[RE-wrenches] Small, non-UL listed direct PV grid-tie inverters and UL 1741

Dan Fink danbob at hughes.net
Sat Mar 26 09:07:22 PDT 2011


Hello esteemed Wrenches;

I have been absolutely swamped with inquiries about small, non-UL listed 
(or "UL listing pending") direct PV grid-tie inverters in the last few 
weeks. It appears they are arriving in a flood from China and being sold 
on Ebay, and by other online retailers. They are also being incorporated 
into home solar products, such as window coverings that have PV cells on 
the outside, portable PV systems for renters to reduce their bills, etc.

The common theme here is that these devices "plug into any wall outlet 
and reduce your utility bill."

My questions for the group are;

~ Can any energy-generating device, even if it *was* UL 1741 listed, 
comply with the NEC if it plugs into a wall outlet instead of being 
hard-wired to the breaker panel? For example, a homeowner wiring a 
120VAC plug onto an Enphase and running the cord in through the window.

~ An argument raised by one distributer of these inverters was, "Well, 
here in (minnesota) the customer owns all the wiring in their house up 
to the utility feed. So they can plug in anything they want into the 
house outlets, whether UL listed or not, as long as they don't have a 
net metering agreement with the utility...because this inverter does not 
sell electricity to the utility, it only compensates for house usage."
Doesn't 1741 still apply here?

~ What about latching meters? I understand that some types of utility 
meter will count all generation from the house circuits as electricity 
used.

~ Does this stuff scare you folks as badly as it scares me? Sounds like 
the double-male 120VAC plugs from Y2K.

I sure would appreciate some clarification on UL 1741 from the group, 
though....specifically regarding plugging generation equipment of any 
sort into a wall outlet.

-- 
Dan Fink
Executive Director;
Buckville Energy Consulting
Buckville Publications LLC
NABCEP / IREC / ISPQ accredited Continuing Education Providers
http://www.buckville.com/
info at buckville.com
970.672.4342 (voicemail)
970.373.1311 (fax)




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