Help with grid-interactive EG4 18k config

[SignatureSolarJames]

So I’ve called these “heat pump hot water heaters” and did look into them, they’d be my second choice. I’m aware of the pros and cons of tankless electric and since I don’t have TOU and also pay 6.8c/kWh and also have 1:1 net metering and also want to save space I’m pretty set on the tankless electric.

Really would recommend heat pump, backup would be possible and overall they use less energy

 

[DaBeaver]

For residential installs the 320/400 amp service is typically installed with 2 separate 200amp main panels fed by one meter, and loads are distributed across these 2 panels and because there are 2 separate 200 amp panels the total load can be up to the 320 amp maximum.

In your particular case you could have the circuits for the tank less water heater and the EV changer, along with any other loads that don't need backup in one of the main 200 amp panels. The other 200 amp panel, will be fed thru the 18kpv, and will contain the loads you want backed up. The CTs are used, if desired, to limit power be sent to the grid from your solar and batteries, **but still use your solar or battery for loads on non backed up panel, the one with the water heater and ev charger, when the grid is available. The CTs will be placed close to the meter and around the wires feeding both the inverter, and the other 200 amp panel**.

This sounds like the right set-up. One 200A panel fed through the 18K, but the other can still be backed up by the 18k? How would that work? CTs detecting when the 18k has extra capacity to give to the other panel with a switch of some kind?

 

[Zapper77]

, but the other can still be backed up by the 18k? How would that work? CTs detecting when the 18k has extra capacity to give to the other panel with a switch of some kind?

Backed up, NO.

The CTs only work when the Grid is on. If/When the grid goes down your 2nd non-critical load panel goes down.

 

[DaBeaver]

Backed up, NO.

The CTs only work when the Grid is on. If/When the grid goes down your 2nd non-critical load panel goes down.

This is what I’d assumed would happen. It should be possible to wire a giant manual switch between the panels in case I really wanted the non-critical loads panel backed up though correct? Would probably want to cut the line to the grid at the same time if I ever activated such a thing

 

[Zapper77]

This is what I’d assumed would happen. It should be possible to wire a giant manual switch between the panels in case I really wanted the non-critical loads panel backed up though correct? Would probably want to cut the line to the grid at the same time if I ever activated such a thing

I assume for the EV charging you could reduce the charge rate, but does the Waterheater have a energy save mode or a flow reduction mode to allow lower demand?

 

[pvgirl]

This is what I’d assumed would happen. It should be possible to wire a giant manual switch between the panels in case I really wanted the non-critical loads panel backed up though correct? Would probably want to cut the line to the grid at the same time if I ever activated such a thing

Be sure to note a single 18kpv has a maximum AC output of 12kw or 50 amps, possibly limited to less by battery and/or solar size. When connected to the grid you can use power from solar up to the limit, supplemented by grid power up the full 200amp pass thru capability. If you want to run huge loads off grid, and not just provide limited back up during grid failures, you will likely need multiple 18kpv in parallel, and a large battery bank(also a big cost)

 

[DaBeaver]

I assume for the EV charging you could reduce the charge rate, but does the Waterheater have an energy save mode or a flow reduction mode to allow lower demand?

Yes

 

[DaBeaver]

Be sure to note a single 18kpv has a maximum AC output of 12kw or 50 amps, possibly limited to less by battery and/or solar size. When connected to the grid you can use power from solar up to the limit, supplemented by grid power up the full 200amp pass thru capability. If you want to run huge loads off grid, and not just provide limited back up during grid failures, you will likely need multiple 18kpv in parallel, and a large battery bank(also a big cost)

I did consider multiple 18k, but for now it shouldn’t be necessary, 30kWh of server rack batteries usually have 30kW available though, would it be possible back up the other panel exclusively from the batteries with some manual switching and a dedicated single-function inverter?

 

[Zapper77]

I did consider multiple 18k, but for now it shouldn’t be necessary, 30kWh of server rack batteries usually have 30kW available though, would it be possible back up the other panel exclusively from the batteries with some manual switching and a dedicated single-function inverter?

Assuming Your other panel only includes the EV charger and Hot Water, right?

 

[pvgirl]

I did consider multiple 18k, but for now it shouldn’t be necessary, 30kWh of server rack batteries usually have 30kW available though, would it be possible back up the other panel exclusively from the batteries with some manual switching and a dedicated single-function inverter?

A single 18kpv will only output a maximum 12kw of AC even if the battery has more capacity. Not to mention if your pulling large loads from your battery 30kwh isn't going to last long.

 

[DaBeaver]

Assuming Your other panel only includes the EV charger and Hot Water, right?

Yes

 

[DaBeaver]

A single 18kpv will only output a maximum 12kw of AC even if the battery has more capacity. Not to mention if you’re pulling large loads from your battery 30kwh isn't going to last long.

Right, that’s why I’m positing a second much less fancy but much more powerful inverter. I’m not sure if such a thing exists though. Re battery math, I have a very good intuitive sense of it, batteries are the part of the system I’m most familiar with.

 

[Zapper77]

Right, that’s why I’m positing a second much less fancy but much more powerful inverter. I’m not sure if such a thing exists though. Re battery math, I have a very good intuitive sense of it, batteries are the part of the system I’m most familiar with.

EV batteries come in a wide range of sizes.
33 kWh all the way up to 200 kWh

 

[1201]

@DaBeaver just leave the water heater off solar. They demand is too high to be on solar and will be very expensive long term

 

[DaBeaver]

EV batteries come in a wide range of sizes.
33 kWh all the way up to 200 kWh

Yes, I’m also very familiar with EV battery sizes (and energy math in general, I made a custom button on my iPhone calculator to convert BTU to kWh and vice versa as I did that conversion a lot), not planning on getting a Hummer EV but maybe a dual motor cybertruck (for which I have a reservation), I guess the dual motor CT will have a 110-120 KWh battery.

 

[DaBeaver]

Thank you everyone in this thread for such quick, knowledgeable, helpful responses?. I’ve been part of quite a few forums and this is the most helpful, high-quality set of responses to a noob (me) that I’ve yet experienced.

I’m going to go with 2x 200A panels and feed the main house panel through the 18K, the Electric tankless water heater will be slightly de-rated to make it all work.

 

[y0bailey]

Using CTs on your main feed will allow the 18Kpv to provide maximum power towards all connected loads. I'll draw a quick napkin diagram.

View attachment 173685

Just found this thread, and my setup will be similar with a 320/400A service with two 200A breaker/disconnect panels by the meter. I will be running my "basement" 200A panel with the 18kpv. I cannot get my CT's into my meter without cutting the little "safety clip", so I'm just leaving them in the inverter right at the GRID connection.

I do have net metering so I'm assuming it won't matter much from a "function" standpoint, I just won't have accurate home consumption data because I'm missing an entire 200A panel.

Any issues beyond that with how I'm planning on attaching the CTs?

 

[pvgirl]

Just found this thread, and my setup will be similar with a 320/400A service with two 200A breaker/disconnect panels by the meter. I will be running my "basement" 200A panel with the 18kpv. I cannot get my CT's into my meter without cutting the little "safety clip", so I'm just leaving them in the inverter right at the GRID connection.

I do have net metering so I'm assuming it won't matter much from a "function" standpoint, I just won't have accurate home consumption data because I'm missing an entire 200A panel.

Any issues beyond that with how I'm planning on attaching the CTs?

Without net metering or the CTs installed around both 200amp feeders, you won't be able to use your solar power to feed loads on the other panel. The CTs don't need to be right at the meter, if there's location where you can get the ct's around both feeds to the 200 amp disconnects that would also work.

 

[y0bailey]

Without net metering or the CTs installed around both 200amp feeders, you won't be able to use your solar power to feed loads on the other panel. The CTs don't need to be right at the meter, if there's location where you can get the ct's around both feeds to the 200 amp disconnects that would also work.

I can't do it without getting into the Utility's turf/meter box....the CT's would have to be landed in the meter.

I'm abandoning the original grid-tied inverter disconnect and service taps in place so I can AC couple...and that right 200a disconnect is going to be routed through the 18kpv.

But since I have net metering it doesn't seem like a big deal beyond losing consumption info from the left sided 200A panel, and not directly powering them from the solar panels (sell excess solar to grid, gets sent back from grid to that 200a panel)? Seems like it's always been working that way for me anyways with my original setup?

 

[pvgirl]

View attachment 173953

I can't do it without getting into the Utility's turf/meter box....the CT's would have to be landed in the meter.

I'm abandoning the original grid-tied inverter disconnect and service taps in place so I can AC couple...and that right 200a disconnect is going to be routed through the 18kpv.

But since I have net metering it doesn't seem like a big deal beyond losing consumption info from the left sided 200A panel, and not directly powering them from the solar panels (sell excess solar to grid, gets sent back from grid to that 200a panel)? Seems like it's always been working that way for me anyways with my original setup?

Sorry I misread your post, since you do have net metering it doesn't make a big difference where the cts are installed.