Rapid Shutdown (RSD) with Midnite SOB

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bhsolar
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Posts: 3
Joined: Sun Jun 09, 2019 10:06 am

Rapid Shutdown (RSD) with Midnite SOB

Post by bhsolar » Sun Jun 09, 2019 10:33 am

RSD compliance (NEC 690.12) adds additional equipment and installation costs. So having the most cost-effective option is desirable. Currently Outback has tested the Fire Raptor and Tigo products, which are more cost-effective options than Outback's RSD-1. The RSD-1 is also a fused 3-string combiner. However, when one or two PV strings are used a combiner is not necessary.

The lowest cost product I am aware of is the Midnite SOB (shut-off box). I have tested it with Skybox but unfortunately, it resulted in solar fault #33792. I believe this may be because the SOB uses powerline communication. The SOB consists of only two parts: a transmitter, which uses a current transformer on the PV circuit, and an MC4/T4 connecting receiver installed anywhere within the PV string (multiple strings require one receiver each). The transmitter (when powered) tells the receiver to close the PV circuit within the array; when the transmitter loses power it stops transmitting and the receiver(s) turn off. This RSD solution costs less than $200 for a single string.

The SOB transmitter can be powered by the load panel, allowing PV to operate off-grid. When needed, an outdoor 120V switch can be used for RSD activation. The RSD state can also be activated within the Skybox, depending on requirements.

I would be happy to see this product tested and made compatible with the Skybox.

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Gwendoly Espe
Applications Engineering
Posts: 184
Joined: Wed Feb 22, 2017 11:04 am

Re: Rapid Shutdown (RSD) with Midnite SOB

Post by Gwendoly Espe » Mon Jun 10, 2019 8:08 am

Have you considered Tigo or IMO without a combiner, if a combiner is not necessary? We do not require a combiner for the SkyBox units, so one could connect directly to the SkyBox unit and use Tigo or IMO for the NEC 2017 cycle.

The SkyBox-RSD-1 is more for NEC 2014 requirements. If you were to use that combiner (for whatever reason) and be in NEC 2017 code cycle, you'd still need MLPE's.

I'll have to ask one of the PMs if SkyBox will be compatible with the SOBs, I think we have or are in the middle of testing that.
Gwendoly Espe
Applications Engineer


Alpha Technologies Inc. / OutBack Power Technologies
3767 Alpha Way Bellingham WA 98226 USA
http://www.alpha.com

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Gwendoly Espe
Applications Engineering
Posts: 184
Joined: Wed Feb 22, 2017 11:04 am

Re: Rapid Shutdown (RSD) with Midnite SOB

Post by Gwendoly Espe » Tue Jun 11, 2019 11:48 am

We are focused on testing SkyBox (and FM100) with the SOB for NEC2017 compliance. We donÔÇÖt see a successful path forward.
Gwendoly Espe
Applications Engineer


Alpha Technologies Inc. / OutBack Power Technologies
3767 Alpha Way Bellingham WA 98226 USA
http://www.alpha.com

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