Possible rewiring of my ESS

[CrazyRabbit]

I still waiting for enphase to make a solar injector, 1.5-2kw would be plenty. It would allow me to fill up the gas tank of my 2kw inverter generator and let it run until empty. I only produce about 6.5 kWh on a highly overcast winter day.

 

[Vines]

Your proposal basically reduces the grid supply to 200A, and then combines that with all of your inverter breakers (2 * 60A for PV, and 7 * 30A for PWs, or 330A) into a single panel to supply (2) 200A breakers for your (2) 200A load panels. While it would be logical that that could be done with a 400A panel, as the loads are limited to 400A, there's no provision in the NEC for that analysis. It would require a 600A panel as drawn, so that the sum of the ratings of all the electrical sources is no larger than the panel rating.

This is important: all your loads could draw is 400A through the 2x200 breakers that would feed your existing loads, providing a 600A panel is pretty silly.

You could do it with a 400A panel as follows: take one of your 200A generation panel "outputs" and combine it with the 200A from the grid in a splice box to a single 200A feeder. Then your 400A panel has a 200A breaker for that combined feeder, along with the other generation circuits, and that adds up to under 400A of supply to the panel.

Another way to safely use a 400A subpanel is to limit the backfeed from the controlled sources through PCS settings in the Gateway. Set Export control and add a set of CT's to the feed between the bottom 200A subpanel with 4 Powerwalls and 1 inverter in it and the 400A subpanel.

Without PCS control this panel could contribute 143.5A (180A with 1.25 multiplier) and therefore when combining it with your 119.5A (150A with 1.25 Multiplier) you get 330A so are over the limit by 50A when looking at the 705.12 calculation. The calc would provide you with 280A of backfeed capacity with a 400A subpanel fed from a 200A main breaker.

Therefore if you add PCS control at 104A (actual setting) that panel will be limited to provide 130A of contribution to the calculation. Add 130A to the 150A from other Powerwall and PV sources and you are right at the 280A backfeed limit.

Theoretically you could safely serve loads while on grid within that 400A subpanel that total 480A, with 200A coming from the grid, and 280A from the ESS and PV monstrosity.

And on moving to a single GW, what is the maximum number of PWs a single GW can support?

10, assuming your impedance limit is not surpassed at that point. The lowest impedance I have seen in a new mansion in Atherton with a 600A service would support 12 powerwalls, based on the impedance limit and measurement from the service through the transformer.

Maybe one day I will see and measure a low impedance transformer and hit Powerwall Nirvana! A rural 400A service with a long loop to the transformer will sometimes not support 6 even.

 

[Vines]

@h2ofun 600 amp panel. Run Mike Holt’s toolbox load calculator.
You might consider moving some circuits to non backed up panel, like evse…

I am advising him to leave his EVSE off the backup circuit for now, and if the load calculations support it just run the whole home from the single 200A subfeed.

600A panel is a huge and expensive addition, its only money right? I say if you can do it with smaller equipment that is "Right sized" then why throw away a few thousand dollars? His loads are only 400A, and only 120A of the generation is uncontrolled.

All the Powerwalls are smart enough to control their output, so why not use that feature to save some money?

Once the whole home is fed from a single 200A feed, then the ATS coordination becomes a non issue as well.

 

[BGbreeder]

@h2ofun Couldn't you use an ATS sequencer to "manually" control the switch overs?
Like this sort of item?

Amazon.com: SMARTGEN HAT160 Automatic Transfer Switch Controller (ATS) 230/400VAC 50Hz : Patio, Lawn & Garden

Buy SMARTGEN HAT160 Automatic Transfer Switch Controller (ATS) 230/400VAC 50Hz: Generator Accessories - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

(Despite the title, it does 60Hz)
Eaton sells similar gear...

 

[CrazyRabbit]

He could just do a feeder and taps…. They make 5 terminal blocks, put them in a gutter. Put maybe not as one tap will be far away.

But do 000 wire from service panel to gateway and from gateway to 400amp panel…

 

[wwhitney]

Another way to safely use a 400A subpanel is to limit the backfeed from the controlled sources through PCS settings in the Gateway. Set Export control and add a set of CT's to the feed between the bottom 200A subpanel with 4 Powerwalls and 1 inverter in it and the 400A subpanel.

That works for the 400A panel, but a GW can only do one export control like that, I think? And with 330A of inverts on a 200A service, you'd need to use that export control feature to limit the grid export to 200A.

Cheers, Wayne

 

[Vines]

@h2ofun Couldn't you use an ATS sequencer to "manually" control the switch overs?
Like this sort of item?

Amazon.com: SMARTGEN HAT160 Automatic Transfer Switch Controller (ATS) 230/400VAC 50Hz : Patio, Lawn & Garden

Buy SMARTGEN HAT160 Automatic Transfer Switch Controller (ATS) 230/400VAC 50Hz: Generator Accessories - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

(Despite the title, it does 60Hz)
Eaton sells similar gear...

Certainly, there are ATS solutions that will allow better control of the switching. If this can be made to work, and the current PV+PW system works well, there isn't a large need to change things to a single feed. When the customer has no need for more than 200A from the grid to be backed up, collecting all the resources in one system is generally superior.

That works for the 400A panel, but a GW can only do one export control like that, I think? And with 330A of inverts on a 200A service, you'd need to use that export control feature to limit the grid export to 200A.

Cheers, Wayne

The gateway already limits the amperage through itself to 200A without other meters. This makes sense as it is a 200A device, but can be connected to 300A worth of powerwall breakers. You do not have to set export control even with 10 Powerwalls unless you want to.

If you had more than 200A of uncontrolled PV backfeed then you would have an issue, but the TEG will limit the backfeed of the PW inverters in the rare case of a VPP event where 7 power walls were all trying to participate at once.

 

[holeydonut]

Certainly, there are ATS solutions that will allow better control of the switching. If this can be made to work, and the current PV+PW system works well, there isn't a large need to change things to a single feed. When the customer has no need for more than 200A from the grid to be backed up, collecting all the resources in one system is generally superior.

The gateway already limits the amperage through itself to 200A without other meters. This makes sense as it is a 200A device, but can be connected to 300A worth of powerwall breakers. You do not have to set export control even with 10 Powerwalls unless you want to.

If you had more than 200A of uncontrolled PV backfeed then you would have an issue, but the TEG will limit the backfeed of the PW inverters in the rare case of a VPP event where 7 power walls were all trying to participate at once.

Do you think instead of PV+ESS that h2ofun could add one of these too? They have a distributor in California…

Advanced WindWall® - American Wind, Inc

americanwindinc.com

 

[Vines]

Do you think instead of PV+ESS that h2ofun could add one of these too? They have a distributor in California…

Advanced WindWall® - American Wind, Inc

americanwindinc.com

Theoretically, any generation source could be used as long as the inverter can respond to the frequency shift signal of the powerwall, so as to curtail generation when the batteries are full and off grid. I would love to see someone do this with the V2H inverter, and see how they solve the problems that might arise.

 

[h2ofun]

I am advising him to leave his EVSE off the backup circuit for now, and if the load calculations support it just run the whole home from the single 200A subfeed.

600A panel is a huge and expensive addition, its only money right? I say if you can do it with smaller equipment that is "Right sized" then why throw away a few thousand dollars? His loads are only 400A, and only 120A of the generation is uncontrolled.

All the Powerwalls are smart enough to control their output, so why not use that feature to save some money?

Once the whole home is fed from a single 200A feed, then the ATS coordination becomes a non issue as well.

I am trying to come up with a solution to propose to my installer that is technically the easiest, since they may not have the technical knowledge, or willingness to learn new stuff.
There is not reason to ask load or non load. I am just trying to get everyone on one 200 A feed, so I can use the other for EV charges, if possible.
So, a cleaner, technically easier solution is to buy an expensive 600amp panel, I might have better luck getting my installer to consider, than
Doing other stuff? But am not trying to tell them what to do.
The first thing is just to verify I can get all my loads, which just assume its on the PGE line, to legally be under 200amps. I am still waiting for closure on can the minisplits be use as part of the 40%, rather than counted at 100% over 8000 watts.

Thanks everyone for the ideas and technical support. I am finding my home is pretty corner case, but that is what makes it so much fun.
I hope some of this might help others. Wish I would have look more into this before I had the stuff installed. Oh well

 

[wwhitney]

The gateway already limits the amperage through itself to 200A without other meters.

IIRC, the GW comes with a pair of CTs around the connection on one side of the relay. Some installations involve moving those CTs. But if you don't, then the GW automatically starts throttling inverters it controls if those CTs show net export in excess of 200A? And that's on top of the adjustable limit you can set based on a different pair of CTs?

Thanks, Wayne

 

[BGbreeder]

Do you think instead of PV+ESS that h2ofun could add one of these too? They have a distributor in California…

Advanced WindWall® - American Wind, Inc

americanwindinc.com

Cost?

 

[holeydonut]

Cost?

Waiting for h2olottery2xwinner to source one and Cobalt to install it.

 

[wwhitney]

I am still waiting for closure on can the minisplits be use as part of the 40%, rather than counted at 100% over 8000 watts.

It's clear that the letter of 230.83(A) allows you count the minisplits at 40%, as long as you are not adding any HVAC equipment. It's also clear that makes zero sense, as if you were to be adding HVAC, the existing minisplits would have to be counted at 100% under 230.83(B).

So I'd be inclined to put a 100% factor on the minisplits. But as previously discussed, you'd still be under 200A per your latest load calc, after correcting the HVAC load to only use MCA for the largest unit, and adjusted MCA for the others.

Cheers, Wayne

 

[Vines]

IIRC, the GW comes with a pair of CTs around the connection on one side of the relay. Some installations involve moving those CTs. But if you don't, then the GW automatically starts throttling inverters it controls if those CTs show net export in excess of 200A? And that's on top of the adjustable limit you can set based on a different pair of CTs?

Thanks, Wayne

The newest GW does not allow the relocation of those integrated CT's.

My understanding is that the GW2 will protect itself and automatically throttle controlled sources if there was flow through the GW2 over 200A. Export control is a different function. requiring dedicated CT's.

 

[buckets0fun]

My understanding is that the GW2 will protect itself and automatically throttle controlled sources if there was flow through the GW2 over 200A. Export control is a different function. requiring dedicated CT's.

TEG v1/magic grey box no fancy Tesla external branding will also throttle if current flow exceeds 200a.

 

[Vines]

TEG v1/magic grey box no fancy Tesla external branding will also throttle if current flow exceeds 200a.

Makes sense because the older GW1 could also manage 10 Powerwalls, or 240A of continuous powerwall output.

 

[buckets0fun]

Makes sense because the older GW1 could also manage 10 Powerwalls, or 240A of continuous powerwall output.

Always found it odd... Wouldn't 10pw @ 30a be 300a? I assumed 30a and not 40a because the + models weren't really avail until TEGv2 aka the fancy glass fronted unit.

I've yet to see the TEGv1 allow a draw above 200a for more than a few moments

 

[Vines]

Always found it odd... Wouldn't 10pw @ 30a be 300a? I assumed 30a and not 40a because the + models weren't really avail until TEGv2 aka the fancy glass fronted unit.

I've yet to see the TEGv1 allow a draw above 200a for more than a few moments

Each Powerwall has a 24A maximum continuous output x 1.25 NEC factor = 30A breaker

 

[buckets0fun]

Each Powerwall has a 24A maximum continuous output x 1.25 NEC factor = 30A breaker

hah. it's too early. I messed that one up and knew the NEC factor.