Electrical – Connecting the four terminals of a 14-50P to a homebrew 240v system with three wires

That does indeed describe a properly engineered 50 amp device.

It is normal for appliances to use slightly lighter gauge wire than would be used in building wiring. You can observe that inside electric ranges, dryers, and water heaters, where you will see the 10 or 8 gauge incoming supply wires to a terminal and then 12 or 14 gauge wire going from the terminal block off to the components.

Because the wire is inside an enclosed box, and is not tightly bundled or surrounded by thermal insulating materials, its elevated temperature will not cause any danger. It will run a little warm at peak current, but be far below "hot". The same is not acceptable inside dwelling walls were it will be in contact with wood, fiberglass, cellulose insulation, etc.

As for standards, I have determined this is beyond the scope of the NEC and falls into the domain of the National Fire Protection Association (NFPA) standards. That seems to cost $$ to view.

To increase the amp rating of your circuit breaker, you almost certainly need to increase the gauge of all the wiring on that circuit. Circuit breakers are there to protect the wiring for overloading, overheating, melting the insulation, and eventually starting a fire.

Typically, you have the following wire gauges (this may vary with long circuits and your local codes):

• 15 amps: 14 gauge
• 20 amps: 12 gauge
• 30 amps: 10 gauge
• 55 amps: 8 gauge
• 75 amps: 6 gauge

So going from 30 amps to 55 amps requires you to rewire that circuit from 10 gauge to 8 gauge wiring.

For your oven, check the specs on the oven itself. It may simply have a plug that's designed for multiple ovens and will work on a 30 amp circuit.