Replies

1. 
   FastEddie1 | Aug 03, 2004 03:25pm | #1

   Would it be permissible to run the wire in emt and strap that to every joist?

   Whenever you are asked if you can do a job, tell'em "Certainly, I can!"  Then get busy and find out how to do it.  T. Roosevelt

1. 
   DanH | Aug 03, 2004 04:32pm | #2

   It's permissible to use EMT to protect romex from damage. The EMT needs to have fittings on each end to prevent it from cutting into the romex, but it doesn't need to end in boxes. The romex may need to be derated, though, due to being confined to the EMT.

   Pretty sure (but not positive) that it's also permissible to use a board (1x4 or some such) to protect the cable in this situation.

   It may be, as someone said, that the ceiling is sufficiently high that it doesn't need to be protected.

2. 
   ripmeister | Aug 03, 2004 05:19pm | #3

   I read somewhere that it is permissable to run perpendicular across joists as long as you put a board along either side of the romex.  I replaced a K&T circuit recently by doing drops from my attic.  When I needed to get the romex across the joists I stapled  to the joist top and then ran a length of strapping alone either side effectively creating a channel for the romex to sit in.  That way when walking  around up in the attic one won't be walking or  tripping on the wire.  I would think in an overhead application the same  rationale would apply.  Frankly I've never understood the "hanging" thing with running cable across the bottoms of joists.  Even if its run thorough the joists you can still hang things on it.

3. 
   CPopejoy | Aug 03, 2004 06:56pm | #4

   Use running boards (aka "rat runs").

   Here's the chapter and verse from the 2002 NEC, 334.15(c):

   (for exposed NM cable)--

   "In unfinished basements. Where the cable is run at angles with joists in unfinished basements, it shall be permissible to secure cables not smaller than two No. 6 or three No 8 conductors directly to the lower edges of the joists. Smaller cables shal either be run through bored holes in joists or on running boards." copyright NFPA.

   The inspectors in my neck of the woods insist that if the cable is run through holes in joists, drywall be installed (an 18" wide strip) to keep the cable from being damaged or used to hang stuff.

   The 7' criterion pertains to protecting cable running across the face of rafters or studs in an attic. If the cable is within 7 feet of the floor or floor joists, it has to be protected by guard strips "at least as high as the cable". This is in 320.23(A), which is a section pertaining to AC cable--but the section on exposed NM (334.15) refers back to this AC requirement and makes it applicable to NM.

   Ain't the Code great?

   Good luck with the install. The rat runs might even help stiffen up the floor!

   Cliff

4. 
   Mooney | Aug 04, 2004 03:19am | #5

   Gap covered your question , but there are other alernatives. Im an inspector that inforces the NEC, but I also enforce the International Fire Code . The NEC was adorted by the fire code and all other codes we enforce. The International Fire Code becomes more restrictive mostly over fire issues. Im not quoting code becuse its at the office and I dont have time to play at the office like at home on here.

   If holes are bored in the joices at the edges near walls, crossing joists , no sufficient support is lost , as it would be closer to the middle of the span. Even then its allowed at proper hole sizes per calculations on the joices.

   Any romex cable has to be protected by a 30 minute or greater fire rating if its inside the joist or stud space in living areas. Are you sure you want to keep it an unfinished attic ?

   Gap covered the regs in an unfinished basement , but if it were to ever to be finished , it would need  to be under a fire rating [1/2 inch drywall] , or be ran on top of the ceiling material with metal conduit as per fire code .

   This does not take anything away from Gaps post , just offers some sensible alternatives for the future.

   Tim Mooney

5. 
   Mooney | Aug 04, 2004 07:04am | #6

   All  alarms are wired in one circuit and they all go off together if one trips .

   Tim Mooney

6. 
   brucepirger | Aug 04, 2004 07:58pm | #7

   I understand the derating becuase the romex is in conduit...confined space, less air flow, less cooling, etc

   But, don't we usually bury Romex inside wall cavities filled with insulation?  And what about those burried in spray polyiso isulation?

   Am I missing something?

   Just curious....Thanks.

1. 
   BillHartmann | Aug 04, 2004 09:11pm | #8

   "I understand the derating becuase the romex is in conduit...confined space, less air flow, less cooling, etc"

   Wrong

   Basically it is derated when there are other sources of heat near it.

   Such as when it is run in hot spaces or when a number of cables are run close together.

1. 
   brucepirger | Aug 04, 2004 09:23pm | #9

   So, when cables are stapled next to each other on a stud...burried in insulation....??

   It's all about temperature rise...whether this is from additional heat sources (more wires in confinded closed space) or totally closed space....the heat has to be able to get out, else the copper temp will rise.

1. 
   BillHartmann | Aug 04, 2004 10:04pm | #10

   The amount of heat that it produces is already taken into account.

   If you look at the full range of wire charts you will see much larger ampacity for wires that are run in true, free air. And also with different types of insulation.

   But NM-B is rated for use in "common" residential construction with insulation.

   It is only when extra heat is added, such as from other NM-B and I believe the wording in the code is "tighly bundled, but I would have to look it up.

   There are mounting clips that will take a number of romex cables and hold them apart by about 1/2". With the ones that I used you can run 8 #14 or 4 #12's together without derating.