Protecting conductors on ground mounted arrays

[nosparks1]

Any input as to how contractors have been complying with 690.31(A) in the NEC 2008 on the conductors connected between panels on ground mounted arrays to install the conductors in a raceway since in most cases they exceed the 30 volts and the lower panels are definetly readily accessible.

 

[ggunn]

Any input as to how contractors have been complying with 690.31(A) in the NEC 2008 on the conductors connected between panels on ground mounted arrays to install the conductors in a raceway since in most cases they exceed the 30 volts and the lower panels are definetly readily accessible.

Doesn't building a fence around the array with a locking gate satisfy that requirement?

 

[nosparks1]

Yep, was curious what the industry is actually doing.

 

[jaggedben]

I think the industry is either building fences, or hoping that AHJs don't notice that part of 690.31 (A).

 

[ggunn]

Yep, was curious what the industry is actually doing.

Well, some of us are putting up fences.

 

[nosparks1]

Thanks for the input, as a local inspector I couldnt see any way other than a fence. Seems that any protection on the conductors would prohibit access to the plug connectors between panels or enclosing the backs would introduce heat issues.

 

[jaggedben]

There's at least one product I've seen that comes with a racking system with integrated wiring inside the racking. It's a frameless panel product, I saw it at a trade show, can't remember the name. Also I think was designed with roof mounting in mind. But, point is, the wiring is not readily accessible, as far as I would judge.

Fundamentally there is no reason that racking systems couldn't be designed that enclose the panel leads and make them not readily accessible, or even actually be listed as a raceway. Such products might add a little bit of cost to racking solutions, but probably less than building fences.

In a lot of places security concerns call for building a fence anyway.

 

[ggunn]

In a lot of places security concerns call for building a fence anyway.

And in the case of a couple of jobs I have worked on in ranching areas, cattle concerns. On one of them, before the fences got put in, cattle badly bent a couple of rails and broke three modules. Yes, the fences should have been put up before the arrays were erected, especially seeing as the fencing company managed to cut into a buried conduit and sever some very expensive 4/0 cable. The filled in trench was VERY visible; what were they thinking?

Lessons are learned, and some are learned the hard way.

 

[jaggedben]

Cattle damage. Right. :blink:

I think this issue is most salient with residential installations. When customers use enough electricity and have enough extra land to opt for a ground mount, they are often quite well off and want things to look nice too. Putting a chain-link fence around the array might not be acceptable to them, or it might add enough to the cost that they no longer consider it as worthwhile. That's where I think different racking should come in.

 

[nosparks1]

Thanks again for all the input.

 

[RogerDaisley]

Look at Silicon Energy Modules

Look at Silicon Energy Modules

Silicon Energy modules have "built-in" channels for wiring. It's a slick system.
www.silicon-energy.com
/roger

 

[WizBandit]

Wiring has to be "not readily accessible"

Wiring has to be "not readily accessible"

Any input as to how contractors have been complying with 690.31(A) in the NEC 2008 on the conductors connected between panels on ground mounted arrays to install the conductors in a raceway since in most cases they exceed the 30 volts and the lower panels are definetly readily accessible.

Actually the connectors and wiring need to be made "not readily accessible", mostly of concern are the "solar connectors". Earlier PV modules used Multicontact MC3 connectors, a rubber non-latching connector. These were replaced with the MC4 latching (tool needed) connector. Using MC4 connectors and ty-wraping the wires is sufficient to comply, Joe Q. Public would need more than one step to disconnect the panels, clip the ty-wraps, use tool to open connector. As I read the "not readily accessible" part of the NEC it means "more than one step". Using a ladder and climbing a ladder to get to PV wiring reads Not Readily Accessable to me as well as climbing a fence and walking over to the PV wiring. Laying the PV connectors/wiring into the mounting racks (ProSolar Brand) or covering the back of the module with wire cloth also would comply. Think of it this way, if the lawn boy can walk up to it and using only his hands to "unplug" the PV wiring then it's "Readily Accessible". The compliance here is to make them "NOT READILY ACCESSIBLE" by the above means.

690.31(A) Where photovoltaic source and output circuits operating
at maximum system voltages greater than 30 volts are installed
in readily accessible locations, circuit conductors
shall be installed in a raceway.

 

[jaggedben]

Think of it this way, if the lawn boy can walk up to it and using only his hands to "unplug" the PV wiring then it's "Readily Accessible". The compliance here is to make them "NOT READILY ACCESSIBLE" by the above means.

What if the lawn boy can walk up with his weed-wacker, to trim the grass growing up around the array, and he accidentally cuts through conductors carrying 400+ volts?

We had a situation where we had a very low series of arrays (customer requirement, don't ask) and a bunch of the wiring ended up getting re-done with more raceway to protect against this kind of possibility. It was more of a common-sense decision than looking at code requirements, but I guess my point is that 'readily accessible' goes beyond the plugs on the ends of the wires.

 

[Marvin_Hamon]

The interpretation I see most often, and I agree with, is that the conductors and connectors need to be made not readily accessible, not just the connectors. There are many ways to do this, but not all are universally accepted outside of actually running raceway to the module junction box.

The problem with using a fence is that if personnel not involved with the electrical operation of the PV array can get access to the area inside the fence then the conductor has not been rendered not readily accessible. From what I have seen with landscaping maintenance and trash collection there are a lot of people inside the fence that the NEC is trying to keep away from the exposed conductors. That being said, most people are using a fence to satisfy the requirement, particularly since a fence will be installed anyway. The first time a landscaper gets killed from cutting a live conductor while inside the fence I expect this will all change.

The best way to address this would be conduit to the junction box, but that would require using different junction boxes and losing the connectors. Second best would be mounting a shield that runs across the back of the modules, covers the junction boxes and conductors, and prevents a person from touching the conductors without removing the shield. I have seen these in use but there is an extra cost that most are not willing to add in and risk loosing the job to someone who only puts in a fence.

 

[jaggedben]

The best way to address this would be conduit to the junction box, but that would require using different junction boxes and losing the connectors. Second best would be mounting a shield that runs across the back of the modules, covers the junction boxes and conductors, and prevents a person from touching the conductors without removing the shield.

That just prompts me to repeat the suggestion that (more) panel and racking products with integrated protection for conductors would be a step forward.

 

[Zee]

I have built many of these ground mounts. Just a thought. Always thought a non-conductive mesh (AKA plastic screen or netting) stretched acrosss the bottom of the finished array and rails would provide protection. Advantages:Inexpensive,nearly invisible - no ugly fence easy to install.Attach with sst TEK screws and large sst washers to underside of alu. frames and rails?Disadvantages:Would have to be UV proof. That doesn't really exist, i believe. Possibly "UV resistant" but that won't hold up over decades......Cheap, flimsy.THoughts or improvements anyone?

 

[Marvin_Hamon]

I have seen wire mesh used on the backs of arrays to keep fingers from touching wires and connectors. I doubt that the module manufacturers would condone attaching anything directly to the module frame so the mesh gets attached to the mounting.

If AHJs stopped approving fencing as satisfying the requirement I'm sure there would be products on the market to do it at the back of the array, but until then fencing is usually going in anyway and it's pretty cheap so few will pay more to get the extra protection.

I saw an array completely covered in bird netting once, I wonder if that would count? :blink:

 

[Zee]

Bird netting? Sure! As long as "not readily accessible" was meant...for the birds.
Good to hear that you have seen screens/netting out there. I have yet to implement one.
I agree module mfctrs won't want screws driven into their module frames - but that the railing can be used for attachment.