RV electricity: Reader asks meaning of AC power



Reader Question:
Forgive my electrical ignorance but doesn’t “AC” mean “alternating current”? Does that mean that the hot and neutral wires are constantly reversing?

Mike’s response:
The “Hot” wire is also known as the “Line”, and it is indeed energized with 120 volts AC (in the USA). The Neutral wire is “bonded” to the earth ground rod(s) at the incoming service panel (from the power company), so it should always have a voltage potential very close to earth (maybe 1 or 2 volts). The AC thing is Alternating Current, so 120 times a second the voltage between Hot and Neutral wire changes from a positive swing to a negative swing. Since a full cycle is both a positive and negative swing, that’s 60 cylces per second, also known as Hertz or Hz.

All modern electrical appliances (and your RV) should have the incoming Neutral wire isolated from the chassis. The Chassis is connected (bonded) to the incoming Ground wire in the power cord, officially known as the EGC (Equipment Grounding Conductor), and also know as the Safety Ground.

Getting the Hot and Neutral wires swapped in your extension cord is known as a swapped “Polarity”, even though that’s a poor choice of words which causes much confusion. That’s because the AC voltage itself reverses polarity 120 times a second (see above). However, because the incoming wires are known as “poles”, and electricians definition of “polarity” where the Hot (black) and Neutral (white) wires are reversed is different from an engineer’s definition of “polarity” where the Voltage on those wires reverses itself 60 times a second from the AC current itself.

rv-safety-764Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com.

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