MC cable and voltage drop

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MaxGlez

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Guadalajara, Jal. Mexico
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Aplication Engineer
Hello, good afternoon.

Im currently reviewing a project's single line diagram where there is a panelboard fed by a switchboard breaker with MC cable and want to do a voltage drop calculation, but i don't know what type of raceway to choose from Table 9, chapter 9 of the NEC to consider the effective impedance, can you help me out?

Thanks!
 
Every VD calculation I have done or seen doesn't use cable or raceway. The fault current calculators uses the raceway, I believe. Maybe somebody with more knowledge can be helpful
 
I did not use MC cable, but since the armor material is aluminum, I don't think it could change the magnetic fields and then the cable phase-to-phase reactance will remain unchanged with respect to non-armored cable. The steel conduit may change it [see NEC Table 9].
However, the resistance -due to losses in aluminum armor -it could be increased a bit mainly for large conductor cross section. In my opinion, we can use the aluminum conduit column for resistance.
 
I see what your saying. I'm use to using steel covered MC for feeders.
Using MC light may yield a different ansawer. Thing to watch for using AL is EMI. The steel provides better sheliding. So it really depends on the application. I have seen guys rip it out because they did not catch the spec. I should have mentioned that prior. Sorry
 
Julius Right said:
I did not use MC cable, but since the armor material is aluminum, I don't think it could change the magnetic fields and then the cable phase-to-phase reactance will remain unchanged with respect to non-armored cable. The steel conduit may change it [see NEC Table 9].
However, the resistance -due to losses in aluminum armor -it could be increased a bit mainly for large conductor cross section. In my opinion, we can use the aluminum conduit column for resistance.
Click to expand...
Thank you all for your answers: I think I agree the most with Mr. Right about using the aluminum conduit column, and in the case of a steel armor like Mr. Tulsa says, then we could the steel column. I have seen many times that table 8 is the one used for voltage drop calculations, but never agreed 100% with this because we're talking about AC current which has inductive and capacitive reactance (not the same with DC).

Best regards!
 
Dennis Alwon said:
Every VD calculation I have done or seen doesn't use cable or raceway. The fault current calculators uses the raceway, I believe. Maybe somebody with more knowledge can be helpful
Click to expand...
If you use the southwire calculator, it asks for your conduit type.
 
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