[RE-wrenches] Code reference request

Wed Nov 5 09:55:13 PST 2014

Hi Dana,
If you bond the the ac and dc grounding systems using the optional method
outlined in 690.47(C)(3), then the AC EGC and the DC GEC can be the same
conductor (regardless of TL or not).  And this section of the Code
specifically allows the DC GEC to be sized per 250.122 for *ungrounded*
systems (and not larger than the ungrounded conductors). So in some ways
this is an end run around the GEC question.

However, if the inverter manual says to follow 250.166 sizing requirements,
then I'd think 110.3(B) is going to take precedence for this installation
and you don't have much choice except to have a minimum 8AWG DC GEC
conductor and installed per 250.64  - but it could serve the purpose of the
AC EGC too.
Cheers,
Rebekah

On Wed, Nov 5, 2014 at 12:39 PM, Dana Brandt <dana at ecotechenergy.com> wrote:

> Thanks for the reply and article, August. John Wiles's article makes a
> clear statement that the GEC is not required for TL inverters. I wish the
> code would say it that clearly! I think I'm going to have a tough time
> convincing inspectors the GEC isn't required with such unclear language in
> the code. We'll see....
>
> Thanks again!
>
> Dana
>
> Dana Brandt
> Ecotech Energy Systems, LLC
> www.ecotechenergy.com
> dana at ecotechenergy.com
> 360.318.7646
>
> On Mon, Nov 3, 2014 at 12:45 PM, August Goers <august at luminalt.com> wrote:
>
>> Hi Dana,
>>
>>
>>
>> This is still a confusing issue, I agree. This article helps a bit:
>>
>>
>>
>> http://www.nmsu.edu/~tdi/pdf-resources/IAEI%20Mar_Apr%202012.pdf
>>
>>
>>
>> If you look in a SMA TL inverter installation manual, for example, they
>> only mention equipment grounds – there is no reference to a GEC that I can
>> find. The 2014 code doesn’t seem to have clear wording on not requiring a
>> GEC to me but Rebekah’s recap below is spot on. Luckily it is widely
>> accepted in our neck of the woods that TL inverters don’t need GECs.
>>
>>
>>
>> I’m not familiar with the Solectria TL product. It sounds like it will be
>> best to call them if you need to install one of their inverters.
>>
>>
>>
>> Best,
>>
>>
>>
>> August
>>
>>
>>
>> *From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On
>> Behalf Of *Dana Brandt
>> *Sent:* Monday, November 03, 2014 12:06 PM
>> *To:* RE-wrenches
>> *Subject:* Re: [RE-wrenches] Code reference request
>>
>>
>>
>> I think I'm a bit confused on this point. I can't seem to find the code
>> that specifically exempts the GEC requirement for inverters of ungrounded
>> PV systems. The only exception I can find is only for AC PV modules (2014
>> NEC 690.47 (C) ).
>>
>> I just looked in the installation manual for Solectria's new TL inverters
>> and found this:
>> "Per NEC 690.47, a GEC must be installed, and the Grounding Electrode
>> Terminal (GET) conductor must be sized in accordance with NEC article
>> 250.166."
>>
>> What am I missing?
>>
>> Thanks,
>>
>>
>> Dana
>>
>> Dana Brandt
>> Ecotech Energy Systems, LLC
>> www.ecotechenergy.com
>> dana at ecotechenergy.com
>> 360.318.7646
>>
>>
>>
>> On Tue, Oct 28, 2014 at 11:30 AM, Rebekah Hren <
>> rebekah.hren at o2energies.com> wrote:
>>
>> If you are on 2014:
>>
>>  690.47(B)
>>
>> An ac equipment grounding system shall be permitted
>>
>> to be used for equipment grounding of inverters and other
>>
>> equipment *and for the ground-fault detection reference for *
>>
>> *ungrounded PV systems.*
>>
>>
>>
>> and 690.47(C)(3)
>>
>> *For ungrounded systems, this conductor shall be sized in accordance with
>> 250.122 *and shall
>>
>> not be required to be larger than the largest ungrounded
>>
>> phase conductor.
>>
>>
>>
>> On Tue, Oct 28, 2014 at 2:22 PM, Gary Willett <
>> Gary at icarussolarservices.com> wrote:
>>
>> Kirk:
>>
>> A DC grounding electrode conductor (GEC) is not required for inverters
>> that do NOT have a ground reference for the PV+ and PV- conductor(s) from
>> the PV array.
>>
>> A GEC is not required if the string inverter is one of the new TL
>> (transformerless) types.  Also, this applies to micro-inverters such as the
>> new Enphase M250 and later versions of the M215.
>>
>> Where this applies, only a properly sized equipment grounding conductor
>> (EGC) is required.
>>
>> The EGC is sized according to [NEC 690.45] and can be a minimum of #14AWG
>> when not exposed to damage, or #6AWG when exposed to potential damage.
>>
>> Regards,
>>
>> Gary Willett PE
>> Icarus Engineering LLC
>>
>>
>>
>> On 10/28/14, 12:53 PM, Kirk wrote:
>>
>> Hi,
>> I'm on a jobsite without my code book. Could someone tell me where in the
>> code ungrounded systems do not require the inverter GEC? Basically my
>> onsite electrician doesn't believe me. Thanks.
>>
>> Kirk Herander
>> VSE
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-- 
Tel: 336.266.8800
http://o2energies.com/
Project Engineer
NABCEP Certified PV Installation Professional™ 091209-85
NC Licensed Electrical Contractor

This message, together with any attachments, is intended only for the named
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