Overcoming bonded neutral issues in the setting of a GFI protected Ford Lighting 7.4kw inverter.....

[Supervstech]

Ok.

So why does code allow transfer switches that do not change the NG bond?

And, why do they make portable generators without GFCI?

Are we inventing a problem where one doesn't exist?

Code requires the FIRST main disconnect to have the ONLY neutral to ground bond...
ALL downstream disconnects must have seperated N'S AND G'S...
If the transfer switch has main power passing through it,THAT is where the only N-G bond can be.

 

[Hedges]

I also have a sub panel wired with an interlock that feeds the kitchen and a couple outlets and lights in the master. And an inlet wired to the sup panel.

As you said, I have a $90k truck sitting in the driveway the can power critical loads if I need it and natural gas is out. I just want to know how to do it. I never asked how much it cost.

If you only want the truck to power the sub-panel not the main panel, then a 3-pole double-throw transfer switch input of subpanel should do the trick.

That would be instead of using interlocked breaker in the sub panel. You could still use interlock for yet another source (e.g. generator) but make sure transfer switch is thrown to "main panel" so it inherits neutral/ground bond. Not "Ford Lightning" which wouldn't provide the bond if the truck wasn't connected.

 

[hammick]

I'm on the Lightning forums with the OP cdherman. I have a Lightning ER and initially connected to our main home (200a service) back feeding with a 30a 240v breaker. I had to remove the ground at the generator inlet box so the Lightning wouldn't throw the ground fault error. I read all the neutral/ground opinions on the Lightning forums.

It makes sense to me that there is still protection with the Lightning ground removed. The truck end still has the Lightning GFI protection and the house end still has the neutral/ground bond in the main panel. This being said I would still make sure you generator inlet is wired so it can't get damaged and don't plug into the truck with the Pro Power active.

I ended up installing an automatic 3-pole transfer switch and isolated our subpanel with critical loads. I did this mostly so I wouldn't have to walk down to the basement and flip breakers to power the house from the Lightning. The transfer switch I used is pretty affordable but only 50 amps. However, that is plenty for what I am doing. I have been powering this critical load panel during our 4 - 8 pm peak time where our rates go to .36kwh On this plan our Midnight to 6:00 am rates are .03kwh in the summer and .02kwh in the winter. Obviously we charge at night. We are a two EV household and my initial calculations are we may save up to $1,500 a year on this rate plan charging after midnight and running the AC and furnace (gas obviously) from 4:00 - 8:00 using the Pro Power when we are in town.

I discovered a handful of ground faults at Insteon light switches that I created when I was young, dumb and impatient. Using the 3-pole transfer switch with the Lightning ground connected forced me to find and fix these problems.

This winter I plan to connect the Lightning to our off grid inverter at our place in Montana. I suspect I will have the same ground fault dilemma I'm not going to install a transfer switch and critical load panel there as our inverter is only 5,500 watts (Schneider Conext XW+ 5548). Our battery bank is a 13kwh Lishen 16s so the Lightning has 10 times the capacity. I can charge the Lightning when the sun is out at 8 amps.

So I am comfortable disconnecting the ground at the generator input as long as the wiring is out of harm's way. I think that is what I will have to do to make it work with our XW+ inverter.

When we downsize from our main home I will remove the transfer switch, the breakers and the generator input wiring. I'm guessing 10/4 SOOW without conduit is a violation. The subpanel will be wired back to the main panel.

 

[zanydroid]

Hmm, I guess we just recreated 80% of the ideas tossed around on that forum. Probably would have been nice to get a summary at the top of the thread :laugh: I don't have this truck so I didn't bother going over there to look.

So for connecting to offgrid inverter you can bypass a lot of this issue by plugging in via a Chargeverter. The Chargeverter can be grounded / protected using the truck side, and it's decoupled from your house side. This would also have the additional benefit of retaining inverter-to-inverter AC coupling (if you use that) and preventing backfeed to the car with a misconfiguration if you intended to run with both the XW inverter active and the Lightning inverter active in parallel.

You can also treat the lightning as generator since these good hybrid inverters are designed to not push power back into generator. However you will still have the ground fault risk if you allow someone to plug into the truck bed outlets since ground leakage through house grounding system will go back to the truck through L1/L2.

There are various V2L threads for Ioniq5 on this forum, a lot of the theory would be common to any car.

 

[hammick]

Hmm, I guess we just recreated 80% of the ideas tossed around on that forum. Probably would have been nice to get a summary at the top of the thread :laugh: I don't have this truck so I didn't bother going over there to look.

So for connecting to offgrid inverter you can bypass a lot of this issue by plugging in via a Chargeverter. The Chargeverter can be grounded / protected using the truck side, and it's decoupled from your house side. This would also have the additional benefit of retaining inverter-to-inverter AC coupling (if you use that) and preventing backfeed to the car with a misconfiguration if you intended to run with both the XW inverter active and the Lightning inverter active in parallel.

You can also treat the lightning as generator since these good hybrid inverters are designed to not push power back into generator. However you will still have the ground fault risk if you allow someone to plug into the truck bed outlets since ground leakage through house grounding system will go back to the truck through L1/L2.

There are various V2L threads for Ioniq5 on this forum, a lot of the theory would be common to any car.

My plan was to hook the lightning to the XW+ no different than our diesel generator is hooked to it. AC2 input allows for generator support. Was thinking of using this inexpensive transfer switch so I could use either the Lightning or the diesel genset on AC2 and have generator support for both. I'm guessing the XW+ isn't sophisticated enough to prevent the Lightning from throwing the ground fault if the EGC is connected?.

There would never be a situation where the truck 120v bed outlets would be used if the 240v outlet is connected to the inverter. Maybe the frunk 120v outlets but even then I can't think of a reason why. The frunk outlets are on a separate inverter so I assume they wouldn't pose a safety issue if used while the 240v bed outlet was connected to the inverter.

BTW we are completely off grid. Closest power is 3 miles away as the crow flies. We like it that way.

https://www.amazon.com/dp/B0C2KLSZP3?ref=ppx_yo2ov_dt_b_product_details&th=1

 

[zanydroid]

My plan was to hook the lightning to the XW+ no different than our diesel generator is hooked to it. AC2 input allows for generator support. Was thinking of using this inexpensive transfer switch so I could use either the Lightning or the diesel genset on AC2 and have generator support. I'm guessing the XW+ isn't sophisticated enough to prevent the Lightning from throwing the ground fault if the EGC is connected from the Lightning.

If you already have generator set up then it should be fine. If you only have DC solar then AC coupling is irrelevant.

I think the ground fault is thrown if you have any neutral current going back towards the lightning. If it hits a N-G bond on the way back to the lightning then X% of the current will go over the EGC to the lightning, which will make the GFCI very upset.

If you connect the lightning L-L-G there should not be neutral current going back there because there is no neutral. If there is current going back on EGC and tripping the GFCI, then you need to debug the situation. Neutral forming and neutral load carrying is then completely the responsibility of the XW. It's a big boy it can handle it.

IMO you should just stay away from the truck when it's connected parallel to a second power source like this. It's likely not a tested combination by the vendor compared to charging the truck via L2 or L3 (in the L2 and L3 charging case, Ford surely would have thought through how not to kill people sitting inside & plugging stuff into the receptacles).

 

[zanydroid]

Ah, another risk is that it's against NEC to backfeed/have power on both sides of a GFCI breaker unless it's listed for that. Could cause damage or defeat the safety.

How many people on the Ford forum are doing AC generator assist? I don't think you want to be the first person to try it.

 

[hammick]

Ah, another risk is that it's against NEC to backfeed/have power on both sides of a GFCI breaker unless it's listed for that. Could cause damage or defeat the safety.

How many people on the Ford forum are doing AC generator assist? I don't think you want to be the first person to try it.

I don't want to derail this thread too much but how would using generator support with the Lightning be any different than using it with our 5kw diesel genset (MEP-802a)? It works great with the diesel genny.

The lightning probably doesn't need generator support as our inverter is only 5.5kw but it can do 9.5kw for 60 seconds or 7kw for 30 minutes. We have AC1 input on the inverter free since we are off grid. AC1 input does not have generator support and it can be turned off for AC2

 

[Checkthisout]

Is the EGC of the lightning even bonded to the frame of the truck?

 

[Hedges]

If you connect the lightning L-L-G there should not be neutral current going back there because there is no neutral. If there is current going back on EGC and tripping the GFCI, then you need to debug the situation. Neutral forming and neutral load carrying is then completely the responsibility of the XW. It's a big boy it can handle it.

If you connect ground, it will serve as neutral, carry imbalance from split-phase loads on breaker panel, and trip GFCI.

If you disconnect ground it will not trip GFCI. But there could be a safety issue to be identified.

 

[zanydroid]

I don't want to derail this thread too much but how would using generator support with the Lightning be any different than using it with our 5kw diesel genset (MEP-802a)? It works great with the diesel genny.

Any accidental backfeed energy goes into a inverter output on the lightning instead of into coils on the diesel gen. I guess if the diesel gen was inverter output it’s a similar situation, but probably accidental damage on an inverter generator is easier to deal with than damage on an EV.

 

[zanydroid]

If you connect ground, it will serve as neutral, carry imbalance from split-phase loads on breaker panel, and trip GFCI.

If you disconnect ground it will not trip GFCI. But there could be a safety issue to be identified.

Good point. What do you think about chargeverter vs isolation transformer to make the situation 100% code compliant? Isolation transformer can still push some pulses of energy back to the EV inverter but it will have a low pass filter effect smoothing it out.

What do you think about adding N-G bond relay on the house side and then using N-G bond in truck? The EGC might not be big enough for code.

 

[Hedges]

Chargeverter - does he have an inverter system on the house?

Transformers are brute force, but I think a pair of 7.5kVA or larger transformers could do the isolation, running at half voltage each.
I think the could even rebalance across phases, but then I'd want a pair of 15kVA or larger.

N-G bond relay is how mobile inverters do it. I'd rather not put switched bond in grid connection. But I suggested 3 pole transfer switch.

 

[hammick]

Thanks guys. I will start a new thread on this. I have derailed the OP's bonding question enough. Pretty sure he isn't using an XW inverter.

 

[Shimmy]

Give an example of a real-world failure mode that would result in significant risks as a result of not having an EGC between the truck and house?

What if I plug a hairdryer into the trucks outlet? Hairdryers only have a 2 prong cord, hot and neutral.

Why is the Hairdryers plugged into the truck less "risky" than hooking a house panel up to the truck without and EGC between the truck and house?

The body of the truck becomes energized and the only return path for power is through you when you touch it. True in either direction. It is a big part of why EV chargers in "230V" countries need more safety mechanisms than what is required in the US. (Most now have them with the assumption of a global market, but that is a separate issue.)

 

[zanydroid]

Chargeverter - does he have an inverter system on the house?

Yes, for the latest question/scenario glommed onto the thread. The question around how to AC couple into an XW powering an off grid house

Not in the first two question/scenario which was single power source backup in house.

 

[zanydroid]

It is a big part of why EV chargers in "230V" countries need more safety mechanisms than what is required in the US.

What are the additional safeties?

 

[Checkthisout]

The body of the truck becomes energized and the only return path for power is through you when you touch it. True in either direction. It is a big part of why EV chargers in "230V" countries need more safety mechanisms than what is required in the US. (Most now have them with the assumption of a global market, but that is a separate issue.)

Is the body/chassis of the truck connected to inverter neutral/ground?

 

[CoolWill]

Is the body/chassis of the truck connected to inverter neutral/ground?

I think this is the big hang up in this thread. There is a misconception about what is and isn't grounded if the green wire is not connected on one end. The answer is everything is still grounded. The truck is grounded by the N-G bond at the inverter. The house is grounded by the main bonding jumper in the panel. The cord is still grounded because the green wire is connected on one end or the other, just not both.

 

[Shimmy]

I think this is the big hang up in this thread. There is a misconception about what is and isn't grounded if the green wire is not connected on one end. The answer is everything is still grounded. The truck is grounded by the N-G bond at the inverter. The house is grounded by the main bonding jumper in the panel. The cord is still grounded because the green wire is connected on one end or the other, just not both.

Look at your description. You have two islands with neutral-ground bonds but a common neutral. Any current on the neutral will find its way back to the source in proportion to the path impedances (Kirchoff). So, barefoot on a wet garage floor and you will find yourself part of that path.