Surge Protector Question

[TheSpareTire]

A 50A service is supplied to the trailer as two 120VAC 50A feeds. But . . . these must be opposite phases from a 240VAC feed. If both sides were fed from two 50A breakers on the same 120VAC feed, the single neutral wire would be overloaded.
Rob

I totally should have made that clear, good catch. If they were not out of phase and you did draw all 100amps you would have 100amps traveling back down your netural.

[klenger]

I totally should have made that clear, good catch. If they were not out of phase and you did draw all 100amps you would have 100amps traveling back down your netural.

Totally agree. That's why Onan can make a 5500 watt generator with two outputs that are the same phase, and supply a 50 amp RV. Each output of the generator is limited to 25 amps by the CB on the generator. Combined the total current on the neutral is 50 amps or less. Generators in the 8000 watt capacity and up would be required to have 180° split phases to keep the neutral load below 50 amps, although I have never researched such generators because any RV that it would go in is well out of my price range.

These discussions are always entertaining.

[warsw1]

You can plug into any amperage outlet you like, as long as you use your RV's power cord and the proper adapter.

Electricity does not PUSH itself from the power source, it is PULLED from whatever uses it.


An RB2600 can only pull 30 amps, regardless of whether pedestal has 15, 20, 30, 50, 100, 1000 amp service or whatever.

30 amps is MAX.


The pedestal may have the CAPACITY to provide a bajillion amps, but that trailer can only draw 30.

I guess this is what I was referring to. Maybe I misunderstood what you were saying but the 30 breaker in the trailer only protects what is on the trailer side of the breaker. The power cord is protected by the breaker on the post. With a 30 amp cord and a 50 amp breaker it is possible to over amp the cord if there is a short before the breaker box in the trailer.

[Najataagihe]

I guess this is what I was referring to. Maybe I misunderstood what you were saying but the 30 breaker in the trailer only protects what is on the trailer side of the breaker. The power cord is protected by the breaker on the post. With a 30 amp cord and a 50 amp breaker it is possible to over amp the cord if there is a short before the breaker box in the trailer.

Not a problem.

I wasn't even addressing circuit protection for the supply cord, I was merely pointing out that ON ITS OWN, there is no way to pull more than 30 amps from the trailer.

I may have misread some earlier posts where I got the impression that the poster thought that if you had 100-amp service the trailer could somehow draw 100 amps if something shorted in the trailer.

If the cord, itself, shorts, that current might spike the trailer, but it will not send 100 amps past that 30-amp main breaker.

What usually happens is that dead short in the cord causes ALL current to be cut from the trailer and shunt through the short.

Of course, if that cord shorts, something was wrong with it and it needed replacing, anyway.

[Luv2Ski]

Actually it's more than just the shore power cord we have to consider. There can be components within the confines of the trailer that appear between the twist-loc edge connector (that mates with the shore cable) and the master 30A breaker in the trailer's load center. For example, one might have a hardwired EMS and/or a generator transfer switch. The 10ga, 30A wiring between the edge connector/EMS/transfer switch/30A master breaker is only protected by the upstream pedestal breaker when running on shore power. In the case that we've been discussing, that breaker is sized at 50A exceeding not only the shore cable rating, but that of the internal wiring and electrical components upstream of the RV's master breaker.

The transfer switch - and probably the EMS if present - have mechanical contactors that can fail and potentially fault and pull heavy current. It would be particularly dangerous if this fault current exceeded 30A but was below 50A because it would create sustained heating and may cause a fire. I had a hot tub control board fail this way (drawing < 50A). The board smoked and flamed until a ground fault developed and tripped the 50A branch GFI in the main panel. The control board looked like someone took a torch to it. Fortunately, it was in a grounded aluminum enclosure so the hot tub lives on.

While I've never seen a 50A male to 30A female RV dog bone with an integral 30A breaker or 30A fuse, I still don't think it's safe to use it without one.