3 conductors under zip tie

[monkey_man_100]

Where is the code that says, if you have move than three conductors bundeled you have to derate them. Are they talking about putting more than 3 14-2 romex together with a zip tie, or any situation?

 

[chevyx92]

Where is the code that says, if you have move than three conductors bundeled you have to derate them. Are they talking about putting more than 3 14-2 romex together with a zip tie, or any situation?

No only if you have more than 9 current carring conductors total!

 

[monkey_man_100]

whats the code reference?

 

[chevyx92]

Look at article 310.15 and table 310.15(B)2(A).

 

[stickboy1375]

He's talking about 334.80 Ampacity? but it is TWO NM cables containing two or more current carrying conductors are bundled together, AND pass through wood framing that is fire- or draft-stopped...

Just looked it up, Post #4 is correct, but use my post as a little bit of info also...

 

[chevyx92]

He's talking about 334.80 Ampacity, but it is TWO NM cables containing two or more current carrying conductors are bundled together, AND pass through wood framing that is fire- or draft-stopped...

Where did you get that info?

 

[monkey_man_100]

Ok, so say I have 4 14-2 NM running down a metal framed house, there is no problem straping them all down with one zip tie? I'm pretty new and here all kinds of things about how many wires you can put on one zip tie. I normally don't put more than 4 just because that is what I have been told.

 

[chevyx92]

Ok, so say I have 4 14-2 NM running down a metal framed house, there is no problem straping them all down with one zip tie? I'm pretty new and here all kinds of things about how many wires you can put on one zip tie. I normally don't put more than 4 just because that is what I have been told.

Even there in the worst case you would have 8 current carring conductors. Still not at a point where you need to derate!

 

[Paul B]

Stickboy, that is what I thought he was talking about also. After re-reading he does say zip tie. How many use zip ties?

 

[stickboy1375]

Where did you get that info?

I dont have my 2005 code in front of me but I used a "Significant Changes to the NEC 2005 edition book"

 

[stickboy1375]

Ok, so say I have 4 14-2 NM running down a metal framed house, there is no problem straping them all down with one zip tie? I'm pretty new and here all kinds of things about how many wires you can put on one zip tie. I normally don't put more than 4 just because that is what I have been told.

It goes like this, Single or multiconductor cables are stacked, or bundled longer than 24" without maintaining spacing and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a)

Number of Current-Carring___Percent of Value Adjusted
Conductors:

4-6 80%
7-9 70%
10-20 50%
21-30 45%
31-40 40%
41 and above 35%

I would strongly recommand using these instead

 

[stickboy1375]

Ok, so say I have 4 14-2 NM running down a metal framed house, there is no problem straping them all down with one zip tie? I'm pretty new and here all kinds of things about how many wires you can put on one zip tie. I normally don't put more than 4 just because that is what I have been told.

It's not a problem as long as your derating them... Personally I think ty-raps end up way too tight on the wires...

 

[George Stolz]

Personally I think ty-raps end up way too tight on the wires...
...

I would strongly recommand using these instead

To each their own. I hate those things and prefer zip ties. I can't get stack-its tight enough for my taste.

Monkey man, the key is "bundled." If the AHJ considers NM under staples, zip ties or stackits running parallel over 2' 'bundled' (as they have every right to), then you must derate.

But, bear in mind with NM you derate from the 90? ampacity as the starting point. (334.80)

 

[acrwc10]

I would strongly recommand using these instead

I think stack-its are great. They do say right on the bag that you may need to derate.

 

[infinity]

Ok, so say I have 4 14-2 NM running down a metal framed house, there is no problem straping them all down with one zip tie? I'm pretty new and here all kinds of things about how many wires you can put on one zip tie. I normally don't put more than 4 just because that is what I have been told.

If bundled for more than 24" you must derate these conductors. However derating will not affect the size of the OCPD until you hit more than 9 CCC's.

 

[allenwayne]

I can`t see using zip ties to secure nm on metal studs.That would mean drilling holes to mount a zip tie in the center of the stud.To comply with 300.4 D.I have used a different type of stand off, not sure who made it but it looks like a big P with a 90 on the bottom that has a single hole in it.a framing screw holds it just fine.The wires are secured within the circular part of the p with a locking latch type part built integral in it.when you get into bundling issues you just back to back them and 300.4 D is no longer a problem either is bundling.They are pretty cheap alot cheaper than stackers are.
I had one helper that called them noodles,since that is what he said they resembled.

 

[George Stolz]

I can`t see using zip ties to secure nm on metal studs.That would mean drilling holes to mount a zip tie in the center of the stud.To comply with 300.4 D.

That what we usually used. A zip tie with a hole in the end for the screw, and a self-tapper. Didn't work so hot in tight bays, but much handier to carry around (50 at a time in my bags) than stand-offs.

 

[stickboy1375]

To each their own. I hate those things and prefer zip ties. I can't get stack-its tight enough for my taste.

Monkey man, the key is "bundled." If the AHJ considers NM under staples, zip ties or stackits running parallel over 2' 'bundled' (as they have every right to), then you must derate.

But, bear in mind with NM you derate from the 90? ampacity as the starting point. (334.80)

Are you serious about a zip ty not being bundled? At least stack it's allow air flow around the wires... And thats the whole point, they should not be tight...

 

[allenwayne]

That what we usually used. A zip tie with a hole in the end for the screw, and a self-tapper. Didn't work so hot in tight bays, but much handier to carry around (50 at a time in my bags) than stand-offs.

I`ll have to find the item I mentioned it works great,simply run NM and clip them in the standoff.There is a certain amount of prep work in a metal stud situation but once you prep it the install flys along.

 

[George Stolz]

Are you serious about a zip ty not being bundled? At least stack it's allow air flow around the wires... And thats the whole point, they should not be tight...

Stick, take a look at 310.15(B)(2)(a), exception 4. The NEC considers MC cables on bridle rings "bundled." I'm not saying zip-tied cables are not bundled, I'm saying that they are, as well as bridle rings, stackits, staples, unused Romex wrapped around the current carrying romex and stapled in place, holes in joists, or what have you.

If cables are in close proximity, but not physically secured to each other, they can be considered bundled.

Given the (hopefully) airtight construction in both interior and exterior bays of a building, air movement (convection) is not much of a consideration, IMO. The ability to release heat into it's surroundings (by radiation) seems to be the consideration. If a cable is very neatly surrounded by other cables carrying certain amounts of current, then it's heat cannot escape by radiation as effectively.

Tonight I'll look for some ROPs on this. To see Wayne's proposal for houses, look in the Proposals for 2008 section of the forum, and look for "Hurk 27"s proposal for 310.15(B)(2). His point was that getting away from a panelboard without derating is fairly impossible in some cases, and was trying to ease the requirements for that. I think it had some interesting discussion, if memory serves.