Creating 32 amp outlet from existing wiring

[jhoyle50]

I had my aging heat pump replaced with a gas furnace & air conditioner. The heat pump air handler & strip heat backup were on a 70 amp breaker. The electrician converted one 120 v leg to neutral & added a 20 amp breaker to supply 120 v to the new equipment. It seems to me I can move the neutral leg back to the 70 amp breaker, add a 40 amp breaker for the new 32 amp 6-2 line. Where do I route the existing 120 v neutral after the conversion? Tie in with 240 v ground? Main 200 amp panel uses 3 wires with neutral & ground connected. Pic posted of cutoff configuration. Am I missing anything? Just considering my easiest options before getting an electrician quote.

 

[iluvmacs]

Sorry, without another dedicated neutral wire, you are out of luck. You absolutely cannot tie neutral and ground together here.

 

[Bikeman]

I wouldn't mess with it myself, and would hire a qualified electrician. Tell them you need a 14-50 plug at 240v and 40A. Tell them it is for a large appliance. Which it is. An EVSE is an appliance. If it is going to be outside, the 14-50 outlet will most likely need to be in a weatherproof box.

They might charge you higher if you tell them it is to charge a Tesla. Maybe don't do what I did and limit it to a 40A breaker. If I had to do it all over again, I'd ask for at least a 50A breaker and wiring to match, to help future-proof.

But 40A will work fine, as the current Tesla EVSE will be limited to 32A, which is roughly 80% of the circuit capacity.

Be glad you have a 200A main breaker box. I'm running off a 100A system, and almost half of that is to charge my car!

Here is my outside setup, which is located under my back porch next to the driveway. The 120v 20A is the backup line if the EVSE ever fails to work.

 

[jhoyle50]

I wouldn't mess with it myself, and would hire a qualified electrician. Tell them you need a 14-50 plug at 240v and 40A. Tell them it is for a large appliance. Which it is. An EVSE is an appliance. If it is going to be outside, the 14-50 outlet will most likely need to be in a weatherproof box.

They might charge you higher if you tell them it is to charge a Tesla. Maybe don't do what I did and limit it to a 40A breaker. If I had to do it all over again, I'd ask for at least a 50A breaker and wiring to match, to help future-proof.

But 40A will work fine, as the current Tesla EVSE will be limited to 32A, which is roughly 80% of the circuit capacity.

Be glad you have a 200A main breaker box. I'm running off a 100A system, and almost half of that is to charge my car!

Here is my outside setup, which is located under my back porch next to the driveway. The 120v 20A is the backup line if the EVSE ever fails to work.

I'm now thinking a separate 120 v line to the aforementioned 20 amp breaker box, which would free up the 240 v lines for a 60 amp breaker & 48 amp capacity 6-50 outlet in the event I ever go wall connector. Only 45 ft from breaker box to carport. Thoughts, & what functionality does the juicebox give you?

 

[jhoyle50]

Sorry, without another dedicated neutral wire, you are out of luck. You absolutely cannot tie neutral and ground together here.

Sorry, without another dedicated neutral wire, you are out of luck. You absolutely cannot tie neutral and ground together here.

Probably will run 12-2 with the 20 amp breaker back to main panel (30 ft) seperately & that would free up that box for a 60 amp breaker, 48 amp circuit if needed in the future, thanks for the input.

 

[PJFW8]

Probably will run 12-2 with the 20 amp breaker back to main panel (30 ft) seperately & that would free up that box for a 60 amp breaker, 48 amp circuit if needed in the future, thanks for the input.

6 guage Romex is slightly undersized for 60amp breaker/48 amp load.If your wires are 6 guage pulled in conduit, that is fine Otherwise stick with 50amp breaker for 40 amp continuous load.

 

[mongo]

I'm now thinking a separate 120 v line to the aforementioned 20 amp breaker box, which would free up the 240 v lines for a 60 amp breaker & 48 amp capacity 6-50 outlet in the event I ever go wall connector. Only 45 ft from breaker box to carport. Thoughts, & what functionality does the juicebox give you?

You can't, per NEC, use a 60 amp breaker with a 6-50 50 Amp outlet. If the wiring supports 60 Amps (48 Amp charging), then you can switch to a 60 Amp breaker in the future if you add a WC. When adding the WC, you'll need to transition the aluminum wire to copper before the WC.

 

[iluvmacs]

Probably will run 12-2 with the 20 amp breaker back to main panel (30 ft) seperately & that would free up that box for a 60 amp breaker, 48 amp circuit if needed in the future, thanks for the input.

Yes, that would probably be the most sensible approach. Use the big wire that's already there for the charging station, and run a new 20A circuit for your HVAC.

 

[jhoyle50]

You can't, per NEC, use a 60 amp breaker with a 6-50 50 Amp outlet. If the wiring supports 60 Amps (48 Amp charging), then you can switch to a 60 Amp breaker in the future if you add a WC. When adding the WC, you'll need to transition the aluminum wire to copper before the WC.

Good info, probably will charge through the 6-50 adaptor which I read is limited to 32 amps & approx 30 mph charge which should more than meet my needs & take the charge cable on road trips.

 

[Bikeman]

I'm now thinking a separate 120 v line to the aforementioned 20 amp breaker box, which would free up the 240 v lines for a 60 amp breaker & 48 amp capacity 6-50 outlet in the event I ever go wall connector. Only 45 ft from breaker box to carport. Thoughts, & what functionality does the juicebox give you?

JuiceBox is simply one of dozens EVSE's, that does what a Tesla charger does - yet is older (2017). It is a J1772 type, not the Tesla connector. It could be used with any Tesla, no problem, but would need the J1772 adaptor at the end of the handle. Costs around $500. I bought it to charge up my 2017 Prius Prime.

For a 45 foot run, I would ask the electrician to use 100% copper wire ($$$). Most electricians would use a copper coated aluminum wire which is cheaper, but those can offer more resistance and could heat up while in use for several hours at a time. That could also increase charging times. To fully charge a Y, you're looking at 6+ hours at 32 A / 240v.

 

[iluvmacs]

JuiceBox is simply one of dozens EVSE's, that does what a Tesla charger does - yet is older (2017). It is a J1772 type, not the Tesla connector. It could be used with any Tesla, no problem, but would need the J1772 adaptor at the end of the handle. Costs around $500. I bought it to charge up my 2017 Prius Prime.

Actually, they just came out with a new JuiceBox model early this year. Emotorwerks is also now Enel X.

 

[Bikeman]

Actually, they just came out with a new JuiceBox model early this year. Emotorwerks is also now Enel X.

Yup. And they adopted the interchangeable pig-tail design as Tesla to use with any type of outlet, whether it is 120v are 5 types of 240's. Smart! Old EMotorWerks JuiceBoxes and the new designs all charge a car just the same.

 

[mongo]

For a 45 foot run, I would ask the electrician to use 100% copper wire ($$$). Most electricians would use a copper coated aluminum wire which is cheaper, but those can offer more resistance and could heat up while in use for several hours at a time. That could also increase charging times. To fully charge a Y, you're looking at 6+ hours at 32 A / 240v.

Properly sized aluminum wire is fine for long runs. Resistance per foot ends up only 5% worse for AL that is 2 gauges larger than copper at half the cost. It does need to be converted to copper before the wall connector though which offsets the savings for short runs.
Wire Resistance & Properties

 

[Bikeman]

If the resistance is 5% per foot with aluminum, then what happens at 45 feet? I'm not good enough with the maths to figure that out. Are you saying that over sizing by two gauges would solve the loss problem? And by how much?

They did 10 g. on mine at 240 40 with AL, but the run was less than 12 feet.

 

[mongo]

If the resistance is 5% per foot with aluminum, then what happens at 45 feet? I'm not good enough with the maths to figure that out. Are you saying that over sizing by two gauges would solve the loss problem? And by how much?

They did 10 g. on mine at 240 40 with AL, but the run was less than 12 feet.

If the voltage drop was 2V with copper at 6 gauge, it would be 2.1V with aluminum at 4 gauge.
Or another way to look at it, 21 feet of 6 gauge copper has the same resistance, voltage drop, power loss as 20 feet of Aluminum.

Are you saying they used 10 gauge aluminum for a 40 amp circuit?

 

[Bikeman]

If the voltage drop was 2V with copper at 6 gauge, it would be 2.1V with aluminum at 4 gauge.
Or another way to look at it, 21 feet of 6 gauge copper has the same resistance, voltage drop, power loss as 20 feet of Aluminum.

Good info. Thanks.

Are you saying they used 10 gauge aluminum for a 40 amp circuit?

That's what I remember. And it was much thinner wire than I would have guessed for that application - similar to regular house wiring in diameter.

 

[mongo]

That's what I remember. And it was much thinner wire than I would have guessed for that application - similar to regular house wiring in diameter.

Eek.
That doesn't sound correct.

 

[iluvmacs]

Yeah, I hope that’s not right. For 40A, you need #8 aluminum wire. Might want to verify that!

Also, with aluminum wire to a receptacle, you need to occasionally retighten the wires. The 14-50 we put at the in-laws’ for when we visit started overheating about 1.5 years after it was installed. I just happened to check on the charging in the app one time and it said it was reduced power. Sure enough, the outlet was almost too hot to touch. I knew the electrician had cheaped out and used aluminum, so I suspected right away the wires were coming loose. I tightened the terminals again and it was fine. Caveat emptor.

 

[PJFW8]

Don't work with aluminum wire unless you fully understand its use. For a 50 foot run, the savings is not worth the risk. If your electrician wants to use it and understands the continuous load impact on wire temperature, it is fine.

 

[ai4px]

Neutral and ground can only be connected at one point in your system.... the main panel box. Or the meter socket. If you wire to a nema 14-50, you are required to run a separate neutral and ground. But if you wire to a 6-50, you don’t need the neutral. If you hardwire the EVSE, you also don’t need neutral.