Plugging into an Outlet that is Not 30 Amps

We have been contacted a number of times and also have answered this question on several forums and this article will put it all out as to what and how when you need to plug your 30 amp RV - Roadtrek or any other - into an 110/120 volt electric outlet that is not 30 amps. This might be at home - the most common application of this - when needing to plug in and all that is at your house is an outdoor 15 or 20 amp outlet. Then there is also situations at campgrounds where you find yourself faced with plugging your 30 amp RV into a 50 amp outlet. When you plug in your RV into an outlet whether at home or in a campground no matter how many amps the outlet in the world of RVing you are plugging into "SHORE POWER".

Let's start with the more common - plugging into a 15 or 20 amp outlet. Before we go into details of how you do it, there are a few things to understand and one of what seems to be the most confusing concept involves the limits of a 15 or 20 amp outlet for a 30 amp RV. To start off I would like you to watch this short video clip from a classic television show that has nothing to do with RVs but everything to do with the situation we have here. Watch and laugh - and then we will continue explaining why you watched it. (The video quality is not great - it is not my video but I did not think you wanted to watch the entire episode (which is better quality) for this one scene.)

OK- I find this scene the easiest and funniest way to understand what happens when you plug a 30 amp capacity RV into an outlet that is only 15 or 20 amps. In the scene the magic number is "7". With your 30 amp RV the magic number is "15" or "20" depending on how many amps the outlet is. Home outlets may be 15 or 20 amps. (More on this will come.) In the show if Lisa plugged in a "5" and a "3" the generator would blow - in this show that generator would literally blow (for the sake of comedy) when this would happen. If you plug your 30 amp RV into a 15 amp outlet you can plug in an appliance that uses 6 amps and an appliance that uses 9 amps and (basically - again more on this coming) all will be fine, but plug in a 6 and a 10 and as Lisa would say, "Blooey!" - you will trip the circuit breaker or blow the fuse that is connected to that outlet in your house!  Why? You only have an outlet with the capacity of 15 amps (in this example) and if you start appliances inside your RV that use more than 15 amps - either singly or together - you overload the circuit and as a safety precaution the circuit breaker trips or the fuse blows out. This is better than the alternative of an overloaded circuit where it bursts into flames and burns down the house.

Another extremely important thing to know when plugging into a house outlet is if there are any other outlets inside or outside the house that are on the same circuit breaker or fuse in the house circuit breaker or fuse box. The fast way to find out is shut off the circuit breaker or take out the fuse on the outlet you are going to plug into and then check to see if any other outlets no longer work (or lights or whatever electric in the house no longer work). IF there is another outlet or circuit on that house breaker, you are SHARING the total amps of that outlet - either 15 or 20 (you will know this by looking at the circuit breaker itself - it will be marked 15 or 20 - or on the glass fuse which will also be marked with its amps). If you are sharing the amps with other outlets, if those outlets are in use you must subtract how many amps are plugged into those outlets (or on that circuit in the case of hardwired lights or appliances in the house) from what you have available in the RV. So simple example. Lets say that you have two outlets on a 20 amp circuit and one of those outlets already has 10 amps plugged into it and in use. The outlet you are about to plug your RV into only has 10 amps for you to use. Plug in 11 amps and "Blooey!".

If you have all of this well understood - and not only by you but also anyone who is going to be in the RV with you - kids especially - you will have no problems plugging your 30 amp RV into a 15 or 20 amp outlet at your (or anyone's) house.  SO - just to ask you a question to make sure you understand. You are plugged into a 15 amp outlet. Can you turn your Air Conditioner (high amp appliance) and your Microwave (high amp appliance) on at the same time? If you answered "NO!" you will be fine.  If you answered "Yes" then go back and watch the video and read this all again. I would also not try this on a 20 amp outlet.

Now, that all out of the way - here is how you do it. I plug my Roadtrek into the house twice a month every month to charge the batteries. It works with no problems. You will need a couple of things. Your 30 amp RV has a 30 amp plug on its power cord. A 30 amp plug does not fit in a 15/20 amp outlet. It is too big and the position, size, of the three prongs will not fit. You are going to need a 30 amp female to 15/20 amp male adapter. They are not hard to find and you can find one at many Walmart stores in the RV section of the auto department. They may have two types. Do not buy the one that is a single unit with a plug on one side and the 30 amp socket on the other side of one rubber cylinder. These will work but can be hard to pull apart from your power cord. Buy what is called a "dog bone" adapter. This has a whole 30 amp socket on one end of a thick wire - the same size as your RV's power cord - and on the other end of that wire a whole male 15 amp three prong plug. These are less than ten dollars. They usually have a pull handle on the 30 amp socket (not as pictured here).

 IF your RV power cord will not reach the outlet you want to plug into you also need a 30 amp RV extension cord. Never use a household extension cord - even if it is labeled heavy duty - even if it is 10 gauge wire. Compare that to your RV power cord and you will see that the wire is much thinner. You want to get every amp you can and you do not want an extension cord that could overheat - or worse cause a fire while connected to your RV. Spend the money for an RV 30 amp extension cord. They cost more but will keep your house, your RV, and you safe. The wire on the extension cord should be as thick as the power cord on your RV.

You are now all set!

1. Plug in the 30 amp socket on the adapter to the 30 amp plug of the extension cord.

2. Plug the RV power cord 30 amp plug into the 30 amp socket on the extension cord.

3. Go into the Roadtrek if your RV is a Roadtrek and TURN ON THE BATTERY SWITCH.
    (If you don't have a Roadtrek you may not have to do this - follow the procedure for plugging your RV into "shore power".)

4. Plug the 15 amp plug of the adapter into the 15/20 amp outlet on your house.

DONE.  You now have 110 volts available for use in your RV (with the restrictions we have discussed above). 


If you have a Electric Management System unit - a surge/voltage protector - you might want to plug that in within these connections to. We do - even at home. This is discussed in other articles on our site about hooking up your RV (Roadtrek).

That is all you need to plug in at home - or at someone's home. There are other situations where you might need different adapters and we will look at those now.

When I first arrive at a campground to "check in" and get my site, the first thing I do when I get to the site is test the 30 amp outlet in the power box.  I do this using a Polarity Tester (about $5 generally wherever electric components are sold including home stores and Walmart) and also a 110 volt (AC) volt meter. The meter I use is a device called a "Kill-A-Watt" that is used to test electric appliances for wattage but also will give you the number of volts in an AC outlet just by plugging it in. This also is sold at home stores. You could also buy an AC plug in volt meter on its own - but when I went shopping for one I was not finding any locally and what I saw at RV shops cost twice what the "Kill-A-Watt" costs. Both of these devices have a standard 15/20 amp house plug. To use these to test a 30 amp outlet I use a 15 amp female to 30 amp male adapter - the opposite of what is mentioned and shown above. This has a 30 amp plug and a 15 amp socket. Plug the device into the 15 amp socket and then plug the 30 amp plug into the campground 30 amp power outlet. These devices used this way will correctly read the polarity and the number of volts coming through the 30 amp outlet in the campground box. If they are not right, we go right back to the campground office and let them know that there is a problem. We first ask for another site. If one is not available we ask that they fix the problem immediately.

If the problem cannot be fixed - and there is no other site - the next thing we carry to take care of that situation is a 50 amp male to 30 amp female adapter.

As you can see in this photo, a 50 amp plug - the one on the right - is larger and very different from a 30 amp plug. The 50 amp plug has three blades and one ground. I am not going to confuse you by explaining how the 50 amp plug works, for your 30 amp RV that is not important. What is important is that when you are plugged into a 50 amp outlet using one of these adapters to plug your 30 amp RV into, you are only getting 30 amps coming into your RV. It is no different than having plugged into a 30 amp outlet. You can plug your 30 amp EMS unit (surge and voltage protector) into the line with no problem - it will work exactly as it does when you are plugged into a 30 amp outlet directly. All you are getting are 30 amps.

So plug your 30 amp RV power cord into the 30 amp socket on this adapter and then plug the 50 amp plug into the 50 amp outlet in the campground box. You are now in business - just as if you were plugged into a 30 amp outlet.

If you find yourself looking at a 30 amp outlet in a campground box that is loose or when you plug into it, it just does not seem right - and there is no other site to be moved to - use the 50 amp to 30 amp adapter shown and described above.

Now - one final word of advice -

When plugging in at a campground into a 30 amp outlet - or a 50 amp outlet - there is usually a circuit breaker in the box over the outlets for each outlet in the box. You will know which goes to which as the breaker will be labeled - 30 amp or 50 amp. BEFORE you plug anything in, switch that breaker to OFF. It is always best to do everything safely. Plug into an outlet that is OFF and you will not get shocked. Check the circuit breaker first - unfortunately, not everyone does what is safe and they often disconnect with the breaker on - which YOU should NOT DO, and you will find the circuit breaker was left on. Shut it OFF. Plug the plug in, and then click the circuit breaker to ON. Done! Safe!

We have been to two campgrounds where there was no circuit breaker in the box for the outlets. I was not thrilled plugging in that way, but there was no choice - just use extra caution.

At home you would have to go inside the house to the circuit breaker box to turn off the breaker and then go back in to turn it on. Since we plug appliances into 15 or 20 amp outlets in our homes every day with the circuit breaker on, it is really no big deal to plug the adapter and power cord of the RV into a live 15 or 20 amp outlet. The more amps the more dangerous. It is the same 110 volts but it is the amps that can kill ya! Heard that in some show or movie about a prison electric chair...

"Shocking, simply shocking."