Questions on Generac 6852 setup with Lightning

[CluckFam7]

Hi all,

First time poster, though have read more posts on this topic than I care to count.

I’m trying to understand a proper setup to use the PPO’s 240V outlet as a home backup. I want to do it the “proper” way, meaning to code and safely without hacks.

From what I have gathered, getting a neutral switching transfer switch like the Generac 6852 is the “proper” way to do this.

However, I have some questions:

First, I saw one thread on the 6852 that alluded to this and it prompted me to dig further. On page 7 of the Generac 6852 owners manual, it says “Portable Generator Grounding Requirements. The Upgradeable Manual Transfer Switch is designed for use with portable generators with a bonded neutral, and used as a separately derived system. A grounding system and a grounding electrode system shall be connected to the ground terminal of the portable generator. See NEC Article 250.30(A)(4) and (5) for code compliance.”

I am unclear what this means exactly; does it mean that the truck needs to have its own grounding system (like a ground rod?) to connect it to physical ground when used on the transfer switch? Does this mean a typical setup where the truck doesn’t have this is not code compliant or has a scenario that is not protected against?

Second, with the Generac 6852, would I be able to use a normal portable generator, which I understand has a floating neutral, as well?

Thanks in advance. I fully intend to have a qualified and licensed electrician do the install, but I simply want to arm myself with information. I know everyone including licensed professionals are human, so I’d like to be able to have a general understanding of what is correct vs not vs blindly trust.

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[Maquis]

The PPO’s ground terminal will be connected to your home’s grounding electrode system by the EGC in the cable. Some have contended that isn‘t what’s intended by the NEC, but it’s electrically equivalent and safe.

No, you can’t use this setup with a genny that has a floating neutral. A true “portable” generator with a floating neutral is pretty rare.

 

[Henry Ford]

* I am an idiot and you should assume I'm wrong...

First, I saw one thread on the 6852 that alluded to this and it prompted me to dig further. On page 7 of the Generac 6852 owners manual, it says “Portable Generator Grounding Requirements. The Upgradeable Manual Transfer Switch is designed for use with portable generators with a bonded neutral, and used as a separately derived system. A grounding system and a grounding electrode system shall be connected to the ground terminal of the portable generator. See NEC Article 250.30(A)(4) and (5) for code compliance.”

I think this is more straightforward than a lot of code language. It's basically saying the Generic 6852 is for use with a separately derived system with a bonded neutral and a ground. The Lightning has a bonded neutral and qualifies as a separately derived system except for the ground.

The next logical question is could you bond the Lightning's frame to a grounding rod? Sure, why not. I haven't tried it nor have I read about anyone else trying it. I don't think it would trip the GFCI in the truck and I do think it would make the system code compliant but see my * above.

Based on what I've read, the ground in the separately derived system is there to protect from lightning strikes. Seems like there's a joke in there somewhere... lightning... Lightning...

Second, with the Generac 6852, would I be able to use a normal portable generator, which I understand has a floating neutral, as well?

It is my understanding a portable generator would have to have a bonded neutral and be grounded to quality as a separately derived system. I believe this is possible with most portable generators.

 

[Henry Ford]

The PPO’s ground terminal will be connected to your home’s grounding electrode system by the EGC in the cable. Some have contended that isn‘t what’s intended by the NEC, but it’s electrically equivalent and safe.

No, you can’t use this setup with a genny that has a floating neutral. A true “portable” generator with a floating neutral is pretty rare.

Listen to @Maquis. He knows way more about this than me. I wrote my reply above before I read this. I agree with what I've quoted here but I'll leave my post above for posterity...or something.

 

[CluckFam7]

Thank you both for the replies.

As a follow up question, I think one point where I may be confused about is how the PPO is connected to the home’s grounding system.

I think part of my confusion is that I have in my mind that since the home’s neutral and ground are bonded, when the 6852 switches to generator, both neutral and ground are swapped to the generator; in other words I have in my mind that the 6852 isolates it’s 8 circuits from the home’s ground when it switches to generator. I am now gathering that this is not correct, but rather both the generator and the home are always tied to a common ground bus in the 6852. If it’s the latter, then I can see that the trucks PPO is tied to the home’s ground through the ground wire in the cord. Can you help me confirm my understanding on this?

Separate Questions:
1. On your comment that most portable generators are neutral bonded, I checked my portable generator’s manual (Briggs and Stratton Storm Responder 6250) and it is in fact a bonded neutral. Does that mean that this generator should have a neutral switching transfer switch too? I was under the impression that most of the time a normal transfer switch (not neutral switching transfer switch) is what most people install for home generators; but it seems like they should be installing a neutral switching one if most generators are bonded neutral? I also notice there is a grounding terminal that the manual says to check local code on grounding requirements; is this basically saying some local codes may require the generator ground to be connected to the house’s ground via a separate ground wire vs just using the EGC?

2. Can the 6852 handle 240 circuits (AC unit)?

3. My main panel has several Eaton Blue/Green breakers, which I understand to be GCFI + AFCI. Any issues with these circuits going to the 6852?

Thank you so much!!!

 

[CluckFam7]

Oh one more question on the lightning strike scenario - that’s basically saying if lightning hits the truck, there needs to be a path to ground to discharge that electrical energy? So in this case it would be through the ECG to the home’s ground?

Not that it will influence any decisions but my truck will be in the garage when used as backup power.

 

[carys98]

Thank you both for the replies.

As a follow up question, I think one point where I may be confused about is how the PPO is connected to the home’s grounding system.

I think part of my confusion is that I have in my mind that since the home’s neutral and ground are bonded, when the 6852 switches to generator, both neutral and ground are swapped to the generator; in other words I have in my mind that the 6852 isolates it’s 8 circuits from the home’s ground when it switches to generator. I am now gathering that this is not correct, but rather both the generator and the home are always tied to a common ground bus in the 6852. If it’s the latter, then I can see that the trucks PPO is tied to the home’s ground through the ground wire in the cord. Can you help me confirm my understanding on this?

Separate Questions:
1. On your comment that most portable generators are neutral bonded, I checked my portable generator’s manual (Briggs and Stratton Storm Responder 6250) and it is in fact a bonded neutral. Does that mean that this generator should have a neutral switching transfer switch too? I was under the impression that most of the time a normal transfer switch (not neutral switching transfer switch) is what most people install for home generators; but it seems like they should be installing a neutral switching one if most generators are bonded neutral? I also notice there is a grounding terminal that the manual says to check local code on grounding requirements; is this basically saying some local codes may require the generator ground to be connected to the house’s ground via a separate ground wire vs just using the EGC?

2. Can the 6852 handle 240 circuits (AC unit)?

3. My main panel has several Eaton Blue/Green breakers, which I understand to be GCFI + AFCI. Any issues with these circuits going to the 6852?

Thank you so much!!!

1. The manual is probably telling you to check local codes to cover themselves legally. Their lawyers don’t want to tell you how you should hook up the ground.
2. The 6852 can handle 240 circuits, it comes with one 20A dual pole breaker. The main use is for well pumps. The truck will probably struggle to power most AC units though due to the start current. Anything much over 1.5 ton will probably require a 25-30 A breaker and will pull significantly more on startup. There are soft start units that might help. If you have a small inverter based mini-split you might be OK.
3. I don’t think there is any problem with GFCI or AFCI. Mine has some circuits with GFCI outlets but I don‘t have any GFCI breakers in the panel. I’m less familiar with AFCI.
4. For the lightning strike question, any lightning that hits the truck will probably arc to ground off the bottom of the chassis before it would travel down a 10 gauge wire. In that case grounding the chassis keeps the truck at ground potential and allows any charge to dissipate and reduce the chance of a strike.

 

[v2h8484]

I want to do it the “proper” way, meaning to code and safely without hacks.

Grounding via the EGC is more convenient and practically safe per @Maquis. It's certainly a path to ground for lightning strikes. But it's not code compliant so it appears to fall short of your meaning of the "proper" way. The NEC sections cited in the manual is pretty clear about what's required for code compliance. IMHO, code compliance here does not increase safety significantly but may have implications for warranty and/or insurance claims in case of damages. Perhaps you want to reconsider what the "proper" way means to you.

 

[CluckFam7]

Grounding via the EGC is more convenient and practically safe per @Maquis. It's certainly a path to ground for lightning strikes. But it's not code compliant so it appears to fall short of your meaning of the "proper" way. The NEC sections cited in the manual is pretty clear about what's required for code compliance. IMHO, code compliance here does not increase safety significantly but may have implications for warranty and/or insurance claims in case of damages. Perhaps you want to reconsider what the "proper" way means to you.

I read through what I could understand of those NEC articles. Is there a way to ground the truck chassis to my house ground? E.g. a wire connected to my house water pipe or ground roof that simply needs to be connected to a terminal on the chassis, if such a terminal exists? That doesn’t seem like an inconvenient step when I need to use it.

 

[intensifi]

See if your utility supports these:

 

[Newton]

The Generac transfer switch only switches the neutral, not ground. All grounds are still connected. You can find the manual online which will show a wiring diagram.

The "trick" is that you take the hot and neutral wire of each circuit that you are moving over to the Generac subpanel. (Locating the neutral for a given circuit can be a pain.) You also bring over the house (bonded) neutral. All of those circuit's neutrals are tied to the Generac's neutral bar.

In normal mode, the Generac neutral bar is tied the house neutral (bonded at the house and to the ground stake.) In generator mode, the Generac neutral bar is tied to the truck neutral, which is not tied to the house. Ground for the truck goes to ground for the Generac, which goes to ground for the house. It doesn't matter that the circuits that you didn't move are still bonded.

Here is the link go to page 14 which is too big for me to screenshot and post here (can't figure out how to shrink a page in pdf using IOS.)

Grounding the truck frame might be a good idea because the distance of the cord and associated resistance could mean that the truck ground and the house ground are at a slightly different potential, at 30A I don't know if that is going to be an issue. If you have a pacemaker don't touch the truck and your exposed iron pipes at the same time. It is possible that in this condition circuit breakers or GFCIs might not give the protection that they are supposed to, I just don't know. It isn't going to do any good for lightning (the little l kind) any ground will be vaporized if your truck takes a hit.

220V loads are just fine, it comes down to the amperage. Note that if you need more 120V loads than 220V loads you can put in additional dual circuit breakers like it already has - and vice/versa.

If your house has circuits with a shared neutral (typically kitchen, look for red wires) then things get a little tricky. If you are in Canada then things get even more tricky but nothing beyond a capable electrician.

 

[v2h8484]

I read through what I could understand of those NEC articles. Is there a way to ground the truck chassis to my house ground? E.g. a wire connected to my house water pipe or ground roof that simply needs to be connected to a terminal on the chassis, if such a terminal exists? That doesn’t seem like an inconvenient step when I need to use it.

You could but I am not sure that would be code compliant. The separately derived system examples I have seen use a separate ground rod close to the generator. Since the primary purpose is for lightning protection, the general goal is to have the shortest length and lowest impedance possible wire (code requires 6AWG or larger) between the generator/truck chassis and earth ground. As always, consult your local electricians as they would know most about your local AHJ requirements which may include exemptions from the standard NEC codes.

 

[roddiaz1]

See if your utility supports these:

Wait! What?!? What is this????
You just can’t leave us here wondering…..
Please expand.
Thanks!

 

[Maquis]

Wait! What?!? What is this????
You just can’t leave us here wondering…..
Please expand.
Thanks!

It’s a meter collar that incorporates an automatic transfer switch. The only utility offering them is PG&E in California as far as I know.

 

[roddiaz1]

Awesome! Hope we get this with our local utility company.
Thanks

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