Yes, using #8 THWN conductors for the hot and neutral wires would likely void the warranty, and it's also a significant safety hazard. Here's why: Undersized Conductors

The manufacturer specifically calls for 6/3 copper. This means #6 AWG copper conductors for the two hot wires and the neutral wire, plus a grounding conductor. #8 AWG copper wire is not rated to carry 50 amps safely and continuously. Using it could lead to overheating, insulation breakdown, and potentially a fire.

Code Violation

Electrical codes (like the National Electrical Code - NEC) dictate the minimum wire size for a given ampacity. #8 copper is generally rated for around 40-45 amps, depending on the insulation type and installation conditions. Using it on a 50-amp circuit violates these codes.

Warranty Voidance

Manufacturers specify wiring requirements to ensure safe and reliable operation of their products. Deviating from these requirements, especially using undersized conductors, will almost certainly void the warranty.

Safety Hazard

Undersized wiring can overheat, melt insulation, and create a fire risk. It can also damage the hot tub's components due to voltage drop.

In summary, you MUST use #6 copper wire for the hot and neutral wires as specified by the manufacturer to comply with safety standards, electrical codes, and to maintain your warranty.

Regarding the grounding conductor, you've stated #10 E.G. (equipment grounding conductor). Using a #10 copper grounding conductor is generally acceptable for a 50-amp circuit, according to the NEC. However, you should confirm that the #10 grounding conductor is sized appropriately for the specific hot tub and circuit breaker.

Recommendation



Adhere to Manufacturer's Specifications

Always follow the manufacturer's wiring instructions precisely.

Consult a Qualified Electrician

Have a licensed electrician perform the hot tub wiring. They are knowledgeable about electrical codes and safety practices.

Use the Correct Materials

Use the correct gauge and type of wire (e.g., #6 copper THHN/THWN) and conduit as specified.

Verify Grounding

Ensure the equipment grounding conductor is properly sized and connected.*

Proper Installation: Make sure all connections are tight and secure, and the wiring is protected by the appropriate conduit.Ignoring these requirements is not only illegal but also dangerous. Flag for review