From the FAQ (Powerwall FAQs), Tesla says Powerwall is only compatible with certain inverters:
I'm not sure where the limitation comes from.
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Is there a electrical reason for two+ PowerWall 2s vs PV system size?
- Thread starter NuShrike
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From the FAQ (Powerwall FAQs), Tesla says Powerwall is only compatible with certain inverters:
I'm not sure where the limitation comes from.
The gateway needs a way to shutdown solar production when the Powerwalls are full. For emphase micro inverters, this is done by shifting the electricity phase slightly. I’m not sure how they do it for other systems, but that is probably why only some are supported.
I don’t think the Powerwall gateway supports load sheading (basically a large heating coil that uses any extra electricity produced) which would let it work with any inverter without knowing how to shut them down.
I believe that any inverter labeled "utility interactive" has to conform with UL 1741 and that means it will only operate (in the US) with a frequency between 59.3 and 60.5 Hz. However, this from reading third party documents, I haven't read UL 1741 itself since it costs money to get a copy of the standard.
That would be called a "dump load", it's basically the opposite of load shedding.
I think I recall reading that when operating off-grid, if the Powerwall's battery is nearly full, and solar panels are producing more power than is being consumed, then the Powerwall's inverter will attempt to signal the solar inverter to curtail production by ramping the frequency up from 60 Hz to above 60.5 Hz in steps. Above 60.5 Hz any utility interactive solar inverter should stop producing, but some solar inverters may support stepping down production as the frequency rises, rather than just an all or nothing approach.
If my recollection of the Powerwall's behavior is correct, and if your solar inverter doesn't ramp down production but is all or nothing, then there would still be the possibility of a smart dump load, that has no consumption at 60.0 Hz and ramps up its consumption as the frequency rises to 60.5 Hz. Not sure if such a load controller is commercially available, but it seems like it would be technically very feasible to make such a thing.
Cheers, Wayne
The Enphase IQ 6 micro inverters are programmable as to the power output vs frequency, according to their data sheet. It also calls out the ride through vs must trip limits.
It also has power vs voltage settings since the line should rise with over supply. That (voltage) might be another approach to a load dump. The caveat being what happens if the load dump breaker trips.
I think all grid-tied inverters shutdown when they are disconnected. So it’s seems like the powerwall gateway could cut off the inverters and be done with it. But I guess there must be some reason not to do that.
One good reason would be to provide backup power from the sun.
Gateway only has one set of contactors to connect/disconnect the grid. If solar was on grid side, solar would not be available during an an outage. A second gateway could disconnect the solar with the right SW, but there is still the issue of using as much solar as possible to maximize reserve power.
@mongo
Meanwhile, I briefly researched some Mitsubishi, Trane, Maytag (Nortek), Fujitsu heat-pumps -- very promsing. Their LRAs either don't exist (variable speed inverter powered) or are in the teens of amps. So it can possibly be backed up by only one PW2.
Meantime, I'm going to email my module manufacturer to see how their micro-inverter would respond to the PW2 trying to curtail. They are certified utility-interactive: UL 1741 SA, IEEE 1547-2003, IEEE 1547a-2014, CA Rule 21 Phase 1.
So anybody else having at least UL 1741 may be fine?
I just got an email response from Hyper:
So this product will work for my 105A.
Meanwhile, I briefly researched some Mitsubishi, Trane, Maytag (Nortek), Fujitsu heat-pumps -- very promsing. Their LRAs either don't exist (variable speed inverter powered) or are in the teens of amps. So it can possibly be backed up by only one PW2.
Meantime, I'm going to email my module manufacturer to see how their micro-inverter would respond to the PW2 trying to curtail. They are certified utility-interactive: UL 1741 SA, IEEE 1547-2003, IEEE 1547a-2014, CA Rule 21 Phase 1.
So anybody else having at least UL 1741 may be fine?
Hilarious. So I emailed SunPower technical support about this and their response is they have a product in testing they cannot disclose and not yet launched yet. I'd assume this is the hinted SunPower battery system, whoops. Meantime, no feedback for my simple, direct question.
My installer however, says the micro-inverters turn off when they detect back feed. So when the fully-charged PW2 turns off its inverter (stops pulling load?), the micro-inverters turn off, whether one or more PW2.
As to what this technically means such as if the PW2 is still feeding power into the home's micro-grid, ¯\_(ツ)_/¯ .
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The back feed comment was likely referring to inverters needing to sense an external voltage/ frequency source so that they don't back feed the power grid during an outage.
If the PW turns off its output, then you have no power, PV or otherwise. So that would be a poor control strategy for a backup system.
Parzival
Member
Tesla put a SureStart on my A/C at no cost to me. The thing works like magic. My unit was pulling well over 100A, I don't recall exactly, but now it's like 20A at start. The thing over-delivered. No more dimming lights and it's quieter, too.
Ulmo
Active Member
Hunt around for a decent installation price for that since you're already trying to save money. It seems like your best path for now. Hopefully it works! If I were in your position, that's what I would have done (independent installer for the SureStart, hunt around for price, decent installer).
Did you ever get a real answer as to why the SureStart is not compatible? I'm getting the same story from Tesla. I think the SureStart technology may not be compatible with 2 speed compressors (which I have).I have a 7 Kw solar system and am adding 2 Powerwall 2's.
Parzival
Member
I have a 4-ton two-speed compressor (Carrier/Bryant) and it works fine with the SureStart, so I assume there must be other factors.
In a 27 panel 9.7 kw system Enphase IQ6s will saturate and clip. IQ6s, instead of IQ6+s, were installed by mistake on my system and they are only passing 6.2 kw through from my 26 panel 9.2 kw array. I am now being told by my system designer that even the IQ6+s will likely saturate from my 355 watt panels, so we are looking at replacing them with IQ7Xs.
Also, each PowerWall 2 is limited to 30 amps in or out. So if you panels are producing 40 amperes, one PowerWall 2 won't work. Tesla will only allow whole house backup with 2 PowerWall 2s because of this amperage limitation. Two walls get you to 60 amperes of output so that you can run AC and a few other things and no need for a dedicated critical loads panel.
We put AC in a couple of years ago. The new variable capacity compressors ramp up slowly, so no need for a SureStart if you go that route, and they are so small and quite you cannot tell they are on.
Good luck with your new system. There are some teething problems though so patience is a worthwhile quality.
Also, each PowerWall 2 is limited to 30 amps in or out. So if you panels are producing 40 amperes, one PowerWall 2 won't work. Tesla will only allow whole house backup with 2 PowerWall 2s because of this amperage limitation. Two walls get you to 60 amperes of output so that you can run AC and a few other things and no need for a dedicated critical loads panel.
We put AC in a couple of years ago. The new variable capacity compressors ramp up slowly, so no need for a SureStart if you go that route, and they are so small and quite you cannot tell they are on.
Good luck with your new system. There are some teething problems though so patience is a worthwhile quality.
going back to the OP, the concept of inverter 'clipping' is explained here
What is solar inverter clipping?
the picture about half way down the article speaks a thousand words.
What is solar inverter clipping?
the picture about half way down the article speaks a thousand words.
Bringing this back from the dead, but hoping you can answer my question!
I'm about to buy a new AC system, but want to make sure I could run it with a single PW2. Problem is, I can't find the actual specs for max LRA for a single PW2. I know it's ~30A, but want to find a definitive number and haven't had luck with that.
Thanks!
Peak PW output is 7,000 watts or less than 30A at 240V. Keep in mind that is for all loads , so your AC inrush (LRA of compressor and fan) plus all other loads would need to less than that 7kW.
https://www.tesla.com/sites/default.../Powerwall 2_AC_Datasheet_en_northamerica.pdf
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