We just moved into a new house. The house we just came from I just installed the charger on the side of the house and called it a day. This house is much more complicated. The parking areas for the house are away from the house and the detached garage only has 120v. I am installing 8awg wire and I have tried to tunnel under the driveway with 3 different trenches but each time its a ton of rocks. when they put the driveway in, there must of been on feet of gravel. Add that into a wooded, New England area and it doesn't help. My other solution is to go along the driveway and under a small stream bridge and back up to the parking area...it would be about 200ft, maybe 250. Has anyone done a run that long? The run to the garage is about the same length and has a few obstacles.
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Max Length of charging cable you've run?
- Thread starter newtonfb
- Start date
250 ft is fine, you just need to adjust the wire size or the amperage.
Yes--this. You can do runs that are really long, but it's just going to have high resistance from the length, so you will need to compensate from whichever direction you wish to go. In other words, let's say for a normal short run, you would think 8 gauge for a 40A circuit. It probably will not do well for that long a run. So either you can use that 8 gauge, and probably use it as a 30A circuit, or you could oversize to 6 gauge to make it work as a 40A circuit. I'm just popping off these numbers as examples, so you might want to look at online voltage drop calculators to see what your distance actually does for different gauge thicknesses. And car charging can stand a bit of voltage drop, so it wouldn't need to be too strict about avoiding that or keeping it really tight within a couple %.
I purchased #6 thhn wire. I measured it out and its 220-230ft long. I purchased a 50amp breaker and I only use the mobile charger for 32amps. Would that be okay for wire size?
Ah, you originally said 8 gauge in your first message. I ran a check with this voltage drop calculator:
Voltage Drop Calculator | Southwire.com
I put in 230 feet, and 240V, and turned the allowed voltage drop up a little bit to 6% to see what it would say. It said that could be 6 gauge copper and would have about 4.23% voltage drop, which isn't too bad. You can tweak some of the numbers around to see how they influence this. If you tried to keep it really tight on the voltage drop, like the form says 3% recommended, then it won't even let you do a 50A or 40A circuit with 6 gauge. It has to go down to 30A circuit or increase the gauge to 4. Even that wouldn't be bad--you could use the 6 gauge wire, but make it a 14-30 outlet instead of a 14-50. You would need to buy that 14-30 adapter from Tesla, and it will use 24A instead.
So yes, I think the 6 gauge wire for a 50A circuit would be OK. Technically, the mobile charging cable will only be drawing 32A anyway, so it's going to be treating that as if it's a 40A circuit, so there will be less drop than if you were trying to draw 40A continuous from a 50A circuit.
It is allowed by code to use 14-50 outlets on 40A circuits, and this seems like a good time to apply that since it's pushing voltage drop levels, so a future homeowner might not want to be using this as a full 50A circuit. So I might use a 40A breaker and put a label on the outlet that says it's a 40A circuit.
The part to check on that I am not as familiar with is what type of wire you have to use for burying in conduit. That is considered a wet location, and I'm not sure what you need. I think that's what the "W" in THWN wire type stands for, so it probably needs that. Or, there are direct-bury bundled cables types that you might want to use instead of conduit if that might be simpler. This is getting a bit beyond what I've learned about this stuff.
I run a nema 14-50 extension from my outlet, to the ceiling, to the other side of the garage. So about 20 feet extension. It’s pretty heavy gauge wire so I’m not concerned about risk of fire or what have you.
Edit: wow just read your post. That’s a heck of a long cable.
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