Rat
Posts: 953
Joined: Sun Apr 25, 2010 7:47 pm
Delivery Date: 08 Sep 2011
Location: Silicon Valley

### 220V vs. 240V

Can one of you engineer or electrician types explain to me why all the current (no pun intended) references to the charger are for 240 V? Until recently I always heard that home circuits and sockets were 110V and 220V. Now all I hear on the EV boards are about 120 / 240. Are these really the same thing - i.e. 110=120 and 220=240? Why the different terminology? I have a 220V home dryer plug in my garage, but is this too wimpy to support the charging station? I am concerned that the electrician will charge me to run an entirely new circuit from my panel to the garage, which are at opposite ends of the house.
2011 SL down to 9 capacity bars
OnWords

DeaneG
Posts: 1110
Joined: Tue May 04, 2010 9:20 pm
Delivery Date: 01 Apr 2011
Leaf Number: 594
Location: Cupertino, CA

### Re: 220V vs. 240V

Line voltage in the US was generally 220v or 230v with a center tap for 110v or 115v up until some time (2-3 decades?) ago. It was increased to a standard 240v/120v +-5% in north America. I can't tell you why, maybe someone else knows.

Many people still refer to line voltage as 110 or 220 out of colloquial habit. But it's usually actually 240 or 120v. US appliances are designed to operate at 120v +-10% (108-132v) or 240v +- 10% (208-264v).

A "220v" dryer plug is most likely operating at 240v nominal. It is probably energized by a 30 amp circuit breaker. The current vague information is that the 2011 Leaf can only draw 3.3Kw from the 240v outlet, which is less than 15 amps. Later Leafs are rumored to be able to accept up to 6.6kW (almost 30 amps at 240v). But electrical codes limit steady current draw from a circuit breaker to 80% or less of the breaker's rating, 12A for a 15A breaker, or 24A for a 30A breaker.

We don't know yet if the Leaf's EVSE (wall unit) can be programmed to limit 240v draw to say 15A or 20A. If it can't, then you'd want to have a 30-amp capable circuit installed to operate it (40 amp breaker). If the EVSE can be set to 15A or 20A, your dryer outlet can probably be repurposed (hard wired) as your EVSE supply.

EDIT: fixed incorrect breaker current fraction
Last edited by DeaneG on Sat Jun 19, 2010 8:31 am, edited 1 time in total.
White SL w/L3, 3kWDC Solar PV

mwalsh
Posts: 9633
Joined: Thu Apr 22, 2010 10:10 am
Delivery Date: 05 Jan 2011
Leaf Number: 0213
Location: Garden Grove, CA

### Re: 220V vs. 240V

"220....221, whatever it takes"

*the best line from the movie 'Mr. Mom'
2011 Blue Ocean SL with 81,000 miles
2015 pack on 12/30/15
Tinted windows
Bridgestone Ecopia 422+ tires
FIAMM horns
Superbright LED lighting
2013 sun visors
LED shifter
Heated seats
GT-R map lamp lenses
Altima illuminated door switches

garygid
Gold Member
Posts: 12460
Joined: Wed Apr 21, 2010 8:10 am
Delivery Date: 29 Mar 2011
Leaf Number: 000855
Location: Laguna Hills, Orange Co, CA

### Re: 220V vs. 240V

Minor details:
I have read that 80% is the "permitted" continuous load on a breaker, so 24 amps from a 30-amp breaker.

Also, I believe that the power "standard voltage" is 120v (or 240v) +0% -10% rather than +-5%.

But, if you measure the "110" with a voltmeter in a relatively new neighborhood, you will probably find just over 119v in the (lightly loaded) morning, and rarely below 113 or 114 volts in the afternoon. But at the long end of a heavily-loaded supply wire or cord, it can easily drop to 110 volts.
See SOC/GID-Meter and CAN-Do Info
2010 Prius, now for sale
2011 LEAF, sold in 2015
2018 Tesla Model 3
2014 Tesla S, Model 3 in 2019
PU: SDG&E
Solar PV: 33 x 225W -> 7 kW max AC
To Sell: X-treme 5000Li EV motorcycle

planet4ever
Posts: 4674
Joined: Sat Apr 03, 2010 9:53 pm
Delivery Date: 02 May 2011
Leaf Number: 1537
Location: Morgan Hill, CA, south of San Jose

### Re: 220V vs. 240V

I can't seem to find the source right now, but I remember reading that Nissan (or maybe some code) is going to insist the 240V EVSE must be installed on a dedicated 40A circuit, so your existing dryer line would not be acceptable, even though it can carry enough current for the 3.3kWh charger the first Volts will have.

And I'm sure most people know this, but you also can't just replace the 30A circuit breaker with a 40A breaker. You need to have thicker wires out to the garage.
End of April 2013: Traded my 2011 SL for a 2013 S with charge pkg.

mitch672
Posts: 1956
Joined: Fri Apr 23, 2010 2:10 pm
Location: Boston, MA

### Re: 220V vs. 240V

Here is a little history...

In the United States, the electricity utility powerlines going to residential streets and roads are operated from 2300 to 2400 volts. With a 2400 volt supply, it is very convenient and easy to design and build pole transformers that have a 10-to-1 step-down ratio, thus providing 240 volts to the houses. The transformers also have a center tap to provide 120 volts from each 240-volt leg to the center point. This center point tap also provides a convenient point for a grounding connection. The actual measured voltage in your house receptacle circuits will normally be 120 to 125 volts. All appliances are rated for the minimum operating voltage (110-115), thus there is much confusion about the actual level of the supply voltages."
2012 Advanced Plug in Prius (sold)
I Support OpenEVSE: http://code.google.com/p/open-evse/
My Fuelly page: http://www.fuelly.com/driver/mitch672/prius-plugin
Tesla Model S 85KW Dolphin Grey VIN: 03245, delivered 1/17/2013

LEAFer
Posts: 2647
Joined: Mon May 24, 2010 10:10 am
Delivery Date: 19 Jan 2011
Leaf Number: 000215
Location: Sacramento Area

### Re: 220V vs. 240V

Good summary explanation by DeaneG, except for the 75%. As garygid points out, it is 80%.

Confusion arises partly due to the 80%, which, unless it is specifically referenced, causes trouble especially for the 30A number, because the breakers are rated in 10A increments (except for the lowly 15A single pole). So, the 30A breaker should be used to supply 24A, not 30A. In order to make use of the 30A continuous current you DO need a 40A breaker, but the actual allowable current is 80% of 40 = 32A. I have even seen erroneous references to the 30A draw in connection with some J1772 equipment. But the J1772 does not have a pilot signal for 30A ... the signal is 32A (as it should be, and in which case, gues what, it should sit on a 40A breaker).

(More confusion: many receptacles and plug have a maximum rating of 250V printed on them.)

My house is "overvolted" ... we share a transformer with only one other neighbor. Even under load my "240V" (nominal) supply runs 242V in the mornings and 247V in the afternoons. I have seen as high as 249V, but rarely. I have seen open-circuit voltages (volt meter, no load) on the "120V" (nominal) as low as 115, but usually running 119-122V.

edit: Note: I am getting all sorts of conflicting info in researching about the 30A versus 32A pilot signal in the J1772 spec. (Also see my reply a few posts down.)
Last edited by LEAFer on Sat Jun 19, 2010 9:17 am, edited 1 time in total.
2011 Silver SL+QC [Mfg: 11/2010] 36mo/15k LEASE
06Jun2013 Status [28.5 months][34,173 miles][11 bars]
Lost CapacityBar 6/6/13 @34,173 miles while in LEAF Battery Monitor: 83.41%, 71.4F (avg); cool overnight;

DeaneG
Posts: 1110
Joined: Tue May 04, 2010 9:20 pm
Delivery Date: 01 Apr 2011
Leaf Number: 594
Location: Cupertino, CA

### Re: 220V vs. 240V

Gary, thanks for the correction... edited my post above to improve truthiness.
White SL w/L3, 3kWDC Solar PV

DeaneG
Posts: 1110
Joined: Tue May 04, 2010 9:20 pm
Delivery Date: 01 Apr 2011
Leaf Number: 594
Location: Cupertino, CA

### Re: 220V vs. 240V

The OP is actually a very good question. Maybe it's a good time to start a sticky FAQ thread, since some of our assumed info is becoming fact?
White SL w/L3, 3kWDC Solar PV

garygid
Gold Member
Posts: 12460
Joined: Wed Apr 21, 2010 8:10 am
Delivery Date: 29 Mar 2011
Leaf Number: 000855
Location: Laguna Hills, Orange Co, CA

### Re: 220V vs. 240V

Maybe AndyH can check a recent copy of the J1772 standard and see if the "max current" (duty cycle of a square wave) signal has discrete allowed values, or is a more-or-less "continuous" value.

A graph I "saw" (or maybe only imagined) of duty cycle vs max current was a continuous slope, rather than a series of "allowed" values. But, it might have been old, or only "suggestive" of the meaning of the signal.

If only 6-amp "steps" are allowed, then 12 (from a 15-amp breaker) might be allowed, but the popular 15 (or 16) amps from a 20-amp breaker would not be available.

So, I suspect that mandating only 6-amp steps would be a (another) poor choice for this standard.
See SOC/GID-Meter and CAN-Do Info
2010 Prius, now for sale
2011 LEAF, sold in 2015
2018 Tesla Model 3
2014 Tesla S, Model 3 in 2019
PU: SDG&E
Solar PV: 33 x 225W -> 7 kW max AC
To Sell: X-treme 5000Li EV motorcycle