Replies

1. 
   kcoyner | Dec 16, 2005 03:36am | #1

   So long as the staple is tall enough, you can. 

   k

2. 
   bigman | Dec 16, 2005 04:50am | #2

    Okay,  you have hit on several things, yes you can put 2 NM cables under the same staple, as long as the wires are at least 1-1/4" from the face of the stud. (to protect from nail/screw damage) If you have more than 2 NM cables, use a product like the 3M Stacker, which allows multiple cables to be secured down the side of the stud.

   Part 2, yes you can pull multiple cables of the same circuit thru the same hole, without having to derate. But when you start pulling cables from different circuits thru the same holes you must derate the ampacity of the cable, by pulling the next size larger conductor, or using the next size lower circuit breaker, it depends upon circuit ampacity.

    

1. 
   BillHartmann | Dec 16, 2005 05:20am | #3

   "Part 2, yes you can pull multiple cables of the same circuit thru the same hole, without having to derate. But when you start pulling cables from different circuits thru the same holes you must derate the ampacity of the cable, by pulling the next size larger conductor, or using the next size lower circuit breaker, it depends upon circuit ampacity."That is not true, First the code only talks about bunbdled for 24" or more. A single hole is not bundled unless you tiewrap them all the way.And then you need to derate based on the number of current carrying conductors. It does not say anything about if they are on the same circuit or not. And depending on what and how the circuit is run then you can have max loads on more than one cable.And even when you do have to derate you can have upto 6 equivalent current carrying conductors and for #12 and #14 still have them on 20 and 15 amp circuits. While you to have to derate them to 80% the ampactity of those sizes or more than the 20 and 15 amp circuit that they are limited to.

1. 
   4Lorn1 | Dec 16, 2005 05:37am | #4

   Re: "That is not true,"I agree. He missed that one by a considerable distance. That is assuming his AHJ is using something close to the NEC so there is the off chance it may be a local thing. Oh well, no one bats a thousand.Glad you stepped in and clarified the situation. I was worried I might have to. Happy Holidays and be well.

2. 
   Miko | Dec 17, 2005 01:16am | #5

   Looks like I'm good on the stapling of two NM and running two through the same hole in the floor joist.  What about using 12 guage NM and outlets rated for 20 amp on a 15 amp curcuit.  That would make it easier to switch to a 20 amp curcuit in the future if the load change was acceptable.  I'll check back after 10pm CST. Over and out.

1. 
   BillHartmann | Dec 17, 2005 01:26am | #6

   "What about using 12 guage NM and outlets rated for 20 amp on a 15 amp curcuit. That would make it easier to switch to a 20 amp curcuit in the future if the load change was acceptable."First of all you can not use 20 amp receptacles on a 15 amp circuit.However, you can use 15 amp receptacles on 20 amp circuits, if there is more than one receptacle (and the common duplex receptacle counts as two).If you want to install 20 amp receptacles because they are better quality you don't need to. Consumer grade receptacle, about 40 cents, are only available in 15 amp versions.Better spec grades receptacles ($1.75-2.00) are available in both 15 and 20 amp versions.Besides I have never seen anything that comes with a 20 amp plug.But NEC code requires 20 amp circuits for bathroom, kitchen small applicane, and washing machine. Also some places have modified the code to require 20 amp circuits for all receptacles.And 20 amp circuits for receptacles is considered good practice.So if you are runing #12 I would go ahead and use a 20 amp breaker (and 15 amp receptacles).

1. 
   DanH | Dec 17, 2005 03:21am | #9

   More specifically, you cannot (legally) use recepticles with the T slot (to accept a 20 amp plug) on a 15 amp circuit.It is legal to use a "15 amp" recepticle (with two straight slots) on a multi-recepticle 20A circuit. Most "15 amp" recepticles are actually rated for 20A, at least for pass-through.

   If ignorance is bliss why aren't more people

   happy?

2. 
   Miko | Dec 17, 2005 08:16am | #10

   OK.  It seems odd to someone (me) without an electricians education that something called a 15 amp outlet could be used on a 20 amp curcuit while a 20 amp outlet could not be used on a used on a 15 amp curcuit.  I assumed (incorrectly) that this was a maximum capacity rating for the outlet(recepticle).  Does the 20 amp outlet(recepticle) restrict the flow of current when used on a 15 amp curcuit? 

   What do you mean when you talk about derating?

3. 
   4Lorn1 | Dec 17, 2005 09:39am | #11

   Re: "Does the 20 amp outlet(recepticle) restrict the flow of current when used on a 15 amp curcuit?"As an electronic mechanism no the receptacle doesn't restrict the amperage. The magic is a result of the interaction and use of receptacle and plug design when properly implemented. A 120v/20A male cord cap has the neutral turned sideways. This plug installed on loads which would draw more power than a 15A circuit could safely supply. The horizontal neutral makes it so that the male cord cap will not fit a 15A only receptacle, one with two vertical slots. A 15/20A receptacle has a T shaped hole on the neutral side and this shape accepts either a 15A cord cap, one with two vertical prongs or a 20A cord cap, one with a horizontal neutral prong.Idea being that up to a legal 15A load, one with a 15A cord cap will plug into a 20A or 15A receptacle. A load which requires a 20A circuit will have a 20A cord cap that will not fit a 15A receptacle but will fit into a 20A receptacle.Cord cap and receptacle designs are designed to limit what loads can be plugged into which receptacles and these designs are organized to make sure that the load and circuits are coordinated in circuit ampacity, voltage, number of conductors, phase, whether or not it is a locking design and sometimes usage. This is laid out in article 406 of the 2005 NEC.A chart covering the various configurations:
   http://www.coxhardware.com/pdf_files/NemaPlugChart.pdf

4. 
   BillHartmann | Dec 17, 2005 04:57pm | #12

   Another piece of the puzzle is that for duplex receptacles that the rating is on each of the 2 receptacles separately.And that the 15 amp receptacles, while rated for 15 amps at each connection is rated for 20 amp feed through or total loads.Thus a 15 amp duplex receptacle can handle a load of say 10 amps load in one side and 10 amps in the other one if on a 20 amp circuit. Of course if that is used on a 15 amp circuit the circuit would be overload and the breaker trip after a few minutes.

5. 
   Miko | Dec 17, 2005 10:58pm | #13

   Is it safe to assume that the same rules apply to 15amp and 20amp GFCI outlets?  Thanks to all that have responded.  This is an incredibly helpful forum.

6. 
   DanH | Dec 17, 2005 11:36pm | #14

   Yes. But then, of course, the rules are entirely different in Canada.
   If ignorance is bliss why aren't more people

   happy?

7. 
   BillHartmann | Dec 18, 2005 04:52am | #15

   Yes, in fact look closely at the 15 amp GFCI's they will be mark something like 15-amp receptacles, 20 amp GFCI.

2. 
   JohnSprung | Dec 17, 2005 02:34am | #8

   >  That would make it easier to switch to a 20 amp curcuit in the future ....

   Why not go 20 amp from the beginning?  The extra cost, especially since you have the walls and ceilings open, is small.  With Romex, it's best to put in everything you can imagine ever wanting in the first place, because it's really hard to change later. 

   If you want to protect yourself for large and unpredictable future changes, go with big EMT (3/4" minimum) and big boxes all over the place.  That gives you maximum versatility.   

    

   -- J.S.

    

3. 
   bigman | Dec 17, 2005 02:07am | #7

   "First the code only talks about bunbdled for 24" or more. A single hole is not bundled unless you tiewrap them all the way."

   Sorry, I did not make myself clear, you are correct when pulling thru 1 hole, when he said it was thru the joists, I was thinking of multiple runs thru the same hole, like homeruns pulled thru a 2" hole, which around here will not pass inspection, as this is considered bundling because they are grouped together for more than 24" and the fact that pulling multiple NM runs thru the same hole will wear off the insulation of the cable.

   "And then you need to derate based on the number of current carrying conductors. It does not say anything about if they are on the same circuit or not. And depending on what and how the circuit is run then you can have max loads on more than one cable"

   I was taught, and I guess incorrectly, that the derating factors of conductors and conduit fill percentages were designed around multiple circuits and the effect of Eddy currents which cause heat and that multiple conductors of the same circuit did not create Eddy currents. I guess I have to go find my old shop teacher and pin him to the wall on this one ;-)

   Edited 12/18/2005 4:54 pm ET by Bigman