[RE-wrenches] Tigo TS4-A-F

[Howie Michaelson]

My understanding is that unless something was changed in the last few years
that I'm not aware of (which is entirely possible), if PV conductors even
land on the outside of an interior space where people can be, whether
originating on a ground mount or a roof mount, RSD is required (unless it
meets the newish integrated panel/racking UL listing, typically in
commercial settings).

Howie Michaelson


On Wed, Nov 19, 2025 at 1:52 PM Jay via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Hi Zeke
>
> I’ve never had to do RSS on a ground array because
>
> 1. It’s not a structure
> 2 if it is a structure then it’s only being used for solar which makes it
> exempt from RSS.
>
> Of course your crazy AHJ might have a different opinion
>
>
>
> On Nov 19, 2025, at 8:50 AM, Zeke Yewdall via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> 
> You mention doing RSS on ground mounted PV arrays.  This seems completely
> not required by the code.  From my reading of 690.12, module level remote
> controlled rapid shutdown is only required on inhabited structures -- ones
> that may involve roof operations of the fire department for ventilation.
> Even detached garages with no occupancy do not appear to require it.  If we
> are just talking about the conductors coming off of the array going into a
> home, it seems to me (and my inspectors have always agreed.. not initially,
> but after I discussed it with them) that a switch mounted on the
> groundmount array or where the underground conduit came up to go into the
> building would suffice.
>
> Zeke
>
> On Tue, Nov 18, 2025 at 10:10 PM William Miller <william at millersolar.com>
> wrote:
>
>> 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
>>
>>
>>
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