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Electric Car Charger Loads for Service and Feeder Calculations

jar546

jar546

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Does 625.42 require that electric car chargers be calculated separately and not part of the loads that get the 40% reduction such as in a SFD? Must EV chargers be calculated similar to that of HVAC? What are your thoughts.
 
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Did you mean 625.42? I guess that the world passed me by because I’m not familiar with the 40% reduction that you referred to. Oh .. it’s a continuous load.
 
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jar546 said:
Does 625.42 require that electric car chargers be calculated separately and not part of the loads that get the 40% reduction such as in a SFD?
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No. If Article 625 intended to amend Article 220, it would need some language a lot more explicit than anything in 625.42. And I gather the general ethos is all load calculation info should be in Article 220.

While it is problematic in theory that an EVSE gets a 40% demand factor in the dwelling unit optional method, absent multiple large EVSEs, it's not likely to be a problem in practice, as even the optional method is quite conservative.

Cheers, Wayne
 
steveray said:
Are you talking about 220.82B?
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If you point me in the right direction I'll catch on sooner or later. Even a blind squirrel finds a nut now and then.


220.82(B) General Loads. The general calculated load shall be not less than 100 percent of the first 10 kVA plus 40 percent of the remainder of the following loads:

(1) 33 volt-amperes/m2 or 3 volt-amperes/ft2 for general lighting and general-use receptacles. The floor area for each floor shall be calculated from the outside dimensions of the dwelling unit. The calculated floor area shall not include open porches, garages, or unused or unfinshed spaces not adaptable for future use.

(2) 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit covered in 210.11(C) (1) and (C)

(3) The nameplate rating of the following:
a. All appliances that are fastened in place, permanently connected, or located to be on a specific circuit
b. Ranges, wall-mounted ovens, counter-mounted cooking units
c. Clothes dryers that are not connected to the laundry branch circuit specified in item (2)
d. Water heaters
(4)The nameplate ampere or kVA rating of all permanently connected motors not included in item (3).
 
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jar546 said:
Who here considers a car charger an appliance.
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Appliance. Utilization equipment, generally other than industrial, that is normally built in standardized sizes or types and is installed or connected as a unit to perform one or more functions such as clothes washing, air-conditioning, food mixing,deep frying, and so forth. (CMP-17)

Ya that's a streeeetch. So it's not a nut after all?
 
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There is a section in the NEC specific to Appliances and there is a section in the NEC specific to EV Chargers, They are in different chapters.
 
jar546 said:
Who here considers a car charger an appliance?
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Well, for the purposes of applying 220.82(B), if it's not an appliance we don't include it in the load calculation at all. So let's stick with the expansive interpretation of appliance for 220.82(B).

Cheers, Wayne

PS From an electronics point of view, for normal charging the charger is within the EV itself. The fixed equipment installed to power that charger is an EVSE. It's just a slight smart switch; it provides AC to the EV after completing a handshake protocol which tells the EV how much current it may draw.
 
From Charlie B (moderator) at Mike Holt:

I do not agree that either the car or the charger meets the definition of appliance or of utilization equipment. Neither uses electrical energy for a purpose similar to those listed in the definition of utilization equipment. Neither uses electrical energy to perform a function similar to those listed in the definition of appliance. The charger provides electrical energy to the car, so that the car can be taken somewhere else in order to use the energy. I equate this to a cell phone, which I would also not call an appliance.

But my real problem is with the proposed use of 220.82 or 220.83. They both list the loads that are to be included in the optional calculation method. The charger does not match anything on the list. The code does not tell us to include any and all additional loads that are not covered by the list, before applying the demand factor. The code also does not tell us to add up the items on the list, then apply the demand factor, then add the nameplate rating of any additional loads that are not on the list. It would be the same if the homeowner wanted to use the garage as a machine shop, and installed a welding outlet. That is not covered by the list, so how could we use the optional method? I think you can't use either 220.82 or 220.83.

My suggestion is to have the contractor apply 220.87 by getting a year's worth of electic bills (presuming they show a monthly peak demand, and not just the total energy used) or by performing a 30 day load study.
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This section was written long before there were enough electric vehicle chargers to concern code writers. An electric vehicle charger would be more likely to have long term (several hours continuously) use than the listed appliances. On the other hand, electric vehicles would usually be used during the day and recharged overnight when few of the listed appliances are being used.

Charlie B's suggestion to use demands from a year's worth of electric bills is good for commercial work, but how many residences have demand meters?
 
jar546 said:
Ok Where would the EV Charger go in this calculation?
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With the appliances, the only place it can go, as that is obviously better than leaving it out altogether. And that's how the online calculator (you omitted the link) from the USDOE apparently does it.

As to the quote from Charlie B, I disagree on two points. First I don't agree with the idea that if you ever install a non-appliance in a dwelling unit, you can no longer use the optional method in Article 220. Any such limitation would appear in 220.82(A). That leaves you with the two choices of omitting the load or including it with 220.82(B).

Second, I will say that EV chargers and EVSEs do meet the definition of appliance. The function of moving people and goods from point A to point B fits in with the (non-exhaustive) list in the definition just as well as say cutting wood/shrubbery (chain saw or hedge trimmer) or projecting images on a screen (television). And they do come in standardized sizes--EVSEs are generally 16A, 24A, 30A, 32A, 40A, 48A, or occasionally higher. EV manufacturers likewise are using a handful of sizes of onboard chargers.

Cheers, Wayne
 
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