[RE-wrenches] Enphase grid tie question

Tue Jun 26 10:24:01 PDT 2012

Hi Jesse,

Thank you for specifying Enphase on your commercial project.

At Enphase, we provide design review support for your commercial projects.
You can reach out to your account representative at Enphase or myself for
this design support.

The Envoy that we have been shipping this year can monitor up to 500
microinverters (Model ENV-120-01.)  That is a little more than 100kW.

It is always okay to run 8 of the output circuits to a single load
center.

The numbers below apply to a 3 phase 208/120 wye interconnection.

8 x 24 M215 per circuit would be 41.28kW

(192 modules x 215 watts = 41,280 watts / 208 / 1.732 = 115 Amps x 1.25 =
144A OCPD)

That could be interconnected on a 150A, 3 phase 208V OCPD.  (Busbar
considerations are separate)

An alternative method to calculate the ampacity would be to use the 1.0A
figure for 208V, which we publish on our M1215 spec sheet.  That
calculation would be:
(192 x 1.0A = 192A / 1.732 = 110.9A x 1.25 = 138.6 Amps minimum OCPD)

For systems with multiple Envoys on a single utility transformer, there are
some special considerations, which are addressed in our Multi-Tenant Design
Document at:
EnphaseAppNote_Multi_Tenant.pdf<http://enphase.com/wp-uploads/enphase.com/2011/03/EnphaseAppNote_Multi_Tenant.pdf>

With M215s at 208V 3 phase, you could design for 24 microinverters per
branch circuit

The process of center feeding is not necessary for all systems, but can
allow for you to reduce the total wire loss in the system.  We have an
application note on our website which addresses this at:
EnphaseTechBrief_Vdrop_M215.pdf<http://enphase.com/wp-uploads/enphase.com/2011/12/EnphaseTechBrief_Vdrop_M215.pdf>

For best results, we recommend installing the Envoy system monitor on a
dedicated receptacle off of the PV load center.  The Envoy can be installed
in an outdoor rated junction box.  We have details on outdoor mounting in
the Multi-tenant App Note above.

If any of you have questions about commercial designs with Enphase, feel
free to reach out to me.

On Tue, Jun 26, 2012 at 5:27 AM, Jason Szumlanski <jason at fafcosolar.com>wrote:

> I'll email you off-list a 1-line diagram from a system with 164
> microinverters broken down into 8 strings in a 208V system. This particular
> system used two subpanels to accumulate PV, but that was only because we
> had to backfeed two existing subpanels due to the size of existing 480/208V
> transformers. You will have to look at the utility service and all existing
> equipment.
>
> Regarding the breakers in the subpanel, you will only need a maximum of a
> 20A breaker for each string. The max inverters per string is 25 and the
> calculation for OCPD is:
>
> 215W / 208V x 25 inverters / 1.732 x 1.25 = 18.65A
>
> You DO need to observe the 120% rule for the combining subpanel,
> regardless of whether there are loads present, at least in jurisdictions
> where I have worked. I've heard that some inspectors will allow you to
> ignore it if it is labeled as a PV combiner with "add no loads" notation.
>
> Use a MLO panel with a fusible disconnect between the subpanel and the
> interconnection point. If you use a 225A panel, you can feed it with 270A.
> With eight 20A backfed PV circuits, you would need to protect the line side
> of the panel with a 100A fusible disconnect. That probably isn't going to
> work. You may be best off from a cost perspective using two 225A subpanels
> and two 60A fusible disconnects. Anything larger than a 60A 3P disconnect
> and the price skyrockets. It all depends on your circuit calculations and
> the existing equipment. Of course, you would need two spaces for your
> interconnection point.
>
> Jason Szumlanski
> Fafco Solar
>
>
> On Tue, Jun 26, 2012 at 7:25 AM, Chris Mason <cometenergysystems at gmail.com
> > wrote:
>
>> I would use a 200A sub panel with 8 x 25A breakers to accumulate the PV
>> output, as I doubt you could install 8 3Ph breakers in your main panel, and
>> why would you want to?
>> You shouldn't need to observe the 120% rule for the main breaker on the
>> main panel as there are no loads. Same for the panel rating.
>> The main panel would need a 200A breaker for the PV input and 120% comes
>> into play. Be careful that breaker is rated as bi-directional.
>>
>> Chris
>>
>>
>> On Mon, Jun 25, 2012 at 10:39 PM, Jesse Dahl <dahlsolar at gmail.com> wrote:
>>
>>>
>>> All,
>>>
>>> I'm looking for ideas on the electrical integration of the following
>>> system:
>>>
>>> 800A service
>>> PV system employing enphase 215W inverters broken down into 8 output
>>> circuits.  Each circuit will be 208V 3 phase 20A.
>>>
>>> The question is on how to grid tie this.  My first thought is a sub
>>> panel for PV intertie only.  I saw a similar diagram on the enphase
>>> website, using 5 circuits and a 125A panel....
>>>
>>> What are people doing in situations like this?
>>>
>>> Thanks as always.
>>>
>>>
>>> Jesse
>>> Sent from my iPad!!!
>>> _______________________________________________
>>> 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
>>>
>>>
>>
>>
>> --
>> Chris Mason
>> President, Comet Systems Ltd
>> www.cometenergysystems.com
>> Cell: 264.235.5670
>> Skype: netconcepts
>>
>>
>> _______________________________________________
>> 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
>>
>>
>>
>
> _______________________________________________
> 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
>
>
>

-- 

Cordially,

*Nick Soleil*

*Field Applications Engineer
*

*Enphase Energy*

Mobile: (707) 321-2937
**

1420 North McDowell

Petaluma, CA 94954

www.enphase.com <http://www.enphaseenergy.com/>

P: (707) 763-4784 x7267

F: (707) 763-0784

E: nsoleil at enphaseenergy.com

[image: nabcep logo] Certified Solar PV Installer #03262011-300

“Don’t get me wrong: I love nuclear energy! It’s just that I prefer fusion
to fission. And it just so happens that there’s an enormous fusion reactor
safely banked a few million miles from us. It delivers more than we could
ever use in just about 8 minutes. And it’s wireless! .”

- William McDonough

This email message is for the sole use of the intended recipient(s) and may contain confidential and/or privileged information. If you are not an intended recipient, you may not review, use, copy, disclose or distribute this message. If you received this message in error, please contact the sender by reply email and destroy all copies of the original message. 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20120626/f0522187/attachment-0004.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.jpg
Type: image/jpeg
Size: 1981 bytes
Desc: not available
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20120626/f0522187/attachment-0004.jpg>