[RE-wrenches] Tranformless inverter

[August Goers]

Hi Bill and Wrenches -



For ungrounded arrays what specific fusing and or DC disconnect requirements
are needed compared to grounded arrays?



I'm trying to sort through the code but nothing is popping out at me besides
what was already mentioned about needing to disconnect both the positive and
negative lines on the DC side. In SMA's case I'm guessing that their new
transformerless inverters with integrated DC disconnects and fuses may
already take of all the requirements?



Best,



August





August Goers



Luminalt Energy Corporation

1320 Potrero Avenue

San Francisco, CA 94110

m: 415.559.1525

o: 415.641.4000

august at luminalt.com







*From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Bill Brooks
*Sent:* Friday, October 01, 2010 8:29 AM
*To:* 'RE-wrenches'
*Subject:* Re: [RE-wrenches] Tranformless inverter



All,



Transformerless inverters are simply a subset of ungrounded or resistively
grounded PV systems covered by the NEC in 690.35 since the 2005 code cycle.
Power-One has been marketing their ungrounded inverter in the U.S. for
several years now. It was listed by CSA. The requirements for ungrounded
systems in 690.35 are as follows:



*          "Photovoltaic power systems shall be permitted to operate with
ungrounded photovoltaic source and output circuits where the system complies
with 690.35(A) through 690.35(G).

-      *(A) Disconnects. *All photovoltaic source and output circuit
conductors shall have disconnects complying with 690, Part III.

-      *(B) Overcurrent Protection. *All photovoltaic source and output
circuit conductors shall have overcurrent protection complying with 690.9.

-      *(C) Ground-Fault Protection. *All photovoltaic source and output
circuits shall be provided with a ground-fault protection device or system
that complies with (1) through (3):

*          (1) Detects a ground fault.

*          (2) Indicates that a ground fault has occurred

*          (3) Automatically disconnects all conductors or causes the
inverter or charge controller connected to the faulted circuit to
automatically cease supplying power to output circuits.

-      *(D) *The photovoltaic source and output conductors shall consist of
the following:

-      (1) Nonmetallic jacketed multiconductor cables

-      (2) Conductors installed in raceways, or

-      (3) Conductors listed and identified as Photovoltaic (PV) Wire
installed as exposed, single conductors.

-      *(E) *The photovoltaic power system direct-current circuits shall be
permitted to be used with ungrounded battery systems complying with
690.71(G).

-      *(F) *The photovoltaic power source shall be labeled with the
following warning at each junction box, combiner box, disconnect, and device
where the ungrounded circuits may be exposed during service:

WARNING

ELECTRIC SHOCK HAZARD

THE DC CIRCUIT CONDUCTORS OF THIS

PHOTOVOLTAIC POWER SYSTEM ARE

UNGROUNDED AND MAY BE ENERGIZED

WITH RESPECT TO GROUND DUE TO

LEAKAGE PATHS AND/OR GROUND FAULTS.

-      *(G) *The inverters or charge controllers used in systems with
ungrounded photovoltaic source and output circuits shall be listed for the
purpose.



We now have several products newly on the market to include on the list such
as the SMA and Exeltech products. Ungrounding the array requires additional
fusing and disconnects, but the most significant difference is that the
module wiring and all external cable must be PV Wire/Cable. Therefore only
modules with PV Wire/Cable can be used in these systems. You must confirm
from the manufacturer that they have made the switch. Hopefully all
manufacturers will be installing PV Wire/Cable soon so that this will not be
a problem anymore.



It is a good call to use up your USE-2 and order PV Wire/Cable from now on.



Bill.



*From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Exeltech
*Sent:* Friday, October 01, 2010 6:39 AM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] Tranformless inverter



Transformerless grid-tie inverters are permitted under the National Electric
Code as of 2008.  The Nationally Recognized Testing Laboratories (UL,
ETL/Intertek, CSA, etc.) took a while to develop the testing procedures for
testing to UL1741, which was the basis for most of the delay.

SMA isn't the only company with transformerless grid-tie inverters.  I know
of one American manufacturer with transformerless models on the market as
well.

Transformerless inverters are smaller, much lighter, and tend to be more
efficient than transformer-based units.  No transformer also means lower
product cost, and less shipping expense.  Win-win-win.


Dan


--- On *Fri, 10/1/10, Drake <drake.chamberlin at redwoodalliance.org>* wrote:


From: Drake <drake.chamberlin at redwoodalliance.org>
Subject: Re: [RE-wrenches] Tranformless inverter
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Friday, October 1, 2010, 6:58 AM

I also received this advertisement.  Previously I had investigated the
smaller SMA transformerless inverters, and was told that this type would not
be allowed in the US until the 2011 code.  Has the ban been lifted?



At 12:52 AM 9/29/2010, you wrote:

Wrenches:

I received an advertisement from a distributor that SMA is now shipping 8, 9
and 10 KW transformerless inverters.  Don't these require double insulated
PV wiring and no connection  to ground on the AC side? It's been too long
since this subject last crossed my desk and I want to refresh my memory on
the specifics.

William Miller


*Please note new e-mail address and domain:

*William Miller
Miller Solar
Voice :805-438-5600
email: william at millersolar.com
http://millersolar.com
License No. C-10-773985
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