New Owner - Charger/Install Help

[krazineurons]

Here is a post with actual parts to create your own pigtail for connecting UMC with 5-20 adapter to 6-20 outlet.

Charging from NEMA 6-20 using NEMA 5-20 Adapter

Thanks I accidentally landed on the same post and smacked my lips with the possibility and potential savings in both time and money.

I have asked my electrician if 24A breaker is possible, if it is am going with the wall connector, if not then am cheaping out and building a pigtail. Any reliable way to source a tesla 5-20 adapter than buying directly from the site?

Thanks once again!

 

[AndreSF]

You might be able to find the 5-20 adapter on this forum, but I would probably just buy it from Tesla online store or your Service Center.

 

[tga]

thanks for the education, is there any online calculator available which helps with this estimate?

There's a bunch of spreadsheets out there - try googling "NEC load calculation spreadsheet"

 

[Rocky_H]

I have asked my electrician if 24A breaker is possible,

You're not really using the terminology right; there is no 24A breaker. It is a 30A circuit that uses a 30A breaker. That is the number that will be figured into the load calculations of the panel. The smaller number comes in like this: short term intermittent loads are allowed to use the full capacity of the circuit. So for example, dryers or ovens cycle the heating element on and off, so they are allowed to pull 30 amps or 50 amps or whatever because it will only be for several minutes at a time. The wire doesn't have that much time to continue to heat up. But 4 or more hours continuously is considered a constant load (and new NEC code says electric car charging is ALWAYS defined as a constantly load). So there is a rule that a constant load has to have a circuit 125% of the constant current draw. So add a fourth to the current draw and that's your circuit rating. 16A draw needs a 20A circuit. 24A draw needs a 30A circuit.

 

[krazineurons]

You're not really using the terminology right; there is no 24A breaker. It is a 30A circuit that uses a 30A breaker. That is the number that will be figured into the load calculations of the panel. The smaller number comes in like this: short term intermittent loads are allowed to use the full capacity of the circuit. So for example, dryers or ovens cycle the heating element on and off, so they are allowed to pull 30 amps or 50 amps or whatever because it will only be for several minutes at a time. The wire doesn't have that much time to continue to heat up. But 4 or more hours continuously is considered a constant load (and new NEC code says electric car charging is ALWAYS defined as a constantly load). So there is a rule that a constant load has to have a circuit 125% of the constant current draw. So add a fourth to the current draw and that's your circuit rating. 16A draw needs a 20A circuit. 24A draw needs a 30A circuit.

Sorry what i meant was to get a 24A circuit to have a current draw of 20A, from my search so far it seems that it is not easily possible to have such a circuit. is that true?

 

[tga]

Sorry what i meant was to get a 24A circuit to have a current draw of 20A, from my search so far it seems that it is not easily possible to have such a circuit. is that true?

Actually, it would be a 25A circuit to charge at 20A (20*1.25=25; 25*0.8=20). You generally won't see that, since wire good for 25A (ie, 10ga copper), is good for 30A. So if you're putting in 10ga wire, you wouldn't generally install a 25A breaker; you'd use a 30A one instead. Plus there are no 25A outlets, and 25A breakers are also a little harder to find (since they aren't generally used).

 

[Rocky_H]

Sorry what i meant was to get a 24A circuit to have a current draw of 20A, from my search so far it seems that it is not easily possible to have such a circuit. is that true?

The circuit size is named by the breaker. There just isn't a 24A breaker, and maybe not a 25A either. After the 15, they generally run only on increments of 10. That goes up to about 60, and then the steps usually get bigger than 10 apart.

 

[AndreSF]

The circuit size is named by the breaker. There just isn't a 24A breaker, and maybe not a 25A either. After the 15, they generally run only on increments of 10. That goes up to about 60, and then the steps usually get bigger than 10 apart.

25Amp two pole breaker:

Square D QO 25 Amp Two-Pole Circuit Breaker-QO225CP - The Home Depot

 

[Rocky_H]

25Amp two pole breaker:

Square D QO 25 Amp Two-Pole Circuit Breaker-QO225CP - The Home Depot

Good to know. I didn't want to go look it up to see if it existed or not. I did use "maybe" and "generally". My dad called those "weasel words", and it's a good idea to use them if you are saying something you're not really sure of, so you don't have to be totally wrong.

 

[tga]

I have a Siemens 25A in my garage sub panel, but I had to order it.

 

[Wshowell]

FYI. I was at a hotel with a tesla hpwc today waiting to pick up a business colleague. While I waited I plugged in. It was a 40 amp connection (so a 50 amp breaker) but the volts were 208. I was gaining 20 MPH. On my set up I have an HPWC and I connect at 32 Amps (40 amp breaker) with 230 volts and I get 23 MPH. I'm not positive but I think the lower voltage of the hotel charger was the reason for the slower rate. If this is the situation then I'd worry less about the low amperage and focus on getting to most efficient connection (higher voltage) from your box. Maybe larger gauge wire i.e.:6 versus 8. I'm totally clueless on this stuff but thought I'd share since the concern seems to be about the lower amperage and an HPWC. Of course it could also be that my battery was sitting at a higher rate of charge first thing in the morning versus when I usually check out the data when it first starts to charge. I was at maybe 65%.

 

[Rocky_H]

FYI. I was at a hotel with a tesla hpwc today waiting to pick up a business colleague. While I waited I plugged in. It was a 40 amp connection (so a 50 amp breaker) but the volts were 208. I was gaining 20 MPH. On my set up I have an HPWC and I connect at 32 Amps (40 amp breaker) with 230 volts and I get 23 MPH. I'm not positive but I think the lower voltage of the hotel charger was the reason for the slower rate. If this is the situation then I'd worry less about the low amperage and focus on getting to most efficient connection (higher voltage) from your box. Maybe larger gauge wire i.e.:6 versus 8. I'm totally clueless on this stuff but thought I'd share since the concern seems to be about the lower amperage and an HPWC. Of course it could also be that my battery was sitting at a higher rate of charge first thing in the morning versus when I usually check out the data when it first starts to charge. I was at maybe 65%.

There's a little reading you can do.
3 Phase Power vs Single Phase Power • OEM Panels
Basically home residential electricity systems use what is called "split phase". It has 120V, and then 240V for the higher one. Commmercial/industrial properties usually use what is called "3 phase". You can read the link above to see more details, but in short, it ends up with those two voltage levels actually being 120V and 208V. So at most commercial businesses 208V is actually what you will find, or maybe a few volts lower because of a long wiring run.

And yes, the rate at which the car charges scales directly with power, which is volts times amps, so a difference in either will affect the miles per hour charging rate.

 

[gregd]

If this is the situation then I'd worry less about the low amperage and focus on getting to most efficient connection (higher voltage) from your box. Maybe larger gauge wire i.e.:6 versus 8.

Thicker wire will definitely get you a higher voltage, but not a whole lot.

For scale, I upgraded my Roadster's charging situation recently, moving from the dryer plug's 30 amp breaker fed with #10 wire to a 50 amp 14-50 using #4 (oversized for future upgrades; #6 is customary). The run was shortened (better location) from about 55 feet to about 40. At the original 24 amp charging rate, the new circuit nets me something like a volt or so higher as reported by the car. It's hard to tell, because it's less than the normal variation of the line voltage from one day to the next. Of course, now I can charge at 40 amps instead of 24, but the voltage gain was pretty minimal. Even at 40 amps, the voltage holds firm. (Yea!)

I also added a pair of dedicated 20 amp 120 volt plugs. Same 40 foot run, this with #12 wire. I tried charging from it, just to try it, and the car reported only 117 volts that time. Note that the 120v direct charging cable is skinnier (#12) than the UMC (#8), but overall it seems to have lost 3-ish more volts than I would have expected. Had I wired it up for 240 volts on a 20 amp breaker (16 amp rate), that would have been a 6 volt drop, which might barely be noticed (2.5%, or 15 minutes in 10 hours charging).

So, TL;DR bottom line: paying attention to wire size does matter. But don't expect miracles.

 

[Wshowell]

There's a little reading you can do.
3 Phase Power vs Single Phase Power • OEM Panels
Basically home residential electricity systems use what is called "split phase". It has 120V, and then 240V for the higher one. Commmercial/industrial properties usually use what is called "3 phase". You can read the link above to see more details, but in short, it ends up with those two voltage levels actually being 120V and 208V. So at most commercial businesses 208V is actually what you will find, or maybe a few volts lower because of a long wiring run.

And yes, the rate at which the car charges scales directly with power, which is volts times amps, so a difference in either will affect the miles per hour charging rate.

Makes perfect sense. The hotel would be a 3 Phase set up. Thank you. I enjoyed the linked article.