Sharing Power Pedestal

[JandC]

In a northern CG for a month. After leaving here and completing a run out west we will return and stay in this same site for another 3 weeks or so.

Here is my question. The site next to us has no services. This year they rented it to a local couple for the entire summer as an electrical only site. They have a tiny pop-up there with a small air conditioner sticking out. My site's pedistal has a 50amp (which I am using), a 30amp, and a regular plug in. If I am drawing 50amp with 2 airs and everything else, then they plug into the 30amp and start drawing, will I start tripping breakers? Is there really only 50amp to modern pedestals or more like 100 or 125?

[BB_TX]

There is no way of knowing exactly how they have wired the pedestal without testing it to find out. If they have wired the 30 amp breaker off of the load side of the 50 amp breaker, then you are correct, it could start tripping the 50 amp breaker if both of you are drawing a high load. If they wired the 30 amp breaker independent of the 50 amp breaker, then there should be no problem. You could ask. Or wait and see. When you get there, you could turn on the 30 amp breaker with the 50 amp breaker turned off. If the 30 amp breaker has power, then it is independent of the 50. If the 30 amp does not have power unless you turn on the 50, the the 30 is a sub to the 50.

A 50 amp service is actually two hot legs of 50 amps on each leg, giving the capability of 100 amps total. It is exactly like house wiring in that it is a 220 vac split phase system with two 120 vac hot legs and a common neutral. However, unlike a house, your trailer only uses 120 vac even though 220 vac is there and available.

If they have wired the 30 amp breaker off of the 50 amp breaker, that would mean the other guy could be drawing a significant amount of power from one of your 50 amp hot legs and could lead to tripping. Even though there is theoretically 100 amps available, that is 50 amps each from the two hot legs running thru a 50 amp two pole circuit breaker. And you could have zero amps thru one pole and 60 amps thru the other pole, and it would cause the breaker to trip, even though the total was far less than 100 amps.

[JandC]

Thanks Bill, that is exactly the explanation I was looking for. I will test it as you suggested to see if 50amp is wired separately. They claim there has been campers in that spot before sharing the pedestal but this office manager is not an RVer so I'm not ready to trust her word.

Thanks again.

[Bad Moon]

Was the park in question permitted, constructed and inspected per the National Electric Code (NEC)? 2014 NEC Article 551.73 states that when an electrical service for an RV has more than one receptacle, the load need only be calculated for the highest rated receptacle, which would be the 50 amp. The calculated load for a 50 amp receptacle shall be not less than 9600 volt-amperes, although a higher design load may have been used. There are load reduction factors used for multiple sites.

You can find a link to the 2014 NEC at the Oregon BCD website.