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I would like to add a disconnect to the outside of my house. The idea is to be able to disconnect utility power for first responders or if I'm working on upgrading my main panel. I'm planning to ask the utility (PSE&G) to de-energize the underground feed at the transformer two houses down, or pull my meter. I would prefer that they disconnect it at the transformer in case I need to run new wires from my meter pan. I included a picture of the transformer which I think shows 6 houses being fed from it.

The image below shows my current setup. Underground feed into my utility meter, then a piece of SER to another meter pan that has a Tesla Backup Switch. On the load side of that meter pan is a piece of SER that is feeding the panel inside. The EMT that you see to the right of the Backup Switch is going down to the Tesla Powerwall and up to a tap inside my main panel.

I'm thinking that the easiest way to add an emergency disconnect is by replacing the meter pan that has the Tesla Backup Switch with a small meter/main combo. But it can't be any wider than the current Millbank meter pan(11"), since there is conduit on both sides. I don't think I need any circuits outside (since they would not be backed up), so I only need a 200A breaker. I could put a SPD in that panel.

I'm a bit unclear about the difference between an emergency disconnect and a service disconnect. If it is labeled as an emergency disconnect, do I not need to ground the enclosure and only run 3 conductors to my main panel inside?

Any suggestions how to clean this up and add a disconnect?

Thanks

Edit: I added a single line drawing showing where the disconnect would go. I'm leaning towards adding a separate disconnect instead of a meter/main combo to replace the Tesla Backup Switch based on suggestions below. Single Line Drawing Overview of utility meter and Tesla equipment Closeup of utility meter and backup switch Transformer

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    It isn't clear what/where you want to disconnect. Cut off between PG&E and the Tesla switch? Cut between the switch and the indoor panel?
    – Greg Hill
    Jan 24 at 23:13
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    @GregHill I clarified my question above. I want to have a way to disconnect utility (PSE&G) power, as mentioned in section 230.85 of the NEC. Jan 25 at 2:37
  • @GregHill PSE&G is in NJ, PG&E is in CA :) Jan 25 at 3:13
  • @ThreePhaseEel Yes, it is very confusing. I used to live in PG&E territory, it took me over a year to not mess up PSE&G. Jan 25 at 14:35

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It looks like the load side of the meter is running into your backup power box, where there is a switch that connects it directly to your breaker panel normally. Then, when your utility power goes out, it opens that connection and connects your breaker panel to the backup power. (The open connection between the utility power and the breaker panel prevents your backup power from traveling backward through the meter and powering the other 5 houses.)

If that is how it is connected, you can just install a disconnect on the wire that connects the load side of the backup system to your breaker panel. Then everything would still work exactly as it does now. But when the disconnect is turned off, there will be no path between the utility power or the backup power and your breaker panel.

I am not suggesting that the disconnect be located here. This is just the place in the circuit that looks like the the best place to disconnect your breaker panel from all power sources. That is, assuming it is wired as I described above.

This can be done safely with your meter pulled or disconnecting you from the transformer, if that is what you prefer and the power company will disconnect and reconnect in a timely manner. No changes will be made inside meter enclosure.

enter image description here.

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  • Yes, you are correct, the Tesla Backup Switch is just a switch that allows my panel to be disconnected from the utility. It is not a transfer switch that switches between two inputs (solar and utility, or generator and utility). I think putting in a disconnect switch below the Tesla Backup Switch makes sense. This way I don't have to rewire the utility meter pan. Feb 8 at 20:00
  • I added a single line diagram to my post above to show where the disconnect switch would be as indicated in your picture Feb 15 at 1:22
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I don't think any utility is going to cut power for multiple houses so you can do non-critical work when they can pull the meter for almost any work you need, including replacement of the main panel, installation of battery backup and solar, etc. The standard thing is:

  • Pull the meter
  • Do the work
  • Put the meter back in. In many cases the utility will let an electrician do this, whether they will let a homeowner do it may vary, but if anyone other than the utility does it, the utility will come back later to tag it for security.

The only real reasons I can see, other than emergency maintenance on utility feed lines or the meter base, for cutting power farther up the line are:

  • Heavy-up, as that routinely (but not always) requires replacement of the utility feed to the meter.
  • Replacement of the meter base, particularly with a meter main to provide a disconnect.

You don't need a heavy-up. You want to install a disconnect, though you probably don't need to do so because these things are normally grandfathered until related work is done.

The usual go-to is a meter main. By definition, that becomes the true main panel, including the neutral-ground bond and excluding any neutral-ground bond elsewhere. A true separate disconnect (whether called an emergency disconnect or a service disconnect probably doesn't matter much) does not have that bond and would not become the main panel.

But you have some real complications here. In particular, you have two meter bases - one for the actual meter and one for the Tesla Backup. Ideally you would have only one, and it would be combined with the disconnect that you want. Which, if that can be done with your configuration and your utility, gives you twice the space to work with because one large box would replace two smaller boxes.

My recommendation is to talk to the utility first about:

  • What meter mains are allowed - some utilities have short lists, some have long lists, some have specific requirements but not specific models - but you need to know your options before you buy anything.
  • Whether you can combine a meter - in the right type of meter main - with the Tesla Backup Switch.

These aren't so much technical issues as policy issues. Each utility has its peculiarities, for a variety of reasons - some based on practical or technical concerns, some based on utility history, some for no apparent reason at all. But you have to play by their rules very carefully because otherwise you may find they won't reconnect you until you tear out and replace everything, which would not be a good thing.

One more very important thing to consider is backup disconnect. Not as in "yet another way in case the main way doesn't work" but rather "disconnect that disconnects both the utility feed and the backup power supply". If you have a fire or other serious damage and first responders want to cut power, they want to make sure ALL POWER is off. If cutting off the utility feed means the Tesla Backup automatically kicks in, you haven't really solved the problem from the first responder safety perspective. There are likely some simple solutions since every house with a battery backup or standby generator will have this issue. But it is important to consider it as part of any "disconnect" installation before buying any hardware.

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    I edited my post and added a picture of the transformer. You can see it feeds 6 houses on the secondary, so I think they can just disconnect me. They will let me as a homeowner pull the meter, but I prefer not to do that. I agree that having one meter main with utility meter and Tesla disconnect would be ideal. Two issues with that: PSE&G does not allow the Tesla Backup switch behind their meter, and I've asked the utility about approved meter mains and have not gotten anything back. Others have told me that they don't like Meter Mains. Hence my question about changing the other meter pan Jan 25 at 14:39
  • They don't allow Tesla Backup Switch behind their meter - that's annoying, but they set the rules and I can see some rational reasons for that particular rule. I suspect a lot of people who don't like meter mains are in the same group of people (which is a large group) who wouldn't dream of putting in a disconnect unless required. But key question is since the idea is to have a functional disconnect is to figure out how it will all work with Tesla, etc. Figure it out conceptually and then we can (hopefully) figure out how to do it in terms of actual wires & boxes of equipment. Jan 25 at 15:02
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I'm thinking that the easiest way to add an emergency disconnect is by replacing the meter pan that has the Tesla Backup Switch with a small meter/main combo. But it can't be any wider than the current Millbank meter pan(11"), since there is conduit on both sides.

That's not going to work. #1 nobody makes a meter-main that narrow. UL's contemporary wire-bending-space rules are certainly the reason. #2 it will put the emergency disconnect on the wrong side of the isolation switch, unless you wire the thing upside down and backwards LOL.

The right answer is to replace the actual meter pan with a meter-main.

Replacing meter pans is no big deal, happens all the time. In fact, in NEC 2023, it's a requirement anytime you upgrade the service panel. So it's pretty straightforward, they're going to disconnect your 2 hot wires there at the distribution block on that transformer, or in a handhole in someone's lawn. No one else will be affected. And that meter pan doesn't owe you anything, probably half rusted out anyway. Looks like a 100A pan and I'm sure you'd love to have a 200A pan. (that won't let you go 200A just yet, but it'll position you to be 200A ready).

Now if your heart is set on replacing the meter pan being used by the Tesla isolation switch, then okay. Start by displacing the solar disconnect up and to the right. The wires inside that existing conduit on the left of it should be able to reach. That will also eliminate the goofy U-shaped conduit coming out the bottom of it, you'll be able to go straight into the side of the Tesla inverter. These wires are not huge, they're probably #8 or #6 copper. Just make sure you're on the AC side of the solar - if those are raw DC wires you need to take special precautions.

The fact that you have a disconnect outside does not necessarily make that your main breaker, nor make your main panel a subpanel or rearrange grounds or any of that. You can make a main disconnect NOT the main breaker, simply by labeling it as such, per 230.85(2) or (3).

But the way I see it, an emergency disconnect should disconnect everything, not leave the PowerWall connected to the utility side. This is the folly of making the right "meter" pan into the disconnect, unless (as I say) you wire it backwards and what, install the isolation switch upside down? You can only do that if the labeling and instructions says you can do that.

Lastly, I wouldn't discount a "trailer/ranch panel" which has a meter, main, 8 breaker spaces, and "thru lugs" to carry power onward. I know you think "well then it won't be on the PowerWall" but the PowerWall CAN'T run everything. Things that are just not a priority like a hot tub, dryer, EV charging*, resistance water heater**, etc.

* For a second EV, or really, we don't know how Vehicle to Home is going to develop. Ford's experiments suggest a DC-coupled system for home power, and AC-coupled for routine charging, which could go to the utility side.

** Using solar/battery to run a resistance heating element isn't even stupid. Water heaters can store heat for at least 12 hours, or get a heat pump water heater if your heart is set on it being on battery.

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  • The Tesla Backup Switch is just a switch that allows my panel to be disconnected from the utility. It is not a transfer switch that switches between two inputs (solar and utility, or generator and utility. So putting a disconnect switch between it and the main panel disconnects my main panel, and the Powerwall+PV, since those are connected in my main panel. Leaving the Tesla Backup Switch connected to the utility (upstream from the disconnect) should be fine since it is just an open/close switch. Utility does not allow meter/mains, just straight meter pans (which they supply). Feb 8 at 20:04
  • @ChristianK That's why I called it an isolation switch (DPST) and not a transfer switch (DPDT). "Isolation switch" the proper/generic name for what the Tesla Backup Switch is. Sounds like you assumed I had that wrong, etc. etc. "So putting a disconnect switch between it and the main panel disconnects my main panel, and the Powerwall+PV, since those are connected in my main panel." Exactly why a meter-main as dock for the "Tesla Backup Switch" is not a good idea. Unless you run power through it backwards, utility -> main -> meter pan -> house. Would the TBS support that? Feb 9 at 0:17
  • Thanks for clarification on the terminology of isolation switch vs transfer switch. I added a single-line diagram to my post above. I'm now thinking I won't do a meter-main for the Tesla Backup Switch, but just add a 200A breaker enclosure as disconnect switch between Tesla Backup Switch and main panel. Do you see any issue with the Tesla isolation switch not being disconnected from utility power by the emergency disconnect switch? Feb 15 at 1:21
  • @ChristianK yeah, I prefer the generic name for a thing. As long as the backup/iso switch's instructions allow installation before any breakers, then the only downside is you won't be able to service it without a meter pull, although being a "meter collar style" installation that's not so much of a burden. Feb 17 at 19:42

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