Yes, there's a significant reason to increase the cord size. You've correctly identified the problem: the 8/4 SO cord is only rated for 35 amps, but the receptacle, breaker, and (presumably) the intended load are all designed for 50 amps. This creates a serious safety hazard.Here's a breakdown of the concerns: Overcurrent Protection Mismatch

The 50A breaker is intended to protect the wiring. If the 8/4 cord draws more than 35A, it could overheat and potentially cause a fire _without_ tripping the breaker. The breaker is sized for the panel wiring, not the undersized cord.

Code Violation

The National Electrical Code (NEC) requires that conductors be protected at their ampacity. Using a 35A-rated cord on a 50A circuit violates this fundamental safety principle.

Voltage Drop

While not as immediately dangerous as overheating, undersized conductors also lead to voltage drop, especially with longer runs and high loads. This can cause equipment to operate inefficiently, shorten its lifespan, or even fail.

Liability

If there's a fire or equipment damage related to the undersized cord, you could be held liable as the installer.

Why the 8/4 Cord is Inadequate

The fact that the trailer manufacturer used an 8/4 cord is concerning and potentially negligent on their part. It doesn't automatically make it safe. The 8/4 SO cord is designed for flexible portable power. If this is designed as a semi permanent connection it's also not within code to use it as such.

What You Should Do


Replace the Cord

The immediate and necessary step is to replace the 8/4 SO cord with a cord that is rated for at least 50 amps. The most common wire gauge is 6/4 SO cord.2.

Confirm Trailer Panel Wiring

Double-check the wiring inside the trailer's panel. Make sure the conductors connected to the 50A breaker are also rated for at least 50 amps.3.

Assess Load

You need a better estimate of the actual load. "Just under 5500 watts" is a starting point, but you also need to consider:

Starting Current

Motors (like the AC compressor) draw significantly more current when starting.

Future Load

The customer will likely add more equipment.*

Diversity

Not all equipment will run at its maximum load simultaneously.4.

Consider Hardwiring (If Possible)

If the trailer will be in a fixed location for extended periods, consider a permanent hardwired connection using appropriate conduit and wiring (e.g., THHN). This eliminates the potential issues with a flexible cord.

In summary, replacing the undersized cord is non-negotiable. It's a safety hazard and a code violation. Don't take shortcuts when it comes to electrical safety. Flag for review