Use Your Multi-Meter to Check that RV 50 Amp Receptacle
Not all RV hook-ups are created equal. Make it a habit to check your electric connections BEFORE you plug in your RV power cord. You will save yourself a pile of money and you will be confident your RV site is providing you good electric current. I’ve actually found faulty 50 amp receptacles. The problem could be corrosion, a loose wire or faulty installation. This guy drove off with his power cord still connected to the pedestal and damaged the the receptacle. So, you never know what you’re going to find even at the finest RV parks. In the video at the end of this article I demonstrate how to use your multi-meter to check a typical 50 amp service. Multi-meters are inexpensive and should be in every RVer's toolbox. This is what the inside of a 50 amp receptacle looks like. The “train tunnel” shaped hole is the ground wire (if the cover were on it would be located at the bottom of pattern - it’s the bare copper wire). The white wire is the “common” and feeds under the plastic to the top blade holder in this picture. The black wire on the right and the red wire on the left both carry 120 volts. When you push your 50 amp plug into the receptacle the left blade (red wire) gets 120 volts and the other blade (black wire) also gets 120 volts for a total of 240 volts. To thoroughly check your 50 amp service do the following. 1. Set up your multi-meter (black wire in the “COM” hole on the multi-meter and the red wire in the “AC/DC” hole). Place the wafer switch to 200 on the AC side. 2. Place the pointy end of the red multi-meter cable into the “train tunnel” shaped hole and the pointy end of the black multi-meter cable into the opposite hole. You should read zero which means your ground and common are working properly. 2. Leave the black wire where it is at and move the red wire to one of the side blade holes. The meter should read 120. Move the red wire to the opposite side and the meter should read 120. 3. Leave the red wire where it is and move the black wire to the “train tunnel” shaped hole and read 120. Next move the red wire back to the opposite side and read 120. 4. Leave the red wire where it is and move the wafer switch on the multi-meter to AC 600 and move the black lead to the opposite side from the red wire and read 240. You may get slightly different readings but as long as they are within three or four points from the 120 and 240 readings it shouldn't be a problem. If your readings are weak on one or both sides, your electric system will not appreciate it. You should bring it to the attention of management and move to a different space. However, I would check the alternate space before I moved my RV because it could be a park-wide problem. Caution, electric shock hazards may be present so be very careful when working with electric test equipment. Read and follow the directions and precautions of the multi-meter manual. Keeping you plugged into the grid - Jim Twamley, Professor of RVing
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