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

[Exeltech]

Detailed answers to your questions, as I see this
issue getting worse...


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?

*** No.

Equipment certified and Listed to UL1741 affirms to the
extent possible that the inverter itself is safe.  The
National Electric Code, 690.64(B)(1) mandates connection
of grid-tie inverters to a "dedicated" circuit breaker
or fusible disconnect.

Should a fire result from such an attachment, it's
possible and even likely fine print in the homeowner's
insurance policy may void coverage for this violation.

The probability of a fire depends on several variables:
1) the wattage of the PV and inverter; 2) the loads
connected to that particular circuit; and whether the
loads and inverter are in operation at the same time,
and the total current (utility + inverter-supplied)
exceeds the rated current for the conductors.



~ 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?

*** No.  UL1741 doesn't apply here.  Actual final circuit
connection aspects are outside the scope of UL1741. This is
an NEC issue.

Moreover, the customer does not own the wiring +outside+
their home, nor the grid.



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

*** If loads in the home are small, it's possible the utility
meter could register back-fed power from a low-wattage grid-tied
inverter.  Some mechanical meters will rotate backwards,
effectively "un-using" power consumed at other times.  Other
mechanical meters, as you point out, are "latching", preventing
back-fed power from registering at all.  Without a net metering
agreement between a consumer and their utility company, the new
"smart" (i.e. digital) meters register all power (incoming AND
outgoing) as "consumed", thus the consumer would be *adding* to
their monthly bill by the back-fed power, not reducing it.  An
outlet-connected inverter would be beneficial only if the
consumer's home is using more than the inverter is producing
at all times (given the size of the inverter and PV, this is
probable most of the time), but the amount of energy produced
will likely be very small.

The customer would money ahead to put their investment into
more insulation, sealing leaks, upgrading appliances, etc.



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

*** Yes.


---

And an un-asked question:

If these devices aren't permitted by the NEC to be connected
to the grid using an AC outlet, why are they allowed on the
market?


Answer:
They're sold to take advantage of uninformed consumers
who don't know any better .. don't care .. or both.

Sadly, the inverters in of themselves aren't illegal.
They are only in violation of the NEC when grid connected,
and only then when the consumer is caught.

When will consumers get caught?

When there's a fire and/or fatality.  At that point
ratings-seeking reporters will sensationalize it as
"dangerous solar equipment" .. which, as Marv pointed
out, will leave the solar industry looking like the bad
guys.


Dan


--- On Sat, 3/26/11, Dan Fink <danbob at hughes.net> wrote:

From: Dan Fink <danbob at hughes.net>
Subject: [RE-wrenches] Small, non-UL listed direct PV
grid-tie inverters and UL 1741
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Saturday, March 26, 2011, 11:07 AM

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)