Attached garage subpanel for EV charging

[herbiethemisfit]

Looking for some assistance making some decisions regarding the subpanel I will be adding in my attached garage. I am getting an electric vehicle (Tesla Model S 75D ) this week and need to get a charging outlet installed.

Requirements for charging will be either a 50A (NEMA 14-50) outlet or a 60A circuit for the Tesla 'wall charger'. Also will be adding 3-4 20A 120V circuits for outlets, 1 15A 120V circuit for lighting and 1 15A 120V circuit for my yet-to-be-installed hanging NG furnace. No other 240V loads at the moment, but would like to get a larger air compressor in the near future.

A little more far-fetched would be to add a second EV in the future that would have similar 240V demand. Although it would likely be set up to load-share with the Tesla.

1-man shop. 3-car garage. Doing mostly car repairs (30gal air compressor, 120V) and woodworking (table saw, router table, dust collector - all 120v).

Main panel (200A, SQD QO) is in the unfinished basement. Subpanel will be 100A SQD QO 24 slot main breaker. Wire run will be approximately 50ft and will consist of: up from the main panel to the floor joists, ~30' along floor joist, 90deg turn to go thru garage wall ~5', then 90 deg turn up and into the subpanel.

Option #1 - Full 100A using #3 CU (3-3-3-8) THHN run in 1-1/2 PVC conduit. This would be the most work and most expensive. Would also be the most future-proof.

Option #2 - 85A (90A breaker) using #4 CU (4-4-4-8) THHN run in 1" or 1-1/4" PVC conduit. Same amount of work but less expensive. Maybe a little less work handling the smaller conductors.

Option #3 - 90A using AL 2-2-2-4 SER, no conduit. Least expensive and I'm assuming less work, although would have to wrestle with the larger conductors inside the panels.

I think I would prefer running conduit just for the sake of protection. But I suppose I could run the SER in conduit just for the last portion run into the garage.

I was leaning towards option #1 but the cost differences are pretty significant.

Thanks,
Jim

 

[Bert_]

SER is cheap and very easy to work with in that size, the aluminum will actually bend easier than copper. You can use #1 aluminum if you want 100A VS 90A. No problems sleeving the last few feet it conduit but it is a good idea to go a size or two larger than necessary.

You can also get individual conductors in aluminum either THHN or XHHW.

Might be a good idea to figure out what the car chargers actually draw, not just the breaker size, and what other loads you have planned

 

[Radix2]

You need to keep in mind that car charging is a continuous load so you need to upsize your wire and breaker by 125%.

For example the current top tesla charger is 72A - this needs a 90A breaker and wiring.

When talking about future proofing and combining with noncontinuous loads, it gets a bit more complicated. I just went through this myself, and my conclusion was to see what the max breaker was that would fit in my main panel and size everything to that as a continuous load. My 200a panel only holds up to a 125a breaker, so I went with 125a wire to the 125a subpanel. My thread with more info here: https://www.garagejournal.com/forum/showthread.php?t=344728&highlight=Tesla

 

[herbiethemisfit]

Thanks Bert. The onboard charger will draw 42A from the 50A outlet or 48A from the 60A wall charger. I haven't decided if I want to spend the extra $$ for the Tesla wall charger to get the additional power.

It looks like I would have to special order #1 AL SER around here.

Would 1-1/2" conduit work for 2-2-2-4 AL SER?

 

[75gmck25]

I ran 2-2-2-4 SER about 30 feet across my basement, and I think I drilled 1 1/4" holes in the floor joists. It was not a real easy pull, since the holes in the joists are not that smooth, but it definitely fit. 1 1/2" conduit should work fine, especially if you use LB boxes wherever you need to turn 90 degrees.

I have the same QO panel/sub-panel combination. You will find that HD and other box stores do not stock a QO breaker larger than 60 amps, so you need to order the 90 amp breaker or get it from an electrical supplier. I'm using 60 amps for mine right now since I don't really need more. I also needed to add additional large lugs in the panels because it was an detached garage and I had to isolate the ground. IIRC the main panel had an extra lug/connector for the neutral, but did not have a lug for the ground. It may work a little different for an attached garage.

Bruce

 

[wssix99]

I haven't decided if I want to spend the extra $$ for the Tesla wall charger to get the additional power.

This is where you are today... You'll want to have conduit installed so you can pull different wire in the future. Who knows what the next car will need, also?

A little more far-fetched would be to add a second EV in the future that would have similar 240V demand. Although it would likely be set up to load-share with the Tesla.

This is not where things are moving...

I was moved on to a "smart" meter last year and am now eligible for hourly power. (The cost of my power changes hour-by-hour depending on wholesale market prices.)

At some point, you will have similar options before you and your power company is going to make things attractive for you to charge both EV's at the same time while power is the least cost.

If you could max out at 2 EV's, you should go with a 200A panel to cover what you could need in the next 10 years. If you have conduit to your outlets, it will be easy to pull wire and shuffle breakers later.

 

[Bluevista]

Some people run a dedicated second service from the street to the garage if they call for a lot of juice.
That could get costly but may be cheaper in the long run if you have to do a lot of messing around to upgrade the house wiring to handle it.

I do resto work on older houses near the big city and some of them still have the original electric car chargers bolted to the walls in the garage or coach house. They're fed with cloth covered tube and knob type wiring going to real fuse boxes, very scary.
They look like something that Dr. Frankenstein would have used in his laboratory.

 

[grantw]

IIRC, the tesla wall charger only needs 240V and ground, no neutral. You can get probably get away with #2 thhn and 1" EMT conduit, maybe a ground if you are so inclined. The tesla wall charger has decent instructions.

If you do add conduit and panels, run it through a meter pan so you have the option of getting a second meter with a TOU / EV charging rates. If your utility supports that....

https://www.tesla.com/sites/default/files/blog_attachments/ms_hpwc_installation_guide.pdf

 

[Bert_]

I do resto work on older houses near the big city and some of them still have the original electric car chargers bolted to the walls in the garage or coach house. They're fed with cloth covered tube and knob type wiring going to real fuse boxes, very scary.
They look like something that Dr. Frankenstein would have used in his laboratory.

I want pic's! That stuff is only scary if you don't understand it, I think it's very cool.

 

[yeldogt]

How much are is #1 -- can't be all that much?

 

[Moto]

I do resto work on older houses near the big city and some of them still have the original electric car chargers bolted to the walls in the garage or coach house. They're fed with cloth covered tube and knob type wiring going to real fuse boxes, very scary.
They look like something that Dr. Frankenstein would have used in his laboratory.

Pictures, please.

 

[herbiethemisfit]

Thanks for all the replies. I am likely going with the 2-2-2-4 SER and a 90A breaker for cost and ease of installation. I see that I will have to order the 90A breaker. Menards has 100A DP breakers, but not 90. Thankfully the run is along the joists, so I don't have to drill through a bunch of them like Bruce had to. I will run 1-1/2" conduit where I go from the basement to the garage subpanel. That way if I ever do decide to upgrade to 100A, then at least that part is complete.

My utility (We Engergies) doesn't support any special EV rates. Just TOU, which I would need to analyze to see if it would make financial sense to switch to.

I do have a couple questions on running the SER both into the panel and into the LB/Conduit. For the panel, I don't have any room on top of the enclosure so I'll have to go thru the side which might be a little awkward. Do I just use one of those larger NM-style clamp connectors? Or how about transition to an LB and then into the panel? Also, similar with the transition to the PVC conduit - just use the same clamp connector with a threaded adapter?

Since my car is a 75D, it only has a max 48A charger (at 240V) on it when used with the Tesla wall connector. I'll start with the NEMA 14-50 outlet in the meantime which Tesla automatically limits to 40A thru the Universal Mobile Connector. It will be right next to the panel so I'll just run #4 to it so it'll be ready if/when I get a wall connector, which are $500...

 

[wssix99]

The onboard charger will draw 42A from the 50A outlet or 48A from the 60A wall charger. I haven't decided if I want to spend the extra $$ for the Tesla wall charger to get the additional power.

Aren't you talking about buying a $500 charger? That's what the 100A Tesla charger lists as. So, why not get that one? You can even get them off of eBay for much less. (I assume from people who didn't need them and worked out a deal with their cars.)

My utility (We Engergies) doesn't support any special EV rates. Just TOU, which I would need to analyze to see if it would make financial sense to switch to.

Therefore, they never will? (I think you will find that as soon as they catch up with their Smart Meter program, like larger Utilities, they will be able to offer the enhanced EV programs -> they are in the Utilities' best interest because it motivates EV owners to get on to base load and off of peak load.) My utility had no sign of our program over the summer and, all of a sudden it just showed up under the radar with no promotion or other advertising/fanfare.

I do have a couple questions on running the SER both into the panel and into the LB/Conduit. For the panel, I don't have any room on top of the enclosure so I'll have to go thru the side which might be a little awkward. Do I just use one of those larger NM-style clamp connectors? Or how about transition to an LB and then into the panel? Also, similar with the transition to the PVC conduit - just use the same clamp connector with a threaded adapter?

If you are going to go with conduit, the conduit should go box-to-box and you would want to use single strands of THHN wire. It should be really easy to pull now and if you ever need to upgrade the run.

 

[u3b3rg33k]

Thanks for all the replies. I am likely going with the 2-2-2-4 SER and a 90A breaker for cost and ease of installation. I see that I will have to order the 90A breaker. Menards has 100A DP breakers, but not 90. Thankfully the run is along the joists, so I don't have to drill through a bunch of them like Bruce had to. I will run 1-1/2" conduit where I go from the basement to the garage subpanel. That way if I ever do decide to upgrade to 100A, then at least that part is complete.

My utility (We Engergies) doesn't support any special EV rates. Just TOU, which I would need to analyze to see if it would make financial sense to switch to.

I do have a couple questions on running the SER both into the panel and into the LB/Conduit. For the panel, I don't have any room on top of the enclosure so I'll have to go thru the side which might be a little awkward. Do I just use one of those larger NM-style clamp connectors? Or how about transition to an LB and then into the panel? Also, similar with the transition to the PVC conduit - just use the same clamp connector with a threaded adapter?

Since my car is a 75D, it only has a max 48A charger (at 240V) on it when used with the Tesla wall connector. I'll start with the NEMA 14-50 outlet in the meantime which Tesla automatically limits to 40A thru the Universal Mobile Connector. It will be right next to the panel so I'll just run #4 to it so it'll be ready if/when I get a wall connector, which are $500...

Hey! I'm also on WE Energies, and I save 10-15% per month on my electric bill by using 7-7 TOU. I paid an average of $.12/kWh last month. I've yet to have a month where I didn't save some money, nevermind spend more. a little attention to how you use power goes a long way.

schedule your car charging and fill up at night!

It's pretty easy to figure out - anything that runs 24/7 average costs slightly less than on regular rates, - 24 hour average is basically the same and weekends are 100% off peak. so if you don't charge your car during the day at home (you'll be at work, right?) and you run your electric dryer after hours, hit the delay button on your dishwasher, do your SMAW art after 7pm, own a programmable thermostat, you can probably save money.

 

[bjcouche]

I would advise against trying to put SER into conduit. Either go the entire way with SER and no conduit, or go the entire way with individual conductors inside conduit. Trying to bend SER, (a bundle of 4 conductors) into a LB is difficult if not impossible. There is also different NEC conduit fill rules regarding multi conductor cable versus individual conductors. Without looking it up I'd guess you'd have to be larger than 1.5" conduit to fit your SER cable in it.
If it were me, I'd go conduit the whole way and use individual aluminum conductors. The local electrical distributors around me sell Aluminum THHN/THWN in 2awg and 4awg.
Brian