PSPV Ground with Pole Mount

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sneaky

PSPV Ground with Pole Mount

Post by sneaky » Wed Jul 05, 2006 11:16 pm

Hi all,

I am getting concete for the pole mount foundation this saturday and I need advice on running grounding, namely where in conjunction with the PSVP. I've been told not to run it in the concrete. The array is about 130 ft from the inverter. The top of pole mount will be a Wattsun.

Thanks in advance for any info!

sneaky

Kent Osterberg
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Post by Kent Osterberg » Thu Jul 06, 2006 10:00 am

The 2005 NEC specifies a single bond between DC+ or DC- and ground so you'll need to run a ground wire with the PV conductors. At the PV array you'll need a grounding electrode.

The are many options for the grounding electrode. In rocky soil the easiest is to use 30 or 40 feet of #4 copper wire. Press at least 20 feet of it into the bottom perimeter of the foundation and bring one end up to the PSPV. When pouring the concrete, pull the wire up a couple inches so there is concrete under all of it.

A ground rod can be installed through the foundation before you pour concrete; just leave a couple inches exposed to connect to it later. If you don't like the ground rod running through the concrete, install the ground rod outside the foundation and run a #6 wire through the concrete in 1/2" conduit.

By the way, it is a lot easier to connect all the ground wires in the PSPV if you install a GBB.

sneaky

Post by sneaky » Thu Jul 06, 2006 10:08 am

Thanks, Kent. The soil is heavy clay and is always wet from one foot and lower.

I was told by some folks at a solar supply store that grounding in the pole foundation is a bad idea. I guess this is not the case?

These are all good ideas. Since I am junior member I have a stupid question. javascript:emoticon(':cool:')
Cool

What is a GBB?

Kent Osterberg
Forum Emperor
Posts: 1523
Joined: Mon Jun 09, 2003 11:01 pm
My RE system: SMA Sunny Boy 2500 with eight Mobil Solar Ra 180 modules
Location: Cove, Oregon
Contact:

Post by Kent Osterberg » Thu Jul 06, 2006 10:36 am

Sneaky,

Since you have clay soil, I'd use a ground rod unless there is a rock strata under the clay. Wet clay makes a good ground.

It's interesting that your solar supplier frowns on grounds in concrete. In Oregon, all new houses are required to have a concrete incased grounding electrode made from 20 feet of 1/2" rebar or 20 feet of #4 copper wire.

The GBB is a ground bus bar, the same one that is used in the PS2 and PS4. It is an optional accessory for the PSPV. You can pick up a similar ground bar at any electrical supply.

Since you are doing this installation yourself, I recommend reading Joe Schwartz's artical in Homepower Magazine issues 108 and 109. It goes through the installation of a pole-top array.

sneaky

Post by sneaky » Thu Jul 06, 2006 11:10 am

Thanks again, Kent.

The clay goes deep. I hit a bit of gravel at ~ 8' while digging the hole. I think it may be best to use conduit to run the grounding cable.

I have read the HP articles. I get hung up on details, however....

Looking at the HP 108 article, there is no mention of grounding or conduit sizing issues. My rebar looks likes Joe's, however. :)

I don't have the 109 in front of me at the moment.

My main concern is once it is in stone, it is in. So, I just want to do it right. I've posted other subjects with other questions along these lines.

Again, thanks Kent for taking time to explain. I'm getting there.

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