double 30 amp connection

scjetb · 10-12-2014, 06:03 AM

Can someone explain why I cannot have true sixty amp service while using my box. I went to a campground that had only 30 amp service at the pole. There were two 30 amp connections in the power box. I plugged my box into both 30 amp connection and tripped a breaker (at the power pole) after several minutes of running both ac's.

GaryWT · 10-12-2014, 06:12 AM

Strange that the box would have 2 30 amps. There are times that with one AC and the trailer plugged into a 30 amp that it blows at the post. In that case I move the water heater to gas to get by. Of course if your trailer is 50 amp, two 30 amp will not get you as much power as one 50 amp. The 50 amp is wired differently than a 30 amp or 2.

**JRTJH** · 10-12-2014, 06:13 AM

Possibly because both of the 30 amp outlets are wired to the same leg of the "50 Amp service" ??

Often times a campground without 50 amp service on the pedestal will wire power pedestals using one leg for the even pedestals and the other leg for odd pedestals. That "in theory" would even the power demand on both legs. Then someone in the campground office starts parking campers in "every other slot" which defeats the wiring strategy...

If the pedestal is wired with one leg and they wire two 30 amp plugs, then in actuality, you only have what is available coming into the pedestal. If there's a 30 amp breaker (or even two 30 amp breakers) probably one or both of them will open with any use greater than 30 amps on either plug.

If both legs of the supply are available, one for each of the two 30 amp plugs, then in theory you would have 60 amps available, but this is not true if both of the plugs are wired to the same leg inside the pedestal.

There are a number of campgrounds that "double up" their utilities, one power pedestal, one water upright and one sewer connection with double outlets. In campgrounds that do this, it is common to find two 30 amp outlets on one power pedestal.

christopherglenn · 10-12-2014, 10:28 AM

Assuming you were getting both 30 amp services, I would guess that both of your ac's are on the same leg, as well as enough load (in your rv) to exceed 30 amps on that leg. On a 50 amp service there would be another 20 amps of headroom on that leg.

scjetb · 10-12-2014, 01:46 PM

So I guess the only time I will be able to use my box to run both my ac's at a 30 amp park is if I check to make sure both 30 amp plug- ins are wired separately. Other than that it is pretty much useless..lol

Bob Landry · 10-12-2014, 04:11 PM

Interesting. I've never seen a pedestal with two 30A plugs. The only way you could get 60A with one trailer out of that is if the two legs were 180 degrees out of phase. If they are not, then that would explain a problem with tripping a breaker If two different trailers plugged into the pedestal, each could have 30A service because with the two trailers having separate neutrals, phase would be irrelevant between the two trailers.

I get 60A out of a single pedestal, but I have installed a second 30A service in my trailer and I use a breakout box pugged into the 50A outlet. Actually, I have 80A of service because I also have a separate 20A inlet that I installed to run electric heaters.

wayfun · 10-12-2014, 04:37 PM

I would suspect both AC units are on the same leg in your breaker panel. Mine were. I rewired mine to separate them. They had both AC's on one side and the electric fireplace on the other side. I doubt I would ever run the AC and fireplace at the same time so I switched one of the AC units with it.

bobbecky · 10-12-2014, 08:30 PM

You needed to check voltage across the two hotlegs, one on each of the 30 amp sockets. If the voltage was 0 volts, then the same hotleg went to both of the sockets. If you got 240 volts, then the two hotlegs were separate legs on that service. If you had all the correct parts and were trying to power a 50 amp trailer, then you could have built a wye cable to connect to each of the 30 amp sockets to then connect to a 50 amp outlet which a 50 amp plug could be plugged into, giving you 30 amps on each of the hotlegs of the 50 amp trailer panel, not as good as having 50 amps to each leg, but much better than 30 amps spread to both of the legs on a 50 amp panel. The neutrals are all the same, always have ground potential, so that would not be a problem.

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