It doesn’t take a rocket scientist to realize that a 50 amp plug melted is an electrical problem to address immediately. Where there is melting, there is heat and the potential for fire and damage.
Electricity has a potential for electrical arcing, which can cause unwanted heat and melting of plastic and metal parts of a 50 amp plug. The most common cause for a 50 amp RV plug melting is short with a wire causing excessive heat.
This post will review the common causes of the wiring short and what to look for to avoid this melting.
Table of Contents
Heat
Resistance and a short are the two common causes of heat in an electrical system.
Resistance
Resistance in an electrical system is when there is a restriction in the flow of electricity. This resistance causes heat to build up in the power cord.
This is how a toaster works. It uses a wire with resistance to generate heat. This is that glowing wire inside of your toaster.
In an RV plug, heat can also be generated by resistance with the RV extension cord. If the power cord is too long or is not thick enough, there will be resistance and excessive heat. Check your power setup and ensure you are using only rated RV extension cord and that it is not more than 100 feet.
In the case of resistance heat, it is usually the entire wire that heats up and is less likely a melted spot at the RV plug.
Wire Short
Another common cause for excessive heat is a short in the wiring. This is when two wires are directly touching or are close enough that there will be electrical arcing. This arcing can occur anywhere there is a gap in the wire insulation or when it comes close to touching the ground wire.
If your RV plug is melted at a single location, it is more likely a short causing the heat. With that, let’s explore the common causes of a short and resolution.
Power Source
When working with 50 amps, you are in the presence of a lot of electricity. And compared with a 30 amp plug, you are dealing with almost 4 times as much power! How is that possible, as 50 amps are barely twice as many amps as 30 amps? The answer is that the voltage of a 50 amp circuit is 240 volts, whereas a 30 amp circuit is only 120 volts. And using a simple formula of Watts = Power x Voltage, you get 12,000 watts with a 50amp (240v) vs only 3,600 watts with a 30 amp (120v).
This greater source of wattage and amps can easily cause more heat quicker than if you had a short in a 120 volt 30 amp circuit. It is also to say that you must be extra careful when dealing with 240 volts and 50 amps. As you look into your cause, the most important thing to do is go to the breaker panel and turn off the breaker for safety.
Wiring
The first thing to check when checking for a short is a visual inspection of the wire and insulation.
Here is a step-by-step guide to inspecting for a short:
- Visually inspect outer wire insulation (sometimes called jacket). Check for any cracks, splits, or signs of wear that may allow electricity to get through. This could also be areas where a truck or car ran over the wire or cord.
- Check if any wires are touching each other. Open up your 50 amp outlet and inspect the wires. With a 50 amp plug, you will have 3 insulated wires to look for. There are two hot wires, usually one red and one black. The next wire is white, this is the neutral wire. None of those wires should be touching or close to touching other.
- Check ground wire. The ground wire is the bare copper wire. It is usually connected to the outlet and connected to the electrical box. Being exposed copper, it is common for the ground to create a short by coming close to another wire.
Connection
Another cause of a short can be the connection of the wires to an outlet on shore power. As you inspect the wires, also check for a loose connection. The back of your outlet will have brass and silver screws that securely lock in the wires. If these screws are not secure, it will cause a possible short due to the poor connection. And as you plug into the socket, it could cause a short or wires touching as you connect in the male plug.
Adapter
Another potential cause of the plug melting is a defective adapter. Many RVgoers use adapters as they give many options when using a 50 amp plug. You can easily convert it to a 30 amp plug or a regular 120v outlet.
However, not all adapters are built with the same quality, and issues can happen. You can use a continuity tester on your multimeter to check your adapter. To check, ensure no continuity between any connectors on the same side. For example, check all the possible connections between the connectors on one face of the adapter. If there is a short between the wires in the adapter, you will get continuity, which means the wires are touching.
If you are getting continuity as tested or if you do suspect the adapter, they are reasonably priced and best just to be replaced.
Final Thoughts
A 50 amp RV plug melted is something to address immediately. Excessive heat in electricity is generated by either resistance or a short in the wires. Shorts are commonly caused by wire touching or by a bad ground wire. Also, test your adapter to see if it has no short inside. If you suspect a faulty outlet on at-shore power or a defective adapter, it is best to replace them.
Tony is an avid camper and RV traveler. He fell in love with camping on his first RV trip with his wife over 25 years ago. Tony loves sharing lessons learned and tips about RV maintenance and safe traveling.
