DC Wire in Metal Conduit

Use PVC conduit?

No, this does not sound correct.Although I know nothing about solar engineering I can't see why you could not shield your wires.I would go with PVC though.

Here's another solution. There's a product called "Critter Ridder" that you can find in feed stores. It's a sticky obnoxious brew that you can apply to your wires. My parents used it to get rid of a possum living under a backyard shed.

I've never heard of wire not being rated to be put in metal conduit, but I agree that I'd go with PVC. It's cheaper and easier. Get some with a diameter larger than the mouth of your squirrels - like 2" - so they can't get their nasty little teeth into it. Make sure you seal up the ends so you don't end up with wasps or bats or who knows what.

Another solution that occurs to me it so suspend the wire above the roof - loosely so the squirells can't walk on it.

You can run DC power inside conduit. There is nothing sacred to the relation with conduit and AC power. It would require careful labeling to not confuse future wiring. Don't use standard AC outlet connectors. While electrically they can easily handle the load, you don't want somebody trying to just plug into your DC power structure.

I'm afraid that squirrels may also eat through PVC. And, I don't want to use large diameter pipe because it will limit air flow under the panels. I know squirrels do eat through lead roof jacks, the pipe and flange that plumbing vent pipe runs through.

I've thought about the Critter Ridder type products but it's a temporary solution.

Thanks for your comments.

Don

Your starting to slowly add complicating design creep.

You will have to follow conduit fill capacity limits, regardless of AC or DC usage. Conduit for proper cooling cannot be fully packed with wire.

Yes, individual wires are best for many reasons. I got to 70 yrs young before I found out that individual wires were readily available! Also crimps and crimp tools. Now the next job wiil be so much easier!

Sleepy

I have 10-2 gauge running from panel to panel for series, then I used 2 gauge cable running from each series to a block to merge and turn my individual series of panels into parallel into my controller. All my 10-2 and 2g are in metal conduit, on my roof, and that obviously is the sunny side of the roof. On top of the mountain it gets -20 in the winter, but up to 95d (F) in the summer, and I've never had any trouble with "heating" inside the metal conduit from the DC current inside the metal conduit. The DC current coming off a panel (depending on the panel size) is relatively low. I spray painted my conduit dark green to match my metal roof, and I also strung the conduit about six inches off the roof.

Call Backwoods Solar in Idaho (see my previous post/answer to one of your original ?s yesterday for their contact data). Ask for Scott or John, both have over 20 years exp in solar, I've worked with them on my system for over 10 years. If they don't know something they will tell you they don't know.

OK, here's the latest: I called the panel maker and the rep. said that the wires an be run inside metal conduit. I relayed this to my installer and he said that the National Electrical Code (NEC) prohibits this particular type of wire from being run in metal conduit because of heat buildup. I don't like heat buildup. The wire, which is integrated into the panel, is encased insulation. It has the appearance of the round coax used for cable TV. I had a fire, caused by a faulty piece of equipment, in my camper a couple of years ago. One fire is enough. I just want a permanent solution. I like the hot sauce solution but it doesn't last. As I had said in a previous post, I sprayed a cayenne pepper and water solution on wood to deter carpenter bees. Thanks again everyone for your suggestions. Keep 'em coming.

I will call the guys at Backwoods. Thanks.

Don

Your installer is trying to cover up his inexperience by acting like an expert and talking nonsense.

You have to make up your mind to listen to people who are giving you good advice on a site full of people with expertise who have no reason to lie to you. Or listen to the installer (who is obvious to us) is not experienced in electrical engineering or installations.

So quit offering counter arguments from someone we have no respect for.

Easy GRAY HAIRED OLD GOAT,

The installer may be perfectly justified in refusing to install wire not rated for conduit use inside a conduit. (if the wire is indeed not rated for conduit use.)

If the house burns down after he runs unrated wire inside that conduit, who is liable?

He is!

I've just read through the cryptic NEC 2008 article 690 Solar Photovoltaic Systems. Not only is there nothing prohibiting the use of a raceway for wiring, I'd like to quote 690.4 Installation (B), page 70-577

(B) Conductors of Different Systems. Photovoltaic source circuits and photovoltaic output circuits shall not be contained in the same raceway, cable tray, cable, outlet box, junction box, or similar fitting as feeders or branch circuits of other systems, unless the conductors of the different systems are separated by a partition or are connected together.

So not only does this code not prohibit photovoltaic source wiring from being in a raceway, this code has a safety stipulation on how to put these wires in a raceway with more than one circuit wiring.

I recommend that you find another installer.

How about using rabbit wire to wrap the connectors? You could do it in sections, have some galvanized wire to tie it up. That way you don't have to undo all the wires and work them thru conduits, re-doing all the connections and such. Rabbit wire will bend to all sorts of shapes to protect your wires, and you can fasten it down easily.

The wires can be run (electrically OK) inside the metal conduit and that should not give any problem.

In case of solar panel I sincerely don't think that the current will be high enough to create a heat build up.

The metal conduit will be thermally conductive and hence the dissipation will be better than PVC.

But there is the catch- being thermally conductive, external heat (the conduit will be heated up by sun) will be relayed back to the cable and the insulation will be baked by external heat and not the internal.

And that is waht your man means (or should have meant). This is what you have to take care of.

May be the perforated conduits with the wires supported in the center by some insulation like HGL or similar so that the wires do not touch the hot wall and the perforations ensures free air flow, the gauge of the sheet will ensure that the blunting of the teeth.

Guest,

I was thinking about perforated conduit but I really didn't think anyone manufactured it. I agree that if the metal conduit is exposed to the sun, the sun will provide most of the heat but, most of the conduit would be under the panels. I believe that if the conduit had at least two sets of perforations, on opposite sides of the conduit, the heat would be sufficiently dissipated. Thoughts? Any ideas about manufacturers of perforated conduit?

Thanks,

Don

Use Teck90.

Jackal......Thanks for the suggestion. I found Teck90 on a couple of web sites. The problem is, the Teck90 is a solid conduit with wires within the conduit. Most of my wires are salvageable. I really need something to put the wires in that doesn't trap the heat.

Don

What class or type of wire are you trying to reuse?

It's XLPE (the type?), 10AWG (gauge?). That's what is printed on the wire. At the panels the wires terminate in a fitting that is made into the panel. The installer received approval from the manufacturer to use a weather-proof splice on the wires that have been chewed through. The installer's solution, at least under the panels, seems novel and effective. They are going to use perforated, convex shaped, aluminum gutter guards to nest the wires in. The gutter guards are about 4" wide, 3' long and are hinged on one edge. I think we may be able to adapt the gutter guard to encase the wires in where they run from the panel array to the collector box. Do you see any problems in doing this?

Thanks,

Don

I thought about getting rid of the squirrels but it would be an exercise in futility. My backyard is a 65 acre swamp. I am hopelessly outnumbered. And squirrels don't take vacations.

Ok, cross linked polyethylene insulation cables (XPLE) have a high normal temperature operating range close to the boiling point of water. So running these cables through a conduit or raceway that is outside in direct sunlight would not actually be a problem if one stays within all of the other requirements for conduit assembly outside. I suspect your installer is understandably worried about re-using your existing cut to length cables and the added cost of bending and installing the raceway/conduit itself. I'm a little apprehensive that 10AWG maybe undersized since cable heating was a concern of the installer. But without a clear understanding of the circuit topology or the anticipated current running through these cables, I will not say if heavier, more expensive cables should be used.

Getting nature to leave any system alone is a perennial job. I wish you luck.

Wow Wow How complicated can a bunch of "experts" make a situation!!!

Just shoot the squirrels (with air rifle) make squirrel pies for dinner & forget

all the specifications warnings & other impediments to common sense.

Wow Wow How simple-minded can a "simpleton" be??? Shooting is no long-term solution. Maybe it is a release-valve for the frustration of dealing with varmits, but lacks being a "real" solution. Thinking deeply is no sin. Simple often is better... just, not in this case.

Use Kindorf Punched Channel to protect the wires.

A liner of rabbit wire (1 1/2inch wide by 10 feet long) inside and behind the punched holes will give extra protection, and still provide ventilation.

There are competitive brands available besides Kindorf, however this is the brand I am most familiar with.

Thomas and Betts number for 12 Guage 1 1/2 X 1 1/2 inch X 10 ft. is: B 905 10

Google for other sources

Thanks.

you can use emt with compression fittings.

Your installer is incorrect. I am an engineer in photovoltaics and can say with certainty that there is nothing prohibiting the wire from being in conduit!