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Old 09-12-2010, 06:03 PM   #15
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Old 09-12-2010, 07:10 PM   #16
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a little on the queasy side???

while reading this thread, I get a slightly queasy feeling about what I see. Now, mind you, it is probably all in my head. But, for my sake I am going to try to shed some light on this subject. 1) most a/s = 1-30amp 120VAC service 2) some a/s = 1-50amp 240VAC service 3) the converter/battery charger is ignorant of 1) and 2); it is powered from a 20amp 120VAC outlet(receptacle) within the a/s; it supplies (as Inland Andy said) 55amps (or so) of 12VDC power to the DC power distribution. --------------------------------------------------------------------------- If we look at the energy available to the a/s, then: 30A@120v=3600watts (approx) of AC power/energy; 50A@240v=12000watts(approx)!!! did ya get that? 3 times as much power! wow! in a 289sq foot (or less) trailer. --------------------------------------------------------------------- So, some say they only need 3600 watts of AC power. others say to prevent voltage sag at high a/s amp draw adapt your 30amp 3 wire (prong) RV male plug to ONE SIDE OF THE 50amp 240VAC (3 or 4 wire) power pedestal. ----------------------------------------------------------------------- Changing over from 30amp 120VAC to 50amp 240VAC requires no changes to the internal wiring of the a/s; all the circuits in the a/s are 120v and 20 or 15 amp. Such a change does require a change to the shore line, and to the service entrance distribution circuit breaker box. The box you have in the trailer is ONLY rated at 30amps, so you can only serve it with 30amps safely-which is why the main circuit breaker is a 30amp breaker. -------------------------------------------------------------------- The only danger to adapting the 30a service of your a/s to ONE LEG of the 50amp 240VAC pedestal, is IF the shore line faulted to ground (shorted) then said shore line could actually heat up and burn as it would receive 50amps of 120VAC power. The 30amp main breaker would continue to protect the inside of the a/s from drawing too much current. We really should not do this adaptation, but it MOST PROBABLY will NOT cause a problem. I sincerely hope I never have to eat those words. You can STILL adapt your 30amp service to ONE LEG of the 50amp 240VAC safely by increasing the wire size of your shore line. NOW BE CAREFUL HERE; most a/s bring the shore line into a junction box within the trailer, and use 10gauge romex from the junction box to the service entrance distribution circuit breaker box. so to be completely safe, you must upsize that romex to match your new shore line as well. that means 8ga THHW minimum, probably 6 gauge. do not use aluminum wiring, especially if someone has polished it! humor there, smilies aint workin'? -------------------------------------------------------------------- It seems the RV industry jumped right over the 30amp 240VAC service supply. I do not know why-it would have saved the camp grounds a lot of $ in wire, etc. I cannot fathom anything on wheels needing more energy than 7200watts continuous. ------------------------------------------------------------------ One other thing; the user has no real knowledge of how the various outlets on a power pedestal are wired. The 120VAC 30amp receptacle and the 2-120VAC 20amp receptacles may be wired parallel from the same source-so splitting your air conditioner off from the 30 service MAY NOT solve the voltage sag problem; whereas you can have a pretty good feeling that the 50amp 240VAC receptacle and the 30amp 120VAC receptacle are from two different source breakers. But, they are most assuredly on the same distribution tree within the RV camp. That tree's robustness will determine actual voltage sag based on total usage within the park. wow, how's that for 2 cents worth? I hope this clears it up for me!
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Old 09-12-2010, 07:38 PM   #17
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What am I missing here? It is my belief that there is no 240v at the campground box. It's just 30 amp, 120v and 50 amp, 120v. 50 amps is there for larger units which are wired for 50 amp service at the unit's main breaker. The adapter for smaller units is for campground sites which may not have 30 amp plug in, or if you discover that the 30 amp service has low voltage and the 50 amp tests better. If you plug into a 50 amp service with the adapter, you won't get any more current flow than the breaker in the unit can handle. Only difference is, you may trip you unit's main, rather than the site main. Just because you are plugged into 50 amps doesn't mean that you are passing 50 Amps through your shore power line as you are limited by your unit's breaker. If you replace your main in your trailer with a 50 Amp breaker, you're going to let A LOT of the smoke out of the trailer wiring and your shore power line.
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Old 09-12-2010, 08:10 PM   #18
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From what I understand, the campground 50 amp IS 240 volts. The RV's that plug in use each side of the 240 volts to bring in 50 amp/ 120 volts on 2 lines.
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Old 09-12-2010, 08:17 PM   #19
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Ok, then, is one of the legs "dead" with the adapter? If so, how much amperage available to a 30 amp trailer ahead of the unit's 30 amp breaker? Still, you're only going to get 30 amps max of available current downstream of the unit's 30 amp breaker? and you're not going to heat up the shore power cord UNLESS you screw with replacing the unit's 30 Amp breaker with something larger?
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Old 09-12-2010, 09:00 PM   #20
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one leg dead

yep, one leg is dead with the adapter-still you have 50 amps of 120vac on the other leg. the coach is limited to drawing 30 amps due to the main brkr in the coach's box. BUT, if the cord were to be cut, and the hot wire managed to get to the neutral or ground wire (fault or short) then the CORD (shore line) could draw up to 50 amps of 120vac which may cause the cord to heat. very unlikely, but possible.
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Old 09-12-2010, 09:09 PM   #21
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Got it! Thanks to all. Just keep an eye on the condition of your shore power and DON'T screw with tryin' to "up" your power without a pro! I have had instances (only a couple) where having the adapter solved low voltage/weak breakers on the campsite 30 Amp circuit. I understand what wmarsha is saying about the tree serving the whole place, but I have experienced only "local" site voltage issues with the 30Amp service. When using the adapter, so far, voltage has improved....so I suspect it is common to run completely separate service to the site relative to 30A vs. 50A. Doubt that is true with 20A vs. 30 A outlets at the post.
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