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

[CoolWill]

You are right, doesn't. Listen, you all that are willing to have the ground disconnected -- some of us far less experienced guys take it as gospel that every circuit ought to have a ground. I am just trying to figure out in my mind where an inspector would have a problem. Frankly, you have brought me into agreement. My only concern is coming across an inspector who would ask me for that same coherent explanation and under pressure it makes it harder.

Anyhow, big thanks again for those patient enough to keep trying. The Ford Lightning forum was less helpful.

The inspector doesn't have much to say about portable sources of power. He is chiefly concerned with the wiring of the building. If you're not willing to modify the inverter in the truck and you're not willing to separate the neutrals and grounds at the panel, you only have two choices:

1) Abandon the project
2) Disconnect the ground at one end of the cord

Keep in mind that you aren't leaving the cord ungrounded. The ground will still be connected at one end. Let's say you disconnect the ground at the plug. The inverter and truck are still grounded by the neutral-ground bond at the inverter. The green wire in the cord is connected to ground at the panel, so if the cord were to be compromised somehow, the green wire will still carry fault current.

 

[Checkthisout]

You are right, doesn't. Listen, you all that are willing to have the ground disconnected -- some of us far less experienced guys take it as gospel that every circuit ought to have a ground. I am just trying to figure out in my mind where an inspector would have a problem. Frankly, you have brought me into agreement. My only concern is coming across an inspector who would ask me for that same coherent explanation and under pressure it makes it harder.

Anyhow, big thanks again for those patient enough to keep trying. The Ford Lightning forum was less helpful.

Use a generator inlet plug at the house and a main breaker interlock on the backfeed or just a regular 8, 10 (or whatever circuit) transfer switch.

The inspector isn't going to inspect your truck and cord so that never comes into play.

 

[Shimmy]

Safest solution is to have an isolation transformer between the truck and SolArk. Getting rid of the ground connection could cause significant risks if there is ever a low level ground fault in the system.

 

[Checkthisout]

Safest solution is to have an isolation transformer between the truck and SolArk. Getting rid of the ground connection could cause significant risks if there is ever a low level ground fault in the system.

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?

 

[zanydroid]

Hair dryer is double insulated so isn't the best example to use.

If you run an extension cord from truck with EGC disconnected in the cable, plug a splitter on the cord, plug one side of cord into transfer switch and another side into a tool with a metal frame (one way to not be double insulated).

Plugging the transfer switch into the house provides a path from concrete pad / soil -> N-G bond -> N extension cord -> truck

Now let's suppose the tool has a line-to-ground fault due to a loose wire. Then the GFCI on the truck is defeated since there can be fault current from energized frame -> human -> concrete pad -> N-G bond -> N extension cord -> truck. (***)

If you plug double insulated hair dryer with L-N only cord into either Truck, House, or mistakenly added splitter adapter, the double insulation of case provides the protection against the fault scenarios listed here.

If you plug the metal framed tool into house(*), a standard breaker alone will trip immediately. If you plug metal framed tool into truck (**), same thing. If metal framed tool has a double fault - Line to chassis short, chassis to EGC bond broken. Then case (*) will be bad, breaker will not trip, you need GFCI. (**) will still have GFCI available to protect. In fact (*) and (***) would be equivalent since there is a broken EGC bond, the difference is where it is.

I don't think it would be safe to keep a cable with EGC removed on a jobsite where people may not be aware of this. Unless it somehow has a inlet receptacle type that is ungrounded, so that it is impossible to plug the wrong kind of tool or splitter into it. Like inlet and cord should use NEMA 10-30 instead of 14-30.

 

[Checkthisout]

Hair dryer is double insulated so isn't the best example to use.

If you run an extension cord from truck with EGC disconnected in the cable, plug a splitter on the cord, plug one side of cord into transfer switch and another side into a tool with a metal frame (one way to not be double insulated).

Plugging the transfer switch into the house provides a path from concrete pad / soil -> N-G bond -> N extension cord -> truck

Now let's suppose the tool has a line-to-ground fault due to a loose wire. Then the GFCI on the truck is defeated since there can be fault current from energized frame -> human -> concrete pad -> N-G bond -> N extension cord -> truck. (***)

If you plug double insulated hair dryer with L-N only cord into either Truck, House, or mistakenly added splitter adapter, the double insulation of case provides the protection against the fault scenarios listed here.

If you plug the metal framed tool into house(*), a standard breaker alone will trip immediately. If you plug metal framed tool into truck (**), same thing. If metal framed tool has a double fault - Line to chassis short, chassis to EGC bond broken. Then case (*) will be bad, breaker will not trip, you need GFCI. (**) will still have GFCI available to protect. In fact (*) and (***) would be equivalent since there is a broken EGC bond, the difference is where it is.

I don't think it would be safe to keep a cable with EGC removed on a jobsite where people may not be aware of this. Unless it somehow has a inlet receptacle type that is ungrounded, so that it is impossible to plug the wrong kind of tool or splitter into it. Like inlet and cord should use NEMA 10-30 instead of 14-30.

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?

 

[zanydroid]

Ok.

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

Not sure what you mean by this. There are neutral and non-neutral switching transfer switches to accommodate different N-G bonding scenarios for the power sources being connected. You have to use them in correct scenarios.

And, why do they make portable generators without GFCI?

It's probably allowed in some code/OSHA contexts but not others.

If you have a built-in GFCI you are stuck with the trip threshold that it was baked with. If you plug in enough equipment you may accumulate enough ground leakage to trip this. Not having a built-in GFCI means customer can spec it as they need.

For a small generator it's probably not that easy to plug in enough stuff to hit this problem, so it's probably smart to have GFCI for those by default. But you could still have some upset users with quirky equipment.

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

No, I think it's worth having a discussion. I don't think there is a system that will automatically work for all scenarios in a fail-safe way, some intelligent manual configuration is needed. I think the truck's hardwired GFCI and L-N bond errs on the safe for untrained personnel but limits usage scenarios dimension.

We haven't even gotten to what will happen if the accumulated leakage in the house trips the truck's GFCI. In that scenario the isolation transformer would be the least disruptive way to bypass it (if Ford doesn't allow N-G removed they're not going to allow GFCI to be disabled). I would imagine the truck's GFCI is designed for personnel safety, if you have enough, EG, minisplit power supplies in the house it might trip (minisplits come with table to calculate how many can go on a single GFCI/RCD of each protection class, which corresponds to permissible mA leakage before trip).

 

[Checkthisout]

Not sure what you mean by this. There are neutral and non-neutral switching transfer switches to accommodate different N-G bonding scenarios for the power sources being connected. You have to use them in correct scenarios.

It's probably allowed in some code/OSHA contexts but not others.

If you have a built-in GFCI you are stuck with the trip threshold that it was baked with. If you plug in enough equipment you may accumulate enough ground leakage to trip this. Not having a built-in GFCI means customer can spec it as they need.

For a small generator it's probably not that easy to plug in enough stuff to hit this problem, so it's probably smart to have GFCI for those by default. But you could still have some upset users with quirky equipment.

No, I think it's worth having a discussion. I don't think there is a system that will automatically work for all scenarios in a fail-safe way, some intelligent manual configuration is needed. I think the truck's hardwired GFCI and L-N bond errs on the safe for untrained personnel but limits usage scenarios dimension.

We haven't even gotten to what will happen if the accumulated leakage in the house trips the truck's GFCI. In that scenario the isolation transformer would be the least disruptive way to bypass it (if Ford doesn't allow N-G removed they're not going to allow GFCI to be disabled). I would imagine the truck's GFCI is designed for personnel safety, if you have enough, EG, minisplit power supplies in the house it might trip (minisplits come with table to calculate how many can go on a single GFCI/RCD of each protection class, which corresponds to permissible mA leakage before trip).

The generator hooked into a household transfer switch without a switched neutral is more "unsafe" than the GFCI equipped trucked plugged into the house with the EGC severed.

Was my point to @Shimmy.

I don't see how an isolation transformer? would help return "safety" to the system?

 

[zanydroid]

I have no problem supplying a house with generator that does not have GFCI. Most likely those stationary generators do not have GFCI. The protection is no worse than what you get from the utility.

If you look only at the system starting from the transfer switch down, the GFCI equipped truck with EGC severed is pretty safe. But I listed several scenarios above that I would personally want to prevent, where some low levels of ill-informed or accidental usage on the system between transfer switch and truck will lead to problems. Someone could probably make some YouTube clickbait showing how those scenarios have a shock risk.

If I owned this truck -- if nobody touches the house / truck besides me, then EGC severed should have minimal risk and I have no problems with it. Maybe put some permanent tags on the ends of the extension cord:

• on the house side - saying not to use with power tools
• on the truck side - saying not to plug in any tools

Unfortunately this is not bulletproof because it requires people to read, and often code wants physical lockouts against unsafe situations because people don't read.

 

[Checkthisout]

I have no problem supplying a house with generator that does not have GFCI. Most likely those stationary generators do not have GFCI. The protection is no worse than what you get from the utility.

If you look only at the system starting from the transfer switch down, the GFCI equipped truck with EGC severed is pretty safe. But I listed several scenarios above that I would personally want to prevent, where some low levels of ill-informed or accidental usage on the system between transfer switch and truck will lead to problems. Someone could probably make some YouTube clickbait showing how those scenarios have a shock risk.

If I owned this truck -- if nobody touches the house / truck besides me, then EGC severed should have minimal risk and I have no problems with it. Maybe put some permanent tags on the ends of the extension cord:

• on the house side - saying not to use with power tools
• on the truck side - saying not to plug in any tools

Unfortunately this is not bulletproof because it requires people to read, and often code wants physical lockouts against unsafe situations because people don't read.

Agreed.

The stars have to line up though.

Especially when a 30 amp cord/connections are involved.

It also need not involve the cord at all. Just disconnect the EGC going to the power inlet inside the house panel.

Done.

 

[zanydroid]

It also need not involve the cord at all. Just disconnect the EGC going to the power inlet inside the house panel.

This is a code violation. The inlet box / inlet receptacle would no longer be bonded. Not bonding a metal box can probably lead to a Darwin Award scenario.

If you bond the box most likely the receptacle will internally bond the ground pin via the mounting screws unless you go and add insulated screws and other bunch of insulation. This is kind of weird and will also probably fail inspection

My personal favorite so far is to use 10-30 cord end but I’m sure folks will come up with a reason that is bad. IE it will not protect against a fault through something plugged into the truck, back through the grounding system of the house. You need the isolation transformer ($$$) to defeat this.

 

[Checkthisout]

This is a code violation. The inlet box / inlet receptacle would no longer be bonded. Not bonding a metal box can probably lead to a Darwin Award scenario.

Yup. It is.

If you bond the box most likely the receptacle will internally bond the ground pin via the mounting screws unless you go and add insulated screws and other bunch of insulation. This is kind of weird and will also probably fail inspection

Yup.

My personal favorite so far is to use 10-30 cord end but I’m sure folks will come up with a reason that is bad. IE it will not protect against a fault through something plugged into the truck, back through the grounding system of the house. You need the isolation transformer ($$$) to defeat this.

Yes but someone will be killed if the stars line up.

My main point here is they make portable generators without GFCI and people have been connecting these to their houses for years without issue.

A portable generator without GFCI hooked to your house with the EGC in-tact is more "unsafe" than the Ford pickup truck with GFCI connected to your house with the EGC disconnected.

And also, I mean really, we are only talking about this because for some reason guys with $80-$100,000.00 trucks don't want to spend the money to put the proper neutral-switching transfer switch in their house. Something that takes less an afternoon and costs less than $500.00

 

[Hedges]

I would have concerns about interrupting ground between Lightning and house. It might work, using neutral wire only, but I haven't thought through possible failure modes well enough. Maybe an open neutral and a short elsewhere could drive truck chassis to 120V.

An isolation transformer would be a good solution. What may cause you problems is that typical utility power transformers are a far from being an "ideal" transformer and will be a nasty load for an inverter. They draw considerable no-load current, out of phase so returned in the next phase.

I like to feed such transformers at half their rated voltage, which keeps them out of saturation and no-load current more than 10x lower. You will probably need two 240/480 to 120/240 transformers to use them this way.

 

[Dymailbox]

And also, I mean really, we are only talking about this because for some reason guys with $80-$100,000.00 trucks don't want to spend the money to put the proper neutral-switching transfer switch in their house. Something that takes less an afternoon and costs less than $500.00

That is not an accurate statement. I have no trouble spending $500 or $2000. I just need to know what to spend it on, and I've gotten no help from local electricians.

I have 600 amp service with a transfer switch and a natural gas backup generator. 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.

 

[zanydroid]

And also, I mean really, we are only talking about this because for some reason guys with $80-$100,000.00 trucks don't want to spend the money to put the proper neutral-switching transfer switch in their house. Something that takes less an afternoon and costs less than $500.00

You have to move the loads to the transfer switch's subpanel too, which is a design problem. Vs just using an interlock on the main panel. Another option is to either unbond a convertible main panel (tricky) or move all main panel circuits to a subpanel. That trades design problem for spending more work.

I think I prefer refactoring the main and subpanels over isolation transformer.

 

[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.