Ground fault using manual transfer switch

[Hammick]

When I installed our transfer switch last September the plan was just to have it for backup. Then it morphed into powering our house from 4:00 pm to 8:00 pm when our utility rates skyrocket (we are on the EV time of use plan so have the highest peak rates). Once I discovered that the Lightning would power our 5 ton AC and could go several days powering our house without charging we started turning on the Pro Power every morning we are in town.

Our transfer switch is kind of a Unicorn. It's automatic and switches the neutral and has a switch for instant transfer or 30 second delay. It's only 50 amps but that has not been a problem. Basically it's designed for a 50a Class A RV.

We have identical dual panels since we finished the basement 14 years ago. The transfer switch feeds the sub panel with a 50a breaker. The sparse sub panel is now full and the main panel is sparse. We are powering our entire house from the lightning with the exception of our 4 ton upstairs AC system, dryer and a handful of mostly unused outlets and lights.

With the Lightning ground connected to the transfer switch we would get periodic ground faults at the lightning when our 5 ton AC breaker was on. This AC unit is inverter driven and full variable which is the only reason the Lightning can run it. I went through the wiring completely and it is correct, tight, no bugs and no moisture. However, these Inverter units are much different than a tradition AC so no idea why it can cause the Lightning to ground fault. The Lightning cannot start our conventional 4 ton unit.

I finally gave up and dropped the Lightning ground at the transfer switch. All we have to do in the morning is remove the charger, turn on the truck/Pro Power and done. My wife does it most days at about 6:15 am before she makes coffee. Alexa reminds us every night to reverse the procedure.

I am at peace with removing the ground for the reasons stated by others above. Truck is in our attached garage.

When my wife retires in a few years we are selling and moving somewhere with mountains and low humidity. I will remove the transfer switch and move the breakers back to the main panel.

If you came into our house you would have no idea it wasn't running on grid power.

From Midnight to 6:00 am the grid powers our home and charges our EVs at 2 cents per kw in the winter and 3 cents per kw in the summer. On the rare occasion that we have an extended power outage we have backup power on par with super expensive Generac install.

We like sleeping in a cool environment so in the summer our programable thermostats blast all floors with cool AC from Midnight to 6:00 am at .03 cents per kw. Even on 100 degree days our house stays nice and cool until mid afternoon. Then main AC kicks on powered by the Lightning.

Our retirement home will be much smaller, much nicer and much better built. It will have V2L and whatever truck or powered RV trailer is capable of powering it. For now I love our inexpensive system (obviously ignoring the cost of the Lightning).

DISCLAIMER: Don't even think about putting in your own transfer switch unless you have experience working in main breaker panels with hot utility power.

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[ryun]

I know. It took me a long time to wrap my head around the whole thing. But once it clicks, it's like "oh, duh, of course."

With the bond in the panel and the generator, you now have two parallel pathways for neutral current to flow from the house back to the generator (this is where it clicked for me). Whatever split-phase imbalance current exists flows back to the generator on the neutral and the ground. It turns the ground from the panel to the generator into a current carrying conductor, which it is not rated or sized to do. Worse, if the neutral fails (which is a thing that happens), you now have all the current on the ground conductor.

Ah-hah! That's the part I was missing. Man that was super helpful thanks so much for taking the time to write that out.

 

[v2h8484]

With the Lightning ground connected to the transfer switch we would get periodic ground faults at the lightning when our 5 ton AC breaker was on. This AC unit is inverter driven and full variable which is the only reason the Lightning can run it. I went through the wiring completely and it is correct, tight, no bugs and no moisture. However, these Inverter units are much different than a tradition AC so no idea why it can cause the Lightning to ground fault.

The inverter AC is likely creating high frequency transients causing the Lightning GFCI to nuisance trip. Anything that creates high frequency transients could do it.

The Lightning cannot start our conventional 4 ton unit.

A soft starter could make it work.

 

[davehu]

I just had a discussion with my electrician on this very thing and he said basically the same. It would work but he wouldn't do it personally. I pressed but he couldn't say why other than he couldn't even come close to endorsing it otherwise he'd be liable.

I'd love to understand the reasoning behind it -- I'm in no way trying to defeat it (in fact, I already plan on using the EZ Generator Switch talked about above for cost and safety). But here's my hang up: If the truck is neutral-ground bonded and the panel is neutral-ground bonded then the Lightning is safer than most portable generators even with the ground removed from the plug; it already has a path to ground along the neutral line. Most people I know with portable generators and no GFCI protection never ground them while in use.

But okay, I already admit that I don't understand it all so maybe there's still a way for the truck to become energized or something. Or maybe the worry is that the neutral line could be so overloaded with extra current that it could fail and/or cause a fire. But then the GFCI protection would kick in and stop it all, no?

Another reason for my hang up is I've heard from multiple electricians that if I don't have a ground connection in my house at an outlet then it's no big deal. Just slap a GFCI outlet downstream of the rest of the branch and you're good to go. Code compliant. How is Pro Power without a ground any different? Does it come down to the energy potential being way higher in a generator than a 20 amp, 120V circuit?

mine was done that way (ground from truck disconnected) and done by the electrician with 18yrs experience and specializes in generators. He had done this for another customer with an F150 hybrid with pro-power. Had my first outage today losing power for 4 hours. worked just fine.

 

[Tyler Durden]

Also, I found post #14 in this thread educational:

https://www.f150lightningforum.com/...-backup-power-installation.16542/#post-333493

 

[Hammick]

The inverter AC is likely creating high frequency transients causing the Lightning GFCI to nuisance trip. Anything that creates high frequency transients could do it.


A soft starter could make it work.

Interesting about the inverter AC causing high frequency transients. We have two Samsung inverter fridges and they both worked fine on the Pro Power when I had the ground connected. Or I guess it's possible the AC wasn't causing it at all and I was getting my ground faults when one of the fridges was running its compressor. I ran out of patience to figure it out.

I'm sure I could make the 4 ton AC work with a soft start but with both ACs running we would probably overload the Lightning quite a bit. My wife has overloaded it on more than one occasion getting crazy with kitchen gadgets. She did it once when we had guests over for a Chief's playoff game. TVs shut off until the router restarted. I got a lot of shit that night for being a cheap ass

 

[Hammick]

Also, I found post #14 in this thread educational:

https://www.f150lightningforum.com/forum/threads/my-“unintelligent”-backup-power-installation.16542/#post-333493

Yes Maquis knows his stuff inside and out and was a big help to me during my install. I should point out he never recommended I remove the ground. I take full responsibility for that decision.

 

[ctuan13]

When I installed our transfer switch last September the plan was just to have it for backup. Then it morphed into powering our house from 4:00 pm to 8:00 pm when our utility rates skyrocket (we are on the EV time of use plan so have the highest peak rates). Once I discovered that the Lightning would power our 5 ton AC and could go several days powering our house without charging we started turning on the Pro Power every morning we are in town.

Our transfer switch is kind of a Unicorn. It's automatic and switches the neutral and has a switch for instant transfer or 30 second delay. It's only 50 amps but that has not been a problem. Basically it's designed for a 50a Class A RV.

We have identical dual panels since we finished the basement 14 years ago. The transfer switch feeds the sub panel with a 50a breaker. The sparse sub panel is now full and the main panel is sparse. We are powering our entire house from the lightning with the exception of our 4 ton upstairs AC system, dryer and a handful of mostly unused outlets and lights.

With the Lightning ground connected to the transfer switch we would get periodic ground faults at the lightning when our 5 ton AC breaker was on. This AC unit is inverter driven and full variable which is the only reason the Lightning can run it. I went through the wiring completely and it is correct, tight, no bugs and no moisture. However, these Inverter units are much different than a tradition AC so no idea why it can cause the Lightning to ground fault. The Lightning cannot start our conventional 4 ton unit.

I finally gave up and dropped the Lightning ground at the transfer switch. All we have to do in the morning is remove the charger, turn on the truck/Pro Power and done. My wife does it most days at about 6:15 am before she makes coffee. Alexa reminds us every night to reverse the procedure.

I am at peace with removing the ground for the reasons stated by others above. Truck is in our attached garage.

When my wife retires in a few years we are selling and moving somewhere with mountains and low humidity. I will remove the transfer switch and move the breakers back to the main panel.

If you came into our house you would have no idea it wasn't running on grid power.

From Midnight to 6:00 am the grid powers our home and charges our EVs at 2 cents per kw in the winter and 3 cents per kw in the summer. On the rare occasion that we have an extended power outage we have backup power on par with super expensive Generac install.

We like sleeping in a cool environment so in the summer our programable thermostats blast all floors with cool AC from Midnight to 6:00 am at .03 cents per kw. Even on 100 degree days our house stays nice and cool until mid afternoon. Then main AC kicks on powered by the Lightning.

Our retirement home will be much smaller, much nicer and much better built. It will have V2L and whatever truck or powered RV trailer is capable of powering it. For now I love our inexpensive system (obviously ignoring the cost of the Lightning).

DISCLAIMER: Don't even think about putting in your own transfer switch unless you have experience working in main breaker panels with hot utility power.

So just to clarify, you simply cut the ground conductor on your cable headed to your transfer switch? I get that this isn't the "proper" way, but I'm just trying to understand what you did.

 

[v2h8484]

Interesting about the inverter AC causing high frequency transients. We have two Samsung inverter fridges and they both worked fine on the Pro Power when I had the ground connected.
Or I guess it's possible the AC wasn't causing it at all and I was getting my ground faults when one of the fridges was running its compressor. I ran out of patience to figure it out.

Fridge inverters are much smaller and less problematic for GFCI. Large inverter appliances like HVAC, induction ranges, large microwaves are more problematic.

 

[Hammick]

So just to clarify, you simply cut the ground conductor on your cable headed to your transfer switch? I get that this isn't the "proper" way, but I'm just trying to understand what you did.

Yes. I could have done it at the generator inlet box but the transfer switch has a hinged door and it was easiest there. I removed the ground and put a wire nut on it. I left the ground from the main panel and the sub panel connected to the transfer switch. You could also remove the ground on the generator cable frorm the Pro Power to the inlet box but why ruin a perfectly good cord.

 

[bmwhitetx]

Yes. I could have done it at the generator inlet box but the transfer switch has a hinged door and it was easiest there. I removed the ground and put a wire nut on it. I left the ground from the main panel and the sub panel connected to the transfer switch. You could also remove the ground on the generator cable frorm the Pro Power to the inlet box but why ruin a perfectly good cord.

If/when I do this mod, I plan to go the interlock route also. My only concern is that if I die a year later, house sold, yada, yada, that the new owner inherits a generator inlet with the ground disconnected unknowingly. So I’m leaning towards a modified cable that is clearly labeled and discarded before house and truck sold.

 

[Runaway Tractor]

If/when I do this mod, I plan to go the interlock route also. My only concern is that if I die a year later, house sold, yada, yada, that the new owner inherits a generator inlet with the ground disconnected unknowingly. So I’m leaning towards a modified cable that is clearly labeled and discarded before house and truck sold. Sponsored

This is exactly why I did the cable method at the female twist lock end. Also, I have an LPG generator with it's own cable that works fine without a GFCI, so I want everything intact for that.

 

[Newton]

Of the two really bad options, modifying the cable is the worst. It will end up at a garage/estate sale and will be used to power an RV, or it will be sold with the truck and used to power field equipment. What can go wrong, will go wrong. You don't want to end up in court with some lawyer repeating "illegally modified power cord" over and over while the parents sob in the audience.

Modifying the inlet, while bad, at least can be labeled permanently and clearly and is something that might never be used. You can tape a note to the transfer switch so that your new buyer's home inspector has something to get upset by.

I do not know all of the ins and outs of what could go wrong by not following the current state of the art (neutral switching transfer switch) but I am risk averse enough not to want to try it. It wasn't hard to install the proper switch. If something goes wrong at least nobody is going to accuse me of taking a dangerous shortcut and I'm not going to have to find some expert to say "no actually it is quite safe, the eletrocution/fire was caused by something else."

 

[chrisventer]

If/when I do this mod, I plan to go the interlock route also. My only concern is that if I die a year later, house sold, yada, yada, that the new owner inherits a generator inlet with the ground disconnected unknowingly. So I’m leaning towards a modified cable that is clearly labeled and discarded before house and truck sold.

I bought a short extension cable last week and used pliers to remove ground pin. Last night we had a power outage due to a storm and plugged in the lightning though my inlet to the transfer switch and it worked like a dream. I plan to label the cord with a "Warning: Ungrounded, use only where both ends are separately grounded."

I will ensure the cable stays with the truck and I toss it if I no longer have the lightning. I get that there is some risk but in an emergency with no power and sub-zero temperatures on balance I am willing to go this route.

 

[Mmiketa]

I bought a short extension cable last week and used pliers to remove ground pin. Last night we had a power outage due to a storm and plugged in the lightning though my inlet to the transfer switch and it worked like a dream. I plan to label the cord with a "Warning: Ungrounded, use only where both ends are separately grounded."

I will ensure the cable stays with the truck and I toss it if I no longer have the lightning. I get that there is some risk but in an emergency with no power and sub-zero temperatures on balance I am willing to go this route.

I think there is a lot of fear mongering, I don’t think you have anything to worry about. Antoine who looks at your coffers would notice that it’s missing the ground pin. There’s being safe and cautious and then there’s bubble boy.

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