Transfer Switch Gameplan - Thoughts?

[dafish]

let me throw some more mud on this discussion. Do you each consider the PB to be a vehicle mounted generator? And if so would 250.34 of the nec then apply? Does that change the discussion?

That's where being a layman gets me into trouble. I read that and don't think connecting a home can qualify.

The frame of a vehicle shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by a generator located on this vehicle under the following conditions:

1. The frame of the generator is bonded to the vehicle frame, and
2. The generator supplies only equipment located on the vehicle or cord-and-plug-connected equipment through receptacles mounted on the vehicle, or both equipment located on the vehicle and cord-and-plug-connected equipment through receptacles mounted on the vehicle or on the generator, and
3. The normally non-current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.

I see a home connected to a PB as not meeting #2. We're connecting to downstream receptacles with their own GFCI, bonding, and grounding points. This is why I keep sounding hinky about the PB, or portable generator not needing an earth ground.

That's also the root of the issue - If we were connecting "equipment" directly to the genset plugs there would be no issue. We aren't. Layman read: This applies to devices on the jobsite, even devices directly connected from onside a home. but not when backfeeding home panels.

Again, WTH do I know.

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[HammaMan]

Solution: Eliminate one of the bonds:
A: Find a way to temporarily disable the panel bond.
B: Eliminate the temporary power supply (PB or bonded generator) bond.
C: Disconnect the ground link at some point between Panel and temporary power supply.

Assuming I do correctly understand and have worded correctly and withing this laymans undertanding, I'm not sure I see a problem with "C". House ground? Still there, still works, devices remain protected. Temporary power supply ground? Not less effective than it ever was (which I sorta question).

"Risk" domain: I don't see one. One side of the adapter see the home ground, the other sees the generator. Make sure the "adapter" is rubber/plastic so there isn't some no-mans land of risk and it seems fini.

Hamma, why use an adapter? Are you thinking a short 14-50F <-> 14-50P dedicated to this use and labeled as same? This instead of altering a longer cord that can otherwise remain multi-purpose?

Keeping adapter short limits its utility to only this instance. The only time it's needed is GFI equipped "generator" when the structure is wired correctly, and the only place it's safe to do it is the same.

 

[Hullguy]

Let's restate everything here so we're clear.

Issue: PB's GFI inverter trips upon connecting to a generator-to-structure receptacle while having no issues when connected to portable generators.

Cause: The structure's electrical system contains a neutral ground bond allowing current to return to the generator on the grounding conductor.

Solution: Use a marked adaptor to float PB's GFI invertor grounding conductor at point before entering structure.

Risks: As of yet none identified. Vehicle is insulated from earth and if such conditions manifest that do earth the vehicle, such conditions would trip the GFI before presenting an electrocution risk to any life (not just that of adults).

Enhanced variables vs traditional breakers / power sources: Instantaneous trip at 32 amps. Unlike a 15 amp circuit breaker that requires 10-100 seconds to trip at 32 amps.

What if the ground becomes live?

 

[HammaMan]

What if the ground becomes live?

How so? Like someone some how cuts the neutral in the circuit, followed up with shorting L1/2 to ground? Nothing. There's no return path to the source.

Let's take it a step further, all of the above, plus someone walks out to the truck bare foot on wet cement and touches a bare piece of metal on the truck -- GFI trips.

 

[travisN000]

I think I saw a thread here where someone just ran the ground wire from the input plug at the house to a seperate ground rod instead of to the panel... Is this a better or worse solution to removing the ground at the trucks transfer cord?

 

[HammaMan]

I think I saw a thread here where someone just ran the ground wire from the input plug at the house to a seperate ground rod instead of to the panel... Is this a better or worse solution to removing the ground at the trucks transfer cord?

The issue with that is that there's no additional utility added while the neutral, still bonded to the structure's earthed ground, is trying to return current between the ground rods. If the structure has a UFER ground which essentially runs through rebar of the structure's foundation, and a ground rod is driven near it, enough current can return to the auxiliary ground rod on imbalanced loads inducing a nuisance trip on the truck's GFI. Doing such a thing indicates a lack of understanding in why things are configured as they are, and the purposes behind them.

Is it more or less safe? Depends on what is done trying to mitigate the nuisance tripping. By not understanding the issue in the first place, will that lead to something dangerous? I couldn't speak to that. I'm not sure what led them to believe it was viable or needed in the first place. While it's not 'more safe', it could be less safe.

 

[Suns_PSD]

This is all over my head, but it sure appears that Hamma knows what he is talking about so I'm going that route.

The only question I have is: will the '24 PB I have on order still have the bonded neutral issue, or is it possible Ford corrects this issue and I should build my set up to that?

Thanks

 

[HammaMan]

This is all over my head, but it sure appears that Hamma knows what he is talking about so I'm going that route.

The only question I have is: will the '24 PB I have on order still have the bonded neutral issue, or is it possible Ford corrects this issue and I should build my set up to that?

Thanks

GFI isn't going anywhere. The bed of the truck and outside of it is a wet location. GFI will be on all vehicle power generation systems like this going forward.

 

[HammaMan]

This is the “dogbone” adapter I created with some stuff from Amazon, I would imagine similar to what @HammaMan is describing.

Labled it “NO GROUND” and it’s red - different color from everything else. I have other L14-30 cables that attach to the truck, and a 75 footer that has ground attached. The ground cable is clipped inside the female end of the L14-30 plug and insulated with electrical tape.

For what it’s worth, there is a grounding rod right at the bottom of my transfer switch recepticle. I had always assumed the truck was seeing two grounds (house and truck) and only wanted one. I turned every single thing on in the house, well pump, furnace, lights and wasn’t even at 4k watts total.

A lot of my neighbors out here have this exact setup, installed by the same electrician. Nobody has a Powerboost to plug into, but have regular generators. I like knowing the PB will support either of the houses via this setup but most likely will purchase a tri-fuel generator and install a NG line to run it for extended periods.

One thing that is very nice about this setup is the fact I don’t have to run hundreds of ft of extension cords throughout the house, and it takes about 2 minutes to get the truck close enough to plug into the house. I was using ProPower via cords at the end of August from a Thursday @ 10pm until Sunday at 5pm. Hooked it up and turned on the truck before the big storm even started. Sure enough, power went out and I ran everything all weekend. After that, a lot of people were sold on the concept of a hybrid pickup ?

Might protect that labeling with a thick packing tape or similar to prevent rub-off / solvent based removal. Short length limits attempted use elsewhere as well.

 

[dafish]

What if the ground becomes live?

Where? The house has a fully working ground still and GFCI's. The PB and cable has whatever ground it's certified for and GFCI's. The adapter is rubber/plastic. The short adapter cable can even extend the ground over part of it, so only one plug, certainly a rubber/plastic one, is "groundless". Mighty darn short fault domain.

Of course not only should one label said adapter cable, but shut off the inverter before handling the cable. Just like any generator.

This need not be everybody's cup of tea, but if I end up with a PB I'm certainly making one.

 

[Gros Ventre]

Remember: the bonded neutral in the PB is an OSHA requirement, not an NEC requirement. Ford makes a floating neutral generator in some vehicles.

 

[Hullguy]

How so? Like someone some how cuts the neutral in the circuit, followed up with shorting L1/2 to ground? Nothing. There's no return path to the source.

Let's take it a step further, all of the above, plus someone walks out to the truck bare foot on wet cement and touches a bare piece of metal on the truck -- GFI trips.

A wire nut falls off, a cheaply made item that is incorrectly wired is plugged in, someone who thinks they are an Electrician did some electrical work and wired it incorrectly. All things ive seen and fixed.
If you float the ground in the truck you have eliminated the most important wire in your electrical system.

 

[Hullguy]

Where? The house has a fully working ground still and GFCI's. The PB and cable has whatever ground it's certified for and GFCI's. The adapter is rubber/plastic. The short adapter cable can even extend the ground over part of it, so only one plug, certainly a rubber/plastic one, is "groundless". Mighty darn short fault domain.

Of course not only should one label said adapter cable, but shut off the inverter before handling the cable. Just like any generator.

This need not be everybody's cup of tea, but if I end up with a PB I'm certainly making one.

You have removed the PB ground. It’s no longer in the circuit!

 

[Hullguy]

The issue with that is that there's no additional utility added while the neutral, still bonded to the structure's earthed ground, is trying to return current between the ground rods. If the structure has a UFER ground which essentially runs through rebar of the structure's foundation, and a ground rod is driven near it, enough current can return to the auxiliary ground rod on imbalanced loads inducing a nuisance trip on the truck's GFI. Doing such a thing indicates a lack of understanding in why things are configured as they are, and the purposes behind them.

Is it more or less safe? Depends on what is done trying to mitigate the nuisance tripping. By not understanding the issue in the first place, will that lead to something dangerous? I couldn't speak to that. I'm not sure what led them to believe it was viable or needed in the first place. While it's not 'more safe', it could be less safe.

It is Code that you need 2 grounding rods 6’ away from each other. This could be why.

 

[Hullguy]

This is all over my head, but it sure appears that Hamma knows what he is talking about so I'm going that route.

The only question I have is: will the '24 PB I have on order still have the bonded neutral issue, or is it possible Ford corrects this issue and I should build my set up to that?

Thanks

You can do whatever you want, but being a Master Electrician with close to 40 years of experience recommend that you don’t do this and install the correct equipment to make this work

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