The number of current drawing devices on a RV 30 ampere circuit and the standard plug connection is dependent on the condition of the electrical connections involved as long as the โaverageโ current draw for a 30 ampere RV circuit is not exceeded. Average current draw is the Key and what matters, โwhen the current that can flow and electrical components that are protected by the circuit breaker.โ 30-amp circuit breakers do not trip immediately at 31 amps, or even 40 amps, and one can trip at only 25 amps under the right conditions. Electrical current flow results in heat and heat is the most common cause of a tripped circuit breaker, however, magnetism can also trip circuit breakers when the current flow is great enough to cause a strong magnetic field in the breaker such as a direct short.
That being covered, burned 30-amp electrical connections are simply due to electrical resistance in a plug and socket and nothing more at or near full current flow supported by the circuit protection device โthe circuit breaker.โ A basic understanding of OHMs law is necessary to understand the cause of burned and failed 30-amp RV plugs and sockets. Electrical resistance creates heat, oxidized, corroded, unclean, otherwise loose or damaged plugs and sockets will burnout or melt every time they are called upon to carry the full rated load of a 30-amp circuit. Have you ever wondered why your 30-amp cloths dried plug and receptacle and plug never burnout and melt down? Electrical resistance is the key! Look at the blade size of the 30-amp drier plug, it is the same size as 50-amp RV plugs! The 30-amp RV plug is grossly undersized for the job it is required to do and as such, is doomed to constant burnout and melt down especially when connections are loose and dirty. And 30-amp to 50-amp adapters only hasten the demise of the 30-amp receptacle in a campground power pedestal when power hungry RVs stress them.
Now consider this: even before plugging into a 30-amp power pedestal, 120V are measured with a volt meter under no load. The power pedestal receptacle is loose due to wear and has possibly been over heated before so its internal contacts are oxidized creating electrical resistance. You plug in with a good, but not so shiny and or clean 30-amp RV plug or worse yet, one that has copper oxidation already coating its blades. Yes, the copper color, not brass color you see on 30-amp blades is copper oxidation from previous overheating and results in extra electrical resistance. Clean it off or risk a meltdown. OK, so the AC is running, the refrigerator is running and the water heater is heating and the converter is charging our batteries and powering our 12-appliances all from 120V AC. We are near the rated 30-amps, so why does this stuff always burn out?
Simple, too much electrical resistance. If we measured the voltage drop though the power pedestal receptacle and the RV cord plug and realized a 10-volt drop, so what? 110-volts inside the RV is plenty good to power all of our equipment, right? Well what is happening out at the power pedestal and your RV plug? OHMs law is at hard work heating, melting, and burning stuff up. Voltage x Amperes = Watts (electrical heat) 10 volts drop x 30 amps = 300 watts of power dissipation or heat. Converting watts to heat (BTU) that stuff that comes out of you RV furnace, equals roughly 1,000 BTU! Wow and all that heat has to be dissipated in the 30 amp plug and receptacle. Rubber and plastic melt, burn, and char, brass contacts get hot and oxidize, causing copper oxides, first copper color and then becoming black in color as the copper oxide resistance and heat increase and the 20-percent zinc in the brass contacts vaporizes. That is our 30-amp melt down, until something changes in the industry, we are stuck with it.
