EGC Sizing error

[anees ur rahman]

egc sizing


Hello i am having trouble doing EGC sizing


(tag 2 from attached image )
my inverter output current is 120A
continous load = 1.25*120 = 150A
from table 310.15b16
required size is 1/0 AWG ( 170 A)
but for temperature adjustment i take 2/0 AWG and it fullfill my requirement
table 250.122 says that i need 6AWG ,okay cool
but i also increase my egc wire ampacity (NEC apply) so i also need to upgrade EGC wire too

above require wire is 1/0 (AWG , 105600 cir.Mills )

selcted wire is 2/0awg( 133100 cir.mills)
133100/105600 = 1.26

1.26 * 26240 ( 6AWG) == 33073 CIR.MILLS
so my EGC should be 4 AWG

but i am not matching with this image attached calculations for all egc. I do not know where i am wrong

 

[tortuga]

I agree with your calculation.
Since they dont make 5 AWG (33101 kcmil) you would upsize to 4 AWG.

 

[jaggedben]

If the temperature adjustment requires upsizing then you do not have to upsize the EGC.

You only have to upsize the EGC if you upsize ungrounded conductors for a reason not otherwise required by the code, for example to reduce voltage drop.

Your calculation is correct for a situation where you upsize by choice. But a 6awg EGC is fine in this application.

 

[don_resqcapt19]

I agree with your calculation.
Since they dont make 5 AWG (33101 kcmil) you would upsize to 4 AWG.

Not sure if you can buy it, but some type G power cables use odd sized equipment grounding conductors including 5 AWG.

GGC-1/0-3C Type G-GC Portable Cord | Allied Wire & Cable

GGC-1/0-3C Type G-GC Portable Cord features (3) 1/0 AWG fully annealed bare copper conductors and premium grade, color-coded insulation rated for up to 90C. For quality discounts on portable power cable, submit an RFQ online to Allied Wire.

www.awcwire.com

 

[tortuga]

If the temperature adjustment requires upsizing then you do not have to upsize the EGC.

You only have to upsize the EGC if you upsize ungrounded conductors for a reason not otherwise required by the code, for example to reduce voltage drop.

Your calculation is correct for a situation where you upsize by choice. But a 6awg EGC is fine in this application.

Interesting I never got that out of 250.122(B)

 

[anees ur rahman]

If the temperature adjustment requires upsizing then you do not have to upsize the EGC.

You only have to upsize the EGC if you upsize ungrounded conductors for a reason not otherwise required by the code, for example to reduce voltage drop.

Your calculation is correct for a situation where you upsize by choice. But a 6awg EGC is fine in this application.

thanks you are right this pint was missing but now its clear
thanks again