Adjustment Factor for Lighting & small Power circuits

[Sajid khan]

Dear All,

In a hospital project we are using cable trunking instead of conduits in some places. Can any one tell me that whether we need to apply adjustment factors as per NEC 376.12 (B) stated to apply adjustment factors if number of conductors exceed 30??
We have so many conductors in the trunking and if the adjustment factor is applied the capacities of the conductors will be changed and hence the conductor size also while the conductor size for the circuit is fixed 4mm2.


Regards,
Sajid

 

[Smart $]

Dear All,

In a hospital project we are using cable trunking instead of conduits in some places. Can any one tell me that whether we need to apply adjustment factors as per NEC 376.12 (B) stated to apply adjustment factors if number of conductors exceed 30??
We have so many conductors in the trunking and if the adjustment factor is applied the capacities of the conductors will be changed and hence the conductor size also while the conductor size for the circuit is fixed 4mm2.


Regards,
Sajid

Yes, adjustment applies if over 30 current-carrying conductors. However, this only applies where the number exceeds 30 at by cross-sectional count... not entire raceway. For example, you could have 30 enter and go left then another 30 enter to the right of them go right and not have to apply adjustment factors.

It is wiser (read: costs less) to install a second wireway right beside the first (or two smaller wireways in place of one larger one as long as fill is not exceeded) and share the number of conductors through the length where the number exceeds 30.

PS: I think you meant 376.22...

 

[Sajid khan]

Yes, adjustment applies if over 30 current-carrying conductors. However, this only applies where the number exceeds 30 at by cross-sectional count... not entire raceway. For example, you could have 30 enter and go left then another 30 enter to the right of them go right and not have to apply adjustment factors.

It is wiser (read: costs less) to install a second wireway right beside the first (or two smaller wireways in place of one larger one as long as fill is not exceeded) and share the number of conductors through the length where the number exceeds 30.

PS: I think you meant 376.22...

yes 376.22 exactly

 

[Sajid khan]

yes 376.22 exactly

The idea is very good to split the trunking in two if we have more than 30 circuits.
Thanks

 

[m sleem]

First off, i thought there is a conflict between 310.15(b)(3)(a) & 376.22(b) where 310.15(b)(3)(a) consider the adjustment if no of wires more than #3 only not 30, then i found the condition of 31.15(b)(5) has to be applied to consider the adjustment after #30 wires, anyway the mentioned cables type AC & MC under 310.15(b)(5) are not manufactured in Saudi Arabia, thereby the best scenario to calculate the adjustment factors when you refer to the supplier catalog and get proper adjustment factors to the type of wires will be used.