NEC Chapter 9 Tables 8 and 9

[transgenesis]

I have seen a question on this before, but I had a slightly different question. Table 9 shows resistance values for AC conductors in PVC conduit. These to me look like rounded versions of the mechanical properties seen in table 8. Is this correct? I am referring to the values in AC resistance for uncoated wires in PVC conduit. When calculating impedance, I would use resistance and the reactance X_L?

 

[ggunn]

I have seen a question on this before, but I had a slightly different question. Table 9 shows resistance values for AC conductors in PVC conduit. These to me look like rounded versions of the mechanical properties seen in table 8. Is this correct? I am referring to the values in AC resistance for uncoated wires in PVC conduit. When calculating impedance, I would use resistance and the reactance X_L?

No. Table 8 shows straight resistance and table 9 shows "AC resistance", which is actually impedance at 60Hz. Reactance is in there.

 

[transgenesis]

No. Table 8 shows straight resistance and table 9 shows "AC resistance", which is actually impedance at 60Hz. Reactance is in there.

That doesn’t seem correct to me. The table specifies separately impedance, reactance, and resistance. It is titled “ Table 9 Alternating-Current Resistance and Reactance for 600-Volt Cables, 3-Phase, 60 Hz, 75°C (167°F) — Three Single Conductors in Conduit”.

I don’t think the code book would use the word resistance to mean impedance when it is giving you reactance from which you can calculate impedance with, and also providing separately impedance at 0.85PF. Impedance is calculated using phase, and no phase is specified for the column titled "Alternating-CurrentResistance forAluminum Wires".