[RE-wrenches] Multiple inverters
Christopher Warfel
cwarfel at entech-engineering.com
Mon Feb 25 17:59:11 EST 2019
Yes, microinverters and now I would think other typologies will be
included with module level disconnects becoming more common and I guess
required. So, as long as you can disconnect each non microinverter
individually, and microinverter strings by one disconnect, you should
meeting the intent. Labeling is key too. I still think that this was a
big error and the stated intention of making rooftop pv safer has not
been achieved. The wheel fell off of this "safety improvement".
Technology is catching up though. Anyone on a roof better assume the
array is live until proven otherwise no matter what installation type it
is. Chris
On 2/25/2019 5:45 PM, Rebekah Hren wrote:
> I should follow up to say that yes Chris is correct - each inverter
> does require its own equipment disconnects (AC and DC) per 690.15, but
> those can be connectors, like for Enphase, or any number of other
> things, as detailed in 690.15. If you try to keep system and equipment
> disconnect rules separate in your mind, I think it helps - although of
> course the inverter AC disconnect for a string inverter will often
> also be serving as the system disconnect, so there is a lot of overlap.
>
>
> On Mon, Feb 25, 2019 at 5:39 PM Rebekah Hren <rebekah.hren at gmail.com
> <mailto:rebekah.hren at gmail.com>> wrote:
>
> Hi Chris and William
> There was certainly no intention to mandate that all inverters
> connect to one OCPD/disconnect.But 705.12(B)(1) in 2017 clarifies
> that systems like Enphase could have multiple inverters on one
> breaker, certainly not that all inverters in a building have to
> be on breaker.
>
> If an AHJ raises this issue the answer is as follows:
>
> A single inverter can be called a single PV system - see the
> diagrams in 690.1(b). A building can have multiple PV systems per
> 690.4(D).
>
> Each PV system can have no more than 6 system disconnect switches
> per 690.13(D). Circuit breakers are allowed as PV system
> disconnects - 690.13(F)(1).
>
> There is no limit to the number of PV systems allowed on a building.
>
> Therefore, each inverter can be connected to its own breaker/disco
> for that PV system.
>
>
> A few further comments :
>
> A single PV system can have a single inverter, or multiple
> inverters. It is up to you to define the system and the PV system
> disconnect(s) associated with it.
>
> OR multiple inverters (power sources) can be connected to a single
> OCPD/disco up to the manufacturer's maximum OCPD limit, per
> 705.12(B)(1).
>
> OR multiple (let's say 10) inverters in a single system can each
> have their own OCPD/disco and ONE master PV system disconnect for
> all 10 inverters to follow the fules of 690.13(D).
>
>
> Lots of options, all allowed!
>
>
> Best,
>
> Rebekah
>
> Principal, CMP-4
>
>
> On Mon, Feb 25, 2019 at 5:31 PM Christopher Warfel
> <cwarfel at entech-engineering.com
> <mailto:cwarfel at entech-engineering.com>> wrote:
>
> Just reading more slowly, each inverter has to be on its on
> separate disconnect means. You cannot put multiple inverters
> on the same disconnecting means unless there are individual
> disconnecting means upstream.
>
> On 2/25/2019 10:53 AM, William Miller wrote:
>>
>> Friends:
>>
>> I have an NEC code question on an upcoming project. It is a
>> home that has an existing 8 kW ground-mounted grid-tied
>> system. The owner wants to add another 10 kW of grid-tied
>> PV. My question is about 705.12, point of connection.
>> Specifically section (D)(1). That section states:
>>
>> /The source interconnection of one or more inverters
>> installed in one system shall be made at a dedicated circuit
>> breaker or fusible disconnecting means./
>>
>> So if there are going to be two inverters on premise, do the
>> outputs have to be aggregated to connect via one circuit
>> breaker? This might be difficult to do as the exiting
>> inverter is connected via a different sub-panel than the one
>> that is planned to receive the new inverter output.
>>
>> This article
>> <https://iaeimagazine.org/magazine/2014/01/16/load-side-pv-connections/>
>> addresses the question.
>>
>> I would be very grateful if any of you can share any
>> experience you might have in interpreting this section of the
>> code.
>>
>> Thanks in advance.
>>
>> William
>>
>>
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> --
> Christopher Warfel
> ENTECH Engineering, Inc.
> PO Box 871, Block Island, RI 02807
> 401-466-8978
> <http://entech-engineering.com>
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Christopher Warfel
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