Whole home back up - a simple approach

[Johnif]

Do you want to tell them? Or should I?

Please feel free

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[Johnif]

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.

Hmmm, I wonder if one would get a different gfci behavior if combing the two 120V outlets into 240V as shown in a different thread recently

 

[EVpower]

I am not sure I understand the details of the described installation, but I am very concerned that an interrupted neutral condition could occur and put 240 volts into the 120-volt loads if the neutral conductors are separately switched.

Hopefully that is not the case.

Steve

 

[Johnif]

I am not sure I understand the details of the described installation, but I am very concerned that an interrupted neutral condition could occur and put 240 volts into the 120-volt loads if the neutral conductors are separately switched.

Hopefully that is not the case.

Steve

I am not doing that. Please see the other thread a couple weeks back

 

[Mmiketa]

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.

If you got a 4-pole transfer switch rated for what your main panel is then yes because it would switch the neutral.

 

[Mmiketa]

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.

Electricity flows in the path of least resistance. Just because you don’t bring the vehicle ground to the house does not mean it isn’t grounded: you’ve still got you’re house ground and it’s bonded at the panel which is still your service entrance. A fault on the truck side would trip the gfi. A fault on the house side would go to ground.

 

[luebri]

If you got a 4-pole transfer switch rated for what your main panel is then yes because it would switch the neutral.

As I stated it’s an interlock, not a transfer switch

 

[Mmiketa]

I was just answering that there was a way, it just requires a decent chunk of change.

I feel like not bringing the equipment ground is safe enough that I’m using it. It does not meet code so I will not advise someone else to do so.

also: Go Pack!

 

[Maquis]

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.

It doesn’t say that, either.

Remember Charlie’s rule for reading the NEC:

 

[Zprime29]

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...

Hmmm, sorry I wasn't clear. I was talking about using solar and charging the truck while grid power was out. Are you able to do that? I've always been annoyed that I can't use my solar when the power goes out.

 

[MickeyAO]

Charging uses AC current to the OBD (On Board Charger) to convert the AC to DC. You would need an inverter to convert the DC from solar to AC in order to charge the truck.

 

[Johnif]

Hmmm, sorry I wasn't clear. I was talking about using solar and charging the truck while grid power was out. Are you able to do that? I've always been annoyed that I can't use my solar when the power goes out.

I can do this, since I have previously installed battery backup.

 

[Jim Lewis]

Remember Charlie’s rule for reading the NEC:

As someone who's read a lot of regulations (not the NEC's, though - radiation and laser safety regs), all I can say is, "How true!" Maybe someday, though, generative AI will be able to read any regulations and explain to the average Joe/Joeline what the regs mean in plain English in their particular use situation.

My wife just came back from a Grand Rounds medical meeting of the health corporation she works for and said they were told at the meeting that not too far in the future, a derivative of ChatGPT will know a patient's medical history, listen to the conversation between doctor and patient during a medical appointment, write a summary of the important medical points that came up between doctor and patient and offer the doctor advice on the patient's further medical treatment. I imagine the AI interface is to assure that any given doctor is treating the patient in a way that's consistent with best medical practice, the patient's medical history, government and insurance regulations, (and just maybe the corporation's maximum profitability?), etc., and there are fewer oddball doctors slipping through the cracks not doing the best for the patient and making money, etc.

So, if that kind of artificial intelligence is coming to medical practice, it's not hard to imagine it might be applied to other industries -and even be able to explain the NEC code to anyone who wants to know! But perhaps not too many other industries have the financial underpinnings that the practice of medicine does (just look at how it's busting the national piggy bank!).

 

[chl]

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?

Sorry, I get hung up doing three things at once sometimes, and my edits get garbled...my kids say I am 'long winded' also, lol.

The bottom line is you can use the 240V 30A outlet on the bed of the truck through a Transfer Switch that switches the neutrals. When you buy it, tell them you have a bonded generator so they provide the correct type of transfer switch.

Connect all 4 wires, hot, hot, neutral and ground from the truck outlet to the house generator inlet which leads to the transfer switch. You must use wiring rated to handle the 240V 30A continuous load which is what the truck will be providing. Premade wires can be had from generator stores that sell the transfer switches and generator inlets.

You also have to wire the transfer switch to the house service panel (main breaker panel). The instructions with the transfer switch explain how to wire it to the house service panel correctly so that the house panel is disconnected when the generator/Lightning is connected for power.

However, to wire the transfer switch you have to open your house service panel which has live wires from your utility inside, even when the main breaker is off, the service wires are hot. So there is a real risk of shock and death should you accidentally come into contact with them. So best to have a licensed electrician to wire the transfer switch to the panel.

If you want some info on the how and why, NEC code, etc., read on otherwise that's about it.
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The neutral is grounded at/bonded to the truck so you do not want the house neutral which is grounded at/bonded to the panel to be connected at the same time or else the GFCI will open erroneously.

Also, the transfer switch, must in this case transfer the neutral to meet the safety standards according to NEC (National Electrical Code) article 250.

The safety standards of the NEC article 250 require that the neutral must be grounded at the first means of disconnect (which means the nearest possible point), and cannot be grounded twice, to avoid induced transient voltages or currents.

Also extra ground connections on a neutral conductor may bypass the protection provided by a ground-fault circuit interrupter.

Section 250.4(A)(1) states that grounded electrical systems “shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.”

If the neutrals are switched in the transfer switch, the connected neutrals in the house circuits when in transfer mode are only grounded at/bonded to the truck.

Also, the truck GFCI won't open except in the case of a real ground fault.

Though ungrounded circuits with GFCI offer you some protection (the GFCI will sense when there is a ground fault and shut off), they will not protect your electronics in the case of a power surge. You need a ground wire and surge protector for the protection against damaged electronics. Surge protectors pass the excess electricity to ground before it fries your electronics.

So removing the ground wire connection from the Lightning outlet is not a good idea.

Also if the grounding conductor is not intact or of low-impedance, the GFCI may not trip until a person provides a path. In that case, the person will receive a shock, although the GFCI should trip so quickly that the shock will not be harmful. But maybe someone with a pacemaker could experience some harm from even a mild shock?

And what if the GFCI fails to trip? Someone could be electrocuted without the ground wire providing a low impedance path to ground!

A ground connection protects against, for example, a malfunction that causes the metal frame of a tool to become energized. The equipment ground provides another path for the current to flow through the tool to ground. A GFCI protects in against a situation where there is a break in the ground circuit which could otherwise cause a shock or fire hazard.

The code require a ground connection with only a few exceptions.

Summary of Grounding Requirements

• Ground all electrical systems. [for exceptions, see 29 CFR 1926.404(f)(1)(v)]
• The path to ground from circuits, equipment, and enclosures must be permanent and continuous.
• Ground all supports and enclosures for conductors. [for exceptions, see 29 CFR 1926.404(f)(7)(i)]
• Ground all metal enclosures for service equipment.
• Ground all exposed, non-current-carrying metal parts of fixed equipment. [for exceptions, see 29 CFR 1926.404(f)(7)(iii)]
• Ground exposed, non-current-carrying metal parts of tools and equipment connected by cord and plug. [for exceptions, see 29 CFR 1926.404(f)(7)(iv)]
• Ground the metal parts of the following non-electrical equipment:
  • Frames and tracks of electrically operated cranes.
  • Frames of non-electrically driven elevator cars to which electric conductors are attached.
  • Hand-operated metal shifting ropes or cables of electric elevators.
  • Metal partitions, grill work, and similar metal enclosures around equipment of over 1kV between conductors.

 

[Runaway Tractor]

Based on what you're saying, how is it ever possible for a back feed breaker with a UL listed interlock on the main ever able to be safe and legal? My understanding was they are safe and legal with the neutral bonded at the generator. But it seems that only works because the generator doesn't have a GFCI? Whereas the truck is sensing the bond at the house panel as a fault so it doesn't work.?

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