LIghting protection questions....

[NM_Shooter]

Hoping the snow drifts have melted enough to make it up to my cabin next week.  Plan is to build my porch, and mount my shiny new solar panel on the roof.  Since I'm on the roof, I want to get as much done up there as possible.  I want to ground the panel, mounts and metal roof to protect against lightning strikes. 

Questions...

Can I use my electrical system ground rod as my lighting protection ground rod?

If I have a metal roof, do I need to run copper along the entire roof ridge, or can I just make electrical connection to the solar panel, the mount, and a small portion of the roof itself?

For a DC based system, is the negative side of the batteries tied into earth ground?

Thanks...

-f-

[ChuckinVa]

Hopefully someone with some solar experience will chime in here but I would think you would want to keep your lightning protection separate from your electrical system totally.

[NM_Shooter]

Originally, I thought that I would keep the electrical ground and lightning ground separate.  But I realized that if my roof gets whacked, the electrical system will be hot as well since the PV panel is on the roof. 

The lightning supression stuff that you can buy keeps your charge controller safe.  I may look into buying a snubber to place across the controller inputs.

[NM_Shooter]

Some answers here.  Yes to grounding negative side of batteries.

http://www.solarray.com/TechGuides/LightningProtection_T.php

Good data here : http://www.solarray.com/TechGuides/TGmain_T.php

[MountainDon]

I think the roof ground question for lightning protection gets complicated by having PV panel(s) mounted on a metal roof.  Or maybe I've over thought that.

From what I recall reading none of the documents on PV system grounding talked about metal roofs. And none of the lightning protection sites (as in installing lightning rods (air terminals) on a roof to protect the building) talk about PV systems.

Anyhow, with PV panel(s) on a metal roof it would seem for purposes of high voltage lightning everything is tied together. Therefore it would seem logical to think there is no issue with using one ground rod. Especially in Frank's wet location one rod should supply all the grounding required.



On our cabin the roof is just a roof and the electrical system is distant from it. The roof is grounded to an 8 ft ground rod at one end of the cabin. The electrical system has 2 ground rods 15 ft apart at the other end of the cabin. Both the AC and DC sides are connected to these. The two ground rods are connected to each other as well.

Any piece or device that is in the ground chain should be ground connected in such a manner that removal of one piece will not interrupt the ground connection of any of the other pieces. That is something that can easily occur in an array of PV panels, for example.


Also note that when grounding a set of components, like a charge controller, an inverter and so on, it is good practice to use a ground buss. Connect each individual component to the buss. Then connect the buss to the ground rod. If multiple connections to the ground rod are made you then have another set of NEC rules kicking in; the ground wire connections then have to be equal to or larger than any of the wires/cables in the system. Think large battery cable sizes. For some reason using a buss avoids that.

[MountainDon]

Note: There is also some requirement in the NEC about PV panels mounted on metal roofs. There is a special GFCI that's required under NEC. That usually is more of a worry when a number of panels are series connected resulting in high voltages. In a grid tie system it is not uncommon to find series connected panels with outputs of 300+ volts.

Probably not a concern in a small one panel low voltage system.

[glenn kangiser]

Also, Dave Sparks mentioned adding a sparkplug as a spark jump gap to ground for the hot side of the solar - or at least for my wind generator.  Ground the base to an earth ground and hook the terminal to the hot side to protect the positive side of the system from lightning.  The high voltage will jump the spark plug  gap to ground.

[Dave Sparks]

Glen, when am I going to let you buy me an adult beverage? It has got to be soon. I do not have a drinking problem except when I can't get a drink.....

Everything gets earth grounded thru the charge contoller GFI or system GFI since 2008. Tracked, fixed, roofmount the whole shabang. This is the only bond to the negative battery allowed in modern solar. This is bare minimum and you can always do more. The ultimate being separating anything out side the house from it's connection to the house by 10 feet. You do this in a bad storm. The spark plug is great for when you are not there as are all the transorbs and Delta type protectors. Every man needs protection as the old group the Band wrote.

[glenn kangiser]

Dave, dang it... I often think of getting to the other side of the mountain (like... it's about 4 miles and this isn't 1849, eh???)  and seeing you and your wife, but I have not done it yet.  [ouch]..... and Whitlock... you would think he would motivate me to get there as he is about 4000 feet away from you as the crow flies.... and Harry .... on the mountain 2500 feet from me.... we have a big enough group for a few adult beverages....

I'm on the road about 5 days a week now but shortly we will send up a few smoke signals and git 'er done.  

Thanks for the ground protection update - I got a Delta but still need to add spark plugs.

hmm I wonder if the old group "The Band " is old enough that they no longer need protection.. nevermind...

[Dave Sparks]

hmm I wonder if the old group "The Band " is old enough that they no longer need protection.. nevermind...

I can answer that for three of them as I just read "this wheels on fire". Three of them are dead! So yea, no protection required. I too am very guilty of not spying on you guy's more! I could probably ATV to Whitlock if I had a waypoint!
Cheers!

[glenn kangiser]

The old road is brushed in now I think but it goes there.

We will make it soon.

[Dave Sparks]

Raucina has been building roads and drainage all over the side of Paddy Hill next to W. Whitlock. Talk about loving heavy equipment and dirt. I bet I could trespass to Mr. Whitlock's if he approved...

[glenn kangiser]

I think  you could make it.  I think Raucina has torn it up nearly to Whitlocks.  We are moving some logs this weekend.  Maybe we can drop by.

[Dave Sparks]

We be there!  I have a secret black box to show you... Angelini in the phone book!

[glenn kangiser]

Missed that post but....Whitlock and I made it over there today.  A barbecue is in the planning stages -  [bbq]

I better get my sparkplug in working order for the solar pro visit.... heck with that ... I ought to straighten out the spaghetti in the battery box.... aw heck... I'll just let him look, take cover and walk away shaking his head.....

[Dave Sparks]

Aw come-on Glen, it can't have entrophied more from last time, can it? I once knew a guy who had been around the earth 3 times on a 50 foot cement boat that had "issues". So, he has the electrical wiring system from hell, pumps everywhere, fire pumps everywhere, flashing lights. He asks me to take a peak and I start shaking and still to this day, I dream about him starting to sink in a storm. He did have one thing besides his impressive credentials of sailing that boat for so long. He had several gallons of "splash zone" a Dupont I believe underwater epoxy and a little mini breather like the James Bond thing in Thunderball. He said he had practiced using it in 15 foot seas a few times. That really makes the dreams start...

So Glen, as long as your over current protected correctly I will not blush!  And I do not think you have issues!

[glenn kangiser]

Ahhh yes... I have the big red fire ax Sparky gave me tucked away safely in my truck. 

To make you feel better, for positive over current protection,  I am going to mount it near the main inverter feed cables for easy access.

[glenn kangiser]

Dave, I am so bad about procrastinating that I went out this morning and installed my overcurrent protection device right near the batteries and main power cables.

I wanted to get it done before I forgot about it again.

[Dave Sparks]

Very nice Glen! I do not see the listing agency? And the inevitable question, who takes over when you have to go to the store.

[glenn kangiser]

Hmm hmm  I can see I am going to have to put a bit more thought into this, Dave...

Rough guess on the agency...    National Fire Protection Agency