[RE-wrenches] Delta LA's

Fri Sep 3 10:16:15 PDT 2010

"I've also wondered if we should be fusing these things. One hand says
definitely yes, on the other hand, a big lightning strike would trip the
fuse, before the Delta could do its job."

I think a big lightning strike would jump the fuse like it wasn't there. So
the fuse would really make no difference at all.

Midnite has an arrestor coming that looks like it has some good
possibilities and a UL listing! It also has a light system to show if it has
been activated. 

I also have seen lightning damage and the delta seemed unharmed each time.

We need to keep in mind that there is some luck involved; NOTHING is going
to stop a lightning bolt that just traveled 10 or 20 miles across the sky,
so it jumping a meter socket or fuse / breaker would not be hard to
understand.

Later,

Bob

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of R Ray
Walters
Sent: Thursday, September 02, 2010 3:42 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Delta LA's

I know, as Bill pointed out, that the Deltas are supposed to be mounted on
the exterior to allow the damage to stay outside of the combiner box. But
I've also seen a lot of old Deltas damaged by the sun, and seen them cracked
off at the 1/2" nipple attachment point, which then leaves exposed THHN
conductors against the edge of the knock out. Just bumping one with your
foot or shoulder could crack the plastic.

We just finished a project with BOS combiners, and I mounted the Deltas to
the backing plate inside using a 2" PVC conduit clamp. In this case, the
AHJs were very concerned with sealing all KOs on the sides of jboxes, so we
would have had to mount the Deltas on Myer's Hubs. Clunky, and we didn't
have 1/2" hubs.

If conditions allow, I do prefer to hang them off the bottom of a box, as
long as they're protected from physical abuse. Side mounting is definitely
asking for trouble in many situations, they're just too easy to snap off. 

I've also wondered if we should be fusing these things. One hand says
definitely yes, on the other hand, a big lightning strike would trip the
fuse, before the Delta could do its job.

BTW, with over 200 projects in lightning territory, I've never actually had
a Delta blow itself while protecting the system. Plenty of lighting damage,
though, with the Delta still just sitting there.

Anyone using the DIN rail mountable equipment from Citadel?

R. Walters

ray at solarray.com

Solar Engineer

On Sep 1, 2010, at 6:32 PM, Dave Palumbo wrote:

I am concerned with Delta LA 600VDC cans being mounted exterior from J-boxes
(or disconnect switches) on ground mounts.

I remember hearing  from an old hand that these devices can fail in a manner
that could possibly expose the wiring to human hands. The wires would have
high voltage DC potential. Not  something we need in our industry.

Am I worrying about something that can't happen? Or should these be in PVC
boxes?

David Palumbo

Independent Power LLC

Offices in Lamoille and the Champlain Valley, Vermont

802.888.7194

www.independentpowerllc.com <http://www.independentpowerllc.com/> 

NABCEP Certified Solar PV InstallerT

Vermont RE Incentive Program Partner

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of North Texas
Renewable Energy Inc
Sent: Tuesday, August 31, 2010 10:07 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Testing LSAs

For the first time since 2004 we got a residential PV red tag for non-listed
surge supressors. I just took them off and replaced them after we got the
green tag. Of course he also red-tagged the copper ground plate because it
was not thick enough. Go figure....

Jim Duncan

North Texas Renewable Energy

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org]On Behalf Of Andrew Truitt
Sent: Tuesday, August 31, 2010 8:09 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Testing LSAs

Question: Since the Delta lightning arrestors are not UL Listed, do they
threaten the UL compliance of the PV system as a whole?

- Andrew Truitt
Currently of Standard Solar
Free agent in the Denver area as of 10/6/10

On Tue, Aug 24, 2010 at 6:02 PM, Peter Parrish
<peter.parrish at calsolareng.com> wrote:

I would think that an ohmmeter set to the 10 Mega-ohm setting (or the
highest setting possible), would be the first test. I would like to see
something on the order of 750 k-ohms (3/4 of a mega-ohm).

But the system should be tested at a higher voltage, than that available
from a DMM. Apply 240 Vac and measure the RMS current. It should be should
be 0.3 mA or less.

Finally, these puppies really need to be tested at much higher voltages,
perhaps someone knows how to use that megohmmeter to test? What does the
manu recommend, "if suspect, throw it away and buy a new one"?

- Peter

Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885

________________________________________
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kristopher
Schmid
Sent: Tuesday, August 24, 2010 1:30 PM
To: 'RE-wrenches'
Subject: [RE-wrenches] Testing LSAs

What is the best method for testing the integrity of a DC and/or AC
lightning surge arrestor?  Specifically, i use the Delta LA units.  I know
they should be replaced if they look Bar-B-Qued, but otherwise...?

Thanks,
Kris Schmid

Legacy Solar
864 Clam Falls Trail
Frederic, WI 54837
715-653-4295
solman at legacysolar.com
www.legacysolar.com <http://www.legacysolar.com/> 

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