Whole home back up - a simple approach

[v2h8484]

Will you quote the section you are referring to?

Here you go:
(B) Vehicle-Mounted Generators
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:
The frame of the generator is bonded to the vehicle frame, and
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
The normally non-current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.

250.34(B) does not say that.

The section specifies, for vehicle-mounted generators, the only accepted exceptions to grounding electrode/rod required by section 205.52. So, you need to check section 205.52 as well which basically requires a ground rod for separately derive systems. Connecting a neutral bonded truck mounted generator like Pro Power through a neutral transfer switch (i.e. separately derived system) to house wiring does not meet the required exception criteria.

Check this video, specifically starting at 13:23, for further explanation.

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[chl]

For what it’s worth, I don’t think it’s unsafe to not bring over your equipment ground from the truck. You service doesn’t bring you a ground either, you make the ground at the house and then bond the neutral. Treat your car as the utility and it’s the same thing, and its built in ground loop will clear its faults. This method is not code legal though which is also important.

If it is not up to code, it is inherently dangerous.
The codes exist to protect from dangerous installations.

Yes, you have to treat your vehicle like a source.
In your house, the source for all the house circuits is the house panel.
The NEUTRAL from the service is grounded at the utility and has to be grounded/bonded at the panel as well, for a safe install.
In your house, the neutrals of all your house circuits are all grounded/bonded at the panel, where the service is also grounded/bonded.
In the case of using your vehicle 240v outlet in the bed as a source, it already is grounded/bonded.

If you DON"T "bring over" the ground from the lightning, then you effectively have no ground in your house system!! That is dangerous!!

Ground wires are carrying current in case something goes wrong. They're a failsafe, essentially, directing current away from the plugged-in or lighting device if a problem occurs, such a short. The neutral wire completes the circuit and allows electricity to flow.

Problems occur if you have the neutrals grounded/bonded at two places, i.e., at the truck and at the panel.
The house circuits all have their neutrals grounded at the panel unless your transfer switch switches them so they do not connect to the neutral bus bar in the panel which is where the ground connection occurs.
If your transfer switch switches the neutrals as well as the hots, which pretty much all modern transfer switches do, but not all the older ones, (but check to be sure) you will have issues.
The issues will be the GFCI in the vehicle will detect a ground fault because there will be two paths to ground resulting in current differences, and open the circuit.

According to the NEC, metal parts of service equipment shall be grounded to the earth.
In addition, the grounded (neutral) service conductor shall be grounded to the earth at service equipment. With utilities, this is for ground fault elimination and for the purpose of limiting the voltage imposed by lightning, line surges, or unintentional contact with higher voltage lines, grounding is intended to shunt potentially dangerous energy into the earth from the system.

If you're connecting your generator to an electrical panel, such as a building electrical system, you must ground your generator.

The rules permit the frame to act as the grounding point instead of the grounding electrode system. Bonding the neutral to the frame is mandatory when the generator is an independent supply. The Lighting is the supply in this case.

For vehicle mounted generators, the neutral conductor must be bonded to the generator or vehicle frames if the generator supplies equipment and receptacles affixed on the vehicle or trailer.

It is not permitted to connect the grounded conductor (bonded neutral) to the ground in both sources (generator and service panel) simultaneously, as this practice could create parallel paths for the neutral current.

 

[Maquis]

Here you go:
(B) Vehicle-Mounted Generators
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:
The frame of the generator is bonded to the vehicle frame, and
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
The normally non-current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.



The section specifies, for vehicle-mounted generators, the only accepted exceptions to grounding electrode/rod required by section 205.52. So, you need to check section 205.52 as well which basically requires a ground rod for separately derive systems. Connecting a neutral bonded truck mounted generator like Pro Power through a neutral transfer switch (i.e. separately derived system) to house wiring do not meet the required exception criteria.

Check this video, specifically starting at 13:23, for further explanation.

1. Don’t get NEC advice from YouTube.
2. What this is saying is that the frame of the generator must be connected to a grounding electrode system as defined in 250.52. As long as you leave the ground wire from the truck intact, it connects to the home’s grounding electrode system, thus satisfying the requirement.

Nowhere is it stated that an additional grounding electrode system is required.

 

[chl]

Here you go:
(B) Vehicle-Mounted Generators
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:
The frame of the generator is bonded to the vehicle frame, and
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
The normally non-current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.



The section specifies, for vehicle-mounted generators, the only accepted exceptions to grounding electrode/rod required by section 205.52. So, you need to check section 205.52 as well which basically requires a ground rod for separately derive systems. Connecting a neutral bonded truck mounted generator like Pro Power through a neutral transfer switch (i.e. separately derived system) to house wiring does not meet the required exception criteria.

Check this video, specifically starting at 13:23, for further explanation.

The frame of the generator is bonded to the vehicle frame and acts as a ground.
Also, the conductor connecting the generator equipment grounding terminal with the transfer switch is an equipment grounding conductor.

See: https://eepower.com/technical-artic...de-2023-basics-grounding-and-bonding-part-9/#

Key Takeaways of Grounding and Bonding Generators

• The metal frame of a portable generator may act as a grounding electrode under some conditions.
• Under certain conditions, the metal frame or chassis of the vehicle or trailer where a generator is mounted can serve as the grounding electrode.
• Connect to the generator frame any conductor that must be grounded if the generator is a component of a separately derived system.
• The supply conductors of a permanently installed generator must include a conductor providing an effective ground-fault current path.

 

[Howard_Scott_Warshaw]

I don't think you fully understand what's going on here.

Do you want to tell them? Or should I?

 

[Zprime29]

Do you want to tell them? Or should I?

Lol, have at it! I've already got a headache from a lingering cold. No more head bashing for me.

 

[v2h8484]

Nowhere is it stated that an additional grounding electrode system is required.

I believe it has to do with bonding and grounding needs to be at the same point for separately derived systems. Since the bonding is at the truck then grounding at the main panel is likely dozens of feet away so certainly not at the same point.

 

[Runaway Tractor]

If you DON"T "bring over" the ground from the lightning, then you effectively have no ground in your house system!! That is dangerous!!

Your lengthy post kind of goes around In a circle without an actual solution. Not trying to be a dick , you know way more than me, it's just less clear now than it was before.

If it's dangerous and has no ground if you don't bring the ground from the Pro Power, and also will always trip because of the required bonding on the house panel, then what is the correct, safe way to do it?

 

[Henry Ford]

I believe it has to do with bonding and grounding needs to be at the same point for separately derived systems. Since the bonding is at the truck then grounding at the main panel is likely dozens of feet away so certainly not at the same point.

A neutral switching transfer switch definitionally removes any connected equipment from the ground at the panel which allows the lone "ground" (bond?) to occur at the truck.

 

[Henry Ford]

If it's dangerous and has no ground if you don't bring the ground from the Pro Power, and also will always trip because of the required bonding on the house panel, then what is the correct, safe way to do it?

A neutral switching transfer panel like the Generac 6852.

 

[luebri]

A neutral switching transfer panel like the Generac 6852.

Is there a solution that works with a full panel interlock breaker? These small ass "critical loads" panels seem to be way less convenient than a whole panel interlock where I can pick and choose what is critical at any time not just during the original install.

 

[Runaway Tractor]

I use the back feed breaker with UL listed interlock kit as well. My portable generator has a bonded neutral. Always worked flawlessly. I think the difference between this and the truck, is the generator's 240v outlet is not GFCI protected, only it's 120v outlets have GFCI protection. So the bonding in the house panel does not trip anything out. The truck's pro power appears to have GFCI protection on its 240 volt outlet. So that bonded neutral in the house panel is seen as a ground fault, tripping the trucks GFCI.

As far as I can tell, a ground fault or overload on a branch circuit from my house panel will trip the breakers properly. It may not be perfectly correct by code, but best I can tell, it is just as safe for overload and fault protection.

I hope someone who knows more than me can explain better.

 

[luebri]

I use the back feed breaker with UL listed interlock kit as well. My portable generator has a bonded neutral. Always worked flawlessly. I think the difference between this and the truck, is the generator's 240v outlet is not GFCI protected, only it's 120v outlets have GFCI protection. So the bonding in the house panel does not trip anything out. The truck's pro power appears to have GFCI protection on its 240 volt outlet. So that bonded neutral in the house panel is seen as a ground fault, tripping the trucks GFCI.

As far as I can tell, a ground fault or overload on a branch circuit from my house panel will trip the breakers properly. It may not be perfectly correct by code, but best I can tell, it is just as safe for overload and fault protection.

I hope someone who knows more than me can explain better.

Yep, exactly my situation. I would like to have the truck as another option when I don’t need the full 50 Amps And I wanted a little quieter solution.

 

[Johnif]

Very cool. I've been interested in a way to use my solar while backing up power with the lightning. I believe I recall someone saying that excess solar was charging their truck while using the HIS and FCSP setup. Just not sure it's worth that price tag and potential headache.

I should have no problems charging truck from solar, and also selling any excess to grid at same time. The one thing I have no solution for yet is how I could set up a way to be able to sell from truck battery to grid. But there must be some way...

 

[TaxmanHog]

The one thing I have no solution for yet is how I could set up a way to be able to sell from truck battery to grid. But there must be some way...

Ford has visions of such a process ..... BUT ..... it involves the H.I.S. and isn't a feature yet.

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