[RE-wrenches] Line Side Feed In and Disconnects

Tue Mar 10 10:28:28 PDT 2009

Wayne,

As you suggested, because this is a new service, a PV service disconnect is
required. The question of whether a second disconnect is required, a new
disconnect for the main service, is a Code issue, as far as I can tell. It
is also an interpretation, but I¹ll get to that later.

It just so happens that the June/July issue of SolarPro magazine will have
an extensive article on making PV interconnections. The authors are Ryan
LeBlanc and Tarn Yates from SPG Solar. From their article, here are some
Code articles that apply to selecting and locating a disconnect for a line
side connection:

230.66  Disconnect shall be listed for use as service equipment.
230.70(A)(1)  Disconnect shall be installed at a readily accessible
location.
230.72(A)  All service disconnects shall be grouped together.

The last article is no doubt the one that the AHJ is referencing in this
case. 

The reason I feel that this extra expense and effort is an interpretation,
as much as it is a Code issue, is that you could make a load side connection
and still have the math work for the feed-in tariff program and for the
revenue metering. 

How is that? 

Well, a meter on the inverter output circuits will read the total PV kWh for
the feed-in tariff. A bi-directional meter for the revenue meter will read
in-flow from the utility and out-flows to the utility. The difference
between total PV kWh and the out-flow-kWh are the PV generated kWh that the
customer used on site rather than export to the utility. Right? Whatever PV
generated energy is not exported to the utility is used on site.

So for billing purposes the customer is charged as follows:

Total kWh for billing = In-flow kWh + (feed-in tariff kWh  out-flow kWh)

Theoretically, this can also be implemented affordably by the utility: move
the exiting revenue meter to the PV system; add a $100 bi-directional meter
to the original meter can. Finished.

Making a line-side connection is often difficult and expensive, especially
when you now have to add a new service disconnect for the facility. At least
in theory, it is also dangerous; the fault-currents there are higher. You
have these implementation issues on the one hand. On the other hand you have
a spreadsheet, or a one-time fix the the utility¹s billing software.

So I think the utility is making this more onerous than they need to.
Especially for small generators, the cost of this service upgrade will kill
the deal. The utility probably isn¹t interested in this solution, but we can
still dream of the perfect fix.

David Brearley, Technical Editor
SolarPro magazine 
NABCEP Certified PV Installer 
david.brearley at solarprofessional.com
Direct: 541.261.6545
Fax:  541.512.0343

Visit our Web site at solarprofessional.com

On 3/9/09 5:25 PM, "Allan Sindelar" <allan at positiveenergysolar.com> wrote:

> Wayne,
> Use this as a tool: http://www.solarabcs.org/utilitydisconnect/
> and this: http://www.nrel.gov/docs/fy08osti/42675.pdf
>  
>  
> Allan Sindelar 
> allan(at)positiveenergysolar.com <mailto:allan at positiveenergysolar.com>
> NABCEP Certified Solar PV Installer
> Positive Energy, Inc.
> 3201 Calle Marie 
> Santa Fe NM 87507
> 505 424-1112 
> www.positiveenergysolar.com
> 
> Please consider the environment before printing this e-mail.
> 
> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Wayne Irwin
> Sent: Monday, March 09, 2009 4:41 PM
> To: re-wrenches at lists.re-wrenches.org
> Subject: [RE-wrenches] Line Side Feed In and Disconnects
> 
> Hello Wrenches,
> 
> Here in Gainesville, Fla. we have recently adopted a Feed In Tariff.
> So, now we are supposed to directly feed the line side of the utility meter
> (essentially a new service). No big deal.
> As usual we use an AC disco between the inverter and the grid. However, the
> permit department is requiring that we install and additional disco between
> the existing service feed and the distribution panel to group all disco's in
> the same location. This especially adds an additional expense when dealing
> with 3 phase systems as well as the raises the question, is this really the
> National Electrical Code or just an interpretation? Your thoughts?
> 
> Wayne Irwin, President
> Pure Energy Solar International Inc.
> Lic # CVC56695 
>  <mailto:PureEnergySolar at hotmail.com>
> 
> 
> 
> 
> Date: Mon, 9 Mar 2009 18:20:57 -0400
> From: reellison at gmail.com
> To: re-wrenches at lists.re-wrenches.org
> Subject: Re: [RE-wrenches] Small Torque Wrench
> 
> I got mine from "the knife and tool store" http://myworld.ebay.com/don19470/
> on E bay. nice tool, adjustable 10 - 50 In Oz and he has others, just get the
> adapter that lets you use 1/4" drive bits and your good to go. It is a german
> tool and i use it on all breaker connections as well as others.
>  
> Later,
> Bob
> 
> On Mon, Mar 9, 2009 at 12:10 PM, Peter Parrish <peter.parrish at calsolareng.com>
> wrote:
>>  
>>  
>> We have a great torque wrench for  snugging down module clamps, Sharp SRS
>> bolts, etc. What do folks use to insure  that wire terminals are torqued to
>> spec? We¹re talking 1.1 to 3.3 N-m (10-30  in-lbs). I¹m imagining something
>> compact like an over-sized screwdriver.
>>  
>> - Peter
>>  
>> Peter T. Parrish,  President
>> California Solar Engineering, Inc.
>> 820 Cynthia Ave., Los  Angeles, CA 90065
>> Ph 323-258-8883, Mobile 323-839-6108, Fax  323-258-8885
>> CA Lic. 854779, NABCEP Cert. 031806-26
>> peter.parrish at calsolareng.com
>> 
>> _______________________________________________
>> List  sponsored by Home Power magazine
>> 
>> List Address: RE-wrenches at lists.re-wrenches.org
>> 
>> Options  & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>> 
>> List-Archive:  
>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>> 
>> List  rules & etiquette:
>> www.re-wrenches.org/etiquette.htm <http://www.re-wrenches.org/etiquette.htm>
>> 
>> Check  out participant bios:
>> www.members.re-wrenches.org <http://www.members.re-wrenches.org/>
>> 
>> 
>> 
>> 
>> 
>> Windows Live Groups: Create an online spot for your favorite groups to meet.
>> Check it out. 
>> <http://windowslive.com/online/groups?ocid=TXT_TAGLM_WL_groups_032009>
>> 
>> _______________________________________________
>> List sponsored by Home Power magazine
>> 
>> List Address: RE-wrenches at lists.re-wrenches.org
>> 
>> Options & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>> 
>> List-Archive: 
>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>> 
>> List rules & etiquette:
>> www.re-wrenches.org/etiquette.htm
>> 
>> Check out participant bios:
>> www.members.re-wrenches.org
>> 
>> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20090310/a73ada1e/attachment-0003.html>