NEC Table 310.15(B)(16) provides the minimum conductor sizes for overcurrent protection devices. For a 2000 amp breaker, the minimum conductor size is 750 kcmil copper or 900 kcmil aluminum.

Exceptions to the Table



Motor Circuit Conductors

Motors can have reduced conductor sizes based on the motor rating and starting current.

Feeder Conductors

Feeders to panelboards or switchboards can have reduced conductor sizes if the panelboard or switchboard is rated for less than the feeder ampacity.

Conductors in Parallel

When conductors are installed in parallel, the total ampacity must equal or exceed the ampacity of the overcurrent protection device.

Other Factors to Consider



Voltage Drop

The conductor size should be increased if the voltage drop is excessive.

Ambient Temperature

The conductor size should be increased if the ambient temperature is higher than the rated temperature of the conductor.

Mechanical Strength

The conductor size should be increased if the conductor is subject to significant mechanical stresses.

Reasons for Undersizing Conductors



Cost Savings

Larger conductors are more expensive.

Space Constraints

Conduit or cable trays may not have sufficient capacity for larger conductors.

Historical Practice

In the past, undersized conductors were sometimes used without causing problems.

Consequences of Undersized Conductors



Increased Voltage Drop

Undersized conductors can lead to excessive voltage drop, which can affect the operation of equipment.

Overheating

Undersized conductors can overheat and pose a fire hazard.

Premature Failure

Undersized conductors can fail prematurely, leading to downtime and safety concerns.

Recommendation:

It is always best to follow the NEC and other applicable codes and standards when sizing battery conductors. Undersized conductors can pose safety risks and negatively impact the performance of the electrical system. Flag for review