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Can I replace my whole PV or PV/ESS system with a new one that exports up to 1kW more than my existing system? Or am I stuck with (uncontrolled PV inverters that can export up to 1 kW more than the existing system) plus (controlled PV inverters that never export)? Can the Backup Gateway...

Seems not directly related to me, the CTs just have to placed to see the appropriate current for the system to be able to offset the desired load. While the above is true, it's a side effect of the resistance between the CT location and the ESS. In that if the CT sees net current to the grid...

Yes, and this happens seamlessly. In that the system is likely not measuring the voltage at the left where it's 240V, and if it is doesn't use that as part of its control algorithm; the ESS just sees that its terminal voltage rises as it tries to push out more current, and the ESS always...

You seem industrious enough to find the California state law section that codifies what I said. Hand them a copy and tell them they are full of it. Cheers, Wayne

I'm still around, I'm just not spending much time browsing all the new threads to find the ones that have interesting electrical questions. Feel free to tag me on such threads to get my attention. I expect you know this and are speaking tongue-in-cheek, but your contractor has an affirmative...

Installation of exposed electrical cable (be it on the utility side of the service disconnect, or the house side) is allowed under the NEC unless it is "exposed to physical damage". Much of the US (most of the East, I think) considers an install like that not to be "exposed to physical damage."...

I get 124 kWh, using 1 gallon of LPG has a heat content of 84,950 BTUs, and 1 kWh = 3412 BTUs. https://en.wikipedia.org/wiki/Miles_per_gallon_gasoline_equivalent But that's a theoretical number, you could only make that conversion if you had a fictious 100% efficient LPG generator. If your...

If you actually have Single Wire Earth Return, that's pretty rare these days. Hopefully the distribution in your area will be updated some day. Cheers, Wayne

OK, I agree that the sentence I wrote "There is only one phase present in this configuration, and any two voltages you can measure are in phase with each other" is not standard usage. Rather I should have said "any two voltages you can measure are scalar multiples of each other." Generally "in...

I will agree that you would call the two waveforms 180 degrees out of phase, or negative, or something equivalent. But my point is that those two waveforms only form one "phase". Otherwise, you'd never have single phase, as if I give you two wires A and B, the voltage waveforms A-B and B-A...

Not sure about this part, it varies, but I would be surprised if it is as low as 700 VAC on the primary side of the first transformer upstream of your house. I would think 2.4 kV would be a more likely minimum. But my familiarity with this part of the utility network is limited. Basically...

No, that's not correct. A phase is a collection of possible voltage waveforms that are scalar multiples of each other. If I give you a 2-wire supply, with an autotransformer (a coil with multiple taps along its length) you can get as many different voltage waveforms as you like, but they will...

In the first case, 3 wires line side and load side. In the second case, 3 wires line side and 4 wires load side. Cheers, Wayne

To expand on this, both panels U and W in the diagram should be so labeled. And they should both be outside as specified. If for some reason U was not installed, and W is outside, and the "(E) Distribution Panel Left" is inside as I understand it to be, that would be 230.72(A) violation. On...

Is the multi-line diagram you posted accurate? https://teslamotorsclub.com/tmc/threads/installation-is-starting-8-pw-and-12-solar-panels.287981/#post-7255056 If not, please post a corrected mutli-line diagram in this thread. Also, please identify for each piece of equipment on the diagram...

Ah, I see now, it's to combine the two PV sources so that a single AC disconnect for the solar may be installed, which may be something your POCO (power company) requires. If you had only (1) PW+ and (2) PW2s, then you wouldn't need the 125A load center, but you'd use two more spaces in your...

No. Note that your (E) loads are not moving, they are still in the 200A service panel. The new 30A and 100A double pole breakers in your existing 200A service panel are for connecting the new power sources, not any loads. The new 125A Load Center is just a combiner panel for two of those...

Agreed for sure. But for an existing house that is on-grid, if one legally could disconnect from the POCO, it is easy to test the viability. Just install your system that is designed to be 100% grid-independent, and keep it grid connected as a backup for a year. That will generate lots of...

If you really needed to run conduit across that 36" radius circle, you could of course run it concealed in the wall. Open up the siding, sheathing and WRB, install the new wiring through the studs, and repair the same. Or depending on what's happening on the inside of the wall, do it from the...

Actually, I can easily imagine that: ROI NEM2.0 PV only = positive ROI PW given NEM2.0 PV = negative ROI together = positive ROI NEM3.0 PV only = negative ROI PW given NEM3.0 PV = positive ROI together = positive I.e. because the payoff for exporting PV power under NEM 3.0 is so much worse...

Yes. But that doesn't mean the service is 200A, it can be lower. No, that's a 100A double pole main breaker. So the existing service is 100A. Cheers, Wayne

When you have 2 sources (PW and PV) and 2 sinks (house and grid), then it is undefined which sources goes to which sink. All you can say is that the sum of the sources is equal to the sum of sinks. How the graph chooses to further assign the numbers is arbitrary. Cheers, Wayne

This is an artifact of how it is trying to present info and arguably a bug. In your second screenshot, you can see that before 9 a.m. where there is just a little solar, it is showing the solar on the bottom, and the grid above it, and it looks normal. For some reason after 5 p.m. when there...

Just a slight expansion on the above: I infer from your comment that Tesla has come up with a UL 3741 solution that is based on MCIs that limit substring voltage to 165V. But UL 3741 is much broader than that, it's a way to do a hazard analysis on the entire PV system, and there are many...

Say you have a generator with 120V receptacles, and the EGC on the receptacles is connected to the generator case, but there is no connection between the EGC/case and either circuit conductor. And you plug in a tool with a 3 prong cord that has an internal fault of one of the circuit conductors...

No. (1) its provisions only apply to transfer switches at or downstream of the service disconnect, not a transfer service upstream of the service disconnect, like the BPTM, and (2) for such transfer switches, the NEC just says that either you use a bonded neutral generator and transfer the...

Here's a little thought experiment that may be edifying: suppose we lived in a world in which the only conductive things are copper and people. Everything else is effectively an insulator, at least as far as conducting current through you. [Ignore the side questions this raises, like are there...

Again, ground is an unclear term here. The prohibition is on a second neutral-EGC bond, beyond the required neutral-EGC bond in the service disconnect enclosure that creates the EGC system. A path from a generator conductor to earth is only dangerous if there is another path from a different...

OK, ground is an overloaded term and I generally try to avoid it. It can mean the earth; the EGC (equipment grounding conductor); and it's part of the term for one of the circuit conductors, the grounded circuit conductor (neutral). Or upstream of the service disconnect, it can mean a "supply...

BGbreeder mentioned the idea. Yes, if the generator has an EGC-neutral bond. Maybe. I will elaborate in a followup as I don't want to run out of edit time. Cheers, Wayne

Typo on my part, the rest of the post still holds. Cheers, Wayne

I somewhat quickly reviewed this thread. I know no hands on experience with portable engine generators, but I don't see the point of having an earth rod connected at one. What fault scenario is improved by having an earth rod there, other than a direct lightning strike? As to using a...

Do you know if anyone has actually gotten this to work properly? It should work in theory, but requires both the PW and the PV inverter to be configured properly so they will play nicely with each other. Cheers, Wayne

OK, thanks. But the worst case technically is this: (a) In grid following mode (utility is up), the GW equivalent simply will not support CTs to track other solar inverters. So the PW3 charge behavior will ignore the other PV, you couldn't set it up to charge only from solar and count the 3rd...

What's the exact reference for this conclusion? I am doubtful, as it makes little sense technically. Cheers, Wayne

I believe that's only correct if the PW3 installation is in the context of expanding a PV system in excess of the greater of 1 kW or 10%. But if you had an existing PV system and you decided to just replace that inverter with a PW3 without adding panels, then that change wouldn't trigger loss...

Which pilot signal should be broken, control pilot or proximity pilot? I was thinking that breaking proximity pilot would be a bad idea, as I imagine (just based on the name, not studying the protocols) it might let the EV drive off with the cord still connected. Will breaking the control...

Because the NEC requires it. Any metal water pipe buried in the ground for 10' or more is a grounding electrode. All electrodes present have to be bonded together to become the premises grounding electrode system. Water pipe electrodes may not be the only electrode present, so 2 ground rods...

I'd suggest the denominator should be 14000, so just under 75%. Mine are in a passively conditioned basement, are 5 years old, and report 14019 and 13973. Cheers, Wayne

It's $800. The -$1,500 is a reduction in installation cost, not a bonus for being an existing customer. Cheers, Wayne

Given this: Then this is unnecessary, as the service neutral conductor is already earthed: But this part is very important, as each service disconnect initiates its own EGC, and that EGC system needs to be bonded to the neutral to function properly: Like any building with multiple...

Pretty sure yes in principle, and definitely yes in practice, as the bill just checks that the total export does not exceed the modeled PV production over the billing cycle. Yes, it seems to work fairly well. For me, when I've looked at the graphs, it tends to do max export at the start of...

If you have a metal water pipe that is underground for at least 10', and if it is continuous to inside the house, then you need to use it as an electrode by bonding to it outside or within 5' of its entering the house. [If the metal portion doesn't extend inside, it's a little ambiguous whether...

There is no such requirement in the adopted codes; the inspector made it up. Cheers, Wayne

A "dielectric union" is the opposite of a bond, it's a connection for gas or water that avoids electrical continuity while still letting gas or water pass through. A gas meter has a dielectric union so that the building gas piping is not connected electrically to any of the gas piping in the...

Nice write up above. But any current that flows on the grounding electrode system will always flow on all grounding electrodes, in inverse proportion to their impedances. That is, current takes all paths, not just the path of lowest impedance. The NEC requires that all grounding electrodes...

Maybe just run self-consumption for a year and see how the bills turn out? If you're a net zero kWh importer/exporter, then the only way you have a bill in dollars is NBCs and if you are net importer during peak. The more you are a net kWh exporter, the more you can afford to be a net...

Assuming your two years of data accurately covers both inverters and your house loads, you could download the data and calculate for each interval "PV generation - house loads" and find the max positive value of that. Because the issue with having too much PV behind the GW is that when the grid...

So, the issue is that in self consumption mode, the control algorithm doesn't pay attention to peak vs non-peak, and doesn't prioritize failures to self-consume to occur during non-peak? Do you know for sure that this peak grid draw behavior would result in greater dollar costs to you? As if...

Ohio still uses the 2017 NEC, which has a bit of a blind spot in the rules on protecting busbars (705.12(B)), as it does not address feed-thru lugs. I'm assuming that the lugs on the bottom are at the opposite end of the bus as the main breaker. If so, the above setup could allow excess...