saltsman
Member
How are you going to get 60 Amps (4 AWG) inside a 3/4" conduit? Conduit Fill Table.
Cost to run dedicated 240v 60amp line to garage
- Thread starter JeffreyC
- Start date
Why do you keep saying 4 gauge? 6 gauge wire in conduit is rated fine for up to 65A. Are you thinking because of 70 feet being a long run? It's not that long, and code doesn't require oversizing for that. Does it being underground change the requirement in some way I'm not aware of?
saltsman
Member
I was using wire size calculator 1 and 2 and both say 60 Amps at 240V at 70 Ft should be 4 AWG. Fill calculator says 6 AWG is as large as you can go in 3/4 EMT, so that drops to 55 Amps max (thus 50 Amps is the highest you could go practically).
THWN (water-resistant) is specified for underground in conduit so that was what I was using as the specified cable. .Perhaps a specific THWN cable might allow for more heat? Where were you seeing 6 AWG could carry 65A? I'd love to find something that would allow for more amperage.
it’s not 60 amps for the voltage drop calculation. It would be 48 amps. You could also technically put a 70 amp breaker on 6awg thwn depending on derating factors, in which case the maximum current draw allowed would be 56 amps....
I think there is something wrong with the calculator you are using though.
100ft @ 56 amps and 240v
Voltage drop: 4.42
Voltage drop percentage: 1.84%
Voltage at the end: 235.58
Voltage Drop Calculator
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saltsman
Member
You are correct that 48 Amps would be the I variable in the calculation if the EVSE were the only device on the circuit. However in this setting, there could be other loads on the 120V/20Amp leg.
FWIW, I was taught to use the tripping load when calculating the wire size since the circuit could operate up to that level safely. Of course you would never intentionally load beyond 85% but then that's why circuit breakers exists.
No idea on the online calculators - I was lazy and just plugged in the numbers to see what it kicked out.
FWIW, I was taught to use the tripping load when calculating the wire size since the circuit could operate up to that level safely. Of course you would never intentionally load beyond 85% but then that's why circuit breakers exists.
No idea on the online calculators - I was lazy and just plugged in the numbers to see what it kicked out.
Earlier this year, I had two #4 75-foot lines run from my 200A panel to my garage, each terminated in separate 14-50 NEMA connectors. Each line was run inside separate 1" conduits. The total cost by the licensed electrician was about $3200; note that this was in California.
For now, each line is supported by a 50A breaker (I'm using a Juicebox 40 for 1 outlet and the Tesla mobile charger for the other outlet); #4 lines provide me the option to upgrade to 60A breakers and hardwire a 48A Tesla Wall Connector in the future.
For now, each line is supported by a 50A breaker (I'm using a Juicebox 40 for 1 outlet and the Tesla mobile charger for the other outlet); #4 lines provide me the option to upgrade to 60A breakers and hardwire a 48A Tesla Wall Connector in the future.
no. It’s 48 amps max no matter what. In America, 240v is just two 120v legs out of phase with each other so that the potential across them is 240. The 120v circuit would be just one one leg of the 240, but you arn’t allowed to draw more than 80 percent total.
To select the size of the wire, yes. For voltage drop calculation, nope.
saltsman
Member
Aren't we calculating the wire size OP needs? I forget now...
Bottom line, get multiple itemized bids. Go with the company you feel safest with.
Just so I understand, you technically could have used #6 wire and still go up to 60A eventually, is that correct?
Technically, these are the guidelines for wire gauge and amperage:
6/3 Romex = 55A
4/3 Romex = 70A
6 gauge wire is enough to handle a 48A charger (60A breaker, if not using up to 60A). I had 4 gauge wire installed for margin.
Oh, other end of the telescope. You are starting from the perspective of trying to prevent voltage drop. And I do see that in the calculators you were using. Voltage drop calculations are a recommendation, but not a requirement in NEC, and for EVSEs, they don't matter much if they have some voltage drop. If it were a 200 or 300 foot run, I would lean more toward doing this drop calculation, because it could be getting pretty bad, though.
What I was going by was the very general specification table of allowed ampacity:
Ampacity Charts - Cerrowire
So that's not trying to calculate for voltage drop over distance, but is just saying that 6 gauge copper wire in conduit (THWN at 75 degrees C) allows 65 amp circuits.
So you could take that either way: you could use it as a 60 amp circuit if voltage drop is not an issue, or you could limit it to 50 amp if you want to keep the voltage up. Either way would be code compliant.
Romex has lower limits as it's rating is limited to 60C vs THWN at 75C.
Ampacity Charts - Cerrowire
6 Guage Romex == 55A
6 Guage THWN == 65A.
Please keep in mind the limits on the breaks and charging equipment will likely be limited to 75C (Check your equipment and breakers to make sure).
I would get some additional quotes my first quote for the standard Tesla wall connector was $1350. My second quote was $425. How can it be so different. My opinion is that the electricians think if you own a Tesla you are a millionaire!! Good luck
You: It's for my new Tesla!
Electrician: Oh, did I say "hundred"? I meant "thousand".
So I was a DIY guy so I can't comment on the cost... BUT I would suggest asking what kind of wire they are running... I ran 4 gauge wire vs 6 because my run was so long and I wanted to support the 48amps of the Tesla charger... I only bring this up because if you're paying for the run, you might want to upgrade the wire incase you ever want to increase the amps in the future... or at least ask for the extra cost in your estimate and decide then.
Just a thought.
You're in Ridgewood, after all. I'm down in Cherry Hill, and I had a Tesla-recommended electrician do my installation. Estimate was $1250 for the labor and materials (I initially guessed about 75' of 6/3 run across an unfinished basement, through about 15 ft of a nasty crawlspace, then into the garage and around to the side where the charger port would be if the car was nose in). I was given the option of another $250 for the permit (my town is a PITA) and any additional cable would cost $12/ft (material and labor).
In the end, it wound up being a 95' run with drops and rises and I did go the permit route, so the total came to $1750. No sub-panel, though. Took the guy about 3 hrs start to finish, including patching the drywall in the garage and making sure I was getting the full draw when I plugged in. The convenience cannot be understated - being able to "fill-up" at home in a few hours is great.
As others have said, get multiple estimates if you can. I tried three electricians. One never replied. One needed 2 weeks before they could do the estimate and then schedule the work and the one I went with said, "I can be there Monday."
In the end, it wound up being a 95' run with drops and rises and I did go the permit route, so the total came to $1750. No sub-panel, though. Took the guy about 3 hrs start to finish, including patching the drywall in the garage and making sure I was getting the full draw when I plugged in. The convenience cannot be understated - being able to "fill-up" at home in a few hours is great.
As others have said, get multiple estimates if you can. I tried three electricians. One never replied. One needed 2 weeks before they could do the estimate and then schedule the work and the one I went with said, "I can be there Monday."
MrWattson
Member
My electrician came in at $640 to run from the panel in my basement (front side of house) through to the garage and mounting on the exterior between the two garage doors. Permits are another $70-80 in my town.
See if he can run the new 60A line in the conduit alongside the existing 20A line. That would eliminate the subpanel entirely and avoid disturbing the existing wiring. Use the new line exclusively for the Tesla. You might want to spring for the $500 for the Tesla wall unit instead of the NEMA box, unless you want compatibility with other EVs.
You know- it just hit me what you might want to do... Depending on your electric company- many electric companies have an option to install a 2nd power meter just for EVs. This way you can do a time of use rate on that one meter and save money when you recharge on non-peak hours. Since you have to run new wires anyway- maybe it would be more cost effective both now and in the future just to have a 2nd meter installed in your garage. I would check with your electric company... I think you're PSEG and I know they have options with PSEG in Long Island, but NJ... No idea.
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