RV Electrical System Overview
For a person new to RV's, the RV is a perplexing beast. I haven't found lots of beginner materials, so I thought I would write up a little information that can help newbies.
Types of Electrical Systems in an RV – AC and DC
There are two types of electricity in the world, DC and AC. AC is what you get from the wall socket in your house. DC is the type of electricity that is used in cars and is very compatible with battery systems.
An RV has both types of electrical systems. The AC power enters the RV and then is routed to many appliances that operate on AC. It also routes to a device called a converter which converts AC power to DC. The DC from the converter goes to several DC appliances and to the battery. When the AC power goes away (because you are camping without a connection to AC power for example) then DC power from the battery is sent to the DC appliances.
Some devices are ‘dual powered' in odd ways so that you can use them without a connection to AC power and still have many modern conveniences.
Refrigerator : The refrigerator is dual powered but not like you think. It can work off of AC power when you are connected to AC (using AC as heat source), but it can also keep food cold when it is not connected to AC power by using LP gas (surprise). So you can have cold food when you are dry camping (no hookups)!
The following items ARE NOT operable UNLESS you are connected to AC power : Roof Air Conditioner, Microwave Oven, AC converter, AC power outlets, some lights, and the TV.
Your RV Electrical System – A brief overview of Amps versus Volts
This will seem very basic for many RV folks. I've noticed that many, many RV'ers seem to be very technical people. But I think there are a few very simple articles I need to write to help new folks along and I get to double check my facts and learn along the way.
I thought about this article series because a friend of a friend of mine sells a thing called powermaster. Powermaster is a device that (for now I'll just be brief so go with it) basically ‘fixes' wimpy electrical systems.
There were a few questions that came from powermaster in my mind…
- Are wimpy electrical systems commonplace in RV parks?
- Will it really hurt your appliances if you have a wimpy electrical system?
- How much fixing can something do?
- What are the implications of fixing?
As I thought about those questions, I really needed to step through the math.
Today, lets tackle Volts and Amps.
If you MUST know, both terms come from some old guys names who were tinkering with electricity over a 100 years ago. I'm not (honest – this is all from memory) going to look them up, but the names were Voltaire and Ampere. They were two different people.
In America, most outlets are called 110V. The V is for Volt. So in your house, you constantly think Volts.
I've noticed that in RV Parks, everything is Amps. 30 Amp and 50 Amp .But honestly, you need both. Volts and Amps are ying and yang. Antimatter and matter.
I can explain this without being technical.
When you refer to electricity, believe it or not, it has many properties, but for our purposes, you can describe electricity we need with Volts and Amps. Volts and Amps can refer to BOTH AC and DC, but I don't want you to get hung up on AC or DC. That is for later on this page.
Just know that electricity has volts and amps to describe it.
Now, think of electricity as a river. You know that flowing water has power. It can turn a crank, create electricity, destroy cities, and so forth. So really, the POWER is the key word. Water has power. Electricity has power too.
In many ways its the same kind of power.
How powerful can water be? Well there are two questions? How much water are we dealing with (volume of flow and total volume)?
If I have a big LAKE and I compare it to a tiny POND they have a different capability or potential to be powerful. This potential to be powerful is the same as voltage!!
Now, if I poke a hole in the side of the big LAKE versus the tiny POND, then the amount of water that comes through the hole is how much power is being delivered now!
If the hole is tiny, then the power is small, if the hole is a crater, then the power is big.
If you poke a BIG hole in the BIG lake you could destroy a village and the flow might flow for days and weeks. If you poke a BIG hole in a LITTLE lake you might simply just get wet.
This is an example of POWER. It is the combination of things.So Voltage and Amps together define POWER. Actually, the TRUE mathematics is (Power = V * I). V = Volts and I = Amps. And POWER is what gets things done.
Power is what cools your food, cools your RV, heats your food, heats your RV, runs your computer, and so on. True in life (power gets things done) and true with electricity.POWER in your RV is measured in WATTS. 1 volt (times) 1 amp = 1 watt.
Now if I tell you that your Air Conditioning takes 10 Amps and you know that the Air Conditioner factory ASSUMED that you will have a 120 Volt system, then you have a 1200Watt air conditioner.Don't worry too much about exact numbers, if you feel good about the water analogy, and have kind of an understanding of volts and amps now, then we'll do great.
So thats it – a layman's understanding of Volts and Amps.
Understanding your RV Electrical System – What is Power versus Watts in my RV?
The measurement of power is called a Watt. Again this is named after a fellow named, well, Watt.
Power is what gets things done… even in electrical systems.
Power is the most important thing to think about in almost every sense of electricity for a number of reasons. You can power up and get a ‘power budget'. You can just about figure out what things will make you ‘hot' because they waste power in the form of heat instead of utilizing power in the form of ‘getting something done'.
You can roughly figure that the RV power budget for a 30 Amp circuit will be 3600 Watts. The reason the circuits are stated in 30 Amps is because the circuit breaker protection is set for looking for how many Amps go through the system.
Amps through systems is what would cause damage, but you can never lose sight of the idea that the total power needed by the system is what causes the demand for the amps and because the voltage is ‘known' typically people don't worry about stating the voltage. People will go back and forth a little bit, but for subtle reasons you'll use one term or the other.
For a 50 Amp RV, the power budget is 6000 Watts, although I think the 50 Amp units may actually be 50 Amps on TWO sources of power which means you might get to 12,000 Watts. I think how they named this is a bit confusing.
Lots of RV gadgets consume POWER. Your microwave, refrigerator, TV and so on and so forth. When the engineers designed them they made assumptions about available power (delivered as Amps and Volts) and the system usually tries to maintain a constant power internally. As the circuitry tries to maintain a constant power, if either the available Amps or Volts changes, then there will be a corresponding change in Volts or Amps.
So, if voltage is lowered to your system, the system will generally compensate by consuming more Amps or current. That keeps the power constant and everything working.
Except for one small problem. If you remember, Amps is like a very large current of water. It can be destructive. Most waterways are designed to hold so much water/current. If you have lots more water going through them, they overflow their banks and cause trouble.
Many circuits are designed to only carry or handled so many amps. If you ‘up' the amps by just 10% you could reduce their life by 90% of the maximum.
You will increase the heat everywhere in systems and heat is a problem too that wears things out. You might also have many more circuit breaker trips which are good that your system is being protected, but unnecessary breaker trips can wear things out too.
So if you learned one or two things from this section it should be that most things want to consume power and that if voltage is dropped, power demand is constant, so the amps go up and that is a bad thing overall. That is how you burn out motors in things like washing machines.
Oh yea, amps going through wires, exceeding the AMPs ratings can cause fires. That is good to know too. Don't do that.
A Video Explanation of your RVs Electric System – An overview – with converted text
Give me a moment. I'm going to draw as much of the RV as I actually can. Hang tight, and then you're going to see this go fast. Ta-da, done. I'm going to draw the wires to each thing; red is going to be AC. First I'll draw a box around, representing the RV. That's the AC system, so it comes in. You always have breakers for safety. Without breakers, this converter could malfunction or any one of these could malfunction; take so much power that the power makes your wiring hot and burns your RV up, maybe with you inside. Breakers are very important. Anytime you see the word ‘breaker',
it's a switch that flicks off. It's like a fuse, but you can turn the breaker back on. You go in the breaker, goes converter, go over here, go to a breaker box; this could be the same breaker box. I didn't want to redraw this. Then each one of these things is on a circuit, or has its own breaker, and it goes over to them.
Let's draw the DC system. There's the DC system. This is how it works: You go into the converter, converts red AC into blue DC which is used by your system, a battery. When you're on sure power, the battery is charged via the converter. In fact, I want to get rid of the generator just for this picture. I think that's less confusing. The battery gets charged, and one you're on sure power is just being charged, you don't really use the battery. Then the power from the converter goes over to these fuses. The fuses work like breakers, except when a fuse burns out, you just have to replace it. They're usually little, short, colored fuses you push in and out. Then this goes out to each one of . . . that is the DC system in an RV. This is a nice overview on how the AC and DC systems work.
Let's see what happens when we boondock, when we don't have AC power. This is your system when you're boondocking. We can add in generators and we can do other things, but let's just deal with when you're boondocking. Now we got power coming off the battery because this is the only thing that's stored power. You can have more batteries if you wanted, and a lot of people do that. The amount of time you could be boondocking is controlled by how many batteries you have. Remember I told you that Volts x Amps = Watts, which is power? When you buy a battery, you can buy on their sizes based on watt hours; how many watts it can produce over time. Actually, its amp hours is what they call it. This battery is producing all the power for this, and I think something is funny here. The first thing I'm going to actually get rid of is the thermostat, because really without the heating system and the cooling system, you don't really need a thermostat. You got the windows. I'm pretty sure our heater won't run without AC power. You can ignite it, but you can't run the fans and the blowers, not very good. Even if you did run it off DC, it wouldn't run but for just a minute. Let's talk about what you can do.
Your refrigerator uses LP gas. What do you use this for? Ignite; that will ignite your fridge, it'll run the controls, it'll check temperature and all that, so you can have refrigeration when you're boondocking. You can have hot water when you're boondocking; that's cool. All the DC power needs to do is, again, ignite. The flames and the hot water heater, that's to heat your water, you can have hot water. Lights will be your biggest consumer of power, that's why I recommend switching to LED lights. That's why in RV52, I spend a lot of time giving you an RV LED light selector guide. You can find that in my menu at the top; Tools. Home>Tools, and you'll see RV LED Light Selectors. LED are 5 times more efficient, so instead of 5 hours of lighting, you might have 25 hours of lighting. Very important to do. The range; my open range doesn't even require electric DC to ignite because I just light it myself with a clicker, it's got a sparker.
Then finally, this is really cool; you don't need this if you're tapped onto a water source, but if you're not and you filled your freshwater tanks, you can turn on a water pump and have pressure. You can have cool food, cook and eat, see at night, have hot water, take showers, and wash hands; do all these things. You could literally run off a DC battery, especially if you're judicious with your lights, all weekend. You can get your RV in the middle of nowhere. How cool is that? Anyway, that's an overview of the DC system.
A Video Explanation (with converted text) on AC versus DC power in an RV
Hello, friends of Fitty. Marlan here. I thought I would spend a little time today just going over RV power. There's a lot of things about RV power; you got the lights, you got LEDs, you have inverters, converters, generators, AC, DC. It can be so darn confusing that I thought I'd just spend a little time doing a little chalk talk.
We're going to start at the top and just give you some basics. You don't have to be an electrical engineer, you don't have to be a scientist. The way I'm going to do it is super-simple and it will be just enough for you to be able to figure a lot of things out on your own. I think the first thing I'd like to talk about is, what is power? Power is this thing you run your RV on. You got solar power, you got power off the side of the things, you consume power. Let's just go over it a little bit. I'm going to draw. We're going to do chalk talk and see if this can help.
When you plug into the wall, you're plugging into a thing; it looks like this. It's shaped like this and it's got this, this, this, and this. You usually call it a 110 power outlet. I want to tell you a little bit about it. It's AC power, means alternating current, and that's very, very different than what's in a battery. What we mean by AC power is this:
There's this thing called 0 Volts. There is no volts right here, so there's 0 volts. You know what I'm talking about? I'm being facetious; there's no volts on this, it's 0. Then through power generation and all that, you can actually make a voltage level.
The type of power that's inside of the AC power plug looks like this: It goes above 0, it goes below 0, it goes above 0, it goes below zero, and on, and on and on. Between here and here, these waves which occur in time, believe it or not, is 1/60 of a second. The 60 is, we call that the cycles; it's hertz. When you say, “So-and-so has a 60-hertz . . .” they're just meaning how fast their alternating current alternates. This isn't hugely important. It's just fun knowledge, so don't get too hung up on it. Remember that what's in your goes up and down, up and down, up and down, up and down, and up and down. It's AC; it's alternating. It's how the entire United States works, really, Europe and probably every other country for all I know. That's alternating current.
The next type of current we're going to talk about is called DC, which is direct current. More than anything, I'm going to draw a 9-volt battery. Remember the 9-volt battery? It goes in your transistor radio. It's only about yea big, I drew it bigger. One of these terminals is named Plus, and one of them's named Minus, and you hook 2 wires up to it. Remember the other one is AC; there's no such thing as a +/- because when it's above 0, 1's plus, when it's below 0, then that one technically is minus. Batteries are a little different; they have power like this, where there's a 0 on the voltage, and then they have a level of voltage which is 9. This a level of how to a degree of much power . . . that's the wrong thing. It's how much voltage, it's how much potential there is to do something. If you get volts too high, it can destroy things, if you get volts too low, it can destroy things. The point behind this is to explain the difference between AC and DC.
Because your RV runs on battery when you're boondocking, a lot of times, you'll be on DC power because you're not plugged into the power system, entire United States power system, which is AC power; you're on a different power system which is optimal for an RV, a boat, or something very small. That's DC, and it works well with batteries. You see what the United States and the world on is AC. What's inside your RV, what it likes to run on, is DC. They're different. Part of what you get into in power around RVs has to do with that difference.
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30 and 50 Amp Power – Brief Primer on Electrical Connections
I had a good friend ask me, the local “RV Guy”… “What receptacle should I get so that I can have friends RV's be able to connect to my cabin's electric and visit me on a weekend?” He wanted to know what are the correct RV electrical connections?
There are four possible types of electric services (shore power) at the RV Park and 4 possible RV electrical connections:
- 15 AMP – has receptacles (what you plug INTO) just like your home. I won't even show a picture for that receptacle.
- 20 AMP – has a different receptacle VERY similar to your home connector
- 30 AMP – Very common – great for most RV's – but probably won't power your second A/C
- 50 AMP – Very common – will power most RV's
In the 20 Amp AC receptacle pictured above, it looks pretty much like a regular US 110Volt outlet. But there is a difference – one of the prongs looks like the letter “T” laying on its side. Plugging you RV into a 20 AMP Receptacle will be enough power to supply your AC appliances, and certainly enough power to get to your converter so that it can put plenty of power into your DC system for your DC appliances and lighting. I don't think you could reasonably expect to run your air conditioner and running your heat (because of the blowers) might be marginal if you have everything else turned on.
Pictured above is a 30 AMP connector. 30 Amps is adequate for MOST RV's, particularly fifth wheels and travel trailers. I'd say the biggest differentiator is that if you have a 2 (or more) air conditioner rig, then 30 Amp won't cut it for you.
So if you DO have a 50 AMP RV and you HAVE to plug into the 30 AMP system, you'll need to have a 50-30 Amp Adapter and you'll have to keep your 2nd air conditioner turned off.
I've heard that the experienced RV'ers typically check voltage with a voltmeter before plugging into a 50 Amp connector – just in case the connector is miswired.
I'd say that advice is even MORE wise on mom-n-pop RV parks or RV parks where either the park is new OR the pad site you will be using looks new. But if the park has been around awhile, I would think that it would be correct OR leaving a trail of destroyed stuff ahead of you.
I do think a GOOD practice is to turn OFF the breaker on the park pedestal BEFORE connecting your 50 AMP. Here is why… there is a way, accidentally, by the angle you plug in the plug, that you might put 230 Volts onto your 115 Volt appliances, if even for a brief moment. When that happens, your 115 Volt items might get blown up. So this seems like a solid piece of advice to follow.
RV Video Explanation on those darned Watts, Amps, Volts
I'm going to put them over here. We got volts, we got amps, we got watts; these are the 3 big terms you need to know.
These are the terms that would really come in useful for understanding RV power.
When you run a microwave, it consumes power. The measure of power is watts. Volts, amps, and watts. It turns out that Watt = Volt x Amps. You don't need to know too much about this except that you can add watts up. If your microwave consumes 1500 watts, you have 5 light bulbs that consume 12 watts . . . and let's see you have 5 of them, so it'd 5 x 12 = 60 Watts. Then let's say you have a TV that consumes 500 watts; you can add these up and you end up with, we'll say . . . let's just, I don't even want to deal with that. You end up with 2060 watts.
What this gets important in is this helps you figure out how big of equipment you might need. If I had 2000 watts and I knew that's how much I to consumed, that tells me how big of a generator to get. Anyway, we're getting a little ahead of ourselves. Volts x Amps = Watts.
Your equipment consumes watts. If I make volts smaller, I'm going to use more amps. If I make volts bigger I'm going to consume less amps. Now you should know what volts and amps are. I could go into volts, watts, and amps a little bit more. I think I will go into Volts x Amps = Watts. Watts is power; watts is what you consume.
Let's talk a little bit about volts. Volts is called its potential. It's not true power but it's the potential you could have in a system. Amps is the actual flow of electrons. Think of it like this: I have a 2-prong system and I have 1-prong is my + volts and the other prong, we'll say is 0 volts. The question is . . . let's say there is 120 volts behind this system.
What this is akin to is a glass of water, maybe a martini glass. This voltage is akin to how high in the air this glass of water is. If I have my glass of water really high in the air and I pour it out, the water will really come down and make a splash. If I had it really low on the ground and I pour it out, it's not going to do much of anything. It gives you an idea of the power that could be behind that volts, that level.
Amps is actually how big the glass is. If my water is actually the Niagara Falls, lots of amps, and then when that water . . . it's really high in the air, and when that comes down, the power at the bottom of the falls is really huge. If it's just a little glass of water, even though it had a lot of potential because it's high in the sky and I just pour it out; it doesn't do much on the ground. That's a way of thinking between volts and amps.