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That is exactly what was said in post 16.
Electric Vehicle Charging Stations Demand Factors
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T.M.Haja Sahib
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But it had reference to post #15 and also see posts # 4, 5 & 6.
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mivey
Senior Member
... and he goes down swinging!
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jjkind
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In the last few months I've read through the 2008 and 2011 editions about 3 times, working through a few problem books preparing myself for the ICC exam.
That stated, your (iwire) original post confused me, too. The original poster asked about the application of a demand factor to an EV circuit. By definition (70-26 of 2008 NEC) Demand Factor is the ratio of the maximum demand of a system, or part of a system, to the total connected load of a system or the part of the system under consideration. It doesn't make sense for this to be more than 1. I'd expect a demand factor to be something like 0.5, suggesting that half the capacity (receptacles, lights, motors, etc.) is being used at any one given time. Your first response read like you were trying to say that this could be 1.25.
Nonetheless, it was pretty clear what you were saying (I think at least) - that the overcurrent protection and branch circuit ampacity should be sized based on 125% of maximum load because, as per 625.21, an EVCS is considered a continuous load.
Two completely different topics, I think, and potentially confusing to mix things together. Probably no need to call mention to your knowledge of the NEC. I think T.M.Haja Sahib was simply trying to clarify the terms being used. To newbies (like me) who are looking to this page as a reference and a place to clarify our interpretations of the NEC's language, it's actually somewhat of a detractor to asking/answering questions.
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inspector141
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I have traveled all over the country teaching classe on EVSE and this has come up many times and generated some good discussion. The NEC does not distinguish between chargers that may be used intermittently against chargers that serve a fleet of cars that will all be charged simultanously. If you have 20 level II chargers for a fleet of 20 cars, there is a likelihood that all of the chargers will be used continuously for an extended period of time beyond 3 hours. Currently, the NEC requires the branch circuit and the feeder to be sized at 125% of the charger rating. If a Level II AC charger has a charge rate of 6kw, but the car only has a maximum charge rate of 3.5kw, then that charger will only draw a maximum of 3.5kw. But, we will never know for sure what charge rate any given vehicle will actually be. Some vehicles slow down the charge rate for a Liion battery when it reaches an 80% charge due to excessive heat, but it is still considered a continous load.
What does this mean? The branch circuit and the feeder must still be sized at 125% of the EVSE per NEC 625.21. There is no demand that is allowed to be used at this time.
What does this mean? The branch circuit and the feeder must still be sized at 125% of the EVSE per NEC 625.21. There is no demand that is allowed to be used at this time.
Marty is spot on about no DF for EV charging. Another good point about minimum cabling to a charge station wired for a LEAF will not support the optimum charge rates for other EV's such as a TESLA.
A conductor cable rough-in for a continuous charge EVSE would be better to have a feeder optimum sized for high energy draw vehicles to avoid an extra cost to upgrade again. $$$
A conductor cable rough-in for a continuous charge EVSE would be better to have a feeder optimum sized for high energy draw vehicles to avoid an extra cost to upgrade again. $$$
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