75? column of Table 310.16

[tryinghard]

Are there other references about the use of Table 310.16?s 75? column besides 310.15(B) FPN(1)?

 

[480sparky]

Why? .

 

[augie47]

You might try 110.14 and see if that answers your question.

 

[raider1]

I agree with Gus, 110.14(C) usually drives the requirements to use the 75 degree column of 310.16.

Chris

 

[tryinghard]

Thanks guy's, I wanted something more than a fine print note. I am questioning a design that includes parallel 350's with 600A OCP

 

[tryinghard]

This same design includes single 350's with 350AT/400AF OCP; I wonder what "AT" and "AF" stand for? Automatic Trip? Either way the 350's seem to barly comply with the AT but not the AF?

 

[david luchini]

Thanks guy's, I wanted something more than a fine print note. I am questioning a design that includes parallel 350's with 600A OCP

I don't see a problem with parallel 350's from a 600A OCP. Parallel 350's is 620 Amps (without derating.) Unless maybe the parallel sets are installed in the same conduit.

This same design includes single 350's with 350AT/400AF OCP; I wonder what "AT" and "AF" stand for? Automatic Trip? Either way the 350's seem to barly comply with the AT but not the AF?

"AT" is Amp Trip and "AF" is Amp Frame. The single set of 350's from the 350A OCP could be a problem, depending on what the load being served is. For instance, it'd be OK on a chiller unit with a MCA of 300 and an MOCP of 350.

 

[augie47]

This same design includes single 350's with 350AT/400AF OCP; I wonder what "AT" and "AF" stand for? Automatic Trip? Either way the 350's seem to barly comply with the AT but not the AF?

350 AmpTrip 400 AmpFrame Breaker

 

[tryinghard]

I don't see a problem with parallel 350's from a 600A OCP. Parallel 350's is 620 Amps (without derating.) Unless maybe the parallel sets are installed in the same conduit.

310.16 75 degree column for 700kcmil = 460A, 240.4(B) = up to 500A. Am I missing something obvious?

 

[raider1]

310.16 75 degree column for 700kcmil = 460A, 240.4(B) = up to 500A. Am I missing something obvious?

Actually 240.4(B) permits the next size up rule to apply to devices rated up to 800 amps not 500 amps.

Chris

 

[david luchini]

310.16 75 degree column for 700kcmil = 460A, 240.4(B) = up to 500A. Am I missing something obvious?

Yes, you are missing something obvious. You said PARALLEL sets of 350's.

From Table 310.16,75 deg column, 350mcm has an allowable ampacity of 310 Amps. Two sets in parallel would have and ampacity of 310x2 or 620 Amps.

 

[Dennis Alwon]

Parallel 350 KCM are not equivalent to 700KCM. Very different because their is more surface area on two sets of 350 KCM. As David and others have said-- Look up the amps for 350KCM @ 75 C and double it.

 

[tryinghard]

Parallel 350 KCM are not equivalent to 700KCM. Very different because their is more surface area on two sets of 350 KCM. As David and others have said-- Look up the amps for 350KCM @ 75 C and double it.

Dennis, I was doubling the circular mills. Thanks for catching this and correcting. :grin: