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Posted by RBM on May 24, 2008, 7:11 am
>
>>
>>>
>>>>
>>>>> On Thu, 22 May 2008 22:28:43 -0400, gfretwell@aol.com wrote:
>>>>>
>>>>>>On Thu, 22 May 2008 04:13:47 -0500, letterman@invalid.com wrote:
>>>>>>
>>>>>>>I built a leanto on the front of my pole barn. It's 3 sided, so the
>>>>>>>horses can get shelter when the weather is nasty. At the last minute
>>>>>>>I decided to add a light. That required getting the cable (NM Romex)
>>>>>>>thru the wall from inside the barn. This left me two options.
>>>>>>>1. Drill a home thru the top 2x6, and thru the pole barn steel
>>>>>>>siding.
>>>>>>>2. Run the cable thru one of the ribs on the underside of the roof
>>>>>>>steel.
>>>>>>>
>>>>>>>I chose the second option for two reasons. First, it was less work,
>>>>>>>since there is a rib every 10 inches, so there were plenty to choose
>>>>>>>from. Secondly, drilling thru steel siding is going to leave a sharp
>>>>>>>edge on the steel where the cable runs, which could eventually
>>>>>>>puncture the cable.
>>>>>>>
>>>>>>>As far as safety, I think I chose the right way, but is it legal
>>>>>>>acording to the NEC?
>>>>>>>
>>>>>>>(I'm not too worried about this, it wont be inspected, I'm just
>>>>>>>curious).
>>>>>>>
>>>>>>>Thanks
>>>>>>
>>>>>>I will assume the "Romex" is type UF and agree your idea is OK. If it
>>>>>>went through a bored hole in steek it would nee additional protection
>>>>>>pipe or something (meaning a listed raceway used as a sleeve).
>>>>>>You have the serious danger identified, a cable rubbing on a sharp
>>>>>>edge.
>>>>>
>>>>> Yes, I am well aware of NOT putting wire thru a sharp edge. Actually
>>>>> I put an exterior outlet on the same barn. I drilled a hole and since
>>>>> it's an exterior box, it has the threaded hole on the back, so I just
>>>>> used a short piece of steel pipe to go thru the steel and the 2x6
>>>>> behind it. Then I used a bushing on the inside and put my romex thru
>>>>> the pipe.
>>>>>
>>>>> As far as using NM romex. I have never seen UF used in horse barns.
>>>>> This is not a hog barn where there is flying mud and lots of moisture.
>>>>> I have always used NM. However, anywhere there is an outlet or switch
>>>>> below 8 feet, I run the cable thru a length of steel conduit up to 8
>>>>> feet. The reason is because some horses chew on anything. I had one
>>>>> chew thru the cord on a winter tank heater, chewed the cord right in
>>>>> half. Lucky for the horse I use GFIs on all barn outlets. I think it
>>>>> still gave him a jolt though, because he would not go near cords after
>>>>> that. Pissed me off that he ruined a $60 heater though.
>>>>
>>>>Any building that you would call "Barn" is considered an agricultural
>>>>building by the NEC. To be NEC compliant, you can not use type "NM"
>>>>cable
>>>>
>>>
>>> I guess I'll have to change the name of the barn to "shed".
>>> Like I said, I'm not worried about inspctions where I live.
>>>
>>> However, I am curious what makes NM unsuitable?
>>> It's basically the same as UF, in fact the wires inside are identical.
>>> The only difference is the outer coating which is thicker on UF and
>>> the insulated wires are embedded in it, rather than the sleeve around
>>> NM. So what????? I'm not debating the NEC code, just the reason
>>> behind it. UF is made for underground use. These wires are not
>>> underground or exposed to water. Nor does the sun beat on them if it
>>> has to do with UV resistance. A barn is no different than a garage,
>>> except animals are kept in there rather than a car. In a hog barn I
>>> can see where mud and water are sprayed around, but not in a horse
>>> barn, or for that matter, most other livestock. Does this law change
>>> in a garage if I keep my dog in there? Unless someone knows a
>>> meaningful reason behind this, it's just another useless law. I am
>>> not worried in the least about my wiring being any danger, or my
>>> horses would not be in there. All wiring above 8 feet is stapled to
>>> the rafters, anything below that is in conduit, and all outlets are
>>> GFI. Thats safer than most barns I have seen.
>>
>>I feel your pain!!! I've been in the electrical contracting business for
>>over 35 years, and I'm still asking the same questions you are. I believe
>>the main concern in agricultural buildings is combustible dust. They make
>>a
>>tight fitting gland connector to use with UF that would prevent dust from
>>entering boxes and fittings
>>
>
> Ok, now I dont feel so bad about it......
> I have seen some wiring in hay mows (hay lofts), that had special
> boxes, connectors, etc. In that application I can fully understand
> it, since hay is combustible and makes lots of combustible dust. But
> in my case, the only dust is the dirt dust from the floor that blows
> around when the door is open and it's windy. If I was worried about
> the dust I could put some silicone around the clamps where the wire
> enters, but I'm not worried about it because it's not combustible
> dust, and I have opened these boxes after several years and aside from
> a dead fly or two that might have gotten in, there's nothing in there.
>
> From what you said, it appears that the reason for the UF is because
> the outer coating is more rigid, and those "fitting gland connectors"
> require the rigid coating to seal tightly. I think I know what you
> mean by that connector. I believe they have a rubber that seals
> tightly around the cable as the nut is tightened. I used one of those
> on the pressure switch on my well because condensation was running
> down the cable and I did not want it getting in the switch.
You've got the picture. Another thing to consider regarding NEC rules, is
that they consider how the next guy may use your barn
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