Okay, let's break down the wiring requirements for your 2016 Marquis V94 hot tub and address your questions about using aluminum SER cable.

Understanding the Requirements 240V, 40A Max Load, 50A Minimum Supply Conductor

This means the hot tub could draw up to 40 amps, but the wiring MUST be rated for at least 50 amps. This provides a safety margin. The breaker will protect the equipment from overloading.

Copper Wire Only (at Spa)

You are correct. The "copper only" specification is almost certainly referring to the wiring from the disconnect box to the hot tub itself. This is because of the corrosive environment around a hot tub (moisture, chemicals). Aluminum is more susceptible to corrosion than copper.

Can You Use Aluminum SER Cable from Panel to Disconnect?Yes, most likely, but with important considerations.

Here's a detailed breakdown:1. Code Compliance

The National Electrical Code (NEC) does allow aluminum conductors for feeder runs like this, provided they are properly sized and installed. You must adhere to local electrical codes, which may have stricter requirements than the NEC.

Contact your local electrical inspector before proceeding. This is crucial.2. Wire Size for Aluminum

You cannot simply substitute #6 aluminum for #6 copper. Aluminum has a higher resistance than copper, so you need a larger gauge wire to carry the same current safely. To carry a 50A load, you will likely need #4 Aluminum. Confirm with the tables provided in the NEC and verify with the inspector. You must consult the ampacity tables in the NEC (Table 310.16 and related tables) to determine the correct aluminum wire size for 50 amps, considering the insulation type (THHN, XHHW, etc.) and the termination temperature ratings (more on that below).
3.

Termination Compatibility



This is extremely important. You must use connectors (lugs, terminals) that are specifically rated for use with aluminum conductors. These connectors are marked "AL-CU" or "Suitable for Aluminum and Copper". Using standard copper-only connectors with aluminum wire can lead to corrosion, overheating, and fire hazards. Pay close attention to the temperature rating of the terminals at the breaker, disconnect, and hot tub. You must use wire and connectors that are rated for at least the temperature of the terminals.4. Anti-Oxidant Compound

When connecting aluminum wire to any terminal, use an anti-oxidant compound (like Penetrox or Noalox). This helps prevent oxidation and ensures a good electrical connection. Apply it liberally to the aluminum conductor before inserting it into the connector.5.

Tightening Torque

Use a torque wrench to tighten all connections to the manufacturer's specified torque value. Over- or under-tightening can lead to connection failures.6.

Conduit Considerations

You mentioned only a small amount of conduit. Make sure you use a conduit suitable for outdoor use (if applicable) and that the aluminum SER cable is rated for wet locations.

Regarding Pulling Difficulty

Aluminum SER cable can be slightly more difficult to pull than copper due to its larger size for the same ampacity. However, for a 65-foot run with mostly open space and only a short section of conduit, the difference in pulling force should not be massive. Use wire pulling lubricant to make the job easier.

Specific Cable You Mentioned (Hypothetical)

You didn't specify a specific cable, but let's assume you're looking at a #4-4-4-8 Aluminum SER cable with THHN/THWN insulation. That would likely be appropriate for your needs provided the temperature ratings of the wire and connectors are correct, but again, confirm with your electrical inspector.

In Summary



Consult your local electrical inspector BEFORE doing anything. Aluminum SER cable can be used for the feeder run from your panel to the disconnect, provided you follow all the rules about sizing, termination, anti-oxidant compound, and torque. You will likely need #4 aluminum wire, but confirm that based on your specific needs and the NEC tables. "Copper only" likely refers to the wiring from the disconnect to the hot tub. Ensure all connectors are rated for both aluminum and copper ("AL-CU"). Use anti-oxidant compound on all aluminum connections. Use a torque wrench to tighten connections to the manufacturer's specifications.

Recommendation:

While aluminum can save you money, the extra care and attention to detail required with aluminum wiring make it a bit more complex. If you're not extremely comfortable with electrical work, it might be best to hire a qualified electrician. They will ensure the installation meets all code requirements and is safe.If you are comfortable doing the work, prioritize safety, meticulous attention to detail, and code compliance. Good luck! Flag for review