Hopefully the utilities will start to change their policies with more and more demand for meter socket MIDs. They really make a lot of sense, and we've found that the process with our local utility PG&E is fairly straightforward. These socket adapters make sense for emergency generators ( https://www.pge.com/en/outages-and-safety/outage-preparedness-and-support/general-outage-resources/backup-power-transfer-meter-program.html) and eventually vehicle to grid/home as well.
Just to clarify, for PV only, the Tesla Solar Inverter can do PCS panel limits without an MID - you just need CTs around the utility side feed. Anyway, I'm excited for all these changes and hope all manufacturers get PCS rolling. On Wed, Aug 7, 2024 at 7:24 AM Jason Szumlanski < [email protected]> wrote: > I spoke to my engineer, and he had a discussion with Enphase about this > months ago. Apparently, there was a testing issue with PCS, and Enphase was > looking at retesting, maybe with a new NRTL. I reached out to Enphase > engineering and will report back if I get any new information. > > Regarding the sockets... Florida Power & Light vehemently rejected the > ConnectDER and, from what I understand, also does not accept the Tesla > Backup Switch. They do not allow anything connected to the meter socket > that they do not provide. After all, how are they going to steal $12 a > month from people for their surge protector otherwise?! And there is no > more than a snowball's chance that the local municipal electric provider > will allow it. So meter socket based transfer switches are out around here. > > That puts Enphase at an advantage over Tesla here for simple PV only > systems, since Enphase should be able to implement PCS with their > relatively low cost gateway, whereas Tesla will need to install a MID, > which could require a meter disconnect/reconnect, and that can be a > nightmare to schedule and coordinate here. > > > 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 Wed, Aug 7, 2024 at 10:10 AM August Goers <[email protected]> wrote: > >> Hi Jason - I suspect that Enphase is working on the "panel limits" type >> feature, it really makes a lot of sense as you point out. Tesla has been >> rolling out PCS features at a rapid pace - their solar inverter now has >> panel limits whereas it didn't a few months ago. To respond to one of your >> comments, we can also use panel limits with the Backup Switch which is >> Tesla's meter socket Microgrid Interconnect Device (MID). The Backup Switch >> has the site metering built in. Installations with Backup Switch and >> Powerwall for whole-home backup are nearly as fast as PV-only builds. >> >> I heard from our Enphase rep that they are hopefully releasing their >> meter socket adapter product in Q1 of 2025. Game changer! >> >> August >> >> >> On Wed, Aug 7, 2024 at 6:46 AM Jason Szumlanski < >> [email protected]> wrote: >> >>> I confirmed via this video ( >>> https://app.gotowebinar.com/unified/index.html#/webinar/6915785636472410201/attend/2085639858551605341) >>> that Enphase does, in fact, limit backfeed based on the 120% rule when >>> implementing PCS for main panel upgrade avoidance. That is disappointing. >>> >>> Based on my reading of 705.13(B), as long as the utility feed is >>> monitored by the PCS, the PCS only needs to limit the PV source such that >>> the TOTAL current from all sources does not exceed the busbar ampacity >>> rating. Since Enphase can implement consumption monitoring with CTs on the >>> line side of the main panel, they should be able to limit PV backfeed based >>> on how much current is coming from the utility company rather than the far >>> more limiting 120% rule. This seriously diminishes the value of Enphase's >>> PCS implementation for main panel upgrade avoidance. >>> >>> To be fair, Tesla's PCS, to accomplish what I want, requires a Gateway >>> (MID). that significantly adds to the cost and complexity, and is really >>> intended for Powerwall systems. But Enphase should be able to implement PCS >>> this way using it's IQ Gateway *without *their System Controller (MID) >>> for grid-interactive PV systems without batteries. This appears to be a big >>> miss on the part of Enphase. Maybe they are misinterpreting 705.13(B), or >>> maybe there is a technical reason that they can't comply in this manner. >>> >>> >>> 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 10:36 AM Jason Szumlanski < >>> [email protected]> wrote: >>> >>>> 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 >>>> >> >>>> >>>
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