208 volt 20 amp

[Woody5575]

I don’t really want to spend $2000 to install a 50 amp 240 volt circuit in my house, so I’m wondering if I can use a 20 amp 208 volt circuit that I used to run some of my tools. According to the charts, it wouldn’t increase charging speed over my regular house current, so I may be wasting my time. Mostly, I’m just curious.

 

[jjrandorin]

You could use that, and it should be faster than a regular 15 amp 120v circuit. You have a 208v circuit in your house? is it a multi family residence (townhouse, condo, etc)?

 

[Cosmacelf]

I don’t really want to spend $2000 to install a 50 amp 240 volt circuit in my house, so I’m wondering if I can use a 20 amp 208 volt circuit that I used to run some of my tools. According to the charts, it wouldn’t increase charging speed over my regular house current, so I may be wasting my time. Mostly, I’m just curious.

Yeah why do you say it is 208 volts?

But yes, you can use a 250v/20A circuit with a Tesla Mobile Connector and a 6-20 adapter. I’m presuming that the receptacle is a 6-20?

 

[rcho8]

Do you have three phase 208volt commercial power? I dont think tesla power adapter will work with three phase. you might have to use 3rd party three phase power adapters.

 

[Woody5575]

Yeah why do you say it is 208 volts?

But yes, you can use a 250v/20A circuit with a Tesla Mobile Connector and a 6-20 adapter. I’m presuming that the receptacle is a 6-20?

I may need to change the plug/receptacle. It really is 208 single phase. I had it installed years ago to run a table saw. I had no idea what I needed. I just told the electrician what I wanted to plug in.

 

[Woody5575]

You could use that, and it should be faster than a regular 15 amp 120v circuit. You have a 208v circuit in your house? is it a multi family residence (townhouse, condo, etc)?

Yes, it’s a single family. Installed to run my table saw. I was told that the car would see the 208, and draw too much amperage for the 20amp circuit. How does it know how much to draw?

 

[Evee]

Just set it in the car. If you have this setup and don’t wanna spend the money for more power. Then that’s ur setup…..

 

[jjrandorin]

Yes, it’s a single family. Installed to run my table saw. I was told that the car would see the 208, and draw too much amperage for the 20amp circuit. How does it know how much to draw?

Even if it is intended to run a Table saw, it would be pretty rare for a single famly home to have 208v (and not 240v) in the US. Why are you saying its 208v?

I dont understand what you are saying in your above comment. The circuit is what the circuit is, and the mobile connector (what people call the charger) will need to have an appropriate adapter on it to plug into the outlet on the circuit you want to use.

The car will know what the circuit is based on the adapter that is used.

Just set it in the car.

While that "can" work, it should never be a permanent solution, since the car can (and sometimes does) lose that setting after various updates.

The correct way to do this is to get the appropriate adapter for the outlet being used, and put it on the mobile connector, so that the car can never draw more than the circuit is set for.

 

[RandyS]

I'm dying to see photos of a multimeter test that shows 208v on that circuit and 240v on other household circuits....I've certainly never seen that before (assuming they come from the same electric service)...

 

[Big Earl]

You house is either all 208-volt or all 24-volt. 208-volt is two legs of a three-phase system, most commonly found in commercial buildings, apartments and condominiums.

Being a single family, it's mostly likely 240-volt (split-phase). Either way, the Mobile Connector will work just fine on a 20-amp circuit as long as it's wired properly.

 

[DuncanM]

I don’t really want to spend $2000 to install a 50 amp 240 volt circuit in my house, so I’m wondering if I can use a 20 amp 208 volt circuit that I used to run some of my tools. According to the charts, it wouldn’t increase charging speed over my regular house current, so I may be wasting my time. Mostly, I’m just curious.

Many L2 chargers in malls, condos, and other public spaces use 208v and my M3 RWD will charge at 32A on these at ~6.5kwh/h. If you really have only 208v you would be charging at 16A/208v, max which will still give a 50% charge in about 10-12 hrs.

I use a NEMA 6-20 outlet in our winter home. I charge at 15A/~240v which is more than adequate for overnight charging,

 

[Tronguy]

Yeah, to the OP:

Standard wiring for homes in the US and Canada have something called "Split Phase". Up on the power pole, a transformer has three output wires:

1. One wire is Neutral. When it gets to the house, it gets bonded to the ground bar inside your breaker panel and, incidentally, gets connected to a 6 foot copper ground stake that is, natch, pounded into the physical ground.
2. One wire is a Hot. A voltmeter connected between the Hot and Neutral shows up as 120VAC, plus or minus a bit. This particular wire gets bolted onto the back side of the meter on your house; another wire takes this voltage and connects it to one of the two bus "hot" bus bars in your breaker box.
3. The final wire is also a Hot. A voltmeter connected to this hot and Neutral also shows up as 120 VAC. The tricky bit: Each hot is a sine wave. While one sine wave is going up, the other sine wave is going down. A voltmeter connected between the two hots shows up as 240 VAC.

Note that the meter on the house has four big lugs on the back: One for each hot coming in, and one for each hot coming out.

So, in the above situation, if one looks at the breaker box in your house, for a (typical) vertical row of slots, the first slot at the top is on one hot; the next one is on the other hot, then back to the first hot, and so on, all the way down the column of slots. When one wants 240 VAC for, say, the HVAC in the house or an electric drier, a duplex, ganged breaker will be plugged into two adjacent slots, and the voltage between the wires coming off this pair of ganged breakers will be 240 VAC.

Any hot to ground/neutral is 120 VAC, and that's for lighting, standard power sockets, and appliances that work off of 120 VAC.

Now, in commercial properties, people get three-phase AC. There's three hots and a neutral. Each hot to neutral is 120 VAC. The meter will have a total of six lugs on the back, one for each of the three phases coming in, and one for each of the three phases coming out.

Let's call the three phases A, B, and C. Let's arbitrarily say that Phase A is at zero degrees; Phase B is at 120 degrees; and Phase C is at 240 degrees. Do the math with sine waves and all, and one will discover that the voltage between any two phases is 208 VAC. And, if one looks at the breaker box, instead of having this alternating, "first this phase, then that phase, then the first phase again", one will get, in a vertical column, Phase A, Phase B, Phase C, Phase A again, Phase B again, and so on. A duplex breaker on two adjacent slots will give you 208 VAC.

So, go to a public charging station in a Supermarket parking lot? More likely than not, that Supermarket has 3-phase AC, and the Chargepoint (or whatever) charging stations will supply current at 208 VAC, because that's what's available: Two phases of the three-phase system feeding the Supermarket.

Now, that split-phase power that one sees on one's house typically comes from some transformer with 440 VAC in (or something) and that split-phase stuff coming out, and the split phase goes not to just one house, but usually several. But it's not written in stone that this might happen. It's Just Possible that, for some weird historical reason, that a bunch of houses on some street somewhere all got supplied with two phases of a 3-phase system, and they've all got 208 VAC between the two phases actually supplied to the house.

If that last thing is what happened to you.. Well, weird, somewhat non-standard, but not harmful in any way. HVAC systems and Tesla Wall Connectors can handle 208 VAC just fine. You'll get less power delivered to the car that way (say, 208 @ 48A = 9.9 kW, 240 @ 48A = 11.5 kW), but not enough to keep one up at night.

But, there's another possibility. Say you had some piece of machinery that was, for some vaguely insane reason, truly specific that it had to have 208 VAC. And you told your electrician that. And your electrician, in this scenario, noted that you had 240 VAC split phase. Well, one can't just connect wires, wave a magic wand, and arbitrarily make 208 VAC happen.

Except that, in a way, one can do that. There is such a thing as a step-down transformer. Heavy, made of iron, with lots of wires running around in small circles, and 240 VAC in, 208 VAC out. Power out is about the same as the power in, minus some losses that make the transformer slightly warm.

However.. these things, assuming you've got such a thing, very positively have power limits. Some of that is how much heating one can have on the wires in this thing (assuming you've got this thing) which, if the heating is enough, leads to breakdown of the insulation inside the transformer, which is arcs, sparks, and breakers popping open time. And there's some heating of all the heavy iron in there. And that transformers have power limits where the iron gets magnetically saturated, which is Bad News.

So, if your electrician knew what the power requirements for your machinery was, and decided that a transformer was the way out, he'd've picked a transformer with the right power rating for your machinery, picked the right breaker on the panel to supply that power, and the right wire to handle that current. You don't want to violate any of that when charging your Tesla.

Another possibility.. It's Really Common for equipment that's rated for 200-odd VAC to be able to handle both 208 VAC and 240 VAC. If your electrician looked at the specs on your gear and it said that it could take 240 VAC, he may have ditched the whole transformer business right off, saved you some money, and saved himself some time. And your understanding about what you've actually got there may be faulty.

You could figure all this out in about ten minutes with a voltmeter. Or a friend with a voltmeter.

208 VAC in residential is, like, odd.

 

[RayK]

Yes, it’s a single family. Installed to run my table saw. I was told that the car would see the 208, and draw too much amperage for the 20amp circuit. How does it know how much to draw?

A photo of the outlet you used to plug in the table saw would help immensely. From that, people here can figure out what kind of adapters are needed; presumedly to convert the assumed twist lock plug into an outlet which a Tesla NEMA adapter of appropriate amperage can be used.

 

[Big Earl]

Yeah, to the OP:

Standard wiring for homes in the US and Canada have something called "Split Phase". Up on the power pole, a transformer has three output wires:

1. One wire is Neutral. When it gets to the house, it gets bonded to the ground bar inside your breaker panel and, incidentally, gets connected to a 6 foot copper ground stake that is, natch, pounded into the physical ground.
2. One wire is a Hot. A voltmeter connected between the Hot and Neutral shows up as 120VAC, plus or minus a bit. This particular wire gets bolted onto the back side of the meter on your house; another wire takes this voltage and connects it to one of the two bus "hot" bus bars in your breaker box.
3. The final wire is also a Hot. A voltmeter connected to this hot and Neutral also shows up as 120 VAC. The tricky bit: Each hot is a sine wave. While one sine wave is going up, the other sine wave is going down. A voltmeter connected between the two hots shows up as 240 VAC.

Note that the meter on the house has four big lugs on the back: One for each hot coming in, and one for each hot coming out.

So, in the above situation, if one looks at the breaker box in your house, for a (typical) vertical row of slots, the first slot at the top is on one hot; the next one is on the other hot, then back to the first hot, and so on, all the way down the column of slots. When one wants 240 VAC for, say, the HVAC in the house or an electric drier, a duplex, ganged breaker will be plugged into two adjacent slots, and the voltage between the wires coming off this pair of ganged breakers will be 240 VAC.

Any hot to ground/neutral is 120 VAC, and that's for lighting, standard power sockets, and appliances that work off of 120 VAC.

Now, in commercial properties, people get three-phase AC. There's three hots and a neutral. Each hot to neutral is 120 VAC. The meter will have a total of six lugs on the back, one for each of the three phases coming in, and one for each of the three phases coming out.

Let's call the three phases A, B, and C. Let's arbitrarily say that Phase A is at zero degrees; Phase B is at 120 degrees; and Phase C is at 240 degrees. Do the math with sine waves and all, and one will discover that the voltage between any two phases is 208 VAC. And, if one looks at the breaker box, instead of having this alternating, "first this phase, then that phase, then the first phase again", one will get, in a vertical column, Phase A, Phase B, Phase C, Phase A again, Phase B again, and so on. A duplex breaker on two adjacent slots will give you 208 VAC.

So, go to a public charging station in a Supermarket parking lot? More likely than not, that Supermarket has 3-phase AC, and the Chargepoint (or whatever) charging stations will supply current at 208 VAC, because that's what's available: Two phases of the three-phase system feeding the Supermarket.

Now, that split-phase power that one sees on one's house typically comes from some transformer with 440 VAC in (or something) and that split-phase stuff coming out, and the split phase goes not to just one house, but usually several. But it's not written in stone that this might happen. It's Just Possible that, for some weird historical reason, that a bunch of houses on some street somewhere all got supplied with two phases of a 3-phase system, and they've all got 208 VAC between the two phases actually supplied to the house.

If that last thing is what happened to you.. Well, weird, somewhat non-standard, but not harmful in any way. HVAC systems and Tesla Wall Connectors can handle 208 VAC just fine. You'll get less power delivered to the car that way (say, 208 @ 48A = 9.9 kW, 240 @ 48A = 11.5 kW), but not enough to keep one up at night.

But, there's another possibility. Say you had some piece of machinery that was, for some vaguely insane reason, truly specific that it had to have 208 VAC. And you told your electrician that. And your electrician, in this scenario, noted that you had 240 VAC split phase. Well, one can't just connect wires, wave a magic wand, and arbitrarily make 208 VAC happen.

Except that, in a way, one can do that. There is such a thing as a step-down transformer. Heavy, made of iron, with lots of wires running around in small circles, and 240 VAC in, 208 VAC out. Power out is about the same as the power in, minus some losses that make the transformer slightly warm.

However.. these things, assuming you've got such a thing, very positively have power limits. Some of that is how much heating one can have on the wires in this thing (assuming you've got this thing) which, if the heating is enough, leads to breakdown of the insulation inside the transformer, which is arcs, sparks, and breakers popping open time. And there's some heating of all the heavy iron in there. And that transformers have power limits where the iron gets magnetically saturated, which is Bad News.

So, if your electrician knew what the power requirements for your machinery was, and decided that a transformer was the way out, he'd've picked a transformer with the right power rating for your machinery, picked the right breaker on the panel to supply that power, and the right wire to handle that current. You don't want to violate any of that when charging your Tesla.

Another possibility.. It's Really Common for equipment that's rated for 200-odd VAC to be able to handle both 208 VAC and 240 VAC. If your electrician looked at the specs on your gear and it said that it could take 240 VAC, he may have ditched the whole transformer business right off, saved you some money, and saved himself some time. And your understanding about what you've actually got there may be faulty.

You could figure all this out in about ten minutes with a voltmeter. Or a friend with a voltmeter.

208 VAC in residential is, like, odd.

Odd, but not unheard of. I have a friend in Michigan with a mid-century multi-split-level home with three-phase power.

Regardless, the receptacle on a 20-amp circuit will be the same whether it's 208 or 240 volts. Twist-lock is a different story, and would require a custom adapter or changing the receptacle. The Wall Connector and Tesla won't care what the voltage is and will charge the car safely as long as the correct adapter is used for the circuit amperage.

 

[Tronguy]

Odd, but not unheard of. I have a friend in Michigan with a mid-century multi-split-level home with three-phase power.

Regardless, the receptacle on a 20-amp circuit will be the same whether it's 208 or 240 volts. Twist-lock is a different story, and would require a custom adapter or changing the receptacle. The Wall Connector and Tesla won't care what the voltage is and will charge the car safely as long as the correct adapter is used for the circuit amperage.

Yep. But the thing what threw me was that he has asked the electrician specifically for 208 VAC.

If the Electrician had said, "That's not a problem, you've got that in the house." that'd be one thing,, and the OP probably wouldn't have mentioned it.

If the Electrician had said, "That's unusual. It'll be $$X to make that happen." that'd be another. And odd.

 

[Cosmacelf]

I may need to change the plug/receptacle. It really is 208 single phase. I had it installed years ago to run a table saw. I had no idea what I needed. I just told the electrician what I wanted to plug in.

So the 208V number came from the faceplate/specs of the table saw? If so, that's just the minimum voltage that the saw needs to operate correctly. It'll happily use 240V, which is probably the nominal voltage of your receptacle.

ANYWAYS, this all doesn't matter. The Tesla Mobile Connector will happily work with 208V or 240V or whatever. Chances are very good that the table saw was plugged into a NEMA 6-20 receptacle:

Which looks like a standard 20A household outlet, but is different. If that is what you have for a receptacle, then just buy the Tesla NEMA 6-20 adapter along with the Mobile Connector and the car will happily be charging at 16A/240V (or whatever). NO WORRIES if your power is really 208V, the car won't draw more than 16A no matter what the voltage is, unlike a table saw.

And yes, that will be a fine charge rate for most uses.

 

[Eric33432]

Lots of 208 volt 3 phase power running around the single family neighborhoods of Queens, NYC, for some reason. Maybe because mixed in with the house there is a lot of commercial stuff. I noticed that when driving out to JFK airport once. You see four wires running between the poles instead of 3.

My apartment in NYC on the 40th floor of a high-rise also had 208 coming in, but again, just one phase.

I can confirm the Tesla Wall Connector and Tesla Mobile Connector is quite happy with anything from probably 190 volts to at least 250 volts. Amps will stay what it is set for, the power will be volts times amps.

Unlike in a lot of places in Europe, they only drop off one phase to the houses (I suppose a guy with a large shop *could* get 3 phase at his house if he wanted to pay for it).

 

[ucmndd]

Lots of people say “208” the same way they say “220”. Most people have no clue as to the difference or the likelihood that neither of them are correct.

In any case, it’s completely inconsequential to OP’s question.

The answer is: buy an adapter for the mobile connector that matches the receptacle on the wall. Plug it in. It will work and provide plenty of power for most daily charging needs. That’s it. There’s no more magic to it.

/thread

 

[Cosmacelf]

I’m wondering if I can use a 20 amp 208 volt circuit that I used to run some of my tools. According to the charts, it wouldn’t increase charging speed over my regular house current, so I may be wasting my time. Mostly, I’m just curious.

Don't know what chart you are looking at, but it will increase charging speed a lot compared to a regular household circuit.

/thread

You've been here long enough to know better

 

[hsfrank]

Yeah, to the OP:

Standard wiring for homes in the US and Canada have something called "Split Phase". Up on the power pole, a transformer has three output wires:

1. One wire is Neutral. When it gets to the house, it gets bonded to the ground bar inside your breaker panel and, incidentally, gets connected to a 6 foot copper ground stake that is, natch, pounded into the physical ground.
2. One wire is a Hot. A voltmeter connected between the Hot and Neutral shows up as 120VAC, plus or minus a bit. This particular wire gets bolted onto the back side of the meter on your house; another wire takes this voltage and connects it to one of the two bus "hot" bus bars in your breaker box.
3. The final wire is also a Hot. A voltmeter connected to this hot and Neutral also shows up as 120 VAC. The tricky bit: Each hot is a sine wave. While one sine wave is going up, the other sine wave is going down. A voltmeter connected between the two hots shows up as 240 VAC.

Note that the meter on the house has four big lugs on the back: One for each hot coming in, and one for each hot coming out.

So, in the above situation, if one looks at the breaker box in your house, for a (typical) vertical row of slots, the first slot at the top is on one hot; the next one is on the other hot, then back to the first hot, and so on, all the way down the column of slots. When one wants 240 VAC for, say, the HVAC in the house or an electric drier, a duplex, ganged breaker will be plugged into two adjacent slots, and the voltage between the wires coming off this pair of ganged breakers will be 240 VAC.

Any hot to ground/neutral is 120 VAC, and that's for lighting, standard power sockets, and appliances that work off of 120 VAC.

Now, in commercial properties, people get three-phase AC. There's three hots and a neutral. Each hot to neutral is 120 VAC. The meter will have a total of six lugs on the back, one for each of the three phases coming in, and one for each of the three phases coming out.

Let's call the three phases A, B, and C. Let's arbitrarily say that Phase A is at zero degrees; Phase B is at 120 degrees; and Phase C is at 240 degrees. Do the math with sine waves and all, and one will discover that the voltage between any two phases is 208 VAC. And, if one looks at the breaker box, instead of having this alternating, "first this phase, then that phase, then the first phase again", one will get, in a vertical column, Phase A, Phase B, Phase C, Phase A again, Phase B again, and so on. A duplex breaker on two adjacent slots will give you 208 VAC.

So, go to a public charging station in a Supermarket parking lot? More likely than not, that Supermarket has 3-phase AC, and the Chargepoint (or whatever) charging stations will supply current at 208 VAC, because that's what's available: Two phases of the three-phase system feeding the Supermarket.

Now, that split-phase power that one sees on one's house typically comes from some transformer with 440 VAC in (or something) and that split-phase stuff coming out, and the split phase goes not to just one house, but usually several. But it's not written in stone that this might happen. It's Just Possible that, for some weird historical reason, that a bunch of houses on some street somewhere all got supplied with two phases of a 3-phase system, and they've all got 208 VAC between the two phases actually supplied to the house.

If that last thing is what happened to you.. Well, weird, somewhat non-standard, but not harmful in any way. HVAC systems and Tesla Wall Connectors can handle 208 VAC just fine. You'll get less power delivered to the car that way (say, 208 @ 48A = 9.9 kW, 240 @ 48A = 11.5 kW), but not enough to keep one up at night.

But, there's another possibility. Say you had some piece of machinery that was, for some vaguely insane reason, truly specific that it had to have 208 VAC. And you told your electrician that. And your electrician, in this scenario, noted that you had 240 VAC split phase. Well, one can't just connect wires, wave a magic wand, and arbitrarily make 208 VAC happen.

Except that, in a way, one can do that. There is such a thing as a step-down transformer. Heavy, made of iron, with lots of wires running around in small circles, and 240 VAC in, 208 VAC out. Power out is about the same as the power in, minus some losses that make the transformer slightly warm.

However.. these things, assuming you've got such a thing, very positively have power limits. Some of that is how much heating one can have on the wires in this thing (assuming you've got this thing) which, if the heating is enough, leads to breakdown of the insulation inside the transformer, which is arcs, sparks, and breakers popping open time. And there's some heating of all the heavy iron in there. And that transformers have power limits where the iron gets magnetically saturated, which is Bad News.

So, if your electrician knew what the power requirements for your machinery was, and decided that a transformer was the way out, he'd've picked a transformer with the right power rating for your machinery, picked the right breaker on the panel to supply that power, and the right wire to handle that current. You don't want to violate any of that when charging your Tesla.

Another possibility.. It's Really Common for equipment that's rated for 200-odd VAC to be able to handle both 208 VAC and 240 VAC. If your electrician looked at the specs on your gear and it said that it could take 240 VAC, he may have ditched the whole transformer business right off, saved you some money, and saved himself some time. And your understanding about what you've actually got there may be faulty.

You could figure all this out in about ten minutes with a voltmeter. Or a friend with a voltmeter.

208 VAC in residential is, like, odd.

Great explanation and very clearly put.