - if no neutral is present, then the OP's only real option is an EVSE/HPWC, correct?

You can have three wire circuits, but they have to have a three wire receptacle. a 6-30 or 6-50 would be fine with L1, L2, GND. The problem lies in the fact that Tesla doesn't offer an adapter for 6-30, and they discontinued the 6-50 (which wouldn't help anyway since it assumes a 50a circuit). You can create an adapter for 14-30 to 6-30, which doesn't solve the problem of no neutral it just keeps it from being a code issue since it's not permanently installed. If you do that, label the adapter for EV use only.

 

[Chris TX]

Terminating it with a NEMA 14-50 is not against NEC -- the code allows for it, but plugging the Tesla into it then violates code because it's considered a 50A load (with 125% continuous load provision). Technicality, but hey.

So even though the receptacle says "250VAC 50A" it's still code to put a lower gauge wire and breaker behind it? I know the breaker protects the circuit and will trip at its rating, regardless of the receptacle.

So my earlier suggestion to put a 14-50 outlet on that 40A circuit (wire and breaker), then dial down the Model S to only charge at 32A would be fine. Additionally, install a 14-50 plug on the end of the wires going to the sauna (or put a high amp switch in the middle to go back and forth between hardwired sauna and 14-50 outlet.

This seems like a lot of trouble to go to just to avoid running a dedicated 50A circuit to a dedicated 14-50 outlet (or even a HPWC).

 

[N4HHE]

I'm thinking if there is a sauna nearby with a 40A circuit then how hard would it be to run yet another 50A circuit right beside that one? I didn't see any mention of distances but if one is implemented then why not another?

 

[hemants]

I'm thinking if there is a sauna nearby with a 40A circuit then how hard would it be to run yet another 50A circuit right beside that one? I didn't see any mention of distances but if one is implemented then why not another?

Issue is distance but also cutting through finished basement. Sauna is right beside garage, panel is not

 

[Schmo]

Issue is distance but also cutting through finished basement. Sauna is right beside garage, panel is not

I had the same problem. Electrician installed a 14-50 outlet on the 40 amp circuit. I charge at 32 amps and all is well. Installing a new 50 amp circuit would have cost over a grand.

 

[FlasherZ]

The 14-30 option assumes a neutral - if no neutral is present, then the OP's only real option is an EVSE/HPWC, correct?

Correct.

This one confuses me - aren't they the same case? Sizing the wire and breaker for the expected load, and using a larger outlet rated to handle the current, ie, 20A wire/breaker & 30 A outlet vs 40A wire/breaker & 50 A outlet? I guess the right thing to do on a 20A dryer circuit would be to install a 14-20 (good luck finding that at Home Depot).

Same case, but it revolves around the standardization around receptacles. Table 210.24 summarizes circuit ratings and permitted receptacle ratings. 20 amp circuits may only have 15 amp or 20 amp receptacles (yes, 15A is permitted for 20A/120V circuits, because you typically have a bunch of 15A 120V outlets on a single 20A circuit).

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Yes, because there are NEMA 20a receptacles to choose for this duty, you can't use a 30a receptacle. If you have a 25a circuit, then I think you can use a 30a receptacle...but I'm not an electrician and I'm not 100% sure of that one.

Circuits are sized based on loads and conductors. If you have a 25A plug-connected load, it'll be on a 30A receptacle, which requires 30A conductors and 30A breakers. If you have a 25A direct-wire load, you must use conductors rated for 25A and go the next size up on the breaker (30A).

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So even though the receptacle says "250VAC 50A" it's still code to put a lower gauge wire and breaker behind it? I know the breaker protects the circuit and will trip at its rating, regardless of the receptacle.

Correct, although the 40A/50A case is the only case permitted by code.

So my earlier suggestion to put a 14-50 outlet on that 40A circuit (wire and breaker), then dial down the Model S to only charge at 32A would be fine. Additionally, install a 14-50 plug on the end of the wires going to the sauna (or put a high amp switch in the middle to go back and forth between hardwired sauna and 14-50 outlet.

Yes.