Thor Forums

[Thehobe1]

The power connections are probably at fault here. As connector pins wear or even under heavy loads (air conditioner starting currents), the pin connections are not very good when left connected for long periods of time. Normally, when plugging in plugs, there is a wiping action that helps to give a "cleaning" to the contact surfaces. When high current loads switch on and off, (air conditioner) motor back EMFs can result in much high switching currents that can cause arcing across the connection surfaces resulting in surface oxidation. As this oxidation increases, resistance builds up in the physical connection resulting in heat being generated by IxR (current times voltage) loss in the pin contact area. Unfortunately heat results in more oxidation, more resistance and even more heat. When the air conditioner is on and drawing let's say 15 Amperes, the air conditioner continues to operate even when the AC power drops to 90VAC. In this case, there is (15A)(120VAC-90VAC) = 450 Watts! This is more than enough power to melt the socket and it's surroundings. Note that the breaker will NOT trip because the current is well below 30A. Surge protectors trip typically at 170VAC and also do not see any issue with the incoming AC voltage. Surge protectors are fairly small electronic devices that breakdown (provide a very low resistance) when voltages exceed their breakdown rating which results in overcurrent that trips a breaker. There is NO excessive voltage here, just a lot of power being dissipated in the plug/socket connection.
The connections in these RV parks are typically very worn already and can also cause extreme heat in the RV service box when providing heavy air conditioner or oven type loads.
By the way, when you first turn on an incandescent 100 Watt light bulb, the inrush current is typically 10 times the nominal current for just a few 10s of milliseconds until the filament warms up! Air conditioners are kind of the same idea, initially they draw much more (stall) current until the motor speed up from it's stopped condition. Circuit breakers and fuses are built to pass these higher current for a short amount of time but contacts can degrade under these conditions.
I would suggest to all RV'ers that they feel their plug connections after 10-20 minutes of running the high current loads including air conditioners, ovens, washing machines and electric dryers to make sure they can feel the warmth of the plug under normal conditions so they would know what normal feels like.