What is 2 + 2 ?

[ToolHound]

Apparently I can not add today,
nor read a Table (T310.16).

Please give me a hint....how does Table 310.16
say the below conductor sets make a 400 Amp feeder? Thanks.
( I can't see how. But my book, with below pic, sez it is so. ).


A 400A feeder with a neutral load of 240A can be paralleled as follows: (see Figure below)

? Phase A, Two?250 kcmil THHN aluminum, 100 ft
? Phase B, Two?3/0 THHN copper, 104 ft
? Phase C, Two?3/0 THHN copper, 102 ft
? Neutral, Two?1/0 THHN aluminum, 103 ft
? Equipment Ground, Two?3 AWG copper, 101 ft

 

[GoldDigger]

Apparently I can not add today,
nor read a Table (T310.16).

Please give me a hint....how does Table 310.16
say the below conductor sets make a 400 Amp feeder? Thanks.
( I can't see how. But my book, with below pic, sez it is so. ).


A 400A feeder with a neutral load of 240A can be paralleled as follows: (see Figure below)

• Phase A, Two—250 kcmil THHN aluminum, 100 ft
• Phase B, Two—3/0 THHN copper, 104 ft
• Phase C, Two—3/0 THHN copper, 102 ft
• Neutral, Two—1/0 THHN aluminum, 103 ft
• Equipment Ground, Two—3 AWG copper, 101 ft

I do not see your problem.
Step 1: Use the 75C column for all conductors.
Step 2: 250Kcm Al is good for 205A, 410 is greater than 400.
Step 3: 3/0 Cu is good for 200A, 400 is equal to 400.
Step 4: Same as above, but different length.
Step 5: 1/0 Al is good for 120A, 240 equals 240 (reduced neutral since max neutral current is known to be 240.)
Step 6: Size of required EGC is derived separately.

This assumes that all of the wires are in a situation where no derating applies and that each raceway holds one full set of conductors.

 

[ToolHound]

Apparently I can not add today,
nor read a Table (T310.16).

I'm sorry. Never mind. I think I see now. I must need a cup of coffee, cuz I had 'brain freeze' there for a minute. Thanks. --ToolHound

 

[ToolHound]

I do not see your problem.
Step 1: Use the 75C column for all conductors.
Step 2: 250Kcm Al is good for 205A, 410 is greater than 400.
Step 3: 3/0 Cu is good for 200A, 400 is equal to 400.
Step 4: Same as above, but different length.
Step 5: 1/0 Al is good for 120A, 240 equals 240 (reduced neutral since max neutral current is known to be 240.)
Step 6: Size of required EGC is derived separately.

This assumes that all of the wires are in a situation where no derating applies and that each raceway holds one full set of conductors.

GoldDigger. Thanks. You have it exactly right. I see now. I don't know why I couldn't see it 5 minutes ago. My brain took a brief vacation apparently. Thanks. ToolHound