From: ehsjr@verizon.net
On 2/8/2026 12:05 PM, Don Y wrote:
> I am using devices like this:
>
>
> as volt-free interfaces to the signalling from smoke and CO detectors.
>
> The mains connections are visible (BK/WH). The balance are connections to
> the isolated form C contacts, the "signal" wire from the detector(s)
> and a nominal 9VDC supply (that I would like to avoid using).
>
> First question: does the "device" count as a regular "device" in
> terms of volume computations?
>
> Also, there are separation requirements from the mains when sharing a box.
> Aside from a split enclosure, I can't see how you can guarantee that
> given the rats nest you find in most boxes!
>
> Second question: how would such a device typically be deployed to
> satisfy those requirements (the documentation accompanying it is
> ridiculously sparse).
>
> Third question: if I use the contact to deliver mains voltage to something
> like a small indicator (forfeiting the galvanic isolation) and optically
> couple that state across the boundaries of the enclosure, what can you
> recommend (*listed*!) inside the box?
If the thing in the picture is not a listed device
(per the NEC meaning of "listed") then you cannot
use it as part of the facility wiring and consider
it NEC compliant. Volume computation doesn't come
into it if the device is non-compliant.
If you're wondering about the UL224 marking, it's
for the heatshrink, not whatever is inside.
Question 2: dunno.
Question 3: Either get it listed, operate it under
"engineering supervision" acceptable to the AHJ
(electrical inspector at the usage location), or
build it into an appliance that is not part of the
facility wiring. I'm sure you don't want any of
that; I don't know how else to do it. Sorry.
Ed
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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