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18kpv setup right?? can you feeder tap meter/main panel ?

I'm afraid I'm going to have to dip out of this thread until more concrete / easy to analyze data is supplied.

<Parts list>

That CSED is 200A bus bar. It's in the specs that you linked, contrary to what you had said. This means that you cannot have any breakers on the CSED other than 200A to the next device, or a feed-through lug to the next device.

View attachment 259855

The subpanel is 225A bus bar.

View attachment 259856

The standalone 200A may not be needed, but I'm not going to draw this out & reason it carefully, since it could be wasted work without knowing how close it is to how it's installed.

<Reply to Hedges>

I agree a schematic (one line would be better than the vague English thus far) would be helpful to share; it would also disambiguate what you're getting when you communicate with the electrician.

What does doing it "off the books" mean? Is he working for you under a permit that you pull?

A “tap” (which has a specific NEC meaning, that is different from English) can come at several places. If you take off the service conductors from the meter, that creates a new main panel.

That English can line up (vaguely) with one of the variants described above, and there are no red flags.

I guess the next step is for you to send us pictures of the installation & draw your own post-facto SLD. Backwards way to work IMO vs having it up-front. 18kpv is typically used with an interconnection agreement, and in California you used to need to provide an single line diagram (not sure if this changed with the recent simplifications).
Understood. Sorry, my fault on the CSED specs. He said it was 225 and I didn’t bother to check. However, only the 200a breaker is in there. The sub panel has a 225a bus. I will post pictures tomorrow of the completed project for feedback. The only change he made so far, was to use a 70a stand alone breaker instead of the 200a one.
 
I’ve attached some pics. There are (2) 200a breakers in the CSED. In the sub panel, the interlock is 200a / 70a, and there’s a 70a subpanel. Electrician will be over this evening to finish up some things, so I’ll try to figure out what his thinking is.
 

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Looks like he used the CSED like a Meter Main.
Is that new? Service cut and reconnected? Or just repurposed existing CSED and put new bezel over it?

Consider getting surge arrestor. I think that is now code for new/updated service.
Not sure if allowed in CSED with 100% rule; it isn't a load, but it would be another device.
Otherwise, one in big sub-panel and another in the sub-panel supplying inverter. Is that different brand, Siemens?
 
...

No reason to feed more amps through inverter than it can source. ...
I don't agree with this statement. The primary reason I selected the 18Kpv over a lesser model is because of its 200A pass through capability. It made for a much simpler installation, with no critical loads panel, etc.

I'm using a single 18Kpv as a whole-house backup system. The entire grid service runs through the inverter pass through, but when we have a grid outage we know we're limited to the 50A inverter output and we limit our loads, which basically means just don't try to use the electric clothes dryer or oven. The inverter handles all other backup loads just fine, including well pump, water heater, HVAC, microwave... and all of those listed can operate simultaneously. Not having to decide which loads to move to a critical load panel was important to me.

And I don't understand the need for the backfed interlocked breakers as discussed in this thread. Instead of a manual switchover why not use the automatic transfer switch capability of the 18Kpv? The OP had an opportunity to build this as a whole house automatic backup system as initially desired in the first post.
 
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If you happen to be powering excessive loads at the time of grid failure, the inverter would shut down.
Even if not, how do you become aware, so you don't turn on a heavy load?

Of course you probably can power those loads if not much extra. Dryer will draw about 25A on high, less on low. Oven may also be OK. Especially during the day.

You can use the transfer switch capability of 18kPV, but what if you need to dismount it for repair? Do you rewire to bypass it?
With backfed interlocked breakers you just throw them and power is only interrupted for seconds.

I suppose the 18kpv defaults to pass-through even if shut down, a normally-closed DPST relay inside?
My Sunny Island default to disconnected, normally-open relay. So I need the interlocked breakers and gave my wife instructions on switching them to restore power.

If yours defaults to normally-closed then not so important to have interlocked breakers.
 
If you happen to be powering excessive loads at the time of grid failure, the inverter would shut down.
Even if not, how do you become aware, so you don't turn on a heavy load?
All very good points.

I get a grid outage notification on my phone from the inverter. The utility also sends me a text within a few minutes of an outage starting. There's a very small probability that our loads might exceed 13.5 kW at the moment the grid goes down, but very unlikely.
Of course you probably can power those loads if not much extra. Dryer will draw about 25A on high, less on low. Oven may also be OK. Especially during the day.
Yes, the inverter can handle all the loads we have individually or in certain combinations. When we know we're in backup mode, we'll avoid using high current items mostly just to keep from depleting the battery bank (30 kWh - enough for two or three days for us). If for some reason my wife decided she just had to bake a cake right now, the system could handle it but I'd go throw the water heater breaker first.
You can use the transfer switch capability of 18kPV, but what if you need to dismount it for repair? Do you rewire to bypass it?
With backfed interlocked breakers you just throw them and power is only interrupted for seconds.
The inverter is wired into the house using EG4's recommended installation for a whole house system, which includes a 200A manual transfer switch and a 200A inverter disconnect switch. Those two devices let me switch back to grid-only operation and to isolate the inverter in case of service. The MTS is normally left in the inverter position and I let the inverter's ATS do its thing when needed. It switches over to EPS in 20ms.
I suppose the 18kpv defaults to pass-through even if shut down, a normally-closed DPST relay inside?
My Sunny Island default to disconnected, normally-open relay. So I need the interlocked breakers and gave my wife instructions on switching them to restore power.

If yours defaults to normally-closed then not so important to have interlocked breakers.
No, it defaults to open, no pass-through. The unit has to boot up and software has to decide to throw the bypass relays. The manual transfer switch mentioned above would be used in the event of an inverter failure to restore grid to the house.

One other thing I'll mention here, just to dispel misinformation about the 18Kpv - I noticed a comment earlier assuming that if there's a grid outage the OP's main panel branch circuits (e.g. hot tub) could continue to get backfed power from the inverter. That is not the case. If the 18Kpv does not sense grid energy on it's input, it will not backfeed power to its grid input. All backed up circuits need to be wired downstream of the inverter's load output.
 
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No, it defaults to open, no pass-through. The unit has to boot up and software has to decide to throw the bypass relays. The manual transfer switch mentioned above would be used in the event of an inverter failure to restore grid to the house.

Unfortunate. Given that it has 200A pass-through capability I would rather it defaulted to closed and relied on OCP in case of overload.

What I would like is a highly reliable transfer switch so refrigerators etc. go back to grid if inverter fails while I'm away.
A DPDT relay comes to mind, but there can be an issue with it drawing an arc and shorting grid to inverter output. Need separate switching mechanisms break before make, or knife type transfer switch. I imagine an unpowered dead-man mechanism operating the switch by springs or gravity.

As for loads, my inverter can control signal relays based on two SoC levels, surplus power, on/off grid, etc. so load shedding is possible.
 
Unfortunate. Given that it has 200A pass-through capability I would rather it defaulted to closed and relied on OCP in case of overload.

What I would like is a highly reliable transfer switch so refrigerators etc. go back to grid if inverter fails while I'm away.
A DPDT relay comes to mind, but there can be an issue with it drawing an arc and shorting grid to inverter output. Need separate switching mechanisms break before make, or knife type transfer switch. I imagine an unpowered dead-man mechanism operating the switch by springs or gravity.

As for loads, my inverter can control signal relays based on two SoC levels, surplus power, on/off grid, etc. so load shedding is possible.

Agreed. My plan for the case that we're traveling and the inverter fails is to have a neighbor walk over and throw the MTS. But that assumes I'm even aware that the inverter has shut down...
 
I don't agree with this statement. The primary reason I selected the 18Kpv over a lesser model is because of its 200A pass through capability. It made for a much simpler installation, with no critical loads panel, etc.

I'm using a single 18Kpv as a whole-house backup system. The entire grid service runs through the inverter pass through, but when we have a grid outage we know we're limited to the 50A inverter output and we limit our loads, which basically means just don't try to use the electric clothes dryer or oven. The inverter handles all other backup loads just fine, including well pump, water heater, HVAC, microwave... and all of those listed can operate simultaneously. Not having to decide which loads to move to a critical load panel was important to me.

And I don't understand the need for the backfed interlocked breakers as discussed in this thread. Instead of a manual switchover why not use the automatic transfer switch capability of the 18Kpv? The OP had an opportunity to build this as a whole house automatic backup system as initially desired in the first post.
Doh.. that’s what I was originally thinking and hoping for in a setup. And my thoughts were the same as far as just limiting loads when the grid is down. Oh well, it’s all done now. We did put all loads in a sub panel, so whole house is fed by inverter.

The 200a pass through confuses me. I understand I’m limited to 50a when the grid is down, but with grid up how does that work? Did I limit myself by having the the 18kpv run through a 70a breaker? We put the interlock switch inside the sub panel only for the purpose of isolating inverter if it were to crap out. I thought it was the same purpose as the manual transfer switch but cheaper.
 
70A x 80% = 56A continuous load can be supported by thermal/magnetic breaker without risk of nuisance trip.
If inverter supports 200A pass-through then a larger breaker could be installed.

I would want (and have installed a second sub-panel.) One has 200A main fed from grid, 100A backfeed (I've stacked 4x 6kW inverters.) The other has 70A main, 70A backfeed (limited by wire gauge feeding outbuilding.)

The one I'm working on will be 200A main, 100A backfeed and 100A main, 100A backfeed. Only 12kW of battery inverter, but PV inverters are AC coupled so their current is available as well during the day.

The bigger sub-panel normally fed from grid, the smaller normally fed from inverter as UPS.
I can manually set to backfeed larger panel and manage loads.
I want deadman automatic transfer switch for either the entire smaller panel or the refrigeration loads.
 
70A x 80% = 56A continuous load can be supported by thermal/magnetic breaker without risk of nuisance trip.
If inverter supports 200A pass-through then a larger breaker could be installed.

I would want (and have installed a second sub-panel.) One has 200A main fed from grid, 100A backfeed (I've stacked 4x 6kW inverters.) The other has 70A main, 70A backfeed (limited by wire gauge feeding outbuilding.)

The one I'm working on will be 200A main, 100A backfeed and 100A main, 100A backfeed. Only 12kW of battery inverter, but PV inverters are AC coupled so their current is available as well during the day.

The bigger sub-panel normally fed from grid, the smaller normally fed from inverter as UPS.
I can manually set to backfeed larger panel and manage loads.
I want deadman automatic transfer switch for either the entire smaller panel or the refrigeration loads.

With the grid up, and I run 100a load, am I tripping the 70a breaker? So I don’t have 200a pass through with the way it’s wired?
 
Yes, unless inverter carries part of it.

With 70A breaker you have 70A pass-through, except don't exceed 56A continuous.
What gauge wire, by the way.

Be sure to configure inverter for 56A maximum; then you can exceed 70A and not trip breaker, because inverter will pick up the extra current.

You may already have a peak-shaving setup, in which case it will try to provide up to 100% from battery, then will have to switch to 100% pass-through from grid when battery drained.

Short term you can address this with settings in inverter.
Long term I suggest making a list of loads, kW and kWh/day, and consider putting them on a separate panel.

Also see if some sort of priority switching is available. Would take a bit of hacking, but some dryers will operate as "air fluff" if power is removed from one leg. Possibly a CT at stove could disconnect heating element of dryer, without touching insides of appliances. Just some custom hardware packaged as extension cords. Or do your priority switching manually.
 
I need to see a simple line schematic to know what you've got, but I think yes, you have limited yourself to a 70A total house service whenever the inverter backfeed breaker is on, and all grid power is passing through the inverter to the sub panel bus.

And based on Hedges comments on sizing, the 70A breaker may not even be enough for the inverter output. Note that the inverter is capable of sustained surge loads (10 minutes) of 56 amps on battery, and 65 amps on PV.

I guess you can simply increase the size of the backfeed breaker. But of course you need to increase the size of the cabling accordingly too. I used 2/0 Cu for all of my AC wiring. Also, I'll bet that many people overlook the surge capability when sizing their battery cables. When including the 13.5 kW surge and the 94% inverter efficiency, your DC cables need to be sized for 280 amps.
 
There are rules related to the size of the backfeed breaker and the total bus load of your panel, which I'm not familiar with, so it's unlikely to be a solution as simple as increasing the size of the backfeed breaker and keeping within code requirements.

Based on your photos and the surface mounting that you have, I'd say it's not too late to reconfigure this system in a rational (to me ) way. Route the main panel output to the inverter grid input, and route the inverter load output to the input of the main breaker of your single sub panel. Omit the backfeed breaker. Add the MTS and disconnect I've mentioned to be able to isolate the inverter from the system when needed. Use the EG4 wiring diagram titled "Whole Home Backup using a Feeder Tap."
 
My house is configured the same as yours - with a meter and main disconnect outside and a main panel, with main breaker, inside. It was a simple matter for me to insert the inverter into the service entrance cable path from the outside disconnect to the inside main panel. I chose an inverter large enough to handle the entire house load without needing to worry about splitting off loads and adding multiple distribution panels. You have all the same parts as me. It seems like a no-brainer for you to change the configuration that was just installed.
 
There are rules related to the size of the backfeed breaker and the total bus load of your panel, which I'm not familiar with, so it's unlikely to be a solution as simple as increasing the size of the backfeed breaker and keeping within code requirements.


In this case, I don't think a backfeed breaker subject to 120% rule.

An interlocked "generator" breaker would be the only source feeding a panel, so OK up to 100% of busbar rating.

He would also have a breaker (or fuse) between grid/meter and inverter. If it was a breaker mounted in main panel then it would be subject to 120% or 100% rule. If line side tap then it wouldn't (that's what I've done).

In the event he has a main breaker panel with 225A busbar and 200A main breaker, 120% rule would allow 70A backfed PV breaker. But in this case, could have other loads on the panel too, not fed through inverter. I don't think this is the case, and all loads are on a sub-panel.

A 1-line diagram would give us something to discuss.

My house is configured the same as yours - with a meter and main disconnect outside and a main panel, with main breaker, inside. It was a simple matter for me to insert the inverter into the service entrance cable path from the outside disconnect to the inside main panel. I chose an inverter large enough to handle the entire house load without needing to worry about splitting off loads and adding multiple distribution panels. You have all the same parts as me. It seems like a no-brainer for you to change the configuration that was just installed.

In this case, not too difficult to add an "excessive loads" panel outside by the meter. Assuming things are accessible to stuff branch circuit wires into that new panel.
 
My house is configured the same as yours - with a meter and main disconnect outside and a main panel, with main breaker, inside. It was a simple matter for me to insert the inverter into the service entrance cable path from the outside disconnect to the inside main panel. I chose an inverter large enough to handle the entire house load without needing to worry about splitting off loads and adding multiple distribution panels. You have all the same parts as me. It seems like a no-brainer for you to change the configuration that was just installed.
And that’s how I envisioned the install, like the “whole home back using a feeder tap”. The discussion with the electrician (who is not familiar with 18kpv), went towards cost savings, by eliminating the MTS and using an interlock. We were originally going to use 200a breakers on both sides of the interlock, along with a 200a stand alone sub panel for the inverter. He changed it to 70a.

My meter/main disconnect outside is 200a w/ 200a bus. The sub panel inside is 200a w/ 225a bus.
 
And that’s how I envisioned the install, like the “whole home back using a feeder tap”. The discussion with the electrician (who is not familiar with 18kpv), went towards cost savings, by eliminating the MTS and using an interlock. We were originally going to use 200a breakers on both sides of the interlock, along with a 200a stand alone sub panel for the inverter. He changed it to 70a.

My meter/main disconnect outside is 200a w/ 200a bus. The sub panel inside is 200a w/ 225a bus.
Well, cost is a factor. The 200A MTS was not cheap (~$650), but considering how much money I spent on the entire system, the MTS was one of the cheapest components. I spent more just on the copper cabling.

I think your electrician did not understand that the purpose of the MTS is not for backup changeover like using a generator. The purpose is to isolate the inverter in the case of service or failure.
 

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