[RE-wrenches] DC Disconnect for first responders

[Brian Mehalic]

480.7 is Disconnect Methods, and addresses different scenarios and voltages
(A) is for batteries "with a voltage over 60 volts dc" requiring a
disconnect accessible to and within sight of the battery
(B) is in regards to 1- and 2-family dwellings, and doesn't specify a
voltage, just that an external, emergency disconnect is required
(C) is segmenting strings into 240 Vdc nominal or less segments, and on it
goes to (G)

I don't agree with the earlier statement in this chain (and I didn't dig up
the original thread to see it in context) - based on how the Section is
arranged; if the 60 volt requirement applied to both (A) and (B) then they
would most likely be (A)(1) and (A)(2), under an (A) heading that included
a statement to the effect of "For stationary storage batteries of 60 volts
blah blah the following shall apply."

As it is now, the emergency disconnect requirement (B) doesn't specify a
voltage above which it applies, and the voltage specification in (A)
doesn't apply to (B).

Cheers,

Brian Mehalic
NABCEP Certified Solar PV Installation Professional™ R031508-59
National Electrical Code® CMP-4 Member
(520) 204-6639

Solar Energy International
http://www.solarenergy.org



On Mon, Feb 20, 2023 at 11:40 AM James Jarvis via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Did they ever explain why they were requiring it on a nominal 48 volt
> system? NEC 480.7(B) (from memory, I think that is the right article) says
> it is for nominal voltage of 60 volts or higher. IE your 48 volt system is
> exempt.
>
> Jay pointed this out on February 3rd.
>
>
> -James Jefferson Jarvis
> APRS World, LLC
> +1-507-454-2727
> http://www.aprsworld.com/
>
>
> On Mon, Feb 20, 2023 at 12:36 PM William Miller via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> Friends:
>>
>>
>>
>> Here is how this resolved for my upcoming project:  I submitted a request
>> to the building department to waive the requirement for a DC disconnect. I
>> based the justification on the need to keep a pressure pump for the fire
>> sprinklers and a fire alarm operational.  I will supply an external AC
>> disconnect to de-energize all premise wiring except those circuits
>> mentioned above.  The request was granted.
>>
>>
>>
>> William
>>
>>
>>
>> Miller Solar
>>
>> 17395 Oak Road, Atascadero, CA 93422
>>
>> 805-438-5600
>>
>> www.millersolar.com
>>
>> CA Lic. 773985
>>
>>
>>
>>
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