Basic RV Electricity. Basic Motorcoach Electricity

Basic RV Electricity. Basic Motorcoach Electricity. RV Electricity FAQ

One of the most common questions and concerns I receive is about the RV electrical system. Most people ask if I can explain the RV electrical system in simple to understand terms. The electrical system in your RV can seem complex and confusing until you have a basic understanding of how it works. Your RV actually has three separate electrical systems. It has a 12-volt DC automotive system, a 12-volt DC coach system, and a 120 volt AC coach system. We are primarily concerned with the 12-volt DC and 120 volt AC coach systems.

The majority of campgrounds you go to will provide you with an external 120 volt electric source to plug into. Your RV has a heavy-duty power cord that is normally about 25 feet long. Depending on the type of RV you have, or purchase, it will either be a 30 Amp or 50 Amp system. When you plug into the proper campground electrical source it will supply power throughout your RV. You must have a 120 Volt AC power source if you are going to use the microwave, roof air conditioner, the refrigerator in the electric mode and the 120 Volt electrical outlets. For the most part everything else in the camper works off of 12-volt DC power. When you are plugged in at the campground a portion of the 120 volt AC current is converted to 12-volt DC current for the items in the RV that work off of 12 volts. Some of these items are the overhead lights, the furnace fan, and the fan over the range, the vent fan in the bathroom, the water pump, LP gas leak detector, stereo, and the refrigerator when it’s in the LP gas mode. If you look at the RV’s power distribution panel you will see circuit breakers like you have in your house for the 120-volt AC side, and automotive style blade fuses for the 12-volt DC side.

If you are not plugged into an external power source you can still use the 12-volt DC system if you have a 12-volt deep cycle marine battery on your unit. As long as the battery or batteries are charged you can use everything in the RV except the microwave, roof air conditioner, the refrigerator in the electric mode and the electrical outlets. If you have a motorhome, or you’re going to purchase a motorhome, it will have a battery for the automotive system and an auxiliary battery for the coach system. The coach battery is charged whenever the motorhome is running; the generator is running, or when it’s plugged into an external electrical source.

Before we go any further I would like to offer a few basic battery maintenance tips to keep your RV batteries in top operating condition.

First of all never work around batteries with an open flame. Vapors from the batteries can ignite, causing serious damage. To prevent the possibility of arcing turn off any 12 Volt power sources and disconnect the negative battery cable before working on or around the batteries. If you have a maintenance free battery you will not be able to perform some of these checks. The color of the eye on the battery will indicate the condition of a maintenance free battery. Consult your owner’s manual for more information on maintenance free batteries.

Constant charging depletes electrolyte levels in batteries. Inspect electrolyte levels and add distilled water as required. Add water until it reaches the split-level marker in each cell. Do not overfill.

Inspect all battery cable and terminal connections. Keep all connections clean and tight. Do not over tighten. When battery terminals are clean and tight on the battery post spray the terminals with a battery terminal protector to prevent corrosion.

To clean the battery itself use a diluted baking soda and water solution. After cleaning the battery flush it thoroughly with water.

Check the state of charge and keep batteries fully charged. Specific gravity readings for a charged battery should be between 1.215 & 1.250. If you remove the batteries for storage charge them to a full charge and check them periodically during storage. Re-charge as necessary. Follow proper charging instructions for the type of battery. Deep cycle batteries require a lower amp charge over a longer period of time.

There are numerous electronic devices and equipment in your RV that can drain the coach battery when you’re not using the RV. Some examples are; the TV antenna booster, the LP gas leak detector, clocks in radios, or just leaving a 12-volt light on by accident. If your RV is not equipped with a battery disconnect switch you can purchase a battery disconnect, from an RV dealer, that can be installed directly on the battery post. When you aren’t using the RV or have no requirement for the coach battery you simply raise a lever and disconnect the battery. A battery disconnect can be installed on the chassis battery too.

Lastly, if you are not comfortable performing the maintenance on your RV batteries have it done by a qualified service center.

Motorhomes also provide an additional source of 120 volt AC power with an onboard power generator. This unique feature offers you the convenience of 120-volt AC power whenever you need it, making the unit fully self-contained. The fuel supply for the generator comes directly from the motor home fuel tank. The system is designed so that when the fuel tank gets to 1/4 tank full the generator will stop running so it doesn’t use all of the fuel in the motor home. Some motor homes have an automatic switch over from an external power supply to the generator. Other motor homes require you to plug the motor home power cord into a generator receptacle on the motor home to use the generator.

I would also like to give you a few tips about RV electricity. To start with a 30 Amp system is the most common on RV’s. The plug on your RV is a large three-prong, heavy duty 30 Amp, 120-volt plug.

Most campgrounds you go to will provide you with a 30 Amp outlet that your RV power cord will plug directly into. If you go to a campground that has a regular house type outlet there are adapters that you can use to go from your RV plug to the house type outlet. When you do this you are plugging into a 15 Amp or 20 Amp power source. This means you will be limited as to what appliances you can run in your RV. It is even possible to damage some appliances if they are not getting the required amperage to operate properly. Let’s say for example you plug into a 15 Amp outlet and you are using a small appliance that is drawing 5 Amps, that leaves you with 10 Amps. Now you turn the roof air conditioner on and when the air conditioner compressor engages it needs about 13 Amps, but it’s not available, and it damages the air conditioner compressor.

Even with a 30 Amp service you need to be selective about what you are using. If you try to use too much the RV will let you know by tripping a breaker in the distribution box and hopefully no harm will be done. There is a short formula that may help you with this. 30 Amps X 120 Volts = 3600 watts. This is the total amount of power you can use before you overload the system. Think of it like this, with 3600 watts you could use 36 one hundred watt light bulbs. When you turn on the 37th light you will probably trip a breaker.

It is also a good idea to take a voltmeter along with you that you can plug right into one of the outlets. Campground electricity varies depending on the demand placed on it. If everybody is running his or her air conditioner the voltage may drop below an acceptable level, and it would be wise to wait until it is restored back to normal. You can glance at the voltmeter every time you walk by it and save yourself untimely and costly repairs to your RV appliances. Voltage below 105 volts or above 135 volts can damage electronic equipment and appliances.

Most appliances will tell you what the required wattage or amperage is to run the appliance. Here is the amperage draw for some common RV appliances and electronics.

* Coffee maker - 8.3 amps
* Converter - 8 amps
* Hair dryer - 9 to 12 amps
* Microwave - 13 amps
* Refrigerator - 2.8 amps
* Roof a/c 13.5 amps
* TV - 1.5 amps
* Toaster - 8 to 10 amps
* VCR - 2 amps
* Electric skillet- 6 to 12 amps

Question: “What is a deep cycle battery?”

Answer: RVs come equipped with deep cycle batteries for the coach. Most RVs come with a single Group 24 deep cycle battery. Deep cycle batteries are rated in amp/hours. How many amps the battery can deliver for how many hours before the battery is discharged. Deep cycle batteries are designed to be discharged over and over again and still take a charge. If you enjoy dry camping (without hook-ups) you depend on your deep cycle battery(s) to take care of your 12-volt needs. You can purchase a deep cycle battery with a higher amp/hour capacity that will last longer. The higher the amp/hour capacity is the larger the battery is. If you have room for a larger battery and enjoy dry camping you may want to consider a Group 27 or Group 31 deep cycle battery.

Comment: “You did not cover inverters. I installed one in my motorhome because there are times when you want a little power for the TV or VCR and don’t want to crank the generator.”

Reply: You are absolutely right. Inverters are nice to have at times when you are dry camping and/or when you don’t have access to 120-volts AC. Batteries produce power in Direct Current (DC) that run at low voltages. Power companies and AC generators produce sine wave Alternating Current (AC), which is used to operate 120-volt appliances and electronic equipment. An inverter takes 12-volt DC power from your RV batteries and electronically changes it to 120-volt AC. Some RVers use an inverter just to watch TV or for their personal computer. Other RVers use an inverter to operate microwaves, coffee pots or other larger appliances. When you purchase an inverter the inverter’s output capacity must be capable of operating the loads that will be placed on it.

Inverters have two different capacity ratings. Continuous output rating and surge capacity rating. Continuous output is the maximum wattage the inverter can output for a long time period. Surge capacity is the maximum wattage the inverter can output during initial start up. All appliances require more power when they start, compared to what they use when they are running. They can use as much as two or three times the amount to start then what they use to run, so the starting power required for any appliance that you plan to use with the inverter must be within the surge capacity rating. There are modified sine wave inverters and true sine wave inverters. A true sine wave inverter is more expensive, but they are capable of producing power as good as the power company and all appliances and electronic equipment will run as they are intended to. Keep in mind you are drawing the power from your RV batteries and any power used has to be put back in through some type of effective charging system.

Comment: This is a second comment from the same reader. “You need to tell your reader’s what to do when you only have 15 amps to plug in to, (usually at someone’s home and using the plug on their front porch) and you need the air conditioner.”

Reply: I personally don’t recommend doing this, but I agree that it is possible, like you say to use the A/C if you are plugged in to a 15-amp outlet. If you do, you must exercise caution. When the A/C compressor engages it requires more amps (about 13) than it does once it is running. Because of this you need to turn all appliances off before starting the A/C, to include switching the refrigerator from A/C to LP gas. Once it is running it may be possible to use a small appliance or electronic equipment that operates on low amperage, like a TV, but you need to monitor the voltage to prevent damaging any appliances or electronic equipment.

Comment: This is the third comment from the same reader. “You should also tell your reader’s that if they are using a long extension cord it must be #12 wire or lower, (heavier gauge) to keep the amount of voltage drop from causing problems.”

Reply: You’re right again. If it is possible you should try to avoid using an extension cord when making electrical connections at the campground. The gauges of the wire used in standard household extension cords are not suitable for RV electrical hook-ups. Eventually you will be put in a situation where you will need to use an extension cord. It is a good idea to purchase an RV extension cord that is compatible to the electrical system of your RV, and have it on hand. If you do purchase an extension cord somewhere else I recommend 10-guage wire and use as short of a cord as possible.

Question: “Will it hurt to leave the RV plugged in and the refrigerator on all of the time?”

Answer: I leave my refrigerator on almost all of the time. The RV should be on level ground so the refrigerator operates properly and you will need to monitor it for when it needs to be defrosted. The only other concern with leaving the RV plugged in, not related to the refrigerator, is the coach battery. Whenever the RV is plugged in the coach battery is being charged. It's really just a trickle charge, but over time it can deplete the electrolyte levels in the battery cells. You need to check, or have somebody check the battery at least monthly when the RV is plugged in during storage.

Question: “Is there any danger of damaging your system if you plug a 30-amp system into a 50-amp service using the proper adapter?”

Answer: This is a controversial subject. Some people will argue that if they make an electrical adapter for it than it is safe. Others will argue that it is not safe to use a 50-amp service for a system designed for 30-amps or a 20-amp service for a 30-amp system. Electrical adapters are a necessity for RVers. Eventually you will be in a situation where you have to use some type of electrical adapter to make a connection at a campground. It may be an outdated campground or isolated area that only provides 15 or 20-amp electrical service, or the only site available is a 50-amp service for your 30-amp system. There are adapters that will go from your RV type plug and size down to household type outlets and adapters that go from household type outlets to all types of campground RV connections. It’s nice to have these adapters on hand when you need them, but you must exercise caution and use common sense when you use them. If you have a 30-amp system and you have to use a 50-amp service use your RV electrical system exactly the same way you do when you’re plugged into a 30-amp service. In other words don’t try to run anymore than you normally would. On the other hand if your RV is a 30-amp or 50-amp system and you use an adapter to plug the RV into a 15 or 20-amp outlet you severely limit what you can operate in the RV. In this situation you should only use what appliances or electronic equipment are absolutely necessary. If you place too much of a demand on electrical adapters, or use them for extended periods of time they can overheat and melt resulting in damage to the RV power cord or the electrical system.

Question: “Sometimes the coach battery in our motorhome won’t start the generator and other times it will. My question is why isn’t the RV battery charger keeping my battery charged when I leave it plugged in all the time?”

Answer: The battery charger in the RV converter provides a trickle charge and is only designed to keep the coach battery(s) topped off. It is not designed or capable of recharging a battery that is completely discharged or damaged. The automotive alternator also charges the coach battery when you are driving the RV. I would guess that the alternator is probably charging the battery enough to start the generator sometimes after driving for a while, but the RV battery charger can’t charge it enough to start the generator when it’s plugged in. The constant charging from leaving it plugged in all the time can deplete the electrolyte level in the battery(s) cells. Depending on how often the battery(s) is being charged will determine how often it needs to be checked. You should check the battery(s) at least monthly and if you use the RV on a regular basis and / or you leave it plugged in when you’re not using it you may need to check the battery(s) more often.

I hope these reader’s questions and comments are helpful to you and quite possibly might answer some questions that you had about basic RV electricity.

Sourced: RVEducation101.com