Friends:
I am not familiar with the inverter cited and I am not going to take the time to research it. There are too many options this day to keep up! If this system requires load disconnecting, a touch safe fuse holder is not the correct device. They are not rated for load break. A work-around is to plainly indicate the inverter AC disconnect should be activated or the inverter turned off before opening the fuse disconnect. Also, please consider not shopping at Amazon. They have a terrible record regarding employee safety. PV-Cables carries this fuse holder at a competitive price and they are great people to work with. Here is a link: https://pv-cables.com/product/littelfuse-spf-solarfuse-holder/. There are many other solar vendors that have these and that could use your shopping dollars. Below are some related subjects I have been pondering: RSS as PV disconnecting means: I have been whining at great length about having to install RSS MLPE on off-grid installations. My most pathetic whining has been about having to install these on ground-mount arrays. My understanding is that RSS is supposed to protect fire fighters when they respond to structure fires. How does an RSS system on a ground mount even apply here? However, I do find it handy to have an easy way to de-energize PV circuits so I can safely work in combiners and recombiners. This makes me wonder: Is module level RSS equipment suitable to act as PV disconnecting means? Tigo Transmitter-Where should it be installed? And a warning: I like to be able to measure PV circuits when connected and disconnected. If the Tigo RSS transmitter donut is installed down-stream of the PV disconnecting means then open circuit measurements are not possible. If you open the disconnect, the keep-alive signal goes away and you can’t measure the PV string. I got a surprise when doing just this a few days ago. I have two rows of PV racks and a combiner on each row. If I want injection of Tigo keep-alive signal upstream of the combiner breakers, I need to install a transmitter in both combiners. I looped the feeders to the far combiner through the near combiner. The Tigo donut in the near combiner was near those looped feeders and induced enough signal in the feeders that the RSS MLPE in the next rack were switched on. I got a nasty 200 VDC shock out of the deal. See photo below. Automatic RSS: As noted above, everything I have read about RSS is that it is designed for the safety of fire fighters. RSS is a manually activated system. Someone needs to find and push or twist the disconnect button. If this is not done the RSS provides no protection. Why could we not require AFCI and GFDI equipped inverters and charge controllers to provide a contact closure in case of either fault that could easily be wired into the RSS system to activate the RSS automatically? Seems like a no-brainer to me. True PV safety for fire fighters and the public: I was watching a webinar <https://www.youtube.com/watch?v=MyBe21Q3xCQ&t=629s&ab_channel=MayfieldRenewables> on UL 3741 recently. In it the presenter early on makes the claim that PV systems are “inherently safe” (8:45 in the video). I think this is wrong. String PV systems are inherently *unsafe*, for two reasons: 1. PV panels have no off switch. If the sun is shining the panels are creating power, at potentially fatal levels. 2. PV panels cannot trip OCPD. PV panels are finite in ampacity and we need the OCPD to be rated at above the available current. In case of a fault an AFCI or GFDI equipped inverter or charge controller can detect those faults and shut off, but the fault still exists and is still being fed power. These concerns apply to PV string systems. Micro-inverter systems could be argued as being inherently safe. To get to true PV safety, we need to find a way to shut off power at the source. If we can trigger MLPE RSS to shut off in the case of detectable faults, we are much closer to the holy grail of true safety. The interconnection of AFCI and GFDI inverters and charge controllers with RSS is one way to achieve this goal. This should be easy to achieve-- it requires only a contact closure be built into the electronics. Outback’s FM100 charge controllers have a contact closure that can be programmed to open in the case of an error, but not the errors we need. So close… Thinking this through further, why not build AFCI and GFDI protection right into MLPE electronics? That way in the case of a fault the power is shut off at the source. Maybe Solar Edge does this already. Does anyone know? UL3741: I have just started studying UL 3741. From what I have learned so far, I am not convinced this is the right direction. For one, the standard upgrades the allowed voltage exposure to 160 VDC. Number two, the standard is written only to protect fire fighters. This leaves out protecting the public. This includes kids climbing on a ground mount or using a piece of copper pipe to retrieve a Frisbee from under a PV array, or a homeowner falling into a PV array while hanging holiday decorations on a dormer-- to name just a few scenarios. Number three, the goal is to eliminate MLPE. Until PV panels come with an accessible off switch, we need MLPE. We cannot have power sources so ubiquitous to our lives that can’t be turned off. As an industry, I think we have not prioritized PV safety nearly as much as the industry does for regular electric equipment safety. If you don’t believe me, try running conductors to a roof-top air conditioning unit without conduit protection and see what your inspector thinks about that. I am interested in thoughts any of you may have on the above topics. William Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985 *From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Nick A Lucchese via RE-wrenches *Sent:* Thursday, January 18, 2024 9:50 AM *To:* RE-wrenches *Cc:* Nick A Lucchese *Subject:* Re: [RE-wrenches] Recommendation on DC Breaker The Siemens HNF361RPV is worth looking into. Quite affordable and reliable build quality without having to resort to Amazon. It first appears that it’s limit is 250 vdc but the footnotes indicate 600 once going deeper into the details. Obviously not a fuse though. Nick On Jan 18, 2024, at 7:59 AM, Jason Szumlanski via RE-wrenches < re-wrenches@lists.re-wrenches.org> wrote: Thanks, all, for the quick recommendations. I believe an isolator like the IMO is technically all that is needed since it is a current limited circuit and OCPD shouldn't be required, but the manual calls for a circuit breaker. That is probably just a semantics issue. On the other hand, the 1000V DIN rail breakers on Amazon are a dead cheap option and worth considering, too. 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 Thu, Jan 18, 2024 at 10:48 AM Jay via RE-wrenches < re-wrenches@lists.re-wrenches.org> wrote: I’d use an IMO disconnect as you don’t have any current limitations. I think sometimes things get lost in translation. Jay On Jan 18, 2024, at 8:43 AM, Jason Szumlanski via RE-wrenches < re-wrenches@lists.re-wrenches.org> wrote: I am installing an EG4 off-grid 3k inverter for the first time, and the manual requires a DC circuit breaker on the PV input. It will be a small PV array with adjusted max Voc around 280V @ Isc 10.6A. I'm looking for a cost-effective DC breaker and enclosure for this purpose. Jason Szumlanski Principal Solar Designer | Florida Solar Design Group NABCEP Certified Solar Professional (PVIP) Florida Certified Solar Contractor CVC56956 Florida Certified Electrical Contractor EC13013208 _______________________________________________ List sponsored by Redwood Alliance Pay optional member dues here: http://re-wrenches.org List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org There are two list archives for searching. 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