I'm adding a circuit to my garage for an EV charger. Yes, I have pulled a permit. I live in Massachusetts.
Here's my plan:
I'll be adding a new 60 amp GFCI breaker to the panel. Yes, there is space in the panel. The GFCI is required because the new circuit is in the garage (210.8.A). The nominal load of the charger is 50 amps so 60 amp is appropriate.
Said panel is in the basement, diagonally below the garage. I plan on running the wires exposed up the basement wall, then over along the ceiling to below the basement floor. I'll add a small hole (meeting (304.A.1)) into the floor of the garage. The wires will run on through the hole, up the wall of the garage, along the ceiling, then down a post in the center of the garage. Since the garage space would expose the wires to physical damage (300.4), I will need to protect the wires with conduit.
For this, I'll be using steel EMT which satisfies this requirement (358.E). (I wanted to use schedule 80 PVC but the big box stores are out of stock).
The charger I'm installing can draw as much as 50 amps and calls for a conductor compatible with 90C. In order to satisfy the 1.25x requirement for constant loads ( 215.2.A.1 ), the wire should be rated for 62.5 amps. I'll be using THHN AWG 6 copper which is rated to 65 amps and 90C (B.2(1)). Total wire distance is less than 35 ft.
Questions I don't have answers to:
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My charger only uses the two hot lines plus a neutral. What gauge does the neutral need to be? Citing the code for an answer would be appreciated.
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I will be direct wiring the charger. The hole for direct wiring is on the bottom of the charger while the wires will be coming from above. Is there an elegant way for the wires to do a 180 degree turn?
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I've read that water can condense on the inside of the EMT conduit. This can be addressed by adding weeping holes along the conduit. Should I be worried about this / address this?
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Are there requirements about the hole between the basement and garage besides size (304.A.1)?
products I'm using:
the post
Best Answer
STOP!
These two statements are in conflict.
If you hardwire a charger then you do NOT need a GFCI/breaker. If you install a receptacle for a plug-in charger then you do need a GFCI/breaker.
Hardwire is the preferred way to do this, and one of the reasons is because it removes the need for the GFCI/breaker.
Now let's get on to the sizing.
As you have discovered, 50A actual requires a 62.5A circuit. That means 65A-rated (60 C column cable or 75 C column wire) and general recommendation is either 6 AWG copper wire (not cable) or 4 AWG aluminum wire. Many chargers do not work with aluminum wire - check the specs to find out.
But that is on the order of double what you actually need. 20A (16A actual) or 30A (24A actual) is enough for most people, most of the time, unless they plan on two vehicles charging at the same time.
I would recommend one of two options:
Instead of running a 65A circuit directly to the EVSE, run a 65A (or perhaps 70A or even 90A, depending on load capacity) circuit to a subpanel in the garage. This subpanel might start out with just a 30A circuit for one EVSE (or perhaps a little larger, but do NOT put in a single EVSE at 50A/62.5A - that's just crazy and leaves you no room for anything else.) This has some key advantages over a single circuit: You can use aluminum wire between subpanels and then just short copper wire from the subpanel to the EVSE. You can add a second EVSE later on with just short wires to the new subpanel. You can add other circuits - lighting, tools, etc. to the subpanel.
Keep it small and therefore relatively inexpensive. In fact, if you limit it to 30A, which is more than enough for most vehicles charging overnight based on typical (and even a bit extra) usage, then you can use much more common (and much less expensive) 10 AWG/30A NM cable rather than going with conduit and wires. (Unless there is an outside = wet location component involved.)
Wires vs. Cables
Wires need protection all the time. Any place they are outside of a panel or junction box they need to be in conduit.
Cables only need protection where subject to damage. Typically this means exposed on walls but not inside walls (behind drywall) and not when above 8' (e.g., open ceiling). This protection can be large conduit or it can be a strip of metal or wood covering the cable.
Pick one or the other. If you are going outside then you have to go with wires/conduit. If you are inside then cables are fine (except where not allowed at all - e.g., Chicago).
What you really want to avoid, particularly when using large wires (e.g., for 65A) is connections. With 10 AWG 30A wire and cables, transitions are simple wire nuts. With 6 AWG, 4 AWG, etc. connections between wires requires Polaris or other special connectors which cost more and require more space to install. Plus transitioning between copper and aluminum is problematic. So pick something:
Neutral and Ground
If you install a subpanel, neutral (except at very large sizes) is the same size as the hot wires. From the subpanel to the EVSE no neutral.
If you install an individual circuit, no neutral. But if you do this and use conduit and small wires (e.g., 10 AWG 30A) to save money, I would size the conduit such that it could handle much larger wires for a subpanel in the future, including a neutral wire. Installation work will be the same, conduit cost will be higher but you will be future-proof.
Ground wire size is a little more complicated. According to this ground wire chart for a circuit (or subpanel) up to 60A, 10 AWG copper or 8 AWG aluminum. For a circuit (or subpanel) larger than 60A, up to 100A, 8 AWG copper or 6 AWG aluminum.
Wet Inside Conduit
Any conduit outdoors is presumed to fill with water. Weep holes in conduit bodies or junction boxes are a good idea. I recently saw an NEC update regarding sizing of those holes (if not provided by the manufacturer), essentially formalizing a common practice. If everything is inside conditioned space (garages vary quite a bit) then there may never be any water. YMMV. But if you use wires that are designed so that they can be in water (THWN vs. THHN) then there is no problem.
Load Calculation
You can't just "add big stuff everywhere". If you could do that, everyone could have tankless electric hot water heating, resistance electric heating and 50A EV charging without worrying about their electric supply. But it doesn't work that way.
While it does get complicated, there is a formal NEC Load Calculation procedure to determine how much power your home requires. It incorporates many different things, including:
You do this calculation for your entire house (utility service). That tells you how much room you have to add more things, such as EV charging. If you have enough room, great. If you don't then you can scale back (e.g., 30A instead of 62.5A for charging), change some things (e.g., heat pump instead of resistance heat) or do something to shed loads automatically.
In addition to your entire service, you really need a Load Calculation at each level. In this case, that means the subpanel that will be feeding the EVSE (or feeding a garage subpanel). If you have 200A total with 120A in use then you have 80A available. But if the subpanel you want to use is only being fed 100A and is already using 40A then you only have 60A to send to the garage. The details can vary quite a bit and you may have a major problem (unable to even dedicate 20A to charging) or you may have no problem at all. But you need to find out before you start installing things.