HPWC: about the subpanel

Joe Electric said:

As I look at various user installations, I see some have it and some do not. When is the subpanel needed, and when isn't it?

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Generally, it's needed when you don't have enough space in the main panel or are going to provide power to other circuits close to the HPWC. Although I don't have a HPWC yet, I have a subpanel ready for it (it won't use a 100 amp breaker though). The subpanel also provides power to the washer and dryer and a 6 KVA ups.

A long run, perhaps to a different structure (detached garage), would be another reason.

And to clarify, Tesla does not have a box, official or unofficial. Someone just decorated the box in the photo with a Tesla sticker.

I had a subpanel installed (much smaller) on one side of the garage and then ran the connection to the HPWC from it. They are not next to each other so the HPWC still looks nice. Also my subpanel was installed flush (inside the wall) as opposed to the surface mount installation shown in your photo.

In some of the installation photos you've seen, you might actually be looking at a shut off switch as opposed to a sub panel. There are rules about requiring a disconnect means for the HPWC and in some jurisdictions, that might mean having to put a big box with a switch next to the HPWC.

pgiralt said:

In some of the installation photos you've seen, you might actually be looking at a shut off switch as opposed to a sub panel. There are rules about requiring a disconnect means for the HPWC and in some jurisdictions, that might mean having to put a big box with a switch next to the HPWC.

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Many of those jurisdiction consider a close enough panel the same as a disconnect, so just a panel is cheaper than a panel and a switch and the panel is potentially more useful as additional circuits can be run from it.

Article 625 (EV charging) requires an "accessible disconnect" and spells out a few more items to guarantee the ability for you to lock the supply "open" or de-energized. The inspectors I've talked to have expressed differences in opinion as to what that means -- some believe that as long as you can lock the door to your breaker panel containing the 100A breaker to your HPWC, you're fine. Some AHJ's want it within view, and some want it within the same room or even within reach. It's left to interpretation by your inspector.

Many have a subpanel in the garage because they will have multiple receptacles for EV charging and doing several "home runs" back to the home's panel is more expensive than a single, large feeder to a subpanel and then smaller circuits to individual receptacles and HPWC's. Some people need a subpanel because of the "accessible disconnect" interpretation. Some need it - as mentioned above - because there's no room for more breakers in the main panel. Some need it because of the way their electric service is delivered to their home.

NEC 2014 Section 625.42, "Disconnecting Means", says "for electric vehicle supply equipment rated more than 60 amperes or more than 150 volts to ground, the disconnecting means shall be provided and installed in a readily accessible location. The disconnecting means shall be lockable open in accordance with [section] 110.25." NEC 2011 was worse, and is still in effect in many jurisdictions - there, section 625.23 stated that "portable means for adding a lock to the switch or circuit breaker shall not be permitted", which led a few overzealous inspectors to require a rather expensive separate disconnect... the local inspectors I deal with were okay with a breaker lock-out in the main panel (didn't have to be in the same room).

You can use a smaller subpanel, here are some 125A versions:
http://www.gordonelectricsupply.com/index~path~product~part~5714386~process~search~qdx~0~ds~dept~text~Square+D+Qo148L125Gf+Load+Center+Qo+Mlo
Amazon.com: GE Energy Industrial Solutions TL412CP Main Lug Indoor Load Center, 125-Amp: Home Improvement

Joe Electric said:

Ah, this must be it. The picture in my OP wasn't really representative, I've seen big shutoff switch boxes next to the HPWC.

Are these provided by Tesla, or is that something that we have to supply separately.

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You'd have to provide everything outside of the HPWC itself. A good electrician will know exactly what you need based on your situation and will typically include the parts as part of their cost.

The TESLA setup uses a Hubbell Disconnect switch and as you can see looks functional with the HPWC.
The lockable disconnect switch is only necessary if the HPWC has more than a 60 amp breaker and the loadcenter/breaker panel is not in the same room (readily accessible) with the HPWC.
Of course the inspector may want the disconnect immediately adjacent to the HPWC.
There is also an Elimia 100 amp Disconnect switch that is about 1/4 the cost of the Hubbell unit.
Also the center of the disconnect switch handle can be located up to 2 Meters off the floor so it can be above the HPWC of you don't want the cluttered look of them side by side.
The big metal boxes (disconnect or subpanels) are typically much less expensive.

I used 3 phase disconnects that I bought as industrial take outs on eBay. Only needed to use two of the three poles. They each cost less than $100 as opposed to $400 to $600 new. This allowed me to run #1 copper from the main panels to the disconnects and then #2 copper into the HPWC. #1 copper was less expensive than #2, go figure!
I have two HPWC's both wired this way back to 200amp main panels. One for the Model S and the other for the Model X sometime soon.

Nice salvage there.