Running MC Cable in a Riser

[Tainted]

I have like 40+ MC cables like #4-#2 wires that need to go up in a 15+ story building. I'm trying to avoid bundling and derating of MC cable. What method works in organizing and supporting the cable without bundling? They need to go up the riser. Thank you!

 

[electrofelon]

I have like 40+ MC cables like #4-#2 wires that need to go up in a 15+ story building. I'm trying to avoid bundling and derating of MC cable. What method works in organizing and supporting the cable without bundling? They need to go up the riser. Thank you!

I pretty much already threw out this idea in your other thread, but you could use strut clamps and strut. I do that for MC feeder cables frequently. Or for a little more expediency, zip tie groups of 3 to strut and that would avoid derating.

You could also fasten 2xs and use the appropriate sized 2 hole strap and fasten the cables to that in groups of 3. I think it's going to depend on how much space you have and the construction details.

 

[infinity]

Strut and strut straps. As long as there is a space between the cables there is no bundling issues.

 

[Tainted]

I pretty much already threw out this idea in your other thread, but you could use strut clamps and strut. I do that for MC feeder cables frequently. Or for a little more expediency, zip tie groups of 3 to strut and that would avoid derating.

You could also fasten 2xs and use the appropriate sized 2 hole strap and fasten the cables to that in groups of 3. I think it's going to depend on how much space you have and the construction details.

I thought if you zip tie 3 MC cables you would have to derate as per NEC table 310.15(B)(3)(a) since thats 3 CCC

 

[infinity]

I thought if you zip tie 3 MC cables you would have to derate as per NEC table 310.15(B)(3)(a) since thats 3 CCC

That's correct. If you're using singe phase risers from a 3 phase Wye system that would be 9 CCC (derated to 70%) which will likely require larger conductors.

 

[electrofelon]

That's correct. If you're using singe phase risers from a 3 phase Wye system that would be 9 CCC (derated to 70%) which will likely require larger conductors.

Right. In the other thread I was thinking they might be upsized a bit for VD, in which case bundles of three may have worked. OP never did answer the size question. But yeah the 120/208 definitely hurts you on derating if bundled.

 

[Tainted]

Right. In the other thread I was thinking they might be upsized a bit for VD, in which case bundles of three may have worked. OP never did answer the size question. But yeah the 120/208 definitely hurts you on derating if bundled.

Yes they VD is to be considered, i guess I’ll just go with the 70% derating

 

[Tainted]

I pretty much already threw out this idea in your other thread, but you could use strut clamps and strut. I do that for MC feeder cables frequently. Or for a little more expediency, zip tie groups of 3 to strut and that would avoid derating.

You could also fasten 2xs and use the appropriate sized 2 hole strap and fasten the cables to that in groups of 3. I think it's going to depend on how much space you have and the construction details.

What if I want to do groups of 6 copper, 90 degrees c? What feeders do I need if dwelling units are 125A services?

 

[electrofelon]

What if I want to do groups of 6 copper, 90 degrees c? What feeders do I need if dwelling units are 125A services?

Due to terminal ratings of 75 degrees, you would generally be restricted to the 75 degree ampacity. #6 isn't anywhere close to 125A

 

[Tainted]

no

Due to terminal ratings of 75 degrees, you would generally be restricted to the 75 degree ampacity. #6 isn't anywhere close to 125A

i should have been more clear, i mean groups of (6) cables. what size conductors would I need? It would be 50% derating since it’s 18 CCC. What feeders would I need for the 125A services?

 

[infinity]

no

i should have been more clear, i mean groups of (6) cables. what size conductors would I need? It would be 50% derating since it’s 18 CCC. What feeders would I need for the 125A services?

125 amps/50%= 250 amps. Look at T310.15(B)(16).

 

[Tainted]

125 amps/50%= 250 amps. Look at T310.15(B)(16).

Thanks, I just wanted a second eye to look at it to see if my calculation checks out. I'm gonna go with groups of 3 as the 50% is too much.

 

[electrofelon]

Couldn't one strap in groups of three at the required support intervals , then just stick some sort of spacers in between to avoid derating? They must be bundled "without maintaining spacing" for more than 24 inches to trigger derating.

 

[Tainted]

Couldn't one strap in groups of three at the required support intervals , then just stick some sort of spacers in between to avoid derating? They must be bundled "without maintaining spacing" for more than 24 inches to trigger derating.

Oooooooooh... I feel like an idiot engineer. So you're saying I can strap them in groups of 3 and as long as I provide spacers within 24 inches of the strap, it can avoid the derating?

 

[electrofelon]

Oooooooooh... I feel like an idiot engineer. So you're saying I can strap them in groups of 3 and as long as I provide spacers within 24 inches of the strap, it can avoid the derating?

Well 12 inches above and 12 inches below would make a "non spaced" length of less than 24 inches. It seems that would comply..... What constitutes "spacing" is not really defined, but imo as long as they are not touching they are spaced

 

[Tainted]

Well 12 inches above and 12 inches below would make a "non spaced" length of less than 24 inches. It seems that would comply..... What constitutes "spacing" is not really defined, but imo as long as they are not touching they are spaced

Hmmm, let's play devil's advocate regarding strapped cables.. Does this mean I can strap as many cables as I want avoiding derating if I provide the spacers within the 12" as you mentioned? What if I had 100 cables strapped in 1? I mean Obviously I wouldn't do that, I'm just throwing a exaggerated example lol. Does the NEC limit how many can be strapped?

 

[electrofelon]

What if I had 100 cables strapped in 1? I mean Obviously I wouldn't do that, I'm just throwing a exaggerated example lol. Does the NEC limit how many can be strapped?

I don't see any issue. You do have 300.11(B) but as long as you strap them ALL to the thing that is supporting them and don't strap cables to other cables, seems fine to me.

 

[Julius Right]

See [for information]

type mc-type ac installation guide & catalog - AFC Cable Systems, Inc.

type mc-type ac installation guide & catalog - AFC Cable Systems, Inc.

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