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New paper on implementing EV charging in multifamily facilities

Jared Jones | Posted in Green Building Techniques on

Jeff Gilmore from Ecovillage at Ithaca in Ithaca, NY has recently published the attached paper describing strategies and methods for implementing EV car charging at scale in multifamily residential environments while keeping costs manageable.

It focuses on 5 key, interlinked strategies:

1. Focus on installing 240v charging-ready outlets, not chargers
2. Use daisy-chained wiring for charging circuits.
3. Choose chargers with circuit-sharing capabilities.
4. Standardize on one vendor of networked chargers.
5. Plan ahead for scale.

By following these practices, they now have charger-ready outlets installed for about 80% of their 100 households and have facilitated the purchase of EVs in 25 of them.

I thought it might be of interest to this community.

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Replies

  1. Walter Ahlgrim | | #1

    1. Focus on installing 240v charging-ready outlets, not chargers
    2. Use daisy-chained wiring for charging circuits.
    3. Choose chargers with circuit-sharing capabilities.
    4. Standardize on one vendor of networked chargers.

    Maybe I missed it buy it seems like if everyone’s charger is on a shared circuit then it seems unlimited fuel is included in your rent?

    1. James Howison | | #2

      I *think* the "who used what energy from the shared circuit" is handled through the data collected by the wifi connected chargers. This lets them know which charger spot used what KwH. Then (on the last page) they say they average their KwH costs from their multiple providers and charge that to the individuals.

      So in effect the "meter" is in the plugged in charger rather than in the electricity panel.

      I'm guessing that these are spots associated with individuals? Or maybe the JuiceBox chargers are able to identify which car they are connected to?

  2. Expert Member
    Zephyr7 | | #3

    I would strongly advise against daisy chaining power for EV chargers. There is too much risk of overload here, and tap rule codes limit how much extra capacity you can put on a circuit suppling multiple receptacles.

    For smaller facilities, I would home run the charging outlets back to a central subpanel dedicated to the chargers. This would keep wire lengths short, which is important in this age of spendy copper. I just got off a conference call where minimizing copper costs was one of the topics we were discussion for a new project.

    For medium size facilities, I would daisy chain several small subpanels, spacing those subpanels out throughout the car parking area. One large feeder would supply the subpanels, looping through each one (you can get subpanels with in and out lugs on the busbars). Individual charger receptacles would be fed from the nearest small subpanel.

    For very large facilities, I would feed 480v circuits (600v for our Canadian readers), placing transformers for every small cluster of receptacles. This will allow for the main feeders to run at higher voltage, and reduce copper costs and system losses. This 480v system would likely be a three phase service, and 480v tp 240v single phase transformers could be used with every third panel fed from the next two phases to keep loads balanced. You can daisy chain transformers by feeding each one through a fusible switch or circuit breaker tapped off of a main feed.

    Load balancing can help limit peak loads on the feeders, but you still can't just plug a bunch of chargers into a shared circuit and expect it to work safely. Typical charing runs will exceed 3 hours, which is where the code classifies things as "continous" loads, and you can't exceed 80% of the circuit rating when operating that way without using special equipment and engineering everything.

    Bill

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