Okay, let's break this down and figure out the correct aluminum SER cable size for your 500' run with a 95A load at 208V, aiming for a 5% voltage drop.1. Understanding Voltage Drop (VD) Calculations VD Limit

You're allowed 5% voltage drop on a 208V system. That's 208V 0.05 = 10.4V maximum voltage drop.

Formula

The simplified voltage drop formula for a single-phase circuit (which is relevant if this is a single-phase load or if this is balanced 3-phase and you're calculating VD phase-to-neutral) is:VD = (2 K I D) / CMWhere: VD = Voltage Drop (in volts) K = Material Constant (Aluminum = ~17) (This can vary slightly depending on the specific alloy, but 17 is a good general value for aluminum.) I = Current (Amps) = 95A D = One-way Distance (Feet) = 500' CM = Circular Mils (Area of the conductor)

2. Calculating Required Circular Mils

We need to rearrange the formula to solve for CM:CM = (2 K I D) / VDCM = (2 17 95 500) / 10.4CM = 154134.62We will round up to 1541353. Finding Aluminum SER Cable Size from Circular Mil (CM) Data

You'll need to consult a table that shows the approximate circular mil area for different sizes of aluminum SER cable. I cannot display that for you, but below is the rough calculations:Based on this calculation, you'll need an Aluminum SER cable size that has a circular mil area of approximately 154135 CM. A 2/0 Aluminum SER cable is not large enough. 3/0 AWG Aluminum SER is roughly 167,800 CM and will be the most likely to work.4. Checking Ampacity Consult the NEC (National Electrical Code) Table 310.16 (or the relevant table in your local code) to determine the ampacity of the chosen aluminum SER cable size. The ampacity must be at least 95A. 3/0 AWG Aluminum SER cable, assuming a 75°C termination temperature (which is common), typically has an ampacity of around 140 Amps. This should be sufficient, but always verify with the NEC table for your specific conditions.5. Is Splicing Down Beneficial? Probably not. Splicing introduces additional points of potential failure and complexity. Unless you have a very compelling reason to use a larger cable for a portion of the run (e.g., needing higher short-circuit withstand for a certain section, or existing infrastructure), it's generally simpler and more reliable to run a single cable size the entire distance.6. One Size The Entire Way? Yes, in this case, it's recommended to run one size the entire way. It's simpler and avoids potential issues with connections.

Summary and Recommendations Recommended Cable

3/0 AWG Aluminum SER cable.

Important

Double-check the ampacity of the 3/0 AWG Aluminum SER cable in the NEC Table 310.16 (or your local code) based on the specific installation conditions (temperature rating of terminations, ambient temperature, etc.).

OCPD

You'll need to use a properly sized overcurrent protection device (circuit breaker or fuses) for the 3/0 AWG Aluminum SER cable, and it must be rated to protect the cable's ampacity. A 100A breaker/fuse will probably suffice, but verify ampacity.

Important Considerations and Next Steps Local Codes

Always consult your local electrical codes and regulations. They may have specific requirements or restrictions that supersede the general guidelines above.

Qualified Electrician

Have a qualified electrician perform the installation. Electrical work can be dangerous, and proper installation is critical for safety and performance.

Derating

If the cable is installed in a hot environment or bundled with other cables, you may need to derate the ampacity. The NEC provides guidelines for derating.

Voltage Drop Calculators

Use online voltage drop calculators as a sanity check. There are many available.

Manufacturer's Data

Consult the cable manufacturer's specifications for their specific cable product.

Disclaimer: The information above is for general guidance only. A qualified electrician should perform all electrical work. Flag for review