[RE-wrenches] Location of DC disconnect vis-a-vis rapid shutdown exemption
Ray
ray at solarray.com
Wed Apr 18 00:56:05 EDT 2018
Hi Rebekah;
Thanks for pointing out the changes to the diagrams. I especially
appreciate Note (2). /The PV system disconnect in these diagrams
separates the PV system from all other systems./
That seems simple enough for defining the boundaries of RSS, until you
think about off grid, and look at the last diagram of 690.1(b) titled
"Stand Alone System". The charge controller is not shown at all. Then
Figure 690.1(a) shows a /DC to DC Converter (optional location)/, shows
a fuse after, shows the power going with an arrow to no where, on a line
labeled /PV or DC to DC converter output circuit...../ But finally, the
cause of my greatest confusion: it does not show the *PV System
Disconnect* anywhere.
I have several questions:
Is a charge controller a *DC to DC converter*? What about non MPPT
controllers that don't convert voltage?
Is a charge controller considered *DC* *utilization Equipment* mentioned
in the definition of *PV Output Circuit*, or is the inverter and DC
loads the utilization equipment?
All of which leads to the $20 thousand dollar question: Is the *PV
System Disconnect* before or after the charge controller?
If before the charge controller, where can the PV Disconnect be? Could
it be outside, at the pole, or does it need to be within 3 ft of the
building entry?
Even with all the changes made in 2017, it seems that we still are left
with too much uncertainty about where a PV circuit ends, or what
constitutes the "PV Disconnect" in an off grid system. Not such a big
deal, until we are required to apply 690.12.
Thanks everyone for your answers and opinions,
Ray Walters
Design Engineer
Remote Solar
On 4/17/18 7:15 AM, Rebekah Hren wrote:
> Hi everyone,
>
> I strongly recommend looking at the figures that were added in NEC
> 2017 at the beginning of Article 690 in 690.1(b).
>
> What they show is equipment that is part of the PV system (to the left
> of the PV system disconnect called out in the diagrams), and equipment
> that is not part of the PV system (to the right of the PV system
> disconnect). These are really helpful diagrams, in terms of figuring
> out where the requirements of Article 690 apply.
>
> Equipment *not* part of the PV system is not a "PV system circuit" and
> thus is *not* subject to rapid shutdown requirements per 690.12.
>
> In every type of system you will see that energy storage is *not *part
> of the PV system, and neither is the multimode inverter for a system
> with energy storage. So rapid shutdown requirements shouldn't affect
> any of the loads, multimode inverter, or batteries in an off-grid system.
>
> In the 2017 NEC, the PV system disconnect, as shown on the diagrams,
> is required to be readily accessible per 690.13(A). For a system
> without batteries, the PV system disconnect is *always *an AC
> disconnect, not a DC disconnect. It can be the backfed breaker per
> 690.13(F)(1). For a system with batteries the PV system disconnect is
> always before the batteries.
>
>
> Equipment disconnects, like the DC inverter disconnect, are not
> required to be readily accessible, but must be within 10 feet of the
> equipment, per 690.15(A).
>
> Also note that the boundary for rapid shutdown shrank to *one foot*
> from the perimeter of the array in the 2017 NEC, so the inverter must
> be positioned within one foot of the array if there is not going to be
> any other RS equipment. The PV system disconnect (backfed breaker) or
> the service disconnect can serve as the rapid shutdown initiation
> device in that case.
>
> Best,
> Rebekah Hren, Member of NEC CMP-4 for Solar Energy International
>
> --
> Tel: 336.266.8800
> NABCEP Certified Solar PV Installation Professional™ 091209-85
> NC Licensed Electrical Contractor
>
>
> On Mon, Apr 16, 2018 at 9:00 PM, Ray <ray at solarray.com
> <mailto:ray at solarray.com>> wrote:
>
> For GT using Solar edge or Enphase, its not so hard to comply, but
> If you are looking at off grid systems, it's not just someone's
> opinion, its $1,000s of dollars extra to comply with 690.12. It
> also results in a system that is less reliable, which is less safe
> off grid where lives depend on that power for heat, light,
> refrigeration, and even breathing machines.
>
> Ray Walters
>
> Remote Solar
>
>
> On 4/16/18 7:44 AM, Brian Mehalic wrote:
>> Hey y'all, I'm going to disagree about the NEC getting "worse and
>> worse when it comes to PV," (see disconnect and grounding
>> requirements, for instance!), but as with previous posters,
>> that's just an opinion.
>>
>> Regarding location - the 2014 version had very little to say
>> about the location of any rapid shutdown initiation device; 2017
>> adds the requirement [690.12(C)] that RS initiation devices for
>> one- and two-family dwellings be readily accessible (defined in
>> Article 100), AND outside the building. Seems reasonable for a
>> device that is intended to control energized conductors to make
>> it more safe to enter a building.
>>
>> Cheers,
>>
>>
>> Brian Mehalic
>> NABCEP Certified Solar PV Installation Professional™ R031508-59
>> 520.204.6639
>>
>> Solar Energy International
>> http://www.solarenergy.org
>>
>> SEI Professional Services
>> http://www.seisolarpros.com <http://www.seisolarpros.com>
>>
>>
>> On Mon, Apr 16, 2018 at 12:04 AM, Mark Frye
>> <markf at berkeleysolar.com <mailto:markf at berkeleysolar.com>> wrote:
>>
>> Thanks Darryl.
>>
>> I guess I can add that I am in CA and so looked only at the
>> 2014. I also looked at the 2017 article. Man, I have to say,
>> my impression remains that really starting with 2008 the code
>> has just gotten worse and worse when it comes to PV, but that
>> is just me.
>>
>> Not really sure what might need to be "Outside readily
>> accessible". Is there something other than 690.12 that I need
>> to look at?
>>
>> Mark
>>
>> On 4/15/2018 8:26 PM, Darryl Thayer wrote:
>>> I think the code says Outside readily accessible,
>>>
>>> On Sun, Apr 15, 2018 at 12:22 PM, Mark Frye
>>> <markf at berkeleysolar.com <mailto:markf at berkeleysolar.com>>
>>> wrote:
>>>
>>> Folks,
>>>
>>> As I recall, an inverter and it's integrated DC
>>> disconnect need only be placed in an accessible
>>> location. I am thinking of putting an inverter high up
>>> on the wall inside a garage. That would be OK vis-a-vis
>>> the location of the disconnect (still accessible for
>>> maintenance).
>>>
>>> If I do put the inverter high up on the wall, I can
>>> limit my DC conductors to less that 10 feet total from
>>> the array and less that 5 feet inside the garage.
>>>
>>> That means I get the exemption from the rapid disconnect
>>> requirement, right?
>>>
>>> There is nothing in the Code linking the accessibility
>>> of the DC disconnect to the exemption from rapid
>>> shutdown, right?
>>>
>>> Mark Frye
>>>
>>>
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