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Old 07-12-2012, 07:31 AM   #1
smitty082261
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Electrical Question

This may sound like a dumb question but I would like to know when we go to a campground is the 30amp plug a 120 volt and is the 50amp plug a 240 volt.
Thanks
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Old 07-12-2012, 07:49 AM   #2
SAABDOCTOR
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they should both be 120v
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Old 07-12-2012, 07:52 AM   #3
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scratch that120 for the 30amp 220 for the 50 amp sorry too much noise dirt and fumes. were are getting new lifts
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Old 07-12-2012, 08:13 AM   #4
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Quote:
Originally Posted by SAABDOCTOR View Post
they should both be 120v
Well, yes and no. True, Barney? The way the RV is wired, both the 30 amp and the 50 amp "act" as 120VAC. But the 50 amp does have two hot leads (red and black wires), both at 120VAC and at 180 degrees opposite in phase polarity. So technically, across the two hot leads of the 50 amp, there is 240VAC along with a neutral (white wire) and a ground (green wire). The campground usually puts a 50 amp breaker on each of these hot leads and the two breakers are ganged (joined) together. If you look in the RV's circuit breaker box, there will be two 50 amp master breakers (usually in the center of the circuit breaker panel) that control each hot lead distribution to each side. If you took a multimeter and measured across the two hot leads, you would find 240VAC. Measure across one hot lead to neutral . . . 120VAC. Same for the other hot lead and neutral.

So, technically, a 50 amp connection allows 50 amps per hot lead. If you use a 30 amp to 50 amp adapter (aka, dogbone), the single phase 30 amp hot lead is connected to both 50 amp hot leads inside the adapter. So out of the adapter, you only have a total of 30 amps available, single phase alternating current.

It's all in the wiring. The way the circuit breaker box is wired, one only sees 120VAC inside the RV. This is also a reason, if you have 50 amp service in your RV, and two AC units, you want each AC unit on different hot leads of the circuit breaker box. You probably don't want both AC units on the same side (hot lead).

I do understand that some RVs do utilize 240VAC from 50 amp service for the air conditioning. But I am not aware of any Keystone models that utilize this service.

So, yes, Barney is correct - from the typical RVer's perspective, the 50 amp service supplies only 120VAC power. However, you might want to be aware of what's behind this power.

Ron

Barney - congratulations on the new lifts!
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Old 07-12-2012, 08:18 AM   #5
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thanks they will be great. that was a great discription. i wish i had the time to wite that. but itook the easy way out.
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Old 07-12-2012, 08:20 AM   #6
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Quote:
Originally Posted by smitty082261 View Post
This may sound like a dumb question but I would like to know when we go to a campground is the 30amp plug a 120 volt and is the 50amp plug a 240 volt.
Thanks
The 3 prong 30 amp RV socket is indeed 110vac.

The 4 prong 50 amp RV socket on the CG's power post is 220vac.

HOWEVER, what it delivers to the trailer depends on how the unit is wired. My Cougar is wired for 50amp 110vac service. The supplied 50 amp power cord is 3 conductors at the trailer end, but has a standard 4 prong 220vac RV plug at the power post end. That means it is only using one leg of the 220vac circuit which yields 110vac provided to the trailer.
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Old 07-12-2012, 08:23 AM   #7
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Steve!

That means you are being cheated out of an extra 50 amps! You know Tesla is rolling over in his grave!

Ron
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Old 07-12-2012, 08:29 AM   #8
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in connecticut we are charged a delivery fee for electricity. i call the power company and said i'll come pick it up! they didn't see the humor as far as my lifts go... there is a guy running a back hoe.. the only way to describe it is this was like giving a straight razor to a monkey. hope i have a shop left when they are done right now it don't look good
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Old 07-12-2012, 08:50 AM   #9
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Quote:
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Steve!

That means you are being cheated out of an extra 50 amps! You know Tesla is rolling over in his grave!

Ron
ROFL!!!!

That 50 amp power cord that came with the Cougar is huge! It takes two grown men and a really strong boy to carry it. First thing I did when we got the rig was to buy a trailer-end dogbone that gets down to a standard 30amp RV connector so I can use my regular 30amp cable that was left over from our previous rig. Much more reasonable in size and weight.
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Old 07-12-2012, 09:08 AM   #10
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50 amp

To sum it up:

With 20 amps you have 2,400 watts available.

With 30 amps you have 3,600 watts available.

With a 50 amp cord you have 12,000 watts available because it uses both 120V legs in the panel. You essentially get the equivalent of 120v 100 amp service. Most trailers do not make use of the fact that there is240V available.

If you had a set up where only a single leg was available, due either to to the pedestal being wired that way (rare but probably does exist in some parks) or due to the cable or panel being wired that way ( very unlikely, but possible) you would have 6,000 watts available.

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Old 07-12-2012, 09:13 AM   #11
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thanks for all the great info, I do appreciate it. this group is awesome
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