My wiring project (update)

Personally I feel that having cables strung out and unsupported (as above the garage door) isn't such a good idea, far better to put a support in for them to prevent accidental damage or re-route them.

Cheers ............. Rheilly P

:As you know I am working on wiring a detached garage/shop. I am a :newbie. I have attached a link to my work thus far. I am having a :little trouble figuring out how to route everything. Any helpful :advice is appreciated. : :

By the photo's it appears you are not going to install a ceiling so the cables running across the rafters at right angles as in photo 80 are a definite NO-NO.

Even if you had a ceiling you shouldn't do this. Mains power cabling must be attached and run along a beam or joist in a construction such as yours so that is protected as much as possible. Just imagine carrying a metal ladder in that garage and snagging it on those cables and pulling them down. A disaster waiting to happen.

These are all great suggestions but the NEC is pretty much silent on garage wiring as it applies to securing NM cable on the bottom of roof framing members. If this was a crawlspace or an unfinished basement you would be required to run the wire above the bottom of the joist/truss through bored holes or on running boards but in a garage you only have the ambiguous "where subject to physical damage" language to deal with. That is all in the eye of the installer or the inspector and the range of opinion is vast. Usually nothing above 6'

6" is even considered subject to damage..

te:

I am eventually probably going to install 7/16 osb for a ceiling. But I understnd what you are saying. If I run 2x4's between rafters to support those wires is this acceptable?

Also, If I dont put walls up, is it ok to use those plastic outlet boxes I am using or is that a no-no?

ote:

My celings are right at 10 feet high.

On Sep 7, 8:31=A0pm, stryped wrote:

Were the cable runs across between two trusses, the trusses must be within four and one half feet of each other, and the cable run in such a way as to limit it's unsupported length to four and one half feet. Best practice would be to install a one inch nominal or larger running board of sufficient width to permit the cables to be run directly on the board for better support. If anything will ever be stored on the truss cords then the cable should be run through bored holes with barrier strips above them to avoid the weight of the storage stressing the cable. Obtain a diagram from the trusses manufacturer to locate the permissible locations and sizes of bored holes in the truss members. In my opinion a better practice would be to run the cable through bored holes in the common rafter members of the truss and run down the sides of the truss cords or posts to reach the bottom cord members at the points closest to the outlets they serve. Although that technique uses somewhat more cable it provides the best protection from physical damage. Since your cables are already in place the easiest way to provide fully adequate protection from physical damage would be to add running boards beneath them were they span the gaps between trusses. If there is any chance of future storage on the top of the bottom cords of the trusses you will want to add guard strips to the edges of the running boards to prevent the weight of the storage from resting on the cables themselves. Objects stored on top of nonmetallic cables have caused the insulation on the individual conductors to subside away from the pressure thus leading to inter conductor arcing and ignition of combustible structural components.

-- Tom Horne

:On Sep 7, 10:28 pm, Ross Herbert wrote: :> On Mon, 7 Sep 2009 17:31:56 -0700 (PDT), stryped wrote: :>

:> :As you know I am working on wiring a detached garage/shop. I am a :> :newbie. I have attached a link to my work thus far. I am having a :> :little trouble figuring out how to route everything. Any helpful :> :advice is appreciated. :> : :> :

:> By the photo's it appears you are not going to install a ceiling so the cables :> running across the rafters at right angles as in photo 80 are a definite NO-NO. :>

:> Even if you had a ceiling you shouldn't do this. Mains power cabling must be :> attached and run along a beam or joist in a construction such as yours so that :> is protected as much as possible. Just imagine carrying a metal ladder in that :> garage and snagging it on those cables and pulling them down. A disaster waiting :> to happen. : :I am eventually probably going to install 7/16 osb for a ceiling. But :I understnd what you are saying. If I run 2x4's between rafters to :support those wires is this acceptable? : :Also, If I dont put walls up, is it ok to use those plastic outlet :boxes I am using or is that a no-no?

As Tom Horne suggests, a smaller support timber is adequate. While the height of the unsupported wiring may be higher than the minimum stated in the rules, as long as it is accessible by someone carrying a metal ladder (or similar), or it can be accidentally snagged, then it is inadvisable to leave it unprotected. Who knows how long it will be before the ceiling goes up? And if it never does and you sell the place then somebody else might wear the result.

As long as those plastic wall boxes are fixed and fully enclose the outlet there is no problem without the wall board fitted.

DO NOT drill "truss chords". These are engineered members and drilling holes in them without engineering guidance is dangerous. Most are not rated for attic storage anyway.

Did you miss my subsequent sentence in the posting you took your quote from? It read "Obtain a diagram from the trusses manufacturer to locate the permissible locations and sizes of bored holes in the truss members." Further regardless of what they are rated for I've yet to see any that are completely free of storage after forty years in the craft.

-- Tom Horne

I just realize that sounds good but I doubt the OP has any access to the original engineering. Even if you could find out who made them, actually finding the diagrams would be hard.