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Ingineer
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Leaf Number: 6969
Location: Berkeley, California
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Re: charging on generator

Fri Feb 26, 2016 10:15 pm

It's not just "EU". It's for charging on isolated grounds. Yes TWO resistors, whether 120 or 240.
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EV4Taos
Posts: 40
Joined: Mon Nov 19, 2012 5:00 am
Delivery Date: 19 Nov 2012
Location: Taos, NM

Re: charging on generator

Sun Feb 28, 2016 6:05 pm

Ingineer wrote:It's not just "EU". It's for charging on isolated grounds. Yes TWO resistors, whether 120 or 240.


Great that is very clear. Thank you!

pmmcin
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Leaf Number: 406070

Re: charging on generator

Sun Jul 02, 2017 3:29 pm

So for me to charge my 2013 leaf on a 240 volt (nema L14-30) four pole plug Generator at level two with my upgraded evse I would get two 1/2 watt 100k ohm resistors and solder/screw them from the two hot (x) & (y) to the ground (G)? What about the neutral (w) ? My upgraded evse has a nema L6-30 (3pole) plug and I made an adapter from that to the L14-30 leaving the neutral disconnected to fit my generators 240v plug. Just wanted to be sure before trying & making a costly mistake.
TY.

wwhitney
Posts: 663
Joined: Sat Jul 17, 2010 10:10 am
Delivery Date: 01 Apr 2011
Location: Berkeley, CA

Re: charging on generator

Sun Jul 02, 2017 3:45 pm

pmmcin wrote:So for me to charge my 2013 leaf on a 240 volt (nema L14-30) four pole plug Generator at level two with my upgraded evse I would get two 1/2 watt 100k ohm resistors and solder/screw them from the two hot (x) & (y) to the ground (G)?

This is only necessary if the ground pin on the generator receptacle is unbonded and left floating. So check the generator first. You could just try charging with your EVSE first, and if the EVSE throws a ground fault, check the ground to neutral resistance on the generator receptacle with an ohmmeter.

Cheers, Wayne

GerryAZ
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Location: Phoenix, AZ

Re: charging on generator

Sun Jul 02, 2017 11:41 pm

I recommend a single resistor from neutral to ground because the generator returns to floating neutral operation if the resistor connection(s) come loose. With resistors connected to both hot lines (X and Y on your L14-30 receptacle), failure of one resistor will result in shifting the voltage so that neutral could be as much as 120 volts with respect to ground. Since most generators have duplex receptacles in addition to the twist lock, an easy way to create the neutral to ground reference is to connect a resistor between neutral and ground terminals in a replacement 15-ampere plug (no cord needed). Then you simply insert the grounding plug into one of the duplex receptacles when you need it.
Gerry
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
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pmmcin
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Leaf Number: 406070

Re: charging on generator

Mon Jul 10, 2017 9:20 pm

So I plugged the upgraded evse into the generators 240v 4pole nema l14-30 receptacle via the adapter to the evse's l6-30 plug and the evse faulted. So I then used a jumper cable to ground the frame and the generator leg to my electric poles ground cable & the evse still faulted. So I then added a ground cable to the ground pole of the l14-30 to l6-30 adapter and clamped it to the grounded jumper cables that were also attached to the generator frame, Generator leg and the electric pole's ground cable.
Nothing ! The evse still faulted. I know that he Generator's receptacle is working because I plugged a few lights, microwave & home stereo to it, and the evse works fine on my 120v/240v home receptacles. Btw the evse is NOT plugged into the car when fault occurs.
Also TY for getting back to me, this is really frustrating and you guys seem to be the only ppl on the planet that have any idea what I'm talking about.

wwhitney
Posts: 663
Joined: Sat Jul 17, 2010 10:10 am
Delivery Date: 01 Apr 2011
Location: Berkeley, CA

Re: charging on generator

Mon Jul 10, 2017 10:04 pm

pmmcin wrote:So I plugged the upgraded evse into the generators 240v 4pole nema l14-30 receptacle via the adapter to the evse's l6-30 plug and the evse faulted.

What kind of fault? I take it you are operating the generator in a standalone fashion.

You need to use an ohmmeter to measure the resistance between the neutral pin and the ground pin on the generator's L14-30 receptacle. It should be near 0, indicating that the neutral is bonded to ground at the generator. If it is not, then you will need to make/acquire a ground bonding plug as described earlier in this thread.

Connecting the generator frame or generator receptacle ground pin to any earth or ground external to the generator is basically useless, when the generator is operating in a standalone fashion.

Cheers, Wayne

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JeremyW
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Re: charging on generator

Mon Jul 10, 2017 10:33 pm

What's better: doing the resistor faker trick (one or two resistors to ground) or using an EVSE that doesn't do the ground trick (openEVSE setting)?
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GerryAZ
Gold Member
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Location: Phoenix, AZ

Re: charging on generator

Tue Jul 11, 2017 7:39 pm

JeremyW wrote:What's better: doing the resistor faker trick (one or two resistors to ground) or using an EVSE that doesn't do the ground trick (openEVSE setting)?


I think it would be best to use a single 100,000 ohm resistor. If the EVSE ground fault sensor is disabled for generator use, there is a possibility of forgetting to enable the sensor before using the EVSE on grid power.

It should be noted that the resistor will limit ground fault current below the trip levels of GFCI receptacles or the EVSE so they will not trip if there is a true ground fault on the load circuit. If actual GFCI protection is needed, then the generator frame must be grounded with a ground rod or connection to a building ground and the neutral must be connected to the generator ground with a wire instead of a resistor. I have a resistor grounding plug and direct grounding plug that I keep with each generator because I have different needs for different applications. I use the resistor plug for charging the car or running test equipment that has an internal ground test circuit like an EVSE. I use the solid ground plug for backup power at the house with the generator frame grounded to the house power panel ground. I leave the generator floating (neither plug inserted) for general portable use.
Gerry
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015

wwhitney
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Location: Berkeley, CA

Re: charging on generator

Wed Jul 12, 2017 8:30 am

GerryAZ wrote:It should be noted that the resistor will limit ground fault current below the trip levels of GFCI receptacles or the EVSE so they will not trip if there is a true ground fault on the load circuit.

While that is true, if the current flow is below 6ma, there is no shock hazard.

GerryAZ wrote:If actual GFCI protection is needed, then the generator frame must be grounded with a ground rod or connection to a building ground and the neutral must be connected to the generator ground with a wire instead of a resistor.

Installing a neutral/ground bond has the advantage that in the event of a ground fault, the breaker or GFCI will trip. Connecting the generator frame to an earth electrode just expands what counts as a ground fault--it's not clear to me it enhances safety.

GerryAZ wrote:I use the solid ground plug for backup power at the house with the generator frame grounded to the house power panel ground. I leave the generator floating (neither plug inserted) for general portable use.

If "backup power at the house" means connecting the generator to the building wiring, then you probably DO NOT want to use the solid ground plug in that situation. Unless your transfer equipment switches the neutral, then when the generator is connected to the building wiring the resulting system already has a ground/neutral bond at the house's main panel. Adding an additional neutral/ground bond at the generator would result in undesirable neutral current on the grounding system.

Cheers, Wayne

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