[RE-wrenches] Rapid Shut Down and the 10 Second Rule Questions

[David Brearley]

Mark,

Bill Brooks’ rapid shutdown article for SolarPro does a nice job walking through the individual subsections of 690.12. 

He also addresses initiation device (type and location), which is not covered in the NEC. Here is the relevant text:

What about the rapid-shutdown initiator? NEC 690.12 does not specify where you should locate the initiating device or what type of device you must install. This lack of detail is intended to provide system integrators and AHJs with the flexibility to adapt rapid-shutdown solutions to the complexities of the built environment. While the best location for a rapid-shutdown device and the required label is typically at or near the service equipment, the fire service may have preplanned emergency response tactics for some large commercial or industrial buildings that favor a different location. 

One of the simplest ways to initiate rapid shutdown is to set it up to occur automatically upon loss of ac power. This is why NEC 2014 does not require a specific type of rapid-shutdown initiation device. If you install a roof-mounted residential microinverter system or a commercial PV system using roof-mounted string inverters located within 10 feet of the array, you do not need any special equipment to initiate rapid shutdown; you can accomplish this function simply by interrupting utility-supplied power to the inverters. Some companies have developed various rapid-shutdown switches, and claim that rapid shutdown requires these extra switches. However, you have to install an extra rapid-shutdown switch only when you need to turn the array off by some means other than loss of utility power, as with battery-backup systems or inverters equipped with a daytime backup-power outlet.

NEC 690.12 does not specify how many buttons, switches or movements of the hand are allowed to complete rapid shutdown. Ideally, the process should only require one action. As written today, however, the language in 690.12 provides system integrators and AHJs with the flexibility to consider alternatives. Note that if the system design requires more than one action to initiate rapid shutdown, the 10-second time limit still applies. Therefore, where systems are deployed with more than one initiation device or switch, they should all be in close proximity so that emergency personnel can de-energize all of the PV system circuits on the building within 10 seconds. Further, labeling must clearly identify all of the initiation devices and all of the steps required to complete rapid shutdown.

Here’s a link to the complete article: http://bit.ly/1xuDxx7 <http://bit.ly/1xuDxx7>

I hope this is of some assistance,

David Brearley
Senior Technical Editor, SolarPro magazine
NABCEP Certified PV Installation Professional
david.brearley at solarprofessional.com
Direct: 541.261.6545
Follow us on Twitter: @SolarPro

Check out this AMAZING music video tribute to SolarPro: http://bit.ly/1qfMCCh


> On Feb 3, 2015, at 1:50 PM, re-wrenches-request at lists.re-wrenches.org wrote:
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> Today's Topics:
> 
>   1. Re: Rapid Shut Down and the 10 Second Rule Questions (Mark Frye)
>   2. Re: Rapid Shut Down and the 10 Second Rule Questions
>      (Jerry Shafer)
>   3. Re: Rapid Shut Down and the 10 Second Rule Questions (Mark Frye)
>   4. How to isolate the array DC (Mark Frye)
>   5. Re: How to isolate the array DC (Glenn Burt)
>   6. Re: Rapid Shut Down and the 10 Second Rule Questions
>      (Christopher Warfel)
>   7. Re: How to isolate the array DC (Mark Frye)
>   8. Re: Rapid Shut Down and the 10 Second Rule Questions
>      (william at millersolar.com <mailto:william at millersolar.com>)
>   9. Re: How to isolate the array DC (Jerry Shafer)
>  10. Re: How to isolate the array DC (boB at midnitesolar.com <mailto:boB at midnitesolar.com>)
> 
> From: Mark Frye <markf at berkeleysolar.com <mailto:markf at berkeleysolar.com>>
> To: glenn.burt at glbcc.com <mailto:glenn.burt at glbcc.com>, RE-wrenches <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at lists.re-wrenches.org>>
> Date: February 2, 2015 at 3:06:39 PM CST
> Reply-To: RE-wrenches <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at lists.re-wrenches.org>>
> Subject: Re: [RE-wrenches] Rapid Shut Down and the 10 Second Rule Questions
> 
> 
> I really do wonder then...
> 
> Right now, you go up to the burning house and pull the meter, bingo, no AC anywhere. So why do we need the "kill" switch next to the service (or where ever).... IF you drive the roof top contactor with 120vac or with 24 vdc made from a power supply powered by 120vac. Either way, pull the meter, no more AC and no more power to the contactor coil on the roof, so DC limited to the location of the contactor. 
> 
> Not really sure how the requirement for the stop switch got into the Code.
> 
> Mark Frye

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