30Amp, 50Amp ??? - Page 3 - Fiberglass RV


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Old 06-02-2019, 11:26 PM   #41
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Originally Posted by Lloyd (aka Santa) Coltman View Post
The danger has nothing to do with what the appliances/tools would NORMALLY draw. It has to do with a concealed potential fault, whereby a circuit can supply far in excess of the rated capacity of a concealed connection.
Should a fault occur in an appliance/tool that is openly plugged into a higher capacity circuit, it is easy to unplug and disconnect it.
But when the fault occurs at a 'Hardwired, concealed connection' ie: inside the RV power panel, up to the input to the RV main breaker, it is conceivable that the fault could occur at night, when occupants are sleeping and could be overcome by toxic smoke, thus unable to perform a disconnect.
That is the reason concealed wiring is protected by appropriate sized breakers/fuses. (30 to 50 Amps is NOT appropriate for 12 Ga - 14 Ga.)
Hopefully, the adapter would become the limiting factor, and disconnect the power, because the 'Supply breaker' won't.
Technically, you're right in that a fault in the adapter or cord prior to the in-camper 15A breaker won't be fully protected, but chances of a problem there are pretty slim. Not only would it have to fail in just the right place (between the entry to the camper and the breaker) but it would have to fail only partially. A dead short would still trip the 30A breaker immediately. It's only a problem if it shorts by juuuust the right amount within that specific small section. Even then, I'd expect the adapter to be the first failure point and that it would melt and either short or disconnect.
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Old 06-03-2019, 06:58 AM   #42
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Originally Posted by steve dunham View Post
CPW , I understand your frustration with trying to explain something when people refuse to listen to the explanation .
They don’t understand overcurrent protection , fault currents , trip curves , short circuit ratings etc , etc and this forum does not have enough space to explain it all
It’s up to you if you wish to keep beating your head against the wall , I am done

The only thing to do is to replace your 30 amp service cord with a 50 amp cord
and then you can plug it into anything ???
Thanks, Steve. Knowing your background I trust and appreciate your response as well as John V’s. My FIL was also a licensed electrician and much of my electrical knowledge came from assisting him at times and asking a lot of questions. Though I am out-of-date on the current NEC as it changes occasionally, the way circuits work and electrons flow doesn’t. Unfortunately, there are some people who may have a degree of electrical knowledge whose intentions are good, but create an atmosphere of fear when there is little to fear if one uses a little common sense.
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Old 06-12-2019, 04:58 PM   #43
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can I clarify something on the 50A? as I understand it, its 2 phases of 120V, or 240V combined... is each phase 50A? so its actually 240V at 50A, or about 12KW total power, whereas our 30A is 1 phase of 30A or 3.6KW (give or take).
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Old 06-12-2019, 05:08 PM   #44
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Originally Posted by John in Santa Cruz View Post
can I clarify something on the 50A? as I understand it, its 2 phases of 120V, or 240V combined... is each phase 50A? so its actually 240V at 50A, or about 12KW total power, whereas our 30A is 1 phase of 30A or 3.6KW (give or take).
Correct, although calling it 2 phases is misleading. The correct description is a single phase, 120/240, 100 amp service. It is the output of a transformer with a center tap (the neutral) which results in 240 across the legs & 120V between either leg & the neutral.

A better description is two legs, each leg supplying 50 amps. A connection between them provides 50 amps at 240V, between each leg & the neutral provides 50 amps at 120V. As you noted, either case = 12KW, and the 120V 30 amp service provides 3.6KW.
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Old 06-12-2019, 05:29 PM   #45
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Originally Posted by Jon Vermilye View Post

A better description is two legs, each leg supplying 50 amps. A connection between them provides 50 amps at 240V, between each leg & the neutral provides 50 amps at 120V. As you noted, either case = 12KW, and the 120V 30 amp service provides 3.6KW.
Jon,

Wouldn't 50 amps at 120 volt equal 6KW, not 12 KW, as stated? 12K would be the total of two separate 120 volt lines, each at 50 amps. In other words, 12 KW to the trailer total, arranged with 50 amps on each separate leg. Maybe that is what you meant.

Do any RVs actually use 240 volts for anything? Or do they all just use two separate 120 volt, 50 amp legs? Do they have 240 volt panels that are then divided up as in a house system, with each leg to separate sets of breakers?
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Old 06-13-2019, 07:59 AM   #46
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Jon,

Wouldn't 50 amps at 120 volt equal 6KW, not 12 KW, as stated? 12K would be the total of two separate 120 volt lines, each at 50 amps. In other words, 12 KW to the trailer total, arranged with 50 amps on each separate leg. Maybe that is what you meant.

Do any RVs actually use 240 volts for anything? Or do they all just use two separate 120 volt, 50 amp legs? Do they have 240 volt panels that are then divided up as in a house system, with each leg to separate sets of breakers?
Yes, each leg provides 50 amps @ 120V for at total of 12KW (50 amps X 2 legs X120 volts).

While most of the 50 amp RVs only use 120V since plugging into a 30 amp site (with an adapter) would make any 240V appliances useless, there are sone high end Class A's that have dual inverters that are wired to produce 240V. These are often all electric RVs.
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