UL listing of lightning arrestors [RE-wrenches]

[Dan Rice]

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Kirk,

The 2000 UL Directory covering "General Information for Electrical
Equipment"  says "Many of the products bearing the UL Listing Mark or the UL
Classification Marking incorporate components that bear the UL Recognized
Component Mark -(the backwards UR). The Recognized Component Mark is
applicable to products that are incomplete in construction features or
limited in performance capabilities. The Recognized Component Mark does not
provide evidence of listing or labeling which may be required by
installation codes or standards." The operative term in this last sentence
is "may." See NEC section 110.2 Approval, and NEC article 100 definition of
"approved." For purposes of NEC compliance, these sections and terms
essentially place discretionary choice in the hands of the Authority Having
Jurisdiction. S(he) makes the call. From recent experience in Austin, TX,
the inspector there requires the use of a (recognized, not listed) Delta
LA602DC lightining arrestor on residential grid-tied systems installed under
the muni utility's rebate program. (Isn't Delta a Texas company?). Go
figure.

I've never seen one of the Deltas after it's been fried. Once upon a time I
cut one open that was replaced as a precautionary measure after a lightning
strike fried a charge controller "protected" by the one in question -I
dumped out the sand and found no apparent sign of operation -nothing
crystalized or otherwise burned. I don't know whether they work, or under
what circumstances, but I continue to install them as a talisman of good
luck, based on anecdotal reports of them doing something sometimes -usually
discoloring noticeably after a lightning strike. I agree with you about
recommending and using them per instructions. Use your discretion, then ask
your inspector if (s)he'll sign off on it (or if it's required).

If you're looking for UL listed DC surge (lightning) arrestors, check out
Windy's article on lightning strikes in Home Power 107 -he shows several
units manufactured by Transtector, and also mentions PolyPhaser. Maybe
others have experience with these they'd share -I've only used the Delta
units.

Good luck.

Dan Rice
Abundant Sun, LLC.



----- Original Message ----- 
From: "Kirk Herander" <kirk at vtsolar.com>
To: <RE-wrenches at topica.com>
Sent: Wednesday, April 12, 2006 3:33 PM
Subject: UL listing of lightning arrestors [RE-wrenches]

The Delta brand of arrestors, such as the LA302R (ac) and the LA602DC do
not have a standard "UL" mark but rather the backwards "UR" mark. I
understand this mark is for listed individual components and not
stand-alone electronics. According to the UL website, the UR marks "...
are specifically used on component parts that are part of a larger
product or system. These components may have restrictions on their
performance or may be incomplete in construction."

 I have been told by several inverter OEMs that they can't recommend any
lightning arrestor "because none are UL listed". What then does this
component mark really mean? Nothing? Why not recommend them if used
within their "restrictions"?

Thanks for comments.


Kirk Herander
Vermont Solar Engineering
802.863.1202
fax 802.863-7908
NABCEP(tm) Certified Solar PV Installer
Xantrex Certified Dealer Charter Member
NYSERDA-eligible installer
VT Solar and Wind Partner


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