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Installing a grid intertied
solar electric power system


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LIGHTNING PROTECTION
July 5, 2009
Much of what I have learned about solar electric systems has come from reading Home Power Magazine.  Since it is written by people (like me!) who are directly involved in projects they write about one gets to learn from their experiences.

One of the things that concerns me a lot is the risk of electrical failure or a lightning strike that could destroy my rather large investment in all this equipment.  We do get some pretty dramatic lightning storms here in Maine and I have seen lightning strike the trees and power lines less than 20 feet from the building.  One strike actually damaged the pole transformer and it had to be replaced the next day.  So I consider it prudent to install lightning protection on the building.  As an electrical engineer who has experience making small scale lightning with Tesla coils that produce sparks up to 13 feet, I also understand quite a bit about how lightning forms and how to protect buildings.
I contracted Maine Lightning Protection to install a complete lightning protection system on the building and also on my home which is somewhat exposed.  The system consists of 12" pointed copper spikes mounted to the ridge at the ends and center of the roof that are grounded using 1/2" braided copper wire.  The wires come down on opposite corners of the building to 8 foot ground rods that are pounded in below grade.  The installation took about a half day per building and cost around $1500 for each building.  I gives me peace of mind knowing that I have professionally installed protection.
Delta LA302 lightning protectorDelta surge kitI had already installed a large lightning protector and line filter capacitor in the main breaker box.  These units, made by Delta Surge Protectors are cheap insurance.

A few years ago, I was watching a lightning storm from our porch and saw a strike hit the power pole that feeds our property less then 50 feet from my workshop.  It was a shocking and memorable event!  Thanks to the lightning arrestor, we did not lose any electronics in our home or my workshop.  Well, we did lose the cable modem as the lightning crawled in via the cable and blew that up.  But if we had not installed the LA302 unit (at left) we could have lost thousands of dollars worth of computers, and electrical appliances.  They offer a kit (right) that includes the lightning arrestor, surge capacitor, and phone line circuit protector.  I highly recommend this inexpensive insurance.
SYSTEM GROUNDING
The other piece of the electrical safety issue is to securely ground all the solar panels and inverters.  This is done in many different ways.  The traditional method is to use the ground bond screws on each solar panel and connect all the panels together with heavy gauge bare copper wire.  However that can make for a difficult and sometimes risky installation as you dress all the copper wire around the roof.

WEEB grounding lugs and clipsSeveral years ago a company called Wiley Electronics LLC came up with a really neat scheme that allows the panels to be directly ground bonded to the aluminum mounting rails.  The rails then connect to each other and ground.  Their clever line of WEEB (Washer, Electrical Equipment Bond) parts consist of special washers with sharp ridges on them that penetrate through the non-conductive anodized coating of the aluminum module frames and mounting racks.  Shown at left are the grounding lugs used to connect the rails to each other with copper wire.  And below them are the washers.  The lugs bolt on to the rails with the pronged WEEB clip that bonds the clip to the rail and the ground wire drops into the clip and is secured with a bolt.  I find this system very appealing for it's simplicity and low cost. 

Update April 14, 2010
Enphase has released an app note concerning the WEEB grounding system for their inverters.  Download it here.
WEEB jumper installedShown at left is a slice of the IronRidge Genesis pro mounting rail with a WEEB Bonding jumper partly attached.  This jumper is used to electrically connect 2 lengths of rail.  A simple mechanical connection does not provide a sufficiently reliable ground path so this flexible cable connects the 2 rails via WEEB washers.






Panel mount with WEEB washer
At left is the Genesis bolt and clip that secures 2 solar panels to the rail - the clip at top bridges both panels.  As the panel is tightened down, the WEEB washer on the rail connects the panels to the rail electrically as the round nubs penetrate the anodized surface of the aluminum..
Genesis mounting rails grounded with WEEB clips and 6 gauge wire6 gauge copper ground wire in WEEB clipAt left is a view of the 6 gauge copper ground wire installed.  On the right is a close-up showing how the wire fits in the WEEB lay-in ground lug.  Installing the wire was quick, simple and easy, and I am confident that the rails are well and truly connected electrically.

Also note the Genesis end clip in place ready to secure the solar panel.

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