Okay, let's break down the EGC sizing requirement for parallel conductors and how adding multiple sets affects it.

NEC Governing Sections 250.122

This is the main section for Equipment Grounding Conductor (EGC) sizing. It uses the OCPD (Overcurrent Protective Device) protecting the circuit to determine the minimum EGC size.

250.122(F)

This section covers EGCs run in parallel, requiring the EGC to be increased if the ungrounded conductors are increased in size due to parallel operation.

The Logic1. Base EGC Size (based on OCPD)

First, determine the minimum EGC size based on the 800A OCPD using Table 250.122. Looking at Table 250.122, an 800A OCPD requires a minimum of a 1/0 AWG copper EGC, or a 3/0 AWG Aluminum.
2.

Parallel Conductor Increase (250.122(F))

Because you have parallel conductors, you must increase the EGC proportionately to the increase in the phase conductors. NEC 250.122(F) states "Where ungrounded conductors are increased in size, as permitted in 310.10(H), the equipment grounding conductor(s) shall be increased in size proportionately according to the increase in circular mil area of the ungrounded conductors".
3.

Calculating the Total Circular Mil Area

Determine the circular mil area of the original minimum conductor and of your conductors after paralleling.4.

Applying the Proportion



(Actual Parallel Conductor Circular Mil Area) / (Original Minimum Conductor Circular Mil Area) = Multiplier (Original Minimum EGC Circular Mil Area) Multiplier = Required EGC Circular Mil AreaCalculations1. Original Minimum Conductor

The NEC 310.16 ampacity table shows us that 500 kcmil is capable of carrying 380 amps. If we were not paralleling, and wanted to carry 800 amps with a single set of conductors, we would need to upsize to 600 kcmil. Thus 600 kcmil will be our "original minimum" conductor.
2.

Actual Parallel Conductor

You have six (6) sets of 500 kcmil conductors in parallel. You will need to compare this to our "original minimum" conductor to find our multiplier.3.

Circular Mil Areas

600 kcmil = 600,000 circular mils (CM) 500 kcmil = 500,000 circular mils (CM)4.

Calculate Total Parallel Conductor Circular Mil Area

Six (6) 500 kcmil conductors = 6 500,000 CM = 3,000,000 CM5.

Calculate the Multiplier

Multiplier = (3,000,000 CM) / (600,000 CM) = 56.

Determine the Minimum EGC Size

Based on the 800A OCPD from Table 250.122, the minimum EGC size is 1/0 AWG Copper.
7.

Calculate the EGC increase based on the multiplier

Minimum EGC of 1/0 AWG = 105,600 CM Increased EGC = 105,600 CM 5 = 528,000 CM8.

Determine Minimum Size Per Set

Since the EGC is run in parallel, we can split the required circular mil area across each of the six sets of parallel conductors. (528,000 CM) / 6 = 88,000 CM per set.9.

Select the EGC Size

Find the conductor size that has a circular mil area equal to or greater than the required calculated circular mil area per set of conductors. Referring to Chapter 9 Table 8. The next size conductor greater than 88,000 CM is 1 AWG.

Therefore, each of the six (6) sets of 500 kcmil conductors must have a minimum EGC of 1 AWG copper.Important Considerations



Voltage Drop

While you're calculating conductor sizes, remember to consider voltage drop, especially over long distances. Paralleling helps with ampacity but doesn't inherently fix voltage drop issues.

Material

This calculation assumes copper EGCs. If you use aluminum, adjust the size accordingly.

Terminations

Ensure that the equipment is properly listed and labeled for the number and size of conductors you are using, especially within the termination lugs and equipment grounding bus. You may need to use listed splicing methods or distribution blocks to accommodate the multiple conductors.

Disclaimer: This information is for educational purposes only and should not be considered a substitute for professional electrical engineering advice. Always consult with a qualified electrician or engineer and adhere to local codes and regulations. Flag for review