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Old 05-11-2013, 07:55 PM   #41
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Originally Posted by RenoRock View Post
Thanks for the advice. We'll go back to the wire jumper.
I have no idea why the poster put up the resistor or what it actually does. I'll see if I can find information from that source in the meantime to satisfy my curiosity on the reasoning.
I took a look at the 100-ohm resistor thread, and I don't think the poster has considered all the ground-fault scenarios. A solid G-N bond still seems like the best idea, and exactly what any on-board RV generator gets via the generator transfer switch. The confusion occurs when your RV is powered from a portable generator (which needs a G-N bond to "ground" the RV's electrical system) compared to a shore power connection (CANNOT have an internal G-N bond since it's supplied by the service panel).
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Old 05-11-2013, 08:26 PM   #42
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Thought I would post a couple of pics of the circuit tester that I used prior to plugging my RV in, which was a good test for me to make sure that I had the G-N bond wired correctly.

Here is a picture of what the lights looked like before hand when the genny was running "out of the box":



As you can see from this pic only the center light is on which actually indicates "open ground". You can also see written right on the generator in this pic that it has a floating neutral.

And here is a pic of it with my G-N bond adapter plugged into the available 110 outlet:



Both lights lit up indicate correct wiring and let me know that I wired it properly. I'm a little paranoid, so it was a good test for me.
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Old 05-11-2013, 09:41 PM   #43
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Both lights lit up indicate correct wiring and let me know that I wired it properly. I'm a little paranoid, so it was a good test for me.
I know I'm paranoid, but am I paranoid enough?

But seriously, this is a very good test. One possibl G-N bond plug issue has to do with the combiner boxes for linking a pair of Honda EU2000 generators together. The new Honda generators have a "companion" model with a 30-amp plug, while the early units required a combiner box with two pairs of link cables. One of my readers showed me that if you accidentally flip the link cables on one of the generators, you can created a reversed polarity situation. Not terribly dangerous since the system is floating, but certainly not correct. I'll be writing an article on this specialized situation in a few weeks, so check back on NoShockZone.org for the latest.
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Old 05-11-2013, 09:51 PM   #44
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Everyone.... If you want to help me keep coming up with these NoShockZone articles about RV electrical systems, I could use some manufacturer support. So please pass on this thread to your Forest River Dealer or rep, and tell them you think this sort of safety information is important. I really need your support.
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Old 05-11-2013, 10:32 PM   #45
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I may have started the 100k ohm resistor method used in the bonding plug for PI EMS to recognize the circuit as grounded. RenoRock mentioned more explanation could be useful.

This started with a discussion about charging electric vehicles from a generator over in mynissanleaf forum. The problem is similar because the EV charging cord has a brick that verifies ground and protects the car with GFI. While the copper used to bond neutral-ground does work it usually presents 60 volts onto the ground connection with a 120v generator with floating ground. Go ahead and verify with a voltmeter both the neutral-ground voltage and the hot-ground voltage. Both should be 60 volts and create 120v as they have opposite potential.

So there is an electrical engineer that is modifying the EV charging cords for faster charging with dual voltage and more amps. It was brought up about charging with a generator and the engineer recommended a 100k (100,000) ohm 1/2 watt resistor to fool the charging brick. The reason is that power through this resistor will not be harmful to a person and it otherwise keeps the system in the original condition vs the direct copper bond.

The actual recommendation was to connect both hot and neutral to ground to equalize the potential. However this does not work with the PI EMS. It gives reverse polarity error code. I tried it.

Because the generator does not have a true neutral with zero potential and the generator has a floating ground there is not the same protection or hazard as when connected to utility power. Utility power grounding is to provide a path to ground to avoid the person completing that path to ground during a fault. But again with a portable generator this is not the same issue.

I have a Nissan LEAF and a trailer with PI EMS. I use the bonding plug made with a 100k ohm 1/2 watt resistor with confidence.
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Old 05-11-2013, 11:00 PM   #46
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I have a Nissan LEAF and a trailer with PI EMS. I use the bonding plug made with a 100k ohm 1/2 watt resistor with confidence.
Hmmmm.... Something doesn't quite jive with the Nissan Leaf charging scenario. I need to see a schematic of their charging system to offer anything concrete, but my 40 years of electrical engineering background is yelling at me that it's wrong. Can you provide a schematic of this special charging cord modification or put me in touch with the EE designer of it?

However, I'm pretty certain I'm on solid ground with having a low-resistance generator G-N bond for any RV. So to prove this hypothesis it appears that I'll have to mock up a full-scale test using an RV and a portable generator, then create a variety of fault conditions while measuring potential shock hazards. I'm fairly certain that this full-scale test has not been tried with the 100K resistor G-N bond on an RV, but I'm willing to run this experiment for my solid G-N bond.
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Old 05-11-2013, 11:21 PM   #47
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If the generator was safer with N-G bond then it would be that way from oem. And yes some onboard generators have N-G bond but I think those are 120/240v service with a zero potential neutral.

The resistor provides just enough for the PI EMS or EV brick to allow power to pass. The resistor will not pass enough power to be a hazard. So the effect is to keep the generator same as oem.

The circuitry of an EV is a bit more complex than an RV to comply with the J1772 standard. An offer and acceptance handshake must take place in addition to supply checks before the brick contactor closes and power flows to the vehicle. The full circuit diagram will be Nissan proprietary information.

Here is a link to some of the EV work engineer is doing http://www.evseupgrade.com/

Lengthy discussion here:
http://www.mynissanleaf.com/viewtopic.php?f=26&t=5792

resistor is first discussed on pg 4 by Ingineer, but read it all.
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Old 05-12-2013, 10:29 AM   #48
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If the generator was safer with N-G bond then it would be that way from oem. And yes some onboard generators have N-G bond but I think those are 120/240v service with a zero potential neutral.
Actually, I've discussed this generator bonding issue at length with engineers at Honda and Yamaha, and their viewpoint is that RV users need to comply with local codes, but they don't know what those codes actually are. Most of the public doesn't realize that the National Electrical Code is NOT national law. It's only a suggestion that's adopted locally. Every state and county will pick which parts of the code they want to adopt and every inspector will have their own interpretation of how it should be followed. For instance, my own county and state doesn't even go by the 2011 NEC book yet. And some southern states refuse to comply with the latest code requirements on Arc Fault Protectors, stating that the $300 additional cost for a new $150,000 house would be a hardship to builders and buyers.

So the electrical code is very much a political animal, with board members often coming from various manufacturers, each with their own political (and sales) agenda. For instance, there just was a proposal a few months ago that all campground pedestals have their own ground rod, but not require actual ground fault impedance tests. I think the guy making the proposal was in the business of selling ground rods. While ground rods seem like a good idea at first glance, the earth itself is actually a marginal ground at best, with a ground rod impedance between 50 to 100 ohms being commonplace. It's vitally important that all safety grounds (and your RV's chassis) have a low-impedance connection back to the service panel's G-N-E bonding point. That's the path the fault current will follow if you have a hot-to-chassis short in your RV's electrical system. A ground rod will do almost nothing to sink that fault current. It's really there to help sink lighting strikes to earth and keep them away from the electrical supply.

There's a growing number of electrical engineering professionals I've been in contact lately with who suggest that the NEC is wrong about the floating generator neutral question. We'll be postulating various generator shock scenarios and demonstrations and come up with a specific recommendation to the NEC for the next review cycle. That's when things will get very interesting.
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Old 05-12-2013, 02:06 PM   #49
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The resistor provides just enough for the PI EMS or EV brick to allow power to pass. The resistor will not pass enough power to be a hazard. So the effect is to keep the generator same as oem.

The circuitry of an EV is a bit more complex than an RV to comply with the J1772 standard. An offer and acceptance handshake must take place in addition to supply checks before the brick contactor closes and power flows to the vehicle. The full circuit diagram will be Nissan proprietary information.

Here is a link to some of the EV work engineer is doing http://www.evseupgrade.com/

Lengthy discussion here:
My Nissan Leaf Forum • View topic - charging on generator

resistor is first discussed on pg 4 by Ingineer, but read it all.
So I've read through this thread on powering the Leaf from this aftermarket high-power cable as well as looked some additional info on how this power "brick" works. This is most definitely NOT like the wiring in an RV's 120 or 240 volt service. The Leaf includes an auto-switching power supply to accept voltages over a wide range and convert it for proper battery charging current. This is certainly NOT how your RV's power distribution system works since there's no voltage conversion at all. Whatever voltages come into the RV's power plug is what gets sent to the appliances, the only exception being the battery/inverter circuits on modern RVs. So any G-N bonding trick that might work to power a Leaf from a generator has zero correlation as to electrical safety when powering an RV from a generator. The RV and Leaf systems are basically apples and oranges, with almost no similarity other than the wall plug itself.

I'm not trying to sound flip about this, just that any recommendations for generator and RV grounding issues need to be backed up with schematics, equations, experiments and peer review of the results. Everything I write about has already been through that process.
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Old 05-12-2013, 02:07 PM   #50
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Not really trying to debate the interpretation of NEC, Arc Fault protection, or grounding rods.

Just wanted to explain using the resistor to trick the PI EMS. This allows the PI EMS to continue to monitor voltage while using a generator. It is my opinion that the resistor does not create a hazard and possibly is safer than the copper bond.
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