It has been brought to my attention

[pierre]

This was brought to my attention the other day from a contractor;

3M Stak-It SI-1, Cable Stacker- these are sold in a red plastic bag of 25.

Flat NM cable:
1-8* each 14-2 W/G (15 Amperes)
1-4 each 12-2 W/G (20 Amperes)
1-4 each 10-2 W/G (30 Amperes)

* When placing 5-8 14-2 W/G into the 3M Cable Stacker, derating of the conductor ampacity should be considered.


Two questions arise from the above quote from the package.
1. If placing 5-8 14-2 NM cables, does this mean that derating is required or suggested?

2. Does this also mean that 3-wire NM is not permitted as per listing to be installed with the stackers?


One other question.
Do any other inspectors here permit the use of the Stacker for installing the cable on studs that are less than 2x4 in dimension, to satisfy 300.4(D)?
(this would obviously require the installer to modify the Stacker to fit the smaller dimension stud)

Thanks
Pierre

 

[hbiss]

Re: It has been brought to my attention

The product literature says they can be used with round cable up to .3" diameter. I would say that 14/3NM is a bit bigger than that.

As for derating, I wouldn't consider it bundling but some AHJ's might.

-Hal

 

[pierre]

Re: It has been brought to my attention

Thanks Hal
I just looked at the 3M site and saw the reference to .30 inch diameter - most likely for the CATV, phone and security cabling that is listed for this product.

I also found another product (SIFS-1 Furring Strip Cable Stacker) which is listed for 14/3-10/3 NM Cable. It can be used on furring, as that is what it is designed for.
I emailed 3M and will let you know what they have to say.

Pierre

 

[curt swartz]

Re: It has been brought to my attention

Pierre

When you say ?listed? are you referring to UL or other testing lab listed? I don?t believe any of these products are ?listed?. It is up to the installer and AHJ to determine if they are being used in an acceptable way. I personally feel that there is enough air space around the cables so derating would not be necessary but the AHJ could feel otherwise.

 

[goldstar]

Re: It has been brought to my attention

Pierre,

This is strictly my opinion and a side bar to your question:

When using 3M Stak-Its or Arlington cable stackers the intent of the device is to keep the cable 1 1?/4" back from the front edge of the stud. If you install 8 # 14/2 RX's inside a 3M Stack-It they're sitting side by side in pairs, 4 deep. Technically, they're no longer 1 1?/4" away from the face of the stud. However, the back of the Stack-It is about 1/8" thick so you're technically, no longer near the side of the stud. If a sheet rocker misses the face of the stud and hits your cable with a nail that's his problem.

1) Now, as far as derating I don't see how it can be considered "bundling" because it's not passing through a conduit. The amount of induction generated by the cables going into a 4-gang switch box can't possibly be enough to over heat neighboring cables.
2) Can't address this part of your post because I'm not sure, but I use them often and haven't been called on it to date.
3) I wouldn't use 3-M stackers in this application but the Arlington stackers might work here.

Regards,

Phil,
Gold Star Electric
Ringwood, NJ

 

[a.wayne3@verizon.net]

Re: It has been brought to my attention

We use 3 M stackers all day long and the only time the use was tagged was when an installer tried zip tying a second set of NM cxables to the back of them.Double stack them back to back and all is good.300.4 D is covered at the firdt stack holder.If the AHJ has a problem with this well Too bad

 

[websparky]

Re: It has been brought to my attention

Goldstar,

1) Now, as far as derating I don't see how it can be considered "bundling" because it's not passing through a conduit.

I think you got it backwards.

310.15 (B)(2) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors in a Raceway or Cable. Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are stacked or bundled longer than 600 mm (24 in.) 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).

 

[goldstar]

Re: It has been brought to my attention

cables are stacked or bundled longer than 600 mm (24 in.) without maintaining spacing and are not installed in raceways,

Dave,

Although they are stacked there is a spacing maintained between the cables. But maybe I'm only seeing this the way I most commonly use them and that's down from a plate at the ceiling level, along the side of a stud and into a switch box. Come to think of it, I've seen cable installations where electricians have run multiple cables along the side of a ceiling rafter and have ganged them up as Pierre described in his first post. I guess, in that type of cable installation, there might be an issue with derating, especially if you have high current carrying conductors like air conditioning condenser wiring. When I made my original post I was not thinking of this type of application.

Phil

[ August 15, 2004, 07:56 AM: Message edited by: goldstar ]

 

[pierre]

Re: It has been brought to my attention

I am curious about the use of 3-wire with the standard stacker, especially since I found the other stacker that explicitly permits the use of 3-wire.
I brought up the issue of derating only because the instructions mention it- although vaguely describing their intentions. Remember 110.3(B), if the installations instructions require it, even if it is not in the NEC, it should be followed.

Do't take this wrong, I was using these for quite some time and never noticed the instructions :roll: myself.
As I mentioned earlier, I emailed 3M and will keep you informed of their response.

I have been accepting this type of installation with 3-wire, while inspecting roughings, it should be interesting if 3M says they are not labeled for 3-wire. There may be some angry contractors.

 

[george t. everett]

Re: It has been brought to my attention

Most of the time I use stak-its is for multi-gang switches. If the switches are fed from a single circuit, why would I need to worry about derating the cables?

 

[iwire]

Re: It has been brought to my attention

Originally posted by george t. everett:
If the switches are fed from a single circuit, why would I need to worry about derating the cables?

There is no exception to exempt derating for conductors of the same circuit.

All that matters is how many current carrying conductors are together.

 

[george t. everett]

Re: It has been brought to my attention

Bob,
I agree there is no exception to exempt derating for conductors on the same circuit, but I think there should be. I believe that 15 amps of heat divided by 6 is still 15 amps of heat. No need to derate, just my opinion.

 

[pierre]

Re: It has been brought to my attention

Part of the reason for ampacity adjustment is the number of conductors in a raceway, cable or proximity to each other reduces the ability of the air to dissipate the heat that is developed, even if the heat may not be developed by all of the conductors that are installed.

A poor analogy is when it is hot out and a bunch of people are standing close together, it makes it harder to cool off

Pierre

 

[Local]

Re: It has been brought to my attention

Pierre says:

"A poor analogy is when it is hot out and a bunch of people are standing close together, it makes it harder to cool off"


Not to be a smart *** but....well ok I do mean it....Wouldn't all those people be generating their own heat much as multiple circuits would generate their own heat? Maybe a better poor analogy would be:

"When one person is standing around in the heat and has their arms and legs wrapped around themselves it is harder to cool off."

 

[pierre]

Re: It has been brought to my attention

3M has not responded to my email sent Monday. I am curious why it is taking so long, so I am going to call them tomorrow and see what they have to say.

Pierre