Calculating feeder/service loads for EVSE

[jeffgreef]

A contractor has applied for a permit to add two 50 amp circuits to a house for two EVSEs. The service is 200 amps. We asked for whole-house calculations to confirm that the main panel will handle it. The contractor came back with calculations using the alternative method (220 part IV), with general loads at 100% of first 10kva, remainder of general at 40%, and HVAC at 100%. With these calcs, with the EVSE considered a general load, they just squeek by, but it's the demand factor that gives them that. So, if they plug in both cars at once while about 14000 watts of AC are operating, They could be pulling about 130 amps just through cars and AC alone (cars 35 amps each, AC about 60 amps).

Questions:

1-Is an EVSE, and/or an electric car, an 'appliance'? I say it is, based on definitions of 'appliance' and 'utilization equipment' in Art. 100

2-Can an EVSE and/or an electric car be included in 'General Loads' per 220.82(B)(3)a. which reads- 'All appliances that are fastened in place, permanently connected, or located to be on a specific circuit'? EVSEs are fastened in place but cars are not, EVSEs are permanently connected but cars are not. But- EVSEs and cars are BOTH 'located to be on a specific circuit'.

Thoughts?

 

[bob]

Unless the house has several A/C units, the load you show appears too high. My 4 ton unit pull 28 amps.

 

[jeffgreef]

Yes that's a very high number for AC. That's what he gave me.

Two 35 amp chargers are adding 70 amps to a 200 amp panel, which will work in a lot of scenarios, but in others will push the limitations of the calcs. In that case, contractors will want to apply the demand factor to the charger load to make the calcs work. Unless chargers are excluded from being used with this demand factor, it is compliant to do so.

Anyone have a code reasoning that excludes chargers from the demand factor calc of 220.82?

 

[jeffgreef]

Or220.83, same issue.

 

[charlie b]

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.

 

[bob]

Cost of Gasoline VS Electric
http://www.dailyfinance.com/2013/06/24/gas-vs-electric-cars-cost-comparison/

Interesting information

It is some what off the subject. Hope Charlie won't delete it.:angel:

 

[jeffgreef]

Thanks Charlie, I see your point that this is not the same type of device described in the list of types of appliances. I'm not committed either way on this, but just for the sake of exploration I'm going to play devils advocate here and look at through the eyes of a contractor who is going to hold me to the letter of the code. I think you have expressed what is probably the original intent of the code, but the question I have is, does the letter of the code express that intent?

220.82 says that it shall be permissible to use that alternative instead of the regular method. This seems to imply that it is permissible to use this alternative as the whole calculation, including all loads. But it doesn't say that specifically, and it also makes no provision for any other 'non appliance' loads such as welders and car chargers.

220.82(B)(3)a. Includes in the general loads 'all appliances ... located to be on a specific circuit.' If an EVSE or an EV is an appliance, it is certainly located to be on a specific circuit.

Utilization equipment 'utilizes electric energy for ... electromechanical ... purposes.' (100) That's what a car does. The code doesn't say it has to do so within proximity of the premises wiring system, so one could argue that it can be utilized on the freeway as well as in the kitchen.

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.' (100) At best to exclude auto charging from this is a judgement call about the intent of the writers of the code- did they mean to limit the definition to domestic machinery used only within proximity of the premises wiring system? Is a car domestic machinery? Is a car charger industrial? Is deep frying industrial? Etc etc.

At this point I think that those with decades of experience with the code can speak to the intent, but it seems to me that the specific wording does not clarify that intent. Since we are seeing a lot of these chargers in some places, perhaps there is a need for such clarification.