[RE-wrenches] 1987 NEC

David Brearley david.brearley at solarprofessional.com
Tue Jul 19 14:34:21 PDT 2011 

Presumably the latter‹added as part of the cycle of revisions initiated in
1987. 


On 7/19/11 3:29 PM, "Hans Frederickson" <hans at fredelectric.com> wrote:

> David,
> Thanks for the interesting history on GFPDs. My copy of the 1987 NEC does not
> have 690-5, and it's not missing any pages. Either my code book is an
> incomplete printing or perhaps John Wiles was referring to a 1987 proposal
> that didn't make it into the code until the 1990 NEC.
>  
> Regards,
> -Hans 
> 
> 
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of David Brearley
> Sent: Tuesday, July 19, 2011 12:57 PM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] 1987 NEC
> 
> Hans,
> 
> John Wiles described the evolution of this standard for a Home Power article
> that we referenced later in a SolarPro on PV System Ground Faults:
> 
> http://solarprofessional.com/article/?file=SP2_5_pg60_Mync
> 
> ³As described by John Wiles, program manager for the Institute for the Energy
> and the Environment, in the February/ March 2008 Home Power article
> "Ground-Fault Protection Is Expanding," Article 690.5 was added to the NEC in
> 1987. One of Wiles¹ first projects in the PV industry was to develop
> ³prototype hardware² to meet the new Code requirement. "The basic concept (of
> the original GFPD prototype)," writes Wiles, "was to insert a 0.5- or 1-amp
> circuit breaker in the dc system-bonding conductor." This small circuit
> breaker senses any current between the grounded current-carrying conductor and
> the grounding system, tripping if current exceeds the 0.5 A or 1 A rating. By
> mechanically linking this smaller breaker to larger capacity breakers that are
> installed inline with the ungrounded current-carrying array conductors, it is
> possible to detect, interrupt and indicate that a ground fault has occurred,
> and to disconnect the fault.
> 
> These early GFPDs were manufactured for 48 V or lower PV systems. According to
> Wiles, ³As higher voltage, utility-interactive PV inverters became available
> in the late 1990s, using a 0.5- or 1-amp fuse as the sensing element and the
> inverter¹s control electronics to monitor the fuse was more cost effective.²
> While the sensing equipment may have changed, in general the role of the
> modern GFPD remains the same as it was in 1987:
> 
> 1. Detect ground faults in PV arrays.
> 2. Interrupt the fault current.
> 3. Indicate that a ground fault has occurred.
> 4. Disconnect the faulted part of the array.
> 
> These four GFPD requirements for grounded PV arrays are spelled out in NEC
> 690.5(A) and 690.5(B). The former requires ground-fault detection and
> interruption (GFDI), which includes the provision to indicate the presence of
> a ground fault. The latter requires that faulted circuits be isolated either
> by disconnecting the ungrounded conductors of the faulted circuit or by
> shutting down power to the output power circuits of the inverter or charge
> controller.
> 
> A final GFPD requirement is found in Article 960.5(C), which calls for a
> visible warning in the proximity of the ground-fault indicator. The warning
> could be an LED, an LCD or both. In general, the manufacturer provides this
> electric shock hazard warning as part of the listed grid-tied inverter or
> charge controller. However, where a PV system includes batteries, the
> installer must apply a duplicate warning label near the batteries, stating:
> 
> WARNING 
> ELECTRIC SHOCK HAZARD
> IF A GROUND FAULT IS INDICATED, NORMALLY
> GROUNDED CONDUCTORS MAY BE UNGROUNDED
> AND ENERGIZED 
> 
> One change in the GFPD requirements introduced in 1987 is that it is no longer
> necessary to short-circuit, or ³crowbar,² the PV array in the event of a
> ground fault. This added step had the effect of reducing the PV array voltage
> to zero, minimizing shock hazard. The requirement was dropped in a subsequent
> Code cycle, as leaving the array in a short-circuited condition created
> several other issues.²
> 
> 
> If you¹re a Home Power subscriber, you can access the original article in the
> HP archives. If not, it is summarized above.
> 
> Best,
> 
> David Brearley, Senior Technical Editor
> SolarPro magazine
> NABCEP Certified PV Installer 
> david.brearley at solarprofessional.com
> Direct: 541.261.6545
> 
> 
> On 7/19/11 2:19 PM, "Hans Frederickson" <hans at fredelectric.com> wrote:
> 
>> Kent,
>> I'm not a geezer yet, but thanks to my dad I do have a  copy of the 1987 NEC.
>> 690-5 (Ground Fault Detection and Interruption) was  added in the 1990 NEC.
>> There is no 690-5 or mention of ground fault  detection/interruption in the
>> 1987 NEC.
>> 
>> In the 1990 NEC, section 690-5 is very small compared to 690.5 in  the 2011
>> NEC. Here's the complete text from 1990:
>> 
>> "690-5. Ground Fault Detection and Interruption.  Roof-mounted  photovoltaic
>> arrays located on dwellings shall be provided with ground-fault  protection
>> to reduce fire hazard. The ground-fault protection circuit shall be  capable
>> of detecting a ground fault, interrupting the fault path, and  disabling the
>> array."
>> 
>> The handbook for 1990 goes on to say that the gfp device  must:
>> 1) detect the ground fault
>> 2) open the grounded conductor to  interrupt the ground fault
>> 3) open the ungrounded conductors and short the  photoltaic array source to
>> disable it
>> 
>> For some reason, I've never heard of item #3, specifically the part  about
>> shorting the array. Can anyone shed light on  this?
>> 
>> Regards,
>> -Hans
>> 
>>  
>> 
>>  From: re-wrenches-bounces at lists.re-wrenches.org
>> [mailto:re-wrenches-bounces at lists.re-wrenches.org]  On Behalf Of Kent
>> Osterberg
>> Sent: Monday, July 18, 2011 10:07  PM
>> To: gary at icarussolarservices.com;  RE-wrenches
>> Subject: Re: [RE-wrenches] 1987 NEC
>> 
>> Gary,
>> 
>> No one else has  come up with a 1987 NEC. If you can get a copy of 1987
>> section 690.5 (I think  it was 690-5 back then), I'd appreciate it.
>> 
>> Kent Osterberg
>> Blue  Mountain Solar
>> 
>> 
>> 
>> Gary Willett wrote:
>>  
>>> Kent:
>>> 
>>> I am a member of the  International  Association of Electrical Inspectors
>>> (IAEI), and they're  headquartered here in  the Dallas area.
>>> 
>>> If you aren't successful  getting the info from a  Wrench with the 1987 code
>>> book, let me know  and I am sure I can request a  FAXed copy of 1987 section
>>> 690.5.
>>> 
>>> 
>>>      
>>>  
>>> 
>>> Regards,
>>> 
>>> Gary Willett, PE
>>> Gary at IcarusSolarServices.com
>>> 
>>> On  7/15/2011 4:30 PM, Kent Osterberg  wrote:
>>>  
>>>> I'm looking  for the text of 1987 NEC 690.5  to compare with 2011 version.
>>>> If any of you  geezers have kept copies  that old, please contact me off
>>>> list. Thanks. 
>>>> 
>>>> Kent Osterberg
>>>> Blue Mountain Solar
>>>> _______________________________________________
> 
> 
> 
> 
> 
> 
> 

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