[RE-wrenches] Delta LA's

Thu Sep 2 12:41:58 PDT 2010

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
> NABCEP Certified Solar PV Installer™
> 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
> 
> 
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