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branchement électrique
branchement électrique

Mark My Words: Power supply choices

Editor’s note: This information is provided by the Escapees Club.

Q. When you use a 30-amp into a 50-amp outlet, how is this split throughout the coach? We are in a park that has 50-amp outlets, but they only have a 100-amp circuit feeding seven sites.

The park management said the sites are daisy-chained together. This doesn’t mean much to me other than I know I don’t have 50 amps dedicated to my site.

We are in an older park in Maine, and I don’t think things are going to change much as it would be very expensive to bring new electricity into the park. They installed new wire (not sure what size) into the sites and 50-amp outlets, and I guess they assume they had 50-amp service for each site.

As we are in Maine on the coast, we don’t use AC, but people will be using their heaters before we leave in late September.

Does the voltage drop that much from site one to site seven? In a motorhome with a lot of electronics, what causes the problems when the voltage drops? What are safe levels?

— Jay, Heidi and Maggie

A. The 30-amp RVs are super simple. It’s just a single 30-amp circuit that powers a simple single-ganged breaker panel with a few breakers in it. When you use an adapter to connect a 30-amp RV to a 50-amp receptacle, you still have just a single 120-volt, 30-amp circuit that runs everything in your RV.

Park wiring, if done to code, must meet a number of design criteria. It is normal to have a number of outlets on a single string or circuit, and there are formulas that determine how big the wire size must be for a given main breaker size and how many outlets can be served by that circuit.

The condition of all of the components, as well as the original design, all play a role in how well it works. Unless there are serious design issues, you will see the same voltage at all of the pedestals on a single circuit. There isn’t much voltage drop from the first one to the last.

In most parks, if you have a lot of RVs all running big loads, like air conditioning units, all on the same circuit, you will see lots of transients (dips and spikes) as all of those air conditioner units cycle on and off. The same thing can happen with electric heaters but to a lesser extent as they are not as current-hungry as an air conditioner.

In general, as long as the voltage as measured inside your RV is between 110 and 130 volts, you are fine. When you start to go outside that range, it can cause problems. If the voltage falls below 100 volts and stays there, it can do serious damage to your air conditioner units.

I usually won’t run mine at all if the voltage falls to 105, or I will unplug and go on generator if I must have the air conditioner. Most everything else in your RV is pretty tolerant of lower voltages.

You can use an RV surge suppressor with an under/over voltage protection circuit on your input power cord to help protect your RV, but in a park where the electrical system is marginal, it can drive you crazy by tripping repeatedly.

An alternative is to get a good plug-in 120-volt meter and keep an eye on it, especially if you are in a park that is old or heavily occupied. If you see consistent low voltage, you should shut off air conditioners and, in extreme cases, pull the plug.

Report any site electrical problems to the park office, but be prepared for the standard answer: “Well, we’ve had RVs parking on that site for years, and no one else has ever had a problem.”

The correct response is, “Well, we certainly have a problem now. Please send someone to the site, and I will show them what is happening.”

About Mark Nemeth

In 1997, Mark quit his aerospace engineering job and became a full-time RVer. For almost five years he traveled the country while maintaining his website, Mark’s Fulltime RV Adventure ( posting monthly travel logs. Mark now travels part-time and works as the RV Safety Education Director for Escapees RV Club providing technical training at Escapees Boot Camp seminars, as well as assisting in many other areas of the club. He is also technical advisor for Escapees magazine. Learn more about Escapees RV Club at

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