Well, some of those are questions of what you might use it for in the future. The straightforward answer is probably just 12/2 Romex. The 12/3 means it has three conductors plus ground, so that is only if you need to do one of the dual voltage 120/240 kinds of outlets. A 5-20 wouldn't need that. And up to you if you think you might want to ever convert the outlet to a 30A type and use 10 gauge, so that's your call.
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Anyone use this Romex 6/3 cable during install?
- Thread starter Dugdale
- Start date
Basically @Rocky_H due to the electrical system in my home, my panel is maxed out following a subpanel install for central air a few years ago. There's no room for expansion, and there's no room to consolidate or combine circuits any more than they've already got.
I have an attic "whole house fan" since my house was built in the 30's and it was before central air and probably wall-unit air was a thing. My wife and I had central air on our list of things when the wall units finally broke. A few years ago when our wall a/c units finally gave out, we followed through and had the central air installed - condenser, air handler, and duct work (I have steam heat via radiators so it was all new duct work through closets and stuff!)
The fan runs off a 120V 20A circuit in the attic. Since my electrician said he can't combine anything to make it a 240V circuit - amperage is fine since I've got LED's everywhere and I'm not near the 100A peak - plenty of juice to go around up to ~40A continuous...
I asked about the whole house fan which doesn't get used, and he said that he could disconnect it and run a new 120V20A circuit with a 5-20 outlet to the exterior for a couple hundred ($250-300) bucks and it would be in one of those Taymac weatherproof enclosures for code. I'd obviously lose the whole house fan, but I never used it anyway and not going to start now that we have central air...
Just trying to figure out if I should simply meet or try to exceed code. There's obviously no such thing for the Tesla Adapter to plug into a 5-30, and my understanding is that you can run any 120V15A appliance on a 20A circuit because of the "T" shape of the polarized plug. It could be used in the future for holiday decorations or something as simple as recharging tool batteries or my lawn mower/snow blower (gasoline powered but battery start) so it wouldn't be a total loss.
And, if I found that the 120V20A wasn't enough (I posted in another thread that the 120V@16A continuous load = 1.92 kW * 80% efficiency = 1.536 kW = 5 to 6 miles of range per hour gained = 60 to 72 hours per 12 hour "overnight" charge, double what I drive daily)... I would be willing to upgrade the entire panel and run a 240V30A circuit with a 14-30 outlet but that estimate is around $1,300 (had 3 estimates, all within $100 of each other)... or I could simply go buy a Chademo adapter for $450 and use the Electrify America station that's less than a half-mile from my house (supports CCS and Chademo only, no J1772, damn it!) ... that would cost me around $4 per month to join EA but I think I'd be paying around $0.18 per minute for 50 kW charging on Chademo... that's .8 kW of charging per minute, which isn't half bad considering my home utility is $0.17 per kWh for supply and delivery combined. We don't use time-of-day scheduling here.
The Chademo adapter would be cheaper - about $800 cheaper - but I suppose over time the adapter itself was at risk of failure and I would have more convenience of having the 240V at home. If they offered a "CCS to J1772 to Tesla" adapter, or CCS to Tesla adapter for less than $450, I'd be all over that... lol
I'd honestly look for a Home Wall Connector if I changed out the panel at that point...
I have an attic "whole house fan" since my house was built in the 30's and it was before central air and probably wall-unit air was a thing. My wife and I had central air on our list of things when the wall units finally broke. A few years ago when our wall a/c units finally gave out, we followed through and had the central air installed - condenser, air handler, and duct work (I have steam heat via radiators so it was all new duct work through closets and stuff!)
The fan runs off a 120V 20A circuit in the attic. Since my electrician said he can't combine anything to make it a 240V circuit - amperage is fine since I've got LED's everywhere and I'm not near the 100A peak - plenty of juice to go around up to ~40A continuous...
I asked about the whole house fan which doesn't get used, and he said that he could disconnect it and run a new 120V20A circuit with a 5-20 outlet to the exterior for a couple hundred ($250-300) bucks and it would be in one of those Taymac weatherproof enclosures for code. I'd obviously lose the whole house fan, but I never used it anyway and not going to start now that we have central air...
Just trying to figure out if I should simply meet or try to exceed code. There's obviously no such thing for the Tesla Adapter to plug into a 5-30, and my understanding is that you can run any 120V15A appliance on a 20A circuit because of the "T" shape of the polarized plug. It could be used in the future for holiday decorations or something as simple as recharging tool batteries or my lawn mower/snow blower (gasoline powered but battery start) so it wouldn't be a total loss.
And, if I found that the 120V20A wasn't enough (I posted in another thread that the 120V@16A continuous load = 1.92 kW * 80% efficiency = 1.536 kW = 5 to 6 miles of range per hour gained = 60 to 72 hours per 12 hour "overnight" charge, double what I drive daily)... I would be willing to upgrade the entire panel and run a 240V30A circuit with a 14-30 outlet but that estimate is around $1,300 (had 3 estimates, all within $100 of each other)... or I could simply go buy a Chademo adapter for $450 and use the Electrify America station that's less than a half-mile from my house (supports CCS and Chademo only, no J1772, damn it!) ... that would cost me around $4 per month to join EA but I think I'd be paying around $0.18 per minute for 50 kW charging on Chademo... that's .8 kW of charging per minute, which isn't half bad considering my home utility is $0.17 per kWh for supply and delivery combined. We don't use time-of-day scheduling here.
The Chademo adapter would be cheaper - about $800 cheaper - but I suppose over time the adapter itself was at risk of failure and I would have more convenience of having the 240V at home. If they offered a "CCS to J1772 to Tesla" adapter, or CCS to Tesla adapter for less than $450, I'd be all over that... lol
I'd honestly look for a Home Wall Connector if I changed out the panel at that point...
Well, that's where I was trying to figure out your purpose for the outlet and running the line. If it is primarily for plugging in your car to charge, that never makes any sense to put it in as a 120V circuit. The exact same wire can be used either way, whether it's a 120V or a 240V circuit--that's just a different breaker on it. and you get more than double the charging speed if you put it in as a 240V circuit. So install a 6-20 outlet and buy the 6-20 adapter from Tesla's online store, and that would be a much better home charging outlet, and the installation cost would be the same.
But I wasn't sure if you needed it to be a standard 120V outlet for plugging in other things.
Absolutely, but the problem is that I don't have another breaker that I can "decommision" to turn the sucker into a 240V to have it from both sides of the box. The expanation that was given to me was that there's just nothing on the other side of the box to pull the extra 120V from. So, my only solution to get 240V would be to upgrade the entire box. I'm happy to find some pics of the boxes/sub panels if you want to visualize what I'm trying to explain, but it's complicated. I don't disagree with you about the benefits of 240 - I'm just saying I can't do it without a major undertaking - and convincing my wife that a Model Y is a "smart decision" is hard enough to begin with.
I also failed to mention that I have 3 supercharger sites that are within 10 miles of my house, but these are definitely not convenient from a home perspective. I could use the v3 Supercharger a mile away from my job on lunch breaks at work and get a substantial energy gain in my ~45 minutes if I brown bag it and eat in the car.
Nope. Not eating in the car. Eating outside the car. Win.
I also failed to mention that I have 3 supercharger sites that are within 10 miles of my house, but these are definitely not convenient from a home perspective. I could use the v3 Supercharger a mile away from my job on lunch breaks at work and get a substantial energy gain in my ~45 minutes if I brown bag it and eat in the car.
Nope. Not eating in the car. Eating outside the car. Win.
If you are stuck with 120 I would recommend running 10/2 and install a 30 AMP travel trailer plug:
Amazon.com : rv receptacle 30 amp
Then get one of these plugs for your Gen 2 Mobile Connector:
TT-30 Adapter for Tesla Model S/X/3/Y Gen 2 – EVSE Adapters
That should help your charge times. ~12 MPH
That said replacing the pannel would be my first choice.
Oh, are you just talking about your panel being full? A 120V breaker takes up only one standard width slot, but a 240V breaker takes up two slots next to each other. Do you mean you don't have two spaces for that? So yes, I can see how you would be limited to 120V if you don't have two spaces. The common answer to that is that some panels can use "twin" or "quad" breakers to double up some things into the existing spaces, to free up room, but only some panels are built to allow those--my panel couldn't take either.
Yeah, TT-30 is a good option--forgot about that. It's a 120V 30A circuit.
TomServo
Active Member
That's what my builder installed, it's protected with a 50 amp breaker mated to a NEMA 14-50 outlet. When a buddy with a M3 stopped by we used his J1772 adapter to use my Clipper Creek HCS-50P EVSE and he pulled 40 amps from it.
That's what I'm using as we also have a 2017 Volt that needs to be fed. The UMC will rest in the MY trunk for road trips.
During construction, it cost $250 for that circuit.
That's what I'm using as we also have a 2017 Volt that needs to be fed. The UMC will rest in the MY trunk for road trips.
During construction, it cost $250 for that circuit.
Pluturi
Member
Correct, if you are using Romex (NM cable). 55 amps is the ampacity limit of NM cable. If you are using MC cable or running conduit with THHN/THWN-2 then you can run 80% of 60 amps, or 48 amps, which is the limit of the newer cars and Gen 3 Wall Connector.
If you really want to know where these limits come from, here is the table:
Ampacity Charts - Cerrowire
Someone in another thread said it best. The breaker doesn't really protect the device. It protects the wire. Both have to be capable of serving the device.
If you really want to know where these limits come from, here is the table:
Ampacity Charts - Cerrowire
Someone in another thread said it best. The breaker doesn't really protect the device. It protects the wire. Both have to be capable of serving the device.
Johnny Vector
Member
Yes, IF you are using Metal Clad cable (also called BX; it's the kind in the flexible metal jacket). Also if you are pulling individual THHN (Thermoplastic, High Heat resistant Nylon, referring to the insulation) wires through a conduit.
If you are using ordinary NM (Non-Metallic, often known as Romex but that's technically a brand name), then you can not use a 60 amp breaker on 6 gauge wire. I mean, you can, but you're violating code and risking a fire. Please don't do that.
Johnny Vector
Member
It's safe (i.e. meets code) to use 12 gauge, and you only need two active conductors (hot and neutral), so 12/2 is all you need. Now, you also need a ground wire, which is not counted in the wire number, but noted separately. So the full spec you need is "12/2 with ground".
Now, to go beyond code... It depends what you plan to use it for and how long the run is. You will get less voltage drop with a 10 gauge wire, but unless it's a really long run it's probably not worth it. Let's work an example.
10 AWG is 1 milliohm per foot; 12 AWG is about 60% more. (It varies with temperature too, but let's keep it simple for the example).
Let's say you're drawing 20 A from the circuit (which you shouldn't plan on doing for hours at a time, but it's the max intermittent load that won't trip the breaker).
For a 20 foot run, that's 40 feet of wire (20 feet in each direction), so the voltage drop along the wire will be
- 10 AWG: 0.001 Ω/ft * 40 ft * 20 A = 0.8 V
- 12 AWG: 0.0016 Ω/ft * 40 ft * 20 A = 1.3 V
- 10 AWG: 0.001 Ω/ft * 200 ft * 20 A = 4 V
- 12 AWG: 0.0016 Ω/ft * 200 ft * 20 A = 6.4 V
So, the short answer is "Don't bother with 10 AWG wire for a 20 A circuit unless you have a very long run and a specific need to minimize voltage drop.
If you are running a new circuit with 12 gauge wire, why would you put in a 5-20? You could put in a 6-20 with the same wire, get the $35 adapter from Tesla, and enjoy 14 MPH charge instead of a mere 4 MPH.
Putting in a 6/2 with a 6-50 for 29 MPH with the stock charger is even better, and 4/2 with the HPWC for 42-43 MPH is optimal.
Putting in a 6/2 with a 6-50 for 29 MPH with the stock charger is even better, and 4/2 with the HPWC for 42-43 MPH is optimal.
That's great, thanks for clarifying with the math, I appreciate it!
@MY-Y - I can't do 240V here without major panel replacement. It makes a $200 job closer to $2000. I'm not saying I won't pony up the money if I need to do 240V, I'm just not convinced that I *need* that. It's like using a sledgehammer when I need a finishing hammer.
You still have not answered this question. Why do you think you need a panel replacement for putting in a 240V circuit? Load capacities are generally by the amps. If you can add a 20 or 30 amp circuit, you can do that, regardless of whether it is a 120V or a 240V circuit, as long as you have the physical space to install the breaker.
If you don't have the space, that still would not require an entire main panel replacement, leading to that $2,000 job you were talking about. Even if your main panel can't use twin or quad breakers to free up space, it's still fairly simple to branch one line out of your main over to a very small subpanel that has 4 or 6 slots or something to move a couple of circuits over to that to create space. I don't think that would need to be a $2,000 job, but maybe I am wrong about what electricians would charge for that.
No. Please read the code. You are incorrect.
240.4(B)
This is pointless conversation however, since 6-3 NM cannot provide 48 Amps.
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Oh, I know what you're getting at, and it is a bit splitting hairs. Yes, there is the provision for "next size up" on the breaker, but of course that doesn't actually make it a full 60A rated circuit with the 48A continuous current.
But in context, we are talking about what the set rating of the circuit is, and we are telling OP to not try to use this as a 60A circuit, so you make that more clear by using the more proper lower level breaker so it is consistent throughout the circuit, the wire, and the wall connector.
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