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Should I add a 3rd Powerwall in California?

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I think it mainly has to do with wanting to operate the compressor at variable speeds. AC motors like to operate at a single speed. DC motors can efficiently operate at variable speeds. I have a zoned system so when only heating or cooling one zone the compressor will operate at a lower speed. Interestingly, the outside unit I'm getting isn't continuously variable but has 5 set inverter outputs for 5 set stages, the lowest stage is 20% of high stage.
That does not explain why Tesla would choose a 3 phase AC motor, where speed control is paramount.

I really need to understand motors more, before trying to be helpful lol.
 
I don't think those generators do AC -> DC -> AC do they? I assume they generate DC.
To clarify, I misread the earlier post as being about "generators" (as the above says), not compressors.

The inverter driven compressors do, in fact, rectify AC to DC, and then use the DC to make (invert) variable frequency AC to drive the motor. That is, they have a VFD built-in.

Cheers, Wayne
 
That does not explain why Tesla would choose a 3 phase AC motor, where speed control is paramount.

I really need to understand motors more, before trying to be helpful lol.
Three phase AC has a power transmission over all three phases that is a close approximation of DC, with constant power delivery, like DC. AC motors have power and efficiency advantages over DC motors. I suspect that the choice was largely driven by the improved efficiency, aka range, of AC motors. I have no inside information.
3phase.gif

more here; AC power, RMS and 3-Phase circuits

All the best,

BG
 
As others have mentioned, the reason for the inverter is to drive the compressor motor at a variable speed. As an example, the Tesla Roadster motor is a 3-phase, 4-pole AC induction motor -- a design invented by Nikola Tesla, hence the company name. The frequency of the AC waveform produced by the inverter is constantly adjusted to match the desired rotation of the motor's rotor. To accelerate, the peak of the waveform in the stator winding is just ahead of the pole in the rotor, pulling it to go faster. To decelerate, the peak is just behind.

So the reason for converting AC - DC - AC is to change from the fixed 60Hz AC at the start to a variable frequency feeding the motor. Motors that run directly from 60Hz power typically operate at a fixed RPM like 1800 or 3600, synchronous with the power.
 
For me, there is no financial justification for a 3rd Powerwall under NEM2 and current rates other than backup during outages, and the advantage of a 3rd Powerwall during outages is minimal.

It comes down to whether you'd rather spend the money on something else then if there is no financial justification or minimal benefits from outages :). would you gain more utility by using the money towards a vacation? or new furniture, gifts etc
 
Living in Santa Barbara, and the "end of the line" for the SCE distribution network (lots of power outages), one of the better investments has been a solar PV/Powerwall configuration. A major advantage of multiple powerwalls is the ability to handle the increased current (surge) common to compressor startup, as each powerwall is rated for 5kwh continuous and 7 kwh surge. I had one powerwall fail about 3 months after installation, so redundancy is another advantage. You've been offered a great price, and if your pv/powerwall panel can handle the load it seems like a great deal to me.
 
You’re going to need a NEM2-MT interconnection!
They never made me sign anything that said I need to go from PS to MT. And one of the installers said he has three Powerwalls and is on paired storage. They did make me sign an agreement saying PG&E could install a backup switch. However, I have a 400 amp panel and the backup switches aren't compatible with 400 amp panels.
Reading the system application for the 3rd Powerwall installation, you would never know that I have 2 existing Powerwalls and solar.
I don't know if it matters but I'm the only house on my transformer.
I'm going to wait and see if PG&E says anything or just gives me PTO.
 
@RKCRLR what is wrong with your Enphase system?
Prior to the 3rd Powerwall installation my Enlighten monitoring was working correctly. My system is a little complicated in that I have 2 solar generating systems, an old string system and then I had the Panasonic/Enphase system installed. And then I had 2 Powerwalls installed, and then the third Powerwall. The Enlighten system monitored both solar systems (Enphase doesn't like that) but not the Powerwalls.

The installation plans for the 3rd Powerwall called for 000 gage wiring instead of the existing 00 gage. Technically, the 00 was OK but they didn't want to send it back through the county for approval. So they ripped out the wiring which had the Enphase CTs installed and installed the 000 wiring.

Initially, my Enlighten monitoring was showing consumption but not production. They then switched the wiring around which caused it to show production but not consumption. Another tech came out (he seemed quite knowledgeable) and redid the entire Enphase CT system. He contacted Enphase so they could change the CT settings. At that point my Enlighten monitoring was showing both consumption and production with the nuance that it thinks my home consumption is zero when running off the Powerwalls and thinks that recharging the Powerwalls is home consumption (it had previously ignored the Powerwall operation).

However, my Enlighten monitoring is showing that I have a meter issue and to contact my installer even though the net daily consumption/production is consistent with what PG&E shows. So, I contacted my Enphase system installer and they are looking into it.
 
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Prior to the 3rd Powerwall installation my Enlighten monitoring was working correctly. My system is a little complicated in that I have 2 solar generating systems, an old string system and then I had the Panasonic/Enphase system installed. And then I had 2 Powerwalls installed, and then the third Powerwall. The Enlighten system monitored both solar systems (Enphase doesn't like that) but not the Powerwalls.

The installation plans for the 3rd Powerwall called for 000 gage wiring instead of the existing 00 gage. Technically, the 00 was OK but they didn't want to send it back through the county for approval. So they ripped out the wiring which had the Enphase CTs installed and installed the 000 wiring.

Initially, my Enlighten monitoring was showing consumption but not production. They then switched the wiring around which caused it to show production but not consumption. Another tech came out (he seemed quite knowledgeable) and redid the entire Enphase CT system. He contacted Enphase so they could change the CT settings. At that point my Enlighten monitoring was showing both consumption and production with the nuance that it thinks my home consumption is zero when running off the Powerwalls and thinks that recharging the Powerwalls is home consumption (it had previously ignored the Powerwall operation).

However, my Enlighten monitoring is showing that I have a meter issue and to contact my installer even though the net daily consumption/production is consistent with what PG&E shows. So, I contacted my Enphase system installer and they are looking into it.


You're an hour drive from @h2ofun, you two should meet up and figure out whose system is way more complex (for bragging rights).
 
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