Wiring for an EV charger - advice needed

[travelover]

Most of the expense will be the trenching and installation labor. You could have them lay an empty 3/4" plastic conduit, as well, and use it for any future wiring needs.

 

[OldShooter]

Most of the expense will be the trenching and installation labor. You could have them lay an empty 3/4" plastic conduit, as well, and use it for any future wiring needs.

Good idea. Also consider a 1/2" conduit for a hardwired data* connection from your home router/switch to another router (different SSID) in the garage. (A mesh system would allow the same SSID to be used but may not be feasible given the distance involved. Using a second SSID should not cause any problems. Devices with the correct login information should connect to whichever signal is stronger.)

*You should not run data and power in the same conduit and I'm 99% sure the code does not allow it.

 

[zinger1457]

Good point on hiring it out. I was thinking it might take me a week to dig and it would be great exercise, but paying to have the trench dug is probably money well spent. I could rent a trenching machine, but if I damage something, then that's on me.

In my area hiring a backhoe service to dig a trench is ~$150 to come out then ~$90/hr., shouldn't take long at all to dig a 70' trench assuming a backhoe can access the area you want trenched. Renting a walk behind trencher is ~$225/day here, could easily do 70' in a day unless you have a lot of big boulders to deal with. Digging a 70' trench by hand would be a royal PITA.

 

[NW-Bound]

Currently: old house with fairly new 100 amp main panel in the unfinished basement. There is room in the panel to add a 50 amp breaker...

I'd be charging the car outside of a small detached garage, about 70' from the house, currently has 2 120v 15 amp lines running to it.

What I want: the garage if more like a small old barn, too small to easily park a car inside. So I'd be charging the car outside. I'm thinking I should get a Tesla Wall Connector mounted on the outside of the garage...

Is it possible to charge the car with it parked close to the house? Then, for long-term parking the car can be moved closer to the garage, and the battery maintained with just the 120V circuit?

This would allow you to charge the car with a simple NEMA dryer or stove receptacle mounted in the house, and using inexpensive wiring.

 

[pb4uski]

Just to clarify, I'm not suggesting that you plug into two 120V circuits to charge the Tesla.

But.... a "proper 240V line" is two 120V circuits. That's how you get 240V, you use two 120V circuits that are on different phases (residential US circuits are two phases).

What that means is an electrician can take your two 120V lines (if they are on separate phases which they probably are, or swap one of them at the panel so they are on separate phases), and wire them to a single 240V 15A outlet. With a sub panel, you could also have some 120 V 15 A outlets. That is how all 240V circuits in the US are done. ...

I would pursue this possibility.... if this is feasible then you might not even need a permit... of if you do then the permit would be for the electrical work at the shed using the two existing wires that terminate at the shed... presumably the existing wires would be grandfathered.

 

[NW-Bound]

^^^ While the above is easily done, it only doubles the charging rate (240V 15A vs. 120V 15A).

Going to 240V 30A would quadruple the charging rate compared to the existing 120V 15A.

It's a trade-off the OP needs to make to see if it's worthwhile.

 

[DayDreaming]

Most of the expense will be the trenching and installation labor. You could have them lay an empty 3/4" plastic conduit, as well, and use it for any future wiring needs.

Good idea. Also consider a 1/2" conduit for a hardwired data* connection from your home router/switch to another router (different SSID) in the garage. (A mesh system would allow the same SSID to be used but may not be feasible given the distance involved. Using a second SSID should not cause any problems. Devices with the correct login information should connect to whichever signal is stronger.)

*You should not run data and power in the same conduit and I'm 99% sure the code does not allow it.

I like this idea, thanks! While the trench is open, I can get

• conduit for the new 240v line
• empty conduit for some future electric needs
• 1/2" conduit for network cable

Once I settle on an electrician, I'll ask what he thinks. I.e. is there any issue with running these in the same trench - does there need to be some amount of space between them, and how would the township inspection certify an empty conduit so that there's no question in the future.

 

[DayDreaming]

Digging a 70' trench by hand would be a royal PITA.

But great exercise!

 

[DayDreaming]

Is it possible to charge the car with it parked close to the house? Then, for long-term parking the car can be moved closer to the garage, and the battery maintained with just the 120V circuit?

This would allow you to charge the car with a simple NEMA dryer or stove receptacle mounted in the house, and using inexpensive wiring.

Unfortunately, no. The closest I could park in my driveway is 36' from the house, and parking there would block the driveway for anyone else. Assuming I stick with an EV the rest of my life, I'll spent the money to setup a charger where it's most convenient for me to park.

 

[DayDreaming]

^^^ While the above is easily done, it only doubles the charging rate (240V 15A vs. 120V 15A).

Going to 240V 30A would quadruple the charging rate compared to the existing 120V 15A.

It's a trade-off the OP needs to make to see if it's worthwhile.

Most people that buy an EV say they'll never go back to an ICE car again. Assuming I feel the same way, I'd rather get the charging setup right, right from the start, and 240V / 15A would work for me, but would be far from ideal.

 

[pb4uski]

^^^ While the above is easily done, it only doubles the charging rate (240V 15A vs. 120V 15A).

Going to 240V 30A would quadruple the charging rate compared to the existing 120V 15A.

It's a trade-off the OP needs to make to see if it's worthwhile.

But, depending on the gauge of the wire in the conduit might be able to handle more than 15A... even if it is only capable of 15A, 240v 15A would charge the Model Y for 10 miles per hour... so 100 miles overnight...and that might be sufficient to meet the OPs needs. 240V 30A only slightly more than doubles the charging to 21 miles per hour or 210 miles overnight.

https://www.tesla.com/support/home-charging-installation/wall-connector

I wonder if it is feasible to convert the existing service to the shed to 240V 15A and then if if doesn't meet the OP's needs upgrade it later.

 

[OldShooter]

But, depending on the gauge of the wire in the conduit might be able to handle more than 15A ...

Technically true, but it is unlikely that the OP will find oversized wire. From memory, the code procedure is to size the wire so that there is no more than a 3% voltage drop at full rated load. For short runs in the house 14 gauge copper typically meets this criterion. For the long garage run, the calculation may have called for #12 or even larger. But finding oversized wire would be unusual.

In the unlikely but possible event that the garage run is aluminum wire, it should be cut free at both ends and never used again. A little internet research on house fires caused by aluminum wiring will explain.

 

[pb4uski]

...In the unlikely but possible event that the garage run is aluminum wire, it should be cut free at both ends and never used again. A little internet research on house fires caused by aluminum wiring will explain.

Perceptive glimpse of the obvious.