I have an old house with very, um, interesting wiring. I’m slowly straightening it all out.
I find this tool to be very useful
Available at Home Depot for about 50 bucks.
It seems it would not be difficult to find which circuit goes to which outlet(s). Turn off one breaker. Use a light or radio if you don’t have an outlet tester, test each outlet. Rinse and repeat.
But if the wire does not match at both ends, I would be wary of using it for a heavy load. Junction points are the favourite point of failure, especially if you have no idea where it is or how good the connection is or how close it is to flammable material. You would think if it was intended to provide more than 12A (Max for a 15A circuit) it would be fairly robust and complete end to end, but thinking don’t always make it so.
Yes, a 20A circuit should have that sideways “T” on the socket.
If you are messing with the panel, find a friend of a friend who’s a trained electrician. I agree, like you, my DIY is limited to installing new outlets or changing light fixtures when it comes to electricity.
(and I agree, anyone who plans on 48A on a 50A circuit is looking for trouble plus breaking code. I set my wall charger for a max 40A on a 50A 240V circuit, and have since told it to limit itself to 26A. Even then, charging overnight starting at 1AM is plently of time to get to 80% usually. I gather the newer LPF batteries can consistently charge to 100% without problems.
Model 3 standard range and standard range+ can charge at up to 32 amps , that’s 7.6kW on 240v. The long range battery Model 3s can charge at up to 48 amps, so 11.5kW on 240v.
I’m not going to get involved in the issues of wire size, the sizing of the service, branch circuit loading, etc., but I will offer some advice about routing a new circuit.
Consider trenching in nonmetallic raceway (PVC conduit) between the house and the garage. It must be at least 18" deep. Then use THWN or another conductor type rated for wet (below grade) environments. If you’re going to dig a trench, it’s just a little more expensive to make it suitable for upgrading the conductors or adding another circuit later. I’ve had numerous clients and friends who say, “I really wish I had buried 10 AWG UF cable instead of 12 AWG.”
Plus, if you’re going to trench, install TWO raceways with separate boxes at each end. Again, a few $$$ more but you’ll really appreciate it later if you have some other reason to install some other type of circuit or system. “Always bury at least twice what you think you need.”
A corollary to the old adage in the days of cabled internet in offices:
Cat [whatever 3/4/5/6] cable on the spool? Free.
In the walls? Priceless.
I don’t think we’ve ever gotten confirmation about how the OP’s wiring to the garage is currently run, whether in rigid conduit, PVC conduit, or UF. I do know that he is trying to avoid more trenching.
Agreed. It just seemed like some advice was veering over into the realm of new, direct-buried cable. It does seem unclear if there is existing conduit at all, or if this is speculation.
It’s speculation… I assumed conduit because that’s what I know about trenching and running wire in my limited skillet, and I don’t have an easy way to verify it.
Wild guess…it’s probably direct-burial cable. This is the cheapest and fastest method of installation. (I’m a licensed electrical contractor and I know my fellow contractors well.)
For anyone who was wondering what happened, here’s the lowdown:
An electrician came to my house today and looked over the wiring. We were planning to turn the 20-amp circuit in the garage from 120v to 240v. Unfortunately it turned out that they used a common neutral for all of the wiring in the garage, so if we made the neutral load-bearing, we would burn up anything connected to the other outlets in the garage. We tried to pull a wire through, but it wouldn’t budge. So, womp womp, no 3kwh charging for me in the garage.
We’re waitng til spring to do the bigger job of digging a trench to connect a new service line and wire in a big ol’ L2 charger, 40 or 50 amps,240v, instead.
A clear answer is worth a lot even if it isn’t the answer you prefer. Thanks for the update.
All things being equal, this just sounds like a better implementation, anyway.