MC cable and voltage drop

[MaxGlez]

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!

 

[Dennis Alwon]

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

 

[Tainted]

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

Agreed, usually it is done using table 8

 

[Tulsa Electrician]

Just use R & X values for metal raceway

 

[Tulsa Electrician]

Forgot to add look at the notes #2

 

[Julius Right]

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.

 

[Tulsa Electrician]

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

 

[MaxGlez]

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.

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!

 

[Rock86]

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

If you use the southwire calculator, it asks for your conduit type.

 

[Dennis Alwon]

If you use the southwire calculator, it asks for your conduit type.

I just used a calculator that has a choice between steel, aluminum and pvc and with 30 amps , 500' and 240v copper the answer did not change 6.13% drop

 

[Tulsa Electrician]

If memory serves below 1/0 no big deal.
I'll need to check.