Jason, There are 2 different methods typically utilized, one specified by Tesla for any UL2703 module/racking combination which is as you say and limits the MCI to 165V, which is the tested disconnect limit of the MCI-2.
If you use the MCI-1 then you have an additional option of using the 3741 PVHCS listing of another manufacturer such as Ironridge. Since the MCI-1 has a 600V disconnect limit, you can safely use just (2) MCI-1 on a string, one at the beginning and end, as long as the array is physically contiguous with no gaps larger than 2' between adjacent modules. The GW2/3 is irrelevant to the MCI question, as the Powerwall 3 inverter sends its keep alive signal with PLC over the DC wiring. I think you could make a temporary off grid system work well enough if you simply commissioned it with grid voltage, then removed the grid, but kept the islanding contactor intact. Either GW3/GW2 or the Backup Switch in a meter socket enclosure could serve as this contactor, to keep the PW3 happy and in communication with "the grid." On a separate note, the details and testing of a 3741 PVHCS listing probably means that module level rapid shutdown never added much first responders safety compared with rooftop shutdown at within 1' of the array group. I have seen others on this list agree to as much and the test labs basically validate this in my eyes. From: Jason Szumlanski <[email protected]> To: "RE-wrenches" <[email protected]> Cc: Vincent Jolissaint <[email protected]> Subject: Re: [RE-wrenches] Powerwall 3 (contd) Message-ID: <[email protected]> Content-Type: text/plain; charset="utf-8" Thanks,?Vincent. This is the information I needed. I did read that at least 1 MCI is needed even if you do not require RSD. The MCI instructions are a bit confusing. I know for RSD you need one at the start of a string and at least one every three modules, but it's unclear if you need the MCI-1 or MCI-2 when using the GW3. The reason I was thinking about an off-grid application is I want to use one PW3 in a mobile application (for myself). I was thinking about tricking it into working, but I think it would?take a?PW3, GW2 or GW3, and an AC source to?commission it initially. 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, Sep 11, 2024 at 4:18?PM Vincent Jolissaint via RE-wrenches <[email protected]> wrote: > (sorry sent the previous reply before it was complete) > Hi Jason, > > > Currently Tesla doesn't allow any totally off-grid installations with PW3 or > PW3, they used to support this through the Gateway but no longer do. > > > In addition, the Powerwall 3 will require at least a single MCI per string to > pass the self?test function. This also limits the total string loop length > from MPPT+ to MPPT-. > > > Powerwall 3 does contain the site controller, but it will require some > islanding contactor to function properly. > > > > Vince Jolissaint?|?Director of CAD Services > > 2557 Wyandotte Street | Mountain View, CA? 94043 > Office:?650.938.9574 | Email:[email protected] > [[email protected]] > > > > >From: Jason Szumlanski <[email protected] > [[email protected]]> > >To: RE-wrenches <[email protected] > [[email protected]]> > >Subject: [RE-wrenches] Powerwall 3 > >Message-ID: > ?>? ? ? ?<CAE438R9LWo_VNuTTkOzVbv62LST3_Bf4-x7VfLm=- [email protected] > [rkk6k%[email protected]]> > >Content-Type: text/plain; charset="utf-8" > > >Certified Powerwall installers, > > >Can the PW3 be commissioned for for a completely off-grid system with DC > >coupled solar panels with no MCIs. If so, do you need a Gateway 2/3, or can > >it operate autonomously in this scenario without a Gateway? > > > >Jason Szumlanski > >Florida Solar Design Group *Vince Jolissaint |* *Director of CAD Services* 2557 Wyandotte Street | Mountain View, CA 94043 Office: 650.938.9574 | Email: [email protected]
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