'whole home backup' confusion

[jgbaum]

I recently had a system installed (16kW, 2PW+, backup gateway 2) and all of my paperwork references 'whole home backup'. Basically, they pulled all of my loads from my main panel into a subpanel connected to the gateway. The only breaker in my main panel now is a 100A going to the gateway. What's odd to me is that they had me upgrade my main panel and service (which required significant trenching and $$$) from 100A to 200A, but they're only feeding this subpanel (which is capable of 225A) with 100A. There are several new loads I'd like to add in the coming months (EV chargers, electric dryer, water heater), which my project advisor was aware of, but there doesn't seem to be the bandwidth to support these in the subpanel. Am I mistaken? Should I ask Tesla to update the wiring/breaker to 200A?

My understanding (which may be wrong!) is that in order to be powered by my PV system or PWs when the grid is out, loads would need to be in the subpanel as no electricity would flow to the main.

I've included the wiring diagram below. Any insight would be much appreciated.

Thanks!

 

[wwhitney]

But for real, why would two grounding rods and two neutral to ground bonds within 2 feet of each other actually pose a problem?

Part of the neutral current for all your loads downstream of the TEG2 is possibly flowing through the case of the TEG2 (and the EGC between the TEG2 and the meter main, which if that is metal conduit is also exposed to touch). So in theory that exposed metal may be at an elevated voltage from ground, and it's possibly a shock hazard. It's certainly undesirable current and is prohibited by the NEC.

Cheers, Wayne

 

[holeydonut]

Part of the neutral current for all your loads downstream of the TEG2 is possibly flowing through the case of the TEG2 (and the EGC between the TEG2 and the meter main, which if that is metal conduit is also exposed to touch). So in theory that exposed metal may be at an elevated voltage from ground, and it's possibly a shock hazard. It's certainly undesirable current and is prohibited by the NEC.

Cheers, Wayne

You know it's funny, the Sunrun electrician that was at my house to install the new MSP, Gateway, and these fancy grounding rods actually told me that all grounding rods can have elevated voltage. And that getting shocked by them was unavoidable. And to be careful because you know, getting shocked is no good.

I know you all probably think I'm making up half the stuff I post here. But for real; I'm not. The electrician even went further to say animals sometimes get a little jolt when they go up against grounding rods.

I think wwhitney should offer his services for sale to watch a solar+ess installation go in. So he can boss the people around and make sure they install things correctly when they do stupid stuff that only he knows is stupid while it's happening.

PS, my grounding rods are exposed on the out-side of my stucco walls because my house is on a concrete slab and they didn't want to actually go through the slab to get to ground.

 

[holeydonut]

I recently had a system installed (16kW, 2PW+, backup gateway 2) and all of my paperwork references 'whole home backup'. Basically, they pulled all of my loads from my main panel into a subpanel connected to the gateway. The only breaker in my main panel now is a 100A going to the gateway. What's odd to me is that they had me upgrade my main panel and service (which required significant trenching and $$$) from 100A to 200A, but they're only feeding this subpanel (which is capable of 225A) with 100A. There are several new loads I'd like to add in the coming months (EV chargers, electric dryer, water heater), which my project advisor was aware of, but there doesn't seem to be the bandwidth to support these in the subpanel. Am I mistaken? Should I ask Tesla to update the wiring/breaker to 200A?

My understanding (which may be wrong!) is that in order to be powered by my PV system or PWs when the grid is out, loads would need to be in the subpanel as no electricity would flow to the main.

I've included the wiring diagram below. Any insight would be much appreciated.

Thanks!

Lol I feel like your exact situation was experienced by another user like 2 months ago.

To answer your questions:

1) Yes, the box labeled [X] is the only one that will be powered if you cannot get energy from your power company

2) I feel like you got hit with the unfortunate situation others have had where your power company is forcing you to upgrade your main service panel to comply with whatever interpretation they have; but then Tesla realizes your home is configured in such a way that you only need 100A between your backed-up microgrid and the PG&E grid

3) If you add future loads into the main service panel, it is likely you would want some energy to be able to be exported from your batteries to be consumed by these upstream loads when the utility is operational. As all California utilities move to time of use rate plans, homeowners are incentivized to use their stored battery energy when possible between 4pm and 9pm (or 3pm and 11pm if you're on an EV rate plan).

When the time comes that you have a bunch of loads in the main service panel, you will likely want to have someone add Current Transducers (CT's) to allow your Tesla gateway to sense the upstream loads. With these sensors, you can configure the Tesla ESS system to export energy to feed these upstream loads if they are detected. But good luck finding someone to do this. I had a really rough time trying to set up a partial home backup because electricans/solar-folks/ESS-folks around me just refused to play ball.

And of course if the utility goes offline, the loads in the main service panel will be de-energized as well.

 

[wwhitney]

PS, my grounding rods are exposed on the out-side of my stucco walls because my house is on a concrete slab and they didn't want to actually go through the slab to get to ground.

The NEC requires that a ground rod have 8' of length in contact with the earth. So when using 8' rod as is common, the top of the rod should be below grade, and the rod would not be exposed. If you have 10' rods, then you can leave some of the rod exposed, but there's no real upside, to my knowledge.

I don't know if you can determine the length after driving, even if the end was marked the driving process would probably mess it up. I don't have any direct experience with this, as I've only dealt with houses with new foundations that have CEEs, so they have no need for ground rods.

Cheers, Wayne

 

[BGbreeder]

You know it's funny, the Sunrun electrician that was at my house to install the new MSP, Gateway, and these fancy grounding rods actually told me that all grounding rods can have elevated voltage. And that getting shocked by them was unavoidable. And to be careful because you know, getting shocked is no good.

I struggle to think of a case where a correctly wired home system would shock you at a ground rod. @Vines @wwhitney comments?

"CEEs" = Concrete Encased Electrodes, aka Ufer grounds, i.e. grounding via rebar/conductor(s) in a foundation. More here. For a variety of reasons, including moisture content of soils, salts in the concrete, and a large surface area, Ufer showed that CEEs provide better and more reliable grounds than ground rods.

I agree the @wwhitney has a promising side business as an overseer of installations.

FWIW: Our solar ground rod, CEE, plumbing, and a MSP ground rod are all tied together at the MSP ground, where it is bonded to the neutral. I find grounding to be an interesting subject, and as the frequency and voltage change, different solutions may be optimal.

All the best,

BG

 

[holeydonut]

I struggle to think of a case where a correctly wired home system would shock you at a ground rod. @Vines @wwhitney comments?

"CEEs" = Concrete Encased Electrodes, aka Ufer grounds, i.e. grounding via rebar/conductor(s) in a foundation. More here. For a variety of reasons, including moisture content of soils, salts in the concrete, and a large surface area, Ufer showed that CEEs provide better and more reliable grounds than ground rods.

I agree the @wwhitney has a promising side business as an overseer of installations.

FWIW: Our solar ground rod, CEE, plumbing, and a MSP ground rod are all tied together at the MSP ground, where it is bonded to the neutral. I find grounding to be an interesting subject, and as the frequency and voltage change, different solutions may be optimal.

All the best,

BG

I think the good designers and installers work for wherever Vines works instead of working for Sunrun hah.

BTW, did they bond all of your ground stuffs to your gas riser as well? Of my two ground rods, one is clamped to the home-side of the gas riser (the house-side of the gas meter). From the clamp, there's copper going to a clamp that is affixed to the ground rod that is sticking up from the soil/grade about 5 inches.

Part of me is like... wtf why would you want to direct electricity to the one thing that PG&E keeps thinking will explode? But then I'm thinking all this is a load of BS since my disconnects will protect me.

 

[wwhitney]

Of my two ground rods, one is clamped to the home-side of the gas riser (the house-side of the gas meter). From the clamp, there's copper going to a clamp that is affixed to the ground rod that is sticking up from the soil/grade about 5 inches.

The interior metal gas piping should be bonded to the grounding system, e.g. as you've described. The meter has a dielectric union, so the utility side gas piping is not electrically continuous with the house side gas piping.

Cheers, Wayne

 

[miimura]

Since I was watching just about everything while my house was being built, I know that both of my service lines are plastic. Both gas and water. Expecting such service piping to be useful as a ground is amusing to me. Of course, the gas pipes on the house side of the meter are all iron, so they do need to be grounded somewhere. The most amusing thing to me was the guy who had the job of welding my gas service stub to the underground distribution pipe while it was actively venting gas.

 

[BGbreeder]

I think the good designers and installers work for wherever Vines works instead of working for Sunrun hah.

BTW, did they bond all of your ground stuffs to your gas riser as well? Of my two ground rods, one is clamped to the home-side of the gas riser (the house-side of the gas meter). From the clamp, there's copper going to a clamp that is affixed to the ground rod that is sticking up from the soil/grade about 5 inches.

Part of me is like... wtf why would you want to direct electricity to the one thing that PG&E keeps thinking will explode? But then I'm thinking all this is a load of BS since my disconnects will protect me.

Yes, as NEC requires and @wwhitney points out, there is a dielectric union on the gas entry, and to be complete, yes, bonds across the hot water heater to the gas, just in case. I believe that the latter are targeting at grounding any potential home AC from getting into water.

And to complete the belt and suspenders, there is a whole house surge protector in the main service panel, connected to the same ground MSP and solar ground rods and grounding system.

I do wonder about ground loops in the soil with respect to grounding sub-panels, but I am not an expert. There is already a soil ground loop from the transformer ground to the house grounds. Would grounding and bonding neutral to ground (and ground rods) in sub-panels make it worse? Would that help clamp EMP transients from lightning strikes? Semiconductors aren't very tolerant of voltage transients.

Isn't there a requirement for the tops of lightning ground rods to be buried? (So as not to create sharp electric fields off of the edges?)

All the best,

BG

 

[holeydonut]

Isn't there a requirement for the tops of lightning ground rods to be buried? (So as not to create sharp electric fields off of the edges?)

County inspector actually thought the ground rods were too close to the gas riser (Sunrun had put both within 6 inches of the riser) and asked them to relocate about 12 inches away. He didn't say anything about the ends sticking up.

I still don't understand how a MSP located within 36" from a gas riser =
But funneling a potential lightning strike down within a foot of the same gas riser =

And no weep holes =

 

[BGbreeder]

County inspector actually thought the ground rods were too close to the gas riser (Sunrun had put both within 6 inches of the riser) and asked them to relocate about 12 inches away. He didn't say anything about the ends sticking up.

I still don't understand how a MSP located within 36" from a gas riser =
But funneling a potential lightning strike down within a foot of the same gas riser =

And no weep holes =

Code rules are written by committees of experts, with inputs from others, but at the end of the day, human beings. Generally, the code rules have made homes safer; less likely to fall down, electrocute you, gas you with sewer vapors, or give you typhoid. But that doesn't mean perfect, nor does it mean logical.

And those ground rods are really there to ground stray voltages generated in your system. If you want lighting system, it is a whole different ball game. That 4ga, or whatever you have doesn't cut it for lightning, which is more more on the order of 1/2" or more in diameter, with much more elaborate grounding systems in many soils. Fortunately, lightning strikes are pretty rare in California, relatively speaking, the 2020 lightning blitz notwithstanding.

All the best,

BG

 

[ptdusn]

Code rules are written by committees of experts, with inputs from others, but at the end of the day, human beings. Generally, the code rules have made homes safer; less likely to fall down, electrocute you, gas you with sewer vapors, or give you typhoid. But that doesn't mean perfect, nor does it mean logical.

And those ground rods are really there to ground stray voltages generated in your system. If you want lighting system, it is a whole different ball game. That 4ga, or whatever you have doesn't cut it for lightning, which is more more on the order of 1/2" or more in diameter, with much more elaborate grounding systems in many soils. Fortunately, lightning strikes are pretty rare in California, relatively speaking, the 2020 lightning blitz notwithstanding.

All the best,

BG

I wholly agree @BGbreeder, when I worked on high powered (40kW and 85K plate voltage) transmitters in the Navy, they had a lot of grounding straps all over the place to alleviate stray voltages.

 

[holeydonut]

County inspector actually thought the ground rods were too close to the gas riser (Sunrun had put both within 6 inches of the riser) and asked them to relocate about 12 inches away. He didn't say anything about the ends sticking up.

I still don't understand how a MSP located within 36" from a gas riser =
But funneling a potential lightning strike down within a foot of the same gas riser =

And no weep holes =

Exhibit W on why I am the dumbest-ass-MF-er on TMC. @jjrandorin, can I change my forum username to DAMF? Or is that considered profanity?

It turns out the grounding my installer did is not a compliant install for whatever PG&E requires on grounding near a gas riser.

A county inspector made the installer re-do their original grounding rods. I remember clearly the conversation where the inspector, 2 dudes with a hammer-drill and grounding rods, and me are staring at my goddamn gas riser listening to the inspector tell us clamping leads coming off the rods to the riser is mandatory and standard for all PV+ESS installs in CoCoCo. The inspector said the actual grounding rods penetrating the ground had to be spaced away from the riser, but this clamp was needed.

I don't understand wtf all this means. Why would the CoCoCo inspector tell them to do something that PG&E is literally telling me is now disallowed????

@Vines , have you ever seen this letter before? Probably not... because you guys actually do good installs. And PG&E doesn't come by your customer's house all the time making sure the big beefy 200A disconnect is still on the goddamn wall.

@BGbreeder what is this dielectric Union thing again? Like is it good or is it bad?

I welcome any user on TMC to please post that they've ever dealt with ANY OF THIS GODDAMN CRAP ON THEIR SOLAR INSTALLS. WHYYYYYYY

 

[jgleigh]

Isn't the metal gas pipe touching the ground? SMH

 

[Vines]

Exhibit W on why I am the dumbest-ass-MF-er on TMC. @jjrandorin, can I change my forum username to DAMF? Or is that considered profanity?

It turns out the grounding my installer did is not a compliant install for whatever PG&E requires on grounding near a gas riser.

A county inspector made the installer re-do their original grounding rods. I remember clearly the conversation where the inspector, 2 dudes with a hammer-drill and grounding rods, and me are staring at my goddamn gas riser listening to the inspector tell us clamping leads coming off the rods to the riser is mandatory and standard for all PV+ESS installs in CoCoCo. The inspector said the actual grounding rods penetrating the ground had to be spaced away from the riser, but this clamp was needed.

View attachment 961258

I don't understand wtf all this means. Why would the CoCoCo inspector tell them to do something that PG&E is literally telling me is now disallowed????

@Vines , have you ever seen this letter before? Probably not... because you guys actually do good installs. And PG&E doesn't come by your customer's house all the time making sure the big beefy 200A disconnect is still on the goddamn wall.

@BGbreeder what is this dielectric Union thing again? Like is it good or is it bad?

I welcome any user on TMC to please post that they've ever dealt with ANY OF THIS GODDAMN CRAP ON THEIR SOLAR INSTALLS. WHYYYYYYY

View attachment 961256

View attachment 961257

Oh you get all the fun attention! I'll bet Alex the meter tech knows your house by sight! Its always fun to talk about the EGC, the GEC and the grounding electrodes.

Down to brass tax:
Basically they don't want your electrical system to be grounding through their gas line. There are reasons why you might have an issue with the gas line, such as if your existing grounding electrode system isn't working great and has a larger than 25 ohm resistance to ground. Then they go to replace the meter and get shocked, and there may be a gas ignition event.

What is good to make sure is that the customer side metal piping (gas water and electrical conduit) is all bonded together and then connected to the grounding electrode system at one point through the grounding electrode conductor (GEC). The grounding electrode system is usually a ground rod or a concrete-encased electrode (ufer) or a combination of this and other types all bonded together just above the grade level. The grounding electrode is basically a big connection to the earth.

You want one equipment ground system in your house so all metal is equipotential and connected to the equipment grounding conductor (EGC). Then in and under the dirt you want one grounding electrode system consisting of all the things touching the dirt, and could potentially return current to the source. The GEC is the single wire that connects those 2 systems.

So now the issue is that if your house gas piping becomes your only grounding electrode, the current will try to through the gas meter from the new ground clamp. However, there are usually fittings there (dielectric) designed to insulate the metal of the house side of the gas pipe from the metal of the PGE equipment through the gas meter. If the current starts flowing somehow anyway, it can massively accelerate corrosion so you do not want the gas meter side stuff to become part of the ground electrode system or to have current flowing through it.

Wires at the Gas Meter - IM Home Inspections

This practice in the field is very dependent on the inspector but the typical practice is to bond hot, cold and gas piping at the water heater, and then to connect the main incoming city water line to that same bond, and to the service panel depending if there is PVC piping in the house between the service and the rest of the home plumbing system.

So basically your inspector and or installer doesn't really understand this requirement as well as they should and PGE does. The clamp should be right up against your house gas line or even better continues at the hot-cold-gas bond to the service panel.

 

[miimura]

I saw the PG&E gas service being installed at my house while it was under construction. Two interesting things:

1. There is a specially trained guy who welds onto the pipe in the street, under full pressure, to provide a tap for a new gas service. Yes, gas is spewing out of the pipe the whole time. He has special breathing apparatus and the whole hole is full of gas, so there's no oxygen and the gas doesn't ignite while the arc welder is going.

2. The gas service line between that tap in the street and the meter is some kind of plastic, not metal. There is also a metal tracer line that is buried with the plastic pipe so they can trace it. There are also very specific fill materials that have to be used around the gas line before you back fill the trench with native soils.

 

[BGbreeder]

@holeydonut "Yeah, what he said." @Vines summed it up beautifully. PG&E is on the issue correctly here in my view.

You should have grounds across your water heater, down to the gas line there, and a wire run back to the house ground rod near/by the main service panel which is grounded at that point as well. In an ideal world, everything else, the phone line, your cable, internet and your whole house surge protector grounds are all bonded at that same point. IIRC, code now requires two ground rods spaced at least 6' apart, but notes farther is more effective. The NFPA 780 wants it farther apart than the length of the grounds. I don't know about the spacing from an Ufer connection (grounding via the rebar in a concrete foundation, a far more effective ground for a variety of reasons). Books have been written about effective grounding, and in locations with frequent rainfall, and damp soils, it generally isn't much of an issue. Dry soils, and soils with complex chemistry can be remarkably poor grounds, without additional actions.

@Vines, @wwhitney is it true that the current NEC doesn't require a ground rod if an Ufer ground is used?

I think that the partially buried wire and clamp is probably PG&E's dielectric anode to keep the gas line from corroding. While newer lines are plastic as @miimura points out, older lines are not.

Your CCC inspector seems not only not to understand this part of the code, but also not to understand the theory behind the code. Presumably, as you have passed the CCC code inspection, PG&E's request can be attended to without finger pointing.

Good luck.

All the best,

BG

 

[holeydonut]

Oh you get all the fun attention! I'll bet Alex the meter tech knows your house by sight! Its always fun to talk about the EGC, the GEC and the grounding electrodes.

Down to brass tax:
Basically they don't want your electrical system to be grounding through their gas line. There are reasons why you might have an issue with the gas line, such as if your existing grounding electrode system isn't working great and has a larger than 25 ohm resistance to ground. Then they go to replace the meter and get shocked, and there may be a gas ignition event.

What is good to make sure is that the customer side metal piping (gas water and electrical conduit) is all bonded together and then connected to the grounding electrode system at one point through the grounding electrode conductor (GEC). The grounding electrode system is usually a ground rod or a concrete-encased electrode (ufer) or a combination of this and other types all bonded together just above the grade level. The grounding electrode is basically a big connection to the earth.

You want one equipment ground system in your house so all metal is equipotential and connected to the equipment grounding conductor (EGC). Then in and under the dirt you want one grounding electrode system consisting of all the things touching the dirt, and could potentially return current to the source. The GEC is the single wire that connects those 2 systems.

So now the issue is that if your house gas piping becomes your only grounding electrode, the current will try to through the gas meter from the new ground clamp. However, there are usually fittings there (dielectric) designed to insulate the metal of the house side of the gas pipe from the metal of the PGE equipment through the gas meter. If the current starts flowing somehow anyway, it can massively accelerate corrosion so you do not want the gas meter side stuff to become part of the ground electrode system or to have current flowing through it.

Wires at the Gas Meter - IM Home Inspections

This practice in the field is very dependent on the inspector but the typical practice is to bond hot, cold and gas piping at the water heater, and then to connect the main incoming city water line to that same bond, and to the service panel depending if there is PVC piping in the house between the service and the rest of the home plumbing system.

So basically your inspector and or installer doesn't really understand this requirement as well as they should and PGE does. The clamp should be right up against your house gas line or even better continues at the hot-cold-gas bond to the service panel.

Lol my feeble brain is literally unable to comprehend half of what you posted.

So if that bonding clamp is relocated (see picture below) then everything is ok? Or does this bonding clamp need to be completely removed?

I have two 8' grounding electrodes (they just don't appear in the picture). They are about 5' apart. One of these has the hot water heater connected to it via a long run of copper. And the other grounding rod is connected to some leads comes off the TEG gateway and my MSP. Sunrun neutral-bonded-to-ground on both my TEG2 and MSP... then just connected that common ground to one of those 8' rods.

But both of these rods are then spliced into the gas riser per my pic.

@BGbreeder that little hook-thing wire attached to the riser is a tracer wire. It's supposed to help people know where the actual gas pipe is so they don't spike one of those 8' grounding rods through my gas line I guess lol.

 

[BGbreeder]

Lol my feeble brain is literally unable to comprehend half of what you posted.

So if that bonding clamp is relocated (see picture below) then everything is ok? Or does this bonding clamp need to be completely removed?

I have two 8' grounding electrodes (they just don't appear in the picture). They are about 5' apart. One of these has the hot water heater connected to it via a long run of copper. And the other grounding rod is connected to some leads comes off the TEG gateway and my MSP. Sunrun neutral-bonded-to-ground on both my TEG2 and MSP... then just connected that common ground to one of those 8' rods.

But both of these rods are then spliced into the gas riser per my pic.

@BGbreeder that little hook-thing wire attached to the riser is a tracer wire. It's supposed to help people know where the actual gas pipe is so they don't spike one of those 8' grounding rods through my gas line I guess lol.

View attachment 961292

Your little note from PG&E makes it look like the green circle would not be acceptable. The online Green Book site says at least 36" from the meter;

https://www.pge.com/pge_global/common/pdfs/services/building-and-renovation/greenbook-manual-online/j-15.pdf

Sorry for being complicated; what should I explained better? I'm happy to try.

All the best,

BG

 

[holeydonut]

Your little note from PG&E makes it look like the green circle would not be acceptable. The online Green Book site says at least 36" from the meter;

https://www.pge.com/pge_global/common/pdfs/services/building-and-renovation/greenbook-manual-online/j-15.pdf

Sorry for being complicated; what should I explain better?

All the best,

BG

I'm super confused now... because earlier in this thread it seems like there was agreement where somehow connecting my grounding rods to the natural gas riser and water line was supposed to be some dielectric union. That seemed to correlate with what the Contra Costa County inspector was trying to say when he made Sunrun add some extra leads/clamps connecting my grounding rods to this gas riser.

But then PG&E is telling me I cannot affix any of these clamps on their natural gas equipment.

So where am I supposed to form this dielectric union? Like do I need to find another way to get to the underground gas pipe other than this stuff sticking out of the ground? Like where would I go to be 36" from the riser but still accomplish what the County inspector wanted?