Very interesting. Thanks for this information. It seems like Tesla has implemented PCS in the way that I hoped it would be. They can set an aggregate current limit from all sources feeding a bus.
Unless I am mistaken, Enphase can only limit based on a selected ampacity of *backfeed* from their System Controller to a main panel. It does not measure the incoming utility power and set an aggregate output limit from all sources. That results in a 40A backfeed limit on a 200A panel, which does not make sense to me. I hope I have this wrong. Jason Szumlanski Principal Solar Designer | Florida Solar Design Group NABCEP Certified Solar Professional (PVIP) Florida State Certified Solar Contractor CVC56956 Florida Certified Electrical Contractor EC13013208 On Tue, Aug 6, 2024 at 10:30 AM August Goers <[email protected]> wrote: > > Hi Jason - > > There are many options on how a manufacturer can implement Power Control > Systems (PCS) and based on my experience with Tesla products, I'd say it's > the best thing since sliced bread. I expect that all major manufactures will > be implementing more advanced PCS features as soon as they are able to > develop and list them. > > But, getting back to your question - one PCS variant is a simple conductor > limit setting that stops controlled equipment output when a certain set > current limit is reached. This, as you point out, may not be the best choice > for large PV/inverter systems. Another PCS setting involves setting a > controlled "virtual panel" where all inputs are monitored. This PCS setting > can be, for example, 160 Amps in your 200 A meter/main example. Here is more > info on how that works: > https://service.tesla.com/docs/Public/Energy/Powerwall/Powerwall-2-Backup-Gateway-2-Installation-Manual-NA-EN/GUID-D71DFD63-1414-4915-B7A5-7E48703100DE.html > > I'm working on learning more about Enphase systems currently since SunPower > is filing for bankruptcy, so it's good to learn what Enphase can and can't do > at this point. > > Best, August > > > On Thu, Aug 1, 2024 at 10:40 AM Jason Szumlanski via RE-wrenches > <[email protected]> wrote: >> >> Note: This email is written from the perspective of the Enphase >> terminology, but the concept and question is the same in a general >> sense. >> >> >> I am having a hard time understanding the logic and benefit of a power >> control system that is used for avoiding a main panel upgrade in a >> typical residence. If you have a 200A main panel bus with a 200A main >> breaker, the current limit for a backfed breaker is 32A from the PV, >> no matter what. The PCS will artificially reduce the PV output to 32A >> when it could be capable of a much higher current for large systems >> depending on sunlight availability. That would waste a lot of energy >> if the PV system is significantly larger than a 32A output rating. >> >> The PCS standards seem to have missed the mark. Wouldn't it make more >> sense to limit the total current delivered to the bus from all >> sources? For example, in the example above, if PV is delivering 40A, >> why not allow limiting utility input to 120A for a total of 160A >> continuous delivered to the bus before PV is throttled? If the utility >> is delivering zero, the PV could deliver all the way up to 160A the >> the bus if capable. That way, all of the loads would be powered to the >> maximum extent from PV with the excess exported (if allowed via net >> metering from the serving utility). >> >> Am I missing something about how PCS works? I just don't see many use >> cases for main panel avoidance that are in customers' best interest. >> If we can't meet the 120% rule, we just do supply-side >> interconnections so nothing is wasted. But a backfed breaker would be >> so much easier if PCS were implemented in the way that I would like it >> to work. >> >> Jason Szumlanski >> Florida Solar Design Group >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> Pay optional member dues here: http://re-wrenches.org >> >> List Address: [email protected] >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> There are two list archives for searching. When one doesn't work, try the >> other: >> https://www.mail-archive.com/[email protected]/ >> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> >> List rules & etiquette: >> http://www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> http://www.members.re-wrenches.org >> _______________________________________________ List sponsored by Redwood Alliance Pay optional member dues here: http://re-wrenches.org List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org There are two list archives for searching. When one doesn't work, try the other: https://www.mail-archive.com/[email protected]/ http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: http://www.re-wrenches.org/etiquette.htm Check out or update participant bios: http://www.members.re-wrenches.org
