Turbo Diesel Registry
Issue link: http://read.uberflip.com/i/594528
110 www.turbodieselregister.com TDR 90 ELECTRICITY AND YOU There was some discussion in this TDRV column in issue 89 concerning the differences between 30 amp and 50 amp RV plugs. There is a bit more to the story than what was reported in that column. A 30 amp RV electrical campground service will contain a single 120 volt conductor (top left blade as you look at the campground electrical box), a neutral (top right as you look at the campground electrical box), and a ground (the bottom round hole as you look at the campground electrical box). The neutral wire completes the electrical service circuit, while the ground is tied to the RV frame to prevent any live electrical stray voltage from shocking you as you stand on the ground and grab the door handle. A 30 amp electrical plug will supply your RV with a total of 3,600 watts of power. By looking at the label on each electrical appliance you can total up to see how many appliances you can use at one time without exceeding the 30 amp/3,600 watt supply. You can readily see that with a refrigerator heat element drawing about 400 watts and a hot water heater drawing about 600 watts, and an air conditioner drawing about 1500 watts, there is not much left over wattage potential for using other appliances or lights. Turn on a 1,000 watt hair dryer, and the main breaker will trip—either the one on the campground's power pedestal or the one in your RV. With most RVs, if you need electrical service for another essential item you can switch the water heater and refrigerator to gas and eliminate those electrical loads. A 50 amp RV service will have a four prong plug. As viewed at the campground power box, the top two blades will each be 120 volt service. The next one down will be the neutral, and the bottom one will be a ground for the RV. The wires feeding this box will be larger, so they can carry more amperage. Therefore the total amperage supplied by the two 120 volt legs will supply a total of 12,000 watts of electricity or 50 amps/6,000 watts on EACH leg. The wiring circuits in the RV will be divided into two main circuits, each wired to one of the 120 volt legs coming in to the RV. The neutral wire will be common to both legs. The ground will be tied into the RV frame and body to prevent electrical shocks to you as you grab the door handle or touch any metal while standing on the ground. If an RV has 50 amp service and has two air conditioners, each air conditioner will be supplied from a separate 120 volt leg rather than both air conditioners being wired to only one of the two available 120 volt legs. Thus you can see that a 50 amp service will supply almost four times the total wattage that is available from a 30 amp service. With a 50 amp service, you can run almost every electrical appliance without much concern for running out of available amps or watts. What's next? A few high end motorhomes are now being made with 100 amp service, though very few campgrounds are equipped with 100 amp power pedestals. In this case, there is no real standard hookup. Some will feature two 100 amp legs, while others will feature four 50 amp legs. A few campground plug-ins now have GFI (Ground Fault Interrupter) breakers, and they will become more popular as local electrical codes and regulations advance. Go figure! A WORD ABOUT ELECTRICAL PLUGS It pays to take a look at a campground electrical plug before plugging in your RV. Many are old and weathered with burned 120 volt prongs, showing that corrosion over time has degraded the plug's ability to supply the full 30 or 50 amp load. After making sure the plug's breaker is turned off, you can clean corrosion off of the female prong using a small round brass wire brush that is sold by RV and hardware dealers for this purpose. The brush looks somewhat like the brush you would run down the bore of a small caliber gun to remove lead residue. You can also clean the spades of your RV plug shiny bright to improve electrical contact by using a brush and sandpaper. This will also cut heat at the plug that is generated by a poor electrical contact that often burns out RV cable plugs—which you must then replace at your expense. Application of a small amount of dielectric grease on cleaned electrical contacts will aid in keeping the electricity flowing without undue heat buildup. Many campground electrical supplies use aluminum wire whose connections corrode easily and therefore won't supply the electrical demands of your RV. Since this is a campground problem, the best solution is to move to another site and hope it is better. Most older campgrounds use too small a diameter wire to run the distance from the main electrical supply box to individual campsites or rows of campsites. Thus, you will find that the no-load voltage available at the pedestal will show good on a voltmeter, but quickly drops when any electrical draw is applied. Low voltage under load will quickly kill motor driven appliances such as air conditioners and will cause slow heating of refrigerator and water heater elements. An air conditioner will shut down when voltage reaches 102 volts or less to protect the compressor, and cooling capacity will be cut at any voltage less than 120 volts. Your TV doesn't like low or fluctuating voltage, either. The TDRV column focuses on towing with your truck for work or play. It covers towing accessories and products, related technical discussion, and TDR member experiences. And, just as you'll find in some other TDR columns, we've incorporated some of the Q&A from the website. TDRV is edited by Jim Anderson.