[RE-wrenches] Tigo TS4-A-F

[William Miller]

To paraphrase:  If PV circuits are located on or in any structure RSS is
required. Exception: if the structure’s sole purpose is to house solar
equipment then RSS is not required.

If your inverter is in a shed and there is one rake in that shed, RSS is
required.


William Miller
Miller Solar.com
805-438-5600
www.millersolar.com


On Wed, Nov 19, 2025 at 7:50 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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