?Bundling?

[sparkydon]

derating q..

derating q..

Is derating a necessity purely because of heat dispersion, or is there something else at play here I'm not getting?

Bundling is something a LOT of other EC's do where I have been working lately, and I just don't get how the inspectors don't care? Possibly being a coastal area where local ambient temps. don't reach over 85 degrees, they let more heat-related code compliance stuff go?

 

[e57]

All I can say is read the installation directions that come with them... if they don't require derating then so be it...

I did...

It says, "When placing 5-8 14/2 W/G into the 3M Cable Stacker, derating of the conductor ampacity should be considered." As as they are only rated for up to 4 12/2's or 10/2's it has every appearance that the manufacturer also is considering derating to Table 310.15(B)(2)(a). The magic number being '9' before you need to jump wire sizes. Example 4 2-wires = 8 CCC's no problem as the ampacity for the wire sizes this product can be used for are accomidated by the numbers in Table 310.16 @ 70%, but are not when 10 CCC's are used @ 50%. So it's clear to me that the manufacturer is considering them "Stacked" or "Bundled" as well.

The original question:

I know that to be considered bundling they have to be together for at least 24"...but how tightly do they have to be together for that 24"?

Nobody knows IMO.

 

[e57]

Is derating a necessity purely because of heat dispersion, or is there something else at play here I'm not getting?

Heat created by the conductors inductive effects on each other. Proper spacing (whatever that is?) reduces the inductive heating effect due to proximity, and allows air movent to disapate heat. Open a panel, gutter or for that matter hold your hand next to a bunch of cables that are at the max amperage of their OCP and wire ampacity and you'll feel it. Much more noticeable in commercial installations where there is less load diversity, and higher wattage loads for longer periods of time. It may seem mundane until the day you see the insulation damage it can cause over a long period of time with constant heavy loads.

 

[stwalkover]

stwalkover

stwalkover

If you keep your circuits to 1200 watts for a 14/2, 3 VA psf or 1200va of lighting that is a 10 amp load that you can "bundle, strap, wrap, shove in a conduit etc". 10 -20 CURRENT CARRYING CONDUCTORS (10-20, 120 VOLT CIRCUITS) and derating is not an issue for this load . A 1200 va load is 400 sq ft of area 20' x 20' not unreasonable for a circuit of 14/2 romex. This is based on the 60C column and I believe when using Table 310.15 (B)(2)(a) you can use the 90C column for you calculation. Also basement condition are often at a temperature that is 70F to 77F which would give you a credit of .04 to .08 depending on which column you want to use for your calculations. This also works for 12/2 do the math. If your AHJ is on the ball and looking at the circuitry and not just saying no because it says you have to derate. It does not mean that you can not do it. You need to do the math for every situation and you may have to separate a cable or two but not often.

 

[stickboy1375]

If you keep your circuits to 1200 watts for a 14/2, 3 VA psf or 1200va of lighting that is a 10 amp load that you can "bundle, strap, wrap, shove in a conduit etc".

How do you plan on doing that? Were you planning on telling the homeowner not to plug more than 1200 watts into a circuit?