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Old 03-07-2016, 12:51 PM   #1
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Why a 240 VAC connection?

Maybe this is a dumb question, but if none of my appliances are 240V (and I believe most RV stuff is only 120), then why would I need a 240V shoreline connection? Or a 240V genset connection? Thanks.
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Old 03-07-2016, 01:00 PM   #2
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Your 50A connection is actually two 120 V 50A lines. Your four terminals are two hot, one neutral, and one ground. Hot to neutral is 120 VAC, hot to hot is 240 VAC. When you have a 30A connection, though, you have only three terminals: hot, neutral, and ground. You get 120 VAC at 30A. A 50A connection gives you 12,000 W of available power, while a 30A connection only gives you 3600 W.

BTW, Newell motor homes now use a 240VAC Aqua-hot to take advantage of the possibility of 240 VAC. As far as I know they are the only ones who do that.
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Old 03-07-2016, 01:56 PM   #3
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In addition to the reasons above, a split phase system means that the currents in the two hot legs cancels out and allows the use of a single neutral wire rather than two neutrals.
Also, there is a ton of split phase boxes and panels available at low cost at your nearest Home Depot or Menards.
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Old 03-07-2016, 02:31 PM   #4
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Why a 240 VAC connection?

There is some risk with 240 volt systems. Whereby if the neutral should ever become open. You will fry a lot of stuff in the coach. It is a minute risk but one that does not exist on a 30 amp 3 wire power source.
Unless you have 2 air conditioners I see no need for 240 volt system.
You could wire a 50 amp 4 wire system with 1 hot leg, 1 neutral and one ground. Giving you 6,000 watts of power availability without any risk of open neutral damage.
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Old 03-07-2016, 02:38 PM   #5
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lots of new RV users don't realize that the heavy duty cord is for 30 AMP 110 electricity. It's a horrid mistake, but some folks have had electricians mistakenly wire a home power stand with 240 - and zap all of their appliances.

Another not so funny thing is to see a new person try to unhook a 30 amp cord from the RV without realizing that they have to unscrew a ring first. It's what seals out the weather.
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Old 03-07-2016, 02:50 PM   #6
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Originally Posted by racecannon View Post
Maybe this is a dumb question, but if none of my appliances are 240V (and I believe most RV stuff is only 120), then why would I need a 240V shoreline connection? Or a 240V genset connection? Thanks.
Looking at your earlier posts, it looks like you have a '91 34' trailer. Odds are high that it only has a 30A 120V power inlet. As mentioned by previous commenters, you may be looking at the 3-prong 30A RV plug (called a NEMA TT-30P) and thinking it's a 240v 3-prong dryer plug which is a different critter, with closer spacing of the conductors and an L-shaped neutral prong.

The only downside you'll have from sticking with 30A 120v is that if you have 2 AC units, you'll only be able to run one at a time or you'll need another inlet dedicated to the extra AC unit. You'll also have to balance power between AC, microwave and the water heater (if you have the optional electric heating element in the water heater) to avoid throwing the main breaker.
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Old 03-08-2016, 04:51 PM   #7
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So you can run 2 a/c, hair dryer, and microwave at the same time without tripping breakers.
You are referring to a 50 amp service- 2 120 volt legs-
A 30 amp trailer- 1 120 amp leg- has half the potential-
Microwave and a/c trips breakers.
Microwave and hair dryer trips breakers.
Hair dryer and a/c trips breakers.
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Old 03-08-2016, 05:28 PM   #8
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Originally Posted by kb0zke View Post
Your 50A connection is actually two 120 V 50A lines. Your four terminals are two hot, one neutral, and one ground. Hot to neutral is 120 VAC, hot to hot is 240 VAC. When you have a 30A connection, though, you have only three terminals: hot, neutral, and ground. You get 120 VAC at 30A. A 50A connection gives you 12,000 W of available power, while a 30A connection only gives you 3600 W.

BTW, Newell motor homes now use a 240VAC Aqua-hot to take advantage of the possibility of 240 VAC. As far as I know they are the only ones who do that.
They also use a 240VAC residential clothes dryer and have internal load shed systems that prevent your use of the 240VAC electric element in the Aqua Hot when the dryer is in use (not to worry, as they also have a 120VAC element too), or you have more than 2 roof A/C units(they have 4!) are in use when on a 50 amp shore line.

EVERYTHING works when on then on-board 20KVA generator.
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Old 03-09-2016, 01:33 AM   #9
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I like to be comfortable and I'm lazy so I usually run an extra 12ga. extension cord to my 31' so I can run the microwave and use a heater or hair dryer at the same time. I've never got around to converting to a 50amp cord and breaker box mostly because I seldom stay at campground where I could plug into a 50amp plug. I've been living on 2 20amp breakers feeding my trailer for the last 30 some years. Don't be like me if you are re-wiring, just go for the 50amp! You will be happy you did!
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