I hear your Nth degree concern. Perhaps I will look into changing the 14-50 to a 14-30 (dryer socket that I have) and getting a 14-30 adapter from TESLA. As I tested the line and the 30 amp panel breaker trips at 28, I don' think this will make me feel any safer. It's just semantics. In my view a 30 amp line with a 30 amp breaker that trips at 28 with the car set to 24 and, if it fails, will revert to 40 on a breaker that trips at 28 is about as safe as one can be.
One other comment to add to this thread: Breakers are not meant for repeated tripping. Each trip wears them and damages them. Breaking a circuit while under current load causes arcing which melts things. I know of commercial entities that insist on breaker replacement after just a handful of trip cycles (I think someone told me seven at one point). Proper load calculations and design are the first line of defense, breakers are the last ditch emergency backup. I am solid in my belief that the software settings in the Tesla vehicle don't meet code for load purposes. They are tied to unreliable GPS and they can be adjusted by laymen (i.e. my wife, child, etc...)
You guys sure know a lot about this stuff. So if I understand correctly, and this is my installation, I have 6-3 awg wire coming from a 50 amp breaker
to a NEMA 14-50 outlet, my breaker must be GFCI. Is that correct? I wouldn’t have known to ask my electrician these questions. Thanks very much.
Yes, if permitted under 2017 NEC and your state has not modified that section of the code before adopting it, NEC 625.54 says you must have GFCI protection if you are installing an EV charging outlet.
Now not all AHJ's know this and enforce it as it was a last minute add to the code under an emergency change. When I pointed this out to the head of the code board for Oregon he was pissed that it slipped in because Oregon had struck most of the other new GFCI requirements from the 2017 code but they missed this one.
If you install a 14-50 for some purpose other than an EV (say an RV) the GFCI breaker is not required in a residence under the 2017 code.
My personal feeling is that if the receptacle is installed in a dry location then the GFCI requirement for EV's is stupid since the EVSE always provides GFCI protection downstream. So the only danger is the receptacle from the wall to the EVSE. Normally the reason they require GFCI's in garages is because they think you will use an extension cord and drag the circuit outside into the rain. But that is not a danger with EVSE's.
GFCI breakers commonly have nuisance trip issues with the Tesla UMC's and so that is my hesitation. My 14-50 in my garage does not have a GFCI breaker and I am more than fine with it. Also, I have never seen an RV park with GFCI breakers on the 14-50's which is hilarious since that is massively more dangerous I think since you are commonly plugging in RV's in the rain here in Oregon.
But a 30a breaker would not meet code???
A 30a breaker on a NEMA 14-30 receptacle would meet code always (since the receptacle is equal to or greater than the wire and breaker rating and nothing with a load greater than 30a should have a 30a plug on it). A 30a breaker on a NEMA 14-50 receptacle would meet code as long as "the load to be served" is 30a or below (24a continuous). So if you intended to plug one of those Clipper Creek EVSE's in that have a 14-50 plug on them but draw 30a or below (24a continuous) you would be fine.
No, it draw almost nothing. The car is set to 24a, so when the UMC is then connected to the car, it will draw 24a and the "load to be served" is 24a.
The wide ranging consensus around here is that changing the charge rate settings in the car DOES NOT COUNT as changing the "load to be served". Too many cases of the car forgetting the right setting with software updates, and the method is unreliable (GPS based), and it can be accidentally bumped or changed by a laymen. The "load to be served" is determined by the adapter you use on the UMC (and hence what it sends in the pilot signal to the car as the max amount to be drawn), or in the case of the Wall Connector then by the rotary dial that is part of the installation setting process (under a cover with a bunch of security Torx screws).
Really? So if the homeowner later buys a UMC Gen 1 the 40a branch circuit with 14-50 receptacle fails code retroactively?
Yeah, I know this is the crappy part, but it is how code is written today. I am wholeheartedly onboard with changing the code to require new installs of 14-50 receptacles for EV's to always have 50a circuits. So as code is written today, if you change from a UMC Gen 2 to a UMC Gen 1 you are changing "the load to be served" from 32a continuous (requiring a 40a circuit) to 40a continuous (requiring a 50a circuit). It is not that the receptacle failed code compliance, it is that you are changing the load to be served and that requires re-evaluating the sufficiency of the circuit. I think this is a horrible idea and the code needs fixed. Also, I feel this is one big reason Tesla's new UMC's only do 32a continuous. It avoids the issues with 14-50's installed only 40a circuits.
Question1: Does a Wall Connector require a 100amp circuit? If set for a 30amp circuit, it will only draw 24a. But it the setting is changed, it can draw up to 80a.
A Wall Connector can be installed on any circuit size from 15a to 100a, It has a HARDWARE setting for max current that is buried under a ton of high security Torx screws. The general consensus is that this definitely counts to definitively set "the load to be served". So matching that setting on the Wall Connector to the wire/breaker size is acceptable. It is also acceptable to oversize the wire and breaker into the Wall Connector (up to a max of 100a) but artificially set it lower via the rotary dial in order to deal with load calculation issues (i.e. you don't have enough capacity to allow the higher rate).
Question 2: Does a UMC gen 2 with a 14-50 plug require a 40a circuit? If the car is set for 24a, it will only draw 24a. But if the setting is changed, it can draw up to 32a.
Yes. A UMC Gen 2 with a 14-50 plug adapter installed on it MUST be in a 40a or 50a circuit.
No, because there is a 30amp socket/ receptacle available, so you would install a 14-30. The only reason 40amp is allowed on a 14-50 is because there are common household loads at 40a and there is no 40a socket. The exception is really only intended to accommodate electric stoves and has been in place long before EVs ever came along. I expect them to update the NEC in the future to exclude sockets intended for EV charging from the 40am 14-50 exception.
I have posted this many times in this thread and provided code references. There are situations where installing a 14-50 receptacle on a 30a (or even lower!) circuit could be allowed under the current code. But I would not generally advise it.
There are special rules for stoves and ranges that yes, do call out that 40a is allowed, but they DON'T APPLY to EV charging on a dedicated receptacle circuit. Please read my posts upthread.
I do agree that the NEC should change to require 14-50 or 6-50 receptacles installed for the purpose of EV charging and that are not re-using existing wiring, they should ALWAYS be installed with wire and breakers sufficient for 50a. I would like to see that change made.
The load to be served is the max rated load of the equipment, the mobile cord is rated at either 40 or 32Amps depending on the Gen so the load to be served is either 40 or 30, software on the car does not change the max load of the cord. The wall connector is physically changed to reduce the max rated load and therefore you can install whatever breaker is needed, If you change out the head on the EVSE then you have changed the max rated load as well. But you can't have a 14-50 on a 30a breaker and limit it to 24a on the car.
Just a point of clarification, I think you meant "the load to be served" is either 50 or 40 (after the 125% adjustment for continuous load) for the UMG Gen 1 or UMC Gen 2 respectively.
For that purpose, yes, because you have a 40a circuit you are trying to plug a continuous 40a load into. It's the same as if you have a stove outlet with 40a wiring and then try to plug an RV or welder or EV into, it's not rated for that and therefore does not meet code.
So FWIW, some RV's might actually be fine on a 40a circuit with a 14-50 receptacle. I guess it depends on what all is in the RV that demands power. (note that I have not read RV specific code so I am not sure how this is calculated - it may just be calculated like any regular subpanel draw in a house)
Also, some welders may be fine on a 40a circuit using a 14-50 receptacle depending on their size/output. Note that there are all sorts of special allowances for welders in the code since they are super intermittent use devices. I also have not looked at these code sections deeply.
yes, because the socket is a 14-50 so it's required to have either a 40 or 50a circuit, again the 40amp exception was never intended to be used in reference to EVs and I'm sure they will update section 625 that specifically covers EV circuits. The car is not the device plugged in, the evse is, therefore the car is not used to determine the rated load, the EVSE and plug are. The evse is rated at 32amp continuous and therefore requires a 40amp circuit. Separate from that, the plug is a 14-50 and therefore requires a 40 or 50 amp setup.
Apologies, but this is incorrect. Look upthread at the posts where I have explained this in detail with code references. A 14-50 is not required to only have either a 40a or a 50a circuit. It is required to be on a 50a or below circuit (can't be over the rating of the receptacle) and it must be sufficient for the load to be served. So if your load to be served is the Clipper Creek EVSE that only draws 16a continuous, you can use it on a 20a circuit. (again, not that I would recommend this generally).
Yes, that is what would be installed. But a 14-50 receptacle would meet code for a branch circuit.
Yeah, to clarify, a 14-50 receptacle on a 30a branch circuit would be acceptable if "the load to be served" was 30a or below (24a continuous). But generally a 14-30 is a better solution in that case. Though if you have a Clipper Creek EVSE that has a 14-50 receptacle on it but only draws 16a (continuous) and you only have wiring sufficient for say 30a, then yeah, the solution there is a 14-50 receptacle on a 30a circuit (or even a 20a circuit) and that is totally code compliant under 2017 NEC.
