How to wire a RV 30 amp outlet

[wmtire]

Here is a great little pdf file that hopefully can be made a sticky somewhere by the administrators. It is a handout to electricians, and everyone else on how to correctly wire for a 30 amp rv outlet. We have had several members as of late who have had family and professionals incorrectly wire for their trailers, with ensuing damage.

I wish all RV dealers would include this every time they sell a trailer with 30 amp service....which is 120 volts ONLY.

http://www.myrv.us/Imgs/PDF/30-amp%20Service.pdf

 

[wmtire]

The NEMA TT-30 receptacle is kind of confusing, especially to those with no prior experience to it. It is no excuse for a professional not to know of this variant, or to actually read the receptacle/plug itself...but it is easy to get into a groove and not realize it's 120 volt.

Most everyone (including electricians) are going to be in the habit of only seeing 120 volt receptacles in the NEMA 5 series. These 5 series always have a vertical straight blade, whether it's the 5-15 amp, 5-20 amp, 5-30 amp, or 5-50 amp even.

Where it gets confusing somewhat, and you could just call it force of habit, is that the NEMA 10 series which is 240 volt has angled blades (very similar to the TT-30 120 volt). If you have never seen or know that the TT-30 is 120 volt, it's an easy mistake to mis-indentify at initial glance, since just about all NEMA configurations with angled blades are 240 or more volts.

Whomever created the TT-30 really could have come up with different blade configuration, but what is done is done now.

This chart will show these NEMA 5, 10, and TT series.

For those reading along, the NEMA 14-50 120/240 volt configuration below is what 50 amp RV's use. This is not a special receptacle like a TT-30 is, and is more common to other things. The 50 amp RV utilizes it in it's electrical distribution panel, where although there are actually 2 hot lines feeding the RV, it keeps each line separate and thus 120 volts... just like a 30 amp RV is.

View attachment 157592

 

[wmtire]

One way you may can visually check to see if someone has properly wired a 120 volt 30 amp outlet is to look in the circuit breaker box of your home.

The easy way to check to see that the 120 volt 30 amp outlet is not miswired for 240 volts, is to look in your house/garage electrical distribution panel, and find the circuit breaker that goes to this new outlet. If it's a double pole breaker (twice as wide as a single pole breaker or tandem breaker), then it's 240 volts. If it's on a single pole breaker or tandem breaker, you should be good to go.

The picture below shows examples of double pole circuit breakers (240 volts), single pole circuit breakers (120 volts), and tandem circuit breakers (120 volts). There are different types of circuit breakers so yours may not look like these exactly.

You can notice how in the pic below, the double pole circuit breaker takes up slots #10 and #12 in the panel...which makes it 240 volts. You do NOT want this for a 30 amp RV.

The single pole breaker only takes up one slot. #14, which makes it 120 volts.

The tandem breaker, which allows two circuits on one breaker, also only takes up one slot, #16....which also makes it 120 volts.

 

[wmtire]

What can happen if miswired for 240 volts

We are adding this for those who may have a 30 amp outlet miswired for 240 volts and things that may be damaged and/or need replacing.

In just about all cases, the converters capacitors will blow up. This will be the pop sound and/or smoke (hopefully no fire) that you experience when you connect to the 240 volt wired outlet. The converter will just about always need replacing. See this thread for more details on exactly what the converter does as well as a temporary workaround for the failed converter:

https://www.forestriverforums.com/forums/f215/converter-or-inverter-they-are-different-152813.html

Now microwaves can sometimes be damaged from the 240 volts as well as televisions.

Electric fireplaces (control board) are another appliance that can be damaged.

The control board for the refrigerator can also be damaged from the 240 volts.

Air conditioners can also be damaged, but the ones that have a 12 volt DC thermostat, are usually spared from this.

This is why you want to always make sure that the outlet is wired properly for the application, which there is a nice link to a handy pdf file to insure this in the very first post at the beginning of this thread.

P.S. If you use a good EMS (Electrical Management System) like the one in the link below, it can save you from a miswired 30 amp outlet and will not allow power into the RV in such a scenario, thus protecting your appliances.

https://www.progressiveindustries.net/ems-pt30x