[RE-wrenches] Grid-tied Trace SW

[William Miller]

Russell:

 

I am curious, how do you perform anti-islanding tests?

 

The SW4024 should work great with a 3.3 kW array.  Due to battery and
inverter inefficiencies you would never see the full 3.3 sell back any way,
which is less than the rating of the inverter.

 

The SW4024 was UL listed at one time but the listing was removed due to
failure to apply the testing regimen properly, if I remember correctly.  We
were not required to retrofit existing installations by adding the GTI, only
to add them to pending installations.  Our utility lost a lot of
applications during that era and years later, when forced to reapply, they
accepted the SWs without GTIs.  If you really want one, I have one in the
shop I would sell cheap, but I don't have much faith in the design.

 

Lastly, I can't comment on the efficiency of the SW versus a modern GTBB
inverter.  That question would justify some research.  If the SW is
significantly less efficient than, say, a Sunny Island, the impetus may be
there to upgrade.

 

William Miller

 

Gradient Cap_mini
Lic 773985
 <http://www.millersolar.com/> millersolar.com
805-438-5600

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
Behalf Of Russell Mueller
Sent: Tuesday, September 09, 2014 7:43 AM
To: RE-wrenches at lists.re-wrenches.org
Subject: [RE-wrenches] Grid-tied Trace SW

 

Hello Esteemed Wrenches,

 

I have a prospective client who has an old GTBB system using a Trace SW --
it was permitted and signed off by the utility way back when and has been
operational ever since.  It's a Trace SW 4024 that's feeding the grid
through a Trace T-240 transformer -- I didn't see a GTI.  All he wants me to
do is replace his failing array (which would increase his array size from
1152W to 3300W) -- not pull a permit, not change the BOS other than to add a
2nd charge controller.

 

The original question that lead me to write this post is whether the SW4024
can handle the full 4kW sell-back onto the grid -- I couldn't find any specs
on that on the web.  

 

But the question I have now is whether the Trace SW is UL1741 compliant.  I
didn't think to do an anti-islanding test before I left the site.  If it's
not, then I'm thinking maybe I should insist that he change out his inverter
for a modern one, or I'll pass on the job.  If it fails an anti-islanding
test (which I'll do next time I'm in his neighborhood), then the dangers are
obvious, and I don't want the liability.

 

What would you all do in this situation?  Do any of you have experience with
grid-tied SWs -- any advice?

 

Thanks,

 

Russ


--

Russell Mueller

NM EE98 Electrical Contractor, license #382671

NM ER1J Journeyman Electrician

Photovoltaic Designer / Installer






BUFFALO SOLAR LLC

Taos, New Mexico

575-770-4877

russ at buffalosolartaos.com

 

 






 

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