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Wednesday, November 26, 2008

How to test the accuracy of your campsite's 50 amp electric service

Professor of RVing Jim Twamley shows you how to use a multi-meter to test the accuracy of your campground's electrical hookups, specifically its 50 amp service. All that's required is an inexpensive device available at most discount stores.


  1. I was surprised no mention of a circuit breaker was brought into this. Also, better viewing might have been used. All in all a good demonstration for safe use of Electricity

  2. As already mentioned, it's important to turn the pedestal 50 amp circuit breaker OFF before you plug in. Then turn it back ON after you are plugged in. Similarly, when leaving the site, again turn the 50 amp circuit breaker OFF before unplugging.

  3. "a good demonstration for safe use of Electricity"

    I really don't think so. Did I hear Jim mention what might happen if the red lead was accidentally plugged into the current terminal of the meter? Did I hear anything about accidentally switching to ohms instead of volts? Are the meter leads fused? What will happen to Jim's hands and face if the cheap imported meter blows up?

    Depending on the size of the campground supply transformer, how far away the 50A receptacle is away from the transformer, and how the supply is protected against short circuit currents, there could be over 1000A of short circuit current available at a receptacle. That's not a pretty sight.

    Here's my advice:
    When plugging in or out turn your face away. If there's an electrical arc flash you may burn your hands badly, but at least you may save you sight and handsome good looks. If you must measure the voltage at the receptacle (or anywhere els for that matter), go and buy some fused test leads from a reputable electrical distributor. In my experience the greater campground risk is poor grounding. I always drive a spike into the ground and connect to the RV chassis.

  4. Someone here stated they drive their own ground rod at the campsite. This may be a very dangerous thing to do. You never want to create a ground that's different from the utility company's ground. This could create a potential difference between the two, and if you get in contact between the two grounds- you'll be part of the circuit.

    Even if this doesn't happen, you may drive the rod through something else and have the same thing happen- remember, "call before you dig".

    Remember too that by creating a separate ground from the power company's is against the N.E.C.'s guidelines.

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  6. Thank you for this demo. I just purchased one of those meters on someone's recomendation, but didn't know how to use it.

  7. I usta test this way. Only half the time I would forget, only thinking of it after plugging into the post. Then I realized that my Progressive EMS (Surge Protector) performs that test for me. Now I just make sure I have turned on the EMS. And so I rest easier.

  8. I use a regular electricians test meter. The "Harbor Freight" unit I use is for automotive testing only. Its sometimes hard to check the circuit breaker as some will secure the box where one cannot open it. As long as I can read the amps and voltage with my meters, I'm pretty much happy. I would never advocate the use of a cheap meter as used, rather spend the money and obtain the proper unit.


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