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

[cdherman]

Probably not exactly a "beginner" questions, but seems the generator forum is pretty quiet, and this question involved solar as well.

Ford Lightning owners have been challenged using their massive battery pack for input into backup power in settings via transfer switches, as well as using the Ford as generator input into a AIO, such as Sol-Ark. The Ford has a built in GFI and the instant the the truck sees a bonded neutral anywhere in the system, the GFI throws.

Some persistent owners have tracked down and separated all neutral to ground bonds (to be fair some, perhaps many SHOULD not have been present). Then they unbond the neutral and ground in the main pain and install something that I understand to be a bonding transfer twitch, which unbonds the ground and neutral upon transfer to the generator/inverter source. While this purist approach is certainly laudible, it does not solve plugging the Lightning into a Sol-Arc for instance.

One Sol-Arc user (perhaps not here, but was over at FordLightning forum) took the rather radical approach in my mind --- of removing the ground pin from his transfer cord. Then, with the Lightning no longer grounded to the Sol-Arc, the GFI no longer would break. This approach would presumably *work* running in a system with bonded neutrals as well. Work, as is in the outlets would be hot. Things in such a system would also be protected so long as they were downstream from existing breakers. But the wiring to the transfer switch would be ungrounded. Not to my liking.

A couple others talk about "load balancing transformers". These would add the benefit load balancing of course. But can they be used in some fashion to overcome the GFI / bonded neutral problem?

My family farm has any number of panels that are old and almost certainly were wired with a ground rod and neutral bonded. This was convention until NEC said it wasn't a good idea in 1999 I think. Its not a good idea, but no way am I re-wiring a whole farm. Even a $500 load balancing transformer would be a bargain.

Understand, I COMPLETELY know that I cannot run the whole farm from one lowly 7.4 kw inverter. But the "critical load sub panel" suggestion that people give is just not tenable. Rewiring the water pump to get that circuit over to a critical load sub would involve trenching. The idea is in a pinch to manually shut off pretty much everything and then walk around and turn on pump, deep freeze, fridg, heat etc. But it sure would be nice to have an LED light on a lighting circuit in an enclosed space with no exterior windows...... And longer term, a Sol-Arc or EG4 or similar solution is in the books anyhow.

We currently have a Miller 10K generator welder with I believe bonded ground - neutral in the generator. Its properly installed (or at least was done by a local professional many years ago). Has a nice Siemans 200A generator transfer. Dang there has to be someway to the the 7.4kw into the system.

 

[Checkthisout]

Just don't connect the EGC from the truck to the house or whatever you're trying to power.

In other words just leave the green grounding lead between the truck and whatever disconnected so you have only a hot and neutral or 2 hots and neutral connected or whatever connection it has.

This eliminates the paralell neutral path that is leading to the issue.

 

[Dymailbox]

No answer for you, but I’m in the same situation with the Ford.

I have an inlet I planned to use, but have the same issue you do. I have 600 amp service with a main and two sub panel, transfer switches, etc. The local electricians are stumped. Or uninterested.

 

[CoolWill]

If it were me, I might get the power from upstream of the GFI in the Ford.

 

[cdherman]

If it were me, I might get the power from upstream of the GFI in the Ford.

Does not appear to be an option. Maybe DyMailbox can comment. I do not yet have my truck, but the GFI seems to be pretty integrated into the inverter. And getting power upstream exposes the issue of violating a brand new $70,000 truck wiring while still under warranty.

As for simply not connecting the ground, well yeah, that works. But it leaves the cord less protected. It will would be protected against over current events (so a hot to hot short, or a hot to neutral short), but it would not be protected against ground or neutral faults any more, in the wiring between the inverter and the actual property load centers, after which things would be protected again, but by the premises breakers.

And it would NOT be protected against a short that was say hot to earth, but not of sufficient amperage to cause an overcurrent fault. In otherwords, 20A of 120v running through a human, to earth, then via earth over to the bonded main panel, and then back to the inverter via neutral. The inverter will see that as a normal load. While said human gets injured. NOW, we have always had this danger when plugging extension cords into conventional circuits. GFI and AFI alleviate this, at a cost....

I mean, the ground wire in the cord from the ground will still be "grounded" as in connected to earth and for that matter, bonded to the inverter's neutral in the main panel. (and elsewhere in my case). So overload protection will always be maintained. Just no ground or neutral faults. BTW, why did we call them "ground fault", when in reality it is a neutral fault that we actually detect? Just musing.....

Finally, I do NOT think a GFI on the generator or inverter is required by code. Otherwise, we would be having just this problem with all sorts of generators. Think whole house hard wired, or large gensets with proper service interconnect switches. I think the problem is that Ford correctly envisioned their truck being used on worksites where it will be the primary source of power and the only source of protection, breaker, GFI or otherwise. And for Ford to have built in a "GFI defeat button" is clearly a bad idea if you every have been at a real worksite. It would get shut off the first time it has a trip etc. Legal nightmare for Ford.

 

[Dymailbox]

The power delivery gear is very tightly integrated into the computer system. My guess is that if you tried to go around the GFI, SOMETHING in the computer would tell it to stop working.

Since the vehicle is a rolling computer, I don’t want the liability messing with it. At all.

Also, my vehicle isn’t the Lightening - it’s the eco boost with the 7kw inverter. But the problem we’re dealing with is identical.

 

[Checkthisout]

As for simply not connecting the ground, well yeah, that works. But it leaves the cord less protected. It will would be protected against over current events (so a hot to hot short, or a hot to neutral short), but it would not be protected against ground or neutral faults any more, in the wiring between the inverter and the actual property load centers, after which things would be protected again, but by the premises breakers.

Defeating the EGC does not defeat Ground Fault operation. Your understanding of how GFCI works is incorrect which is leading you to invent a problem where one does not exist.

The neutral and ground go to the same place. A lot of things have to go wrong before the defeating the ground lead between a generator/inverter or whatever and a service panel would lead to a safety hazard.

And it would NOT be protected against a short that was say hot to earth, but not of sufficient amperage to cause an overcurrent fault. In otherwords, 20A of 120v running through a human, to earth, then via earth over to the bonded main panel, and then back to the inverter via neutral. The inverter will see that as a normal load. While said human gets injured. NOW, we have always had this danger when plugging extension cords into conventional circuits. GFI and AFI alleviate this, at a cost....

How is this any different than being connected to a normal service? All GFCI protection in a house, motorhome etc is at the circuit breakers in the main panel or the outlets themselves based on location, not the incoming household service. Again, defeating the ground connection in the cord connecting the truck to the house or whatever does not defeat the GFCI that is native to the truck and does not make the cord any less safe than it already is.

I mean, the ground wire in the cord from the ground will still be "grounded" as in connected to earth and for that matter, bonded to the inverter's neutral in the main panel. (and elsewhere in my case). So overload protection will always be maintained. Just no ground or neutral faults. BTW, why did we call them "ground fault", when in reality it is a neutral fault that we actually detect? Just musing.....

I don't want to tear this apart but your picture of how things work is somewhat incorrect and incomplete. EGC in a house has nothing to do with ground rods. I know you're not driving ground rods in when you park your F150 and hook up the TV and microwave and cook hot wings on the tailgate for the big game.

Finally, I do NOT think a GFI on the generator or inverter is required by code. Otherwise, we would be having just this problem with all sorts of generators. Think whole house hard wired, or large gensets with proper service interconnect switches. I think the problem is that Ford correctly envisioned their truck being used on worksites where it will be the primary source of power and the only source of protection, breaker, GFI or otherwise. And for Ford to have built in a "GFI defeat button" is clearly a bad idea if you every have been at a real worksite. It would get shut off the first time it has a trip etc. Legal nightmare for Ford.

OSHA requires jobsite generators to have GFCI protection thus their truck has GFCI. It's also a good idea since the truck is essentially an "outdoor outlet" and just like kitchen, bathrooms and outside areas in a house, GFCI is required and a good idea.

Some points:

1) The EGC or ground wire has nothing to do with GFCI
2) The cord between the truck and house panel is not less protected by defeating the EGC in the cord
3) Ground rods and the EGC have absolutely nothing to do with each other.

Final point, your house has only 3 conductors from the transformer to the main. Hot/Neutral/Hot.

 

[Checkthisout]

The power delivery gear is very tightly integrated into the computer system. My guess is that if you tried to go around the GFI, SOMETHING in the computer would tell it to stop working.

Since the vehicle is a rolling computer, I don’t want the liability messing with it. At all.

Also, my vehicle isn’t the Lightening - it’s the eco boost with the 7kw inverter. But the problem we’re dealing with is identical.

It has no idea if the EGC is in use or not.

For all intents and purposes, it's a separate power system from that which drives the truck.

 

[Checkthisout]

Lots of misconceptions here that are keeping you guys from fully utilizing two pretty amazing trucks.

 

[cdherman]

Lots of misconceptions here that are keeping you guys from fully utilizing two pretty amazing trucks.

delete

 

[zanydroid]

How can the vehicle GFCI detect a neutral to ground fault, if the ground wire to the vehicle is detached?

GFCI (breakers, EVSE, receptacles) do not monitor EGC. It just checks:

Single phase: current(L)=current(N)
Split phase: current(L1) + current(N) = current(L2)

If EGC was required, why does NEC allow you to retrofit 5-15R onto an ungrounded circuit as long as you use GFCI protection?

If you remove the EGC from truck to panel then there is only one current carrying path back from house system to the truck. Namely on the neutral.

If you don't remove the EGC, then the MSP N-G bond messes things up as follows:

appliance neutral -> MSP neutral -> now it has N and G path back to the truck. Some current will definitely go on G. Truck's GFCI flips out because current(L1) + current(N) < current(L2)

 

[zanydroid]

As for simply not connecting the ground, well yeah, that works. But it leaves the cord less protected. It will would be protected against over current events (so a hot to hot short, or a hot to neutral short), but it would not be protected against ground or neutral faults any more, in the wiring between the inverter and the actual property load centers, after which things would be protected again, but by the premises breakers.

You are allowed to use cordage without ground as long as the appliance meets some requirements, like double insulation.

How does the EGC protect against neutral fault? On-truck GFCI will not protect that either.

What about keeping the EGC in the cable all the way until practically the transfer inlet? And then don't bond it somehow.

I believe line ground fault protection will work again starting at the inlet since it is bonded to premises EGC, and any fault current has to flow through the backfeed breaker for the inlet.

 

[zanydroid]

IMO what Ford should have done was allow N-G to be unbonded as needed, like generators designed to (sometimes) feed into houses. Unbonding N-G is a safety issue with non-double insulated appliances, since it depends on the GFCI to be in working order and will still allow a brief shock. It's better for L-G fault to trip the breaker right away before anyone actually gets a shock. (This is also the case with NEC approved GFCI retrofit of 5-15Rs)

GFCI disable may not be a good idea, it adds complexity.

 

[cdherman]

Thank you zanydroid for your actual explanations, as opposed to condescension. Interestingly, I knew that. But I was not computing. I have retrofitted several old houses that lack ground wires with GFCI breakers through the years. A real nice feature to help with old house wiring. In one case, two circuits with shared neutral could be protected with a 240v 2-pole GFI, though sadly not with AFI.

I have more or less convinced myself that it can be safely done. Though an inspector I think *might* have issues. I like your idea of actually leaving the ground intact in the exposed cord, but terminating the ground close to, or within a connection box, and relying on the premises ground thereafter.

An unprotected drop from a main may be run a "reasonable" distance inside a structure and pretty much any distance outside or in a "concrete raceway" inside IIRC. In my mind, this cord was previously "unprotected" and thus a violation. I don't know how NEC rules exactly apply to temporary stuff like generators. But I get concepts albeit sometimes only after a hint.

Thank you again for your insights.

 

[Dymailbox]

Lots of misconceptions here that are keeping you guys from fully utilizing two pretty amazing trucks.

Lots of misconceptions here that are keeping you guys from fully utilizing two pretty amazing trucks.

And that’s why I’m asking. Thanks for the help.

 

[cdherman]

I believe line ground fault protection will work again starting at the inlet since it is bonded to premises EGC, and any fault current has to flow through the backfeed breaker for the inlet.

I kept re-reading this though. Lets say I have a L fault somewhere between the transfer switch and and its NOT faulted to neutral, but to something else and it finds an alternate path back to the main panel G and then "rejoins" the N wire where it is bonded to G. Now current out on L1 and L2 should still equal current back on N. Pickup cannot see ground anymore. I sooo much want to not understand this and have you be right, BTW.

 

[Dymailbox]

IMO what Ford should have done was allow N-G to be unbonded as needed, like generators designed to (sometimes) feed into houses. Unbonding N-G is a safety issue with non-double insulated appliances, since it depends on the GFCI to be in working order and will still allow a brief shock. It's better for L-G fault to trip the breaker right away before anyone actually gets a shock. (This is also the case with NEC approved GFCI retrofit of 5-15Rs)

GFCI disable may not be a good idea, it adds complexity.

I appreciate the input as well. Sounds like the solutions is pretty simple.

 

[Checkthisout]

IMO what Ford should have done was allow N-G to be unbonded as needed, like generators designed to (sometimes) feed into houses.

They are then setting themselves up foe liability.

On another note, household transfer switches leave the NG bond as is unless the generating equipment is permanently mounted in which case a transfer switch that switches the NG bond is then required.

 

[Checkthisout]

I kept re-reading this though. Lets say I have a L fault somewhere between the transfer switch and and its NOT faulted to neutral, but to something else and it finds an alternate path back to the main panel G and then "rejoins" the N wire where it is bonded to G. Now current out on L1 and L2 should still equal current back on N. Pickup cannot see ground any

What real-world possible fault are you concerned that makes eliminating the egc between truck and house so untenable?

 

[CoolWill]

Just leave the EGC disconnected on one end. The cord will still be grounded by the bond on one side, but the ground loop will be broken allowing the GFCI to operate.