Rapid shutdown required on 12v PV array?

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TrentW

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Field Engineer
Does the rapid shutdown requirement apply to a system that operates at under 30v? Scenario off-grid cabin with utility hookup Utility feeding electrical panel and inverter feeding a seperate stand alone "emergency circuit panel"
  • 800w 12v panels in parallel, max open string voltage 22v (roof mounted)
  • PV Disconnect
  • GFPD
  • 12v battery bank 1300ah with disconnect
  • 3500w (12v) single phase 120v inverter tied to seperate panel powering critical circuits. (Water line heater, well pump, lighting)
  • All UL equipment, breakers, wiring, and piped according to NEC
AHJ failed inspection due to no Rapid shutdown??? Wouldn't this classify as an emergency or a separately derived system? At the very lease be exempt from this because it operates under the 30v threshold requiring it in the first place?
 
You have it with your final sentence. It meets rapid shutdown requirements because its voltages never exceed the controlled limits.

One problem I see is that 690.12 is written as if such a thing is not possible without a 'rapid shutdown switch', which needs signage. (A system design like yours is not at all common these days.) Maybe you can convince the inspector to accept some alternative signage to the normal requirements. It might be a custom placard that says something like: "Array operates under 30V at all times. No rapid shutdown switch is required."
 
Unfortunately for you, all PV systems on or in a building require RSD with only one unhelpful to you exception. The catch with yours is that it complies with the RSD requirements inherently and without the need for any activation. You need to explain to the AHJ that no initiation device is needed to comply with RSD and find out how they want to proceed since the code does not cover this situation.

On a side note, how can this be an off-grid cabin if it has utility service?
 
pv_n00b said:
Unfortunately for you, all PV systems on or in a building require RSD with only one unhelpful to you exception. The catch with yours is that it complies with the RSD requirements inherently and without the need for any activation. You need to explain to the AHJ that no initiation device is needed to comply with RSD and find out how they want to proceed since the code does not cover this situation.

On a side note, how can this be an off-grid cabin if it has utility service?
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They run to separate panels with no connection of any sort between them. The utility could disappear and not affect the PV in any way. So, that makes the PV off grid? :unsure:
 
Just install a 'Readily accessible switch that plainly indicates whether it is in the “off” or “on” position' with no connection to anything. When someone flips the switch to off, waits 30 seconds, and measures the voltages, they will be under 30V. Meets all the requirements.

Cheers, Wayne
 
wwhitney said:
Just install a 'Readily accessible switch that plainly indicates whether it is in the “off” or “on” position' with no connection to anything. When someone flips the switch to off, waits 30 seconds, and measures the voltages, they will be under 30V. Meets all the requirements.

Cheers, Wayne
Click to expand...
There must be a violation in there somewhere, but darned if I can find it.
 
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