Zeke:
When this subject came up one of the wrenches replied to me off-list and shared photos of an Alps RSD that had burned up. He said tech support was of little help. Since then I have heard similar stories about Tigo products. I think the problem is trying to interrupt high voltage / high current PV DC under load. To do this with a mechanical switch you would see large blades surrounded by arc chutes, plastic shields and a metal can. Doing this switching in a small plastic nodule seems impractical. I am the last one to discount safety equipment--electrical fires kill a lot of people. However I am convinced that the RSS requirement preceded the availability equipment to implement the requirement and that gap has not closed. Now with UL3471 diluting the seriousness of hazard levels, RSS seems even more ludicrous. It is especially onerous to require module level RSS on ground mount arrays. Even more galling is the inability to complete a job I am in the middle of because there is apparently a nationwide shortage of RSDs. William Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985 *From:* RE-wrenches [mailto:[email protected]] *On Behalf Of *Zeke Yewdall via RE-wrenches *Sent:* Tuesday, November 18, 2025 10:52 AM *To:* RE-wrenches *Cc:* Zeke Yewdall *Subject:* Re: [RE-wrenches] Tigo TS4-A-F Exactly what kinds of failures have people been having on the APsystems RSD units? That's what I've been using when I encounter a roof (mostly because of availability with my distributors, but also being able to easily tuck them into the channel instead of having to mess with bolts or clips). I have not had any failures that I know of yet... but depends on what their failure mode, failing open or closed or what. If they fail closed, it would not be apparent till someone tested or tried to use the RSD system. Zeke -- Zeke Yewdall PV Engineer NABCEP #031508-89 [email protected] 303-523-3592
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