Conduit fill

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infinity

infinity

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GoldDigger said:
The five ungrounded consist of two 120/240 MWBC's. That gives us four CCCs and uses up two of the grounded conductors. The fifth ungrounded forms a single circuit using one of the remaining grounded conductors. Both of those count. Total = six.
The fourth grounded conductor is a spare, there just to satisfy the neutral requirement for a hypothetical device which may be installed in a switch box at a later time, and is not connected to any outlet of any kind. (Or does its mere presence inside a switch box make it "utlilized"?)
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I guess that if we want to include spares in the calculation then we can spend quite some time debating. :D

For what it's worth raceways to switches do not require a neutral since it can be added later. ;)
 
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petersonra said:
you are right. but as a practical matter if you have 60C terminations don't you have to derate down to what 60C wire would be?
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Nope, see #22.
You use that limit for actual load amps, but not for derating purposes. I guess that the assumption is that the heating along the body of the wire will not have an overriding effect on the temperature of the termination. That will be mostly dependent on the actual amps right at the termination and within the connection. You could make an argument that ambient at the termination should be factored in somehow even though the fill-related numbers are not, but that is not how the Code is written.
 
kwired

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GoldDigger said:
NO. The OP said assume 60C terminations. THHN is not 60C wire no matter what you assume. :)
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petersonra said:
you are right.

I never really thought about that. How does that work?
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In no case can the conductor be smaller than what is required in 60C column, BUT when adjusting for ambient temp and number of conductors in the raceway you are allowed to start adjusting from the values in the 90C column. You are not adjusting termination temperature, you are adjusting for allowable insulation temperature. Should adjustments put you smaller than what you needed at 60C your minimum conductor size is still at least whatever the 60C termination needs.
 
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