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Open Roads Forum  >  Tech Issues

 > 15/30/50 SHORE POWER PLUG IN ?

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llr

Ohio

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Posted: 07/25/19 12:59pm Link  |  Quote  |  Print  |  Notify Moderator

Oasisbob wrote:

So can a 50 amp outlet be 110 volt or are they, or can they be 220 volt? How do you tell?


They are 220, across the 2 hots, the 50-30 adapter only uses 1 hot so no issue

rk911

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Posted: 07/25/19 01:04pm Link  |  Quote  |  Print  |  Notify Moderator

fj12ryder wrote:

Just get a 50 amp to 30 amp adapter. You plug your 50 amp plug into it and then into the 30 amp pedestal. Easy peasy.

and no, a 50-amp RV pedestal is not 220-volts. it is two separate legs of 120-volts, each leg capable of supplying 50-amps. you can safely connect your 30-amp RV to the 50-amp RV pedestal using the 30-female/50-male dogbone adapter


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stevenal

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Posted: 07/25/19 01:46pm Link  |  Quote  |  Print  |  Notify Moderator

Sandia Man wrote:

No circuit breaker required on adapters as your RV has a main breaker that will instantly open upon reaching its rated value
.

Not true, the breaker will pass rated current all day without tripping. It will enter an inverse time-current curve at about 125% of rating. Instantaneous tripping will occur once you get to 3 to 10X rating. Any breaker will only protect for faults and overloads downstream.

Sparkydave,

My profession as well, registered in the state I reside in. I won't be stamping the design proposed. In your appliance example, you are plugging your UL listed #18 wire device into a NEMA 5-15 or 5-20 receptacle without an adapter, else you would be violating its listing.

https://rvnerds.com/2017/06/12/power-adapter-101/

* This post was edited 07/25/19 01:58pm by stevenal *


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westernrvparkowner

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Posted: 07/25/19 02:20pm Link  |  Quote  |  Print  |  Notify Moderator

llr wrote:

Oasisbob wrote:

So can a 50 amp outlet be 110 volt or are they, or can they be 220 volt? How do you tell?


They are 220, across the 2 hots, the 50-30 adapter only uses 1 hot so no issue
Other than the fact the voltage is actually 240 volts AC, this is the correct answer. There is no such thing in residential wiring where a single wire carries 240 volts. All 240 volt outlets are as described, two separate 120 volt lines, out of phase that measure 240 volts AC between them. Measuring between either hot line to either the ground or the neutral the voltage will result in 120 volts AC. Harbor Freight sells volt meters for less than $10.00. They are extremely easy to use. Using one is the best tool and easiest way to confirm a questionable outlet is properly wired.

wa8yxm

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Posted: 07/25/19 04:20pm Link  |  Quote  |  Print  |  Notify Moderator

Your understanding of 50 amps is a bit shakey. It is 50 amps at 240 divided
Basically think of this

1--120 volts - N - 120 volts--2

Now from 1 to n is 120 volts.. likewise n to 2 is 120 volts 1-2 is 240

SO. you can (and should) get a 30-50 "Dogbone" Adapter (30 amp outlet. 50 amp plug short cord between 'em) at your favorite RV supply or Wally World. (Wal*mart though I don't like shopping there if I can help it).

It handles all the differences for you.. IT connects to just ONE leg and neutral so you get 120 volt (At up to 50 amp) but your 30 amp breaker in the RV limits the current.


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sparkydave

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Posted: 07/25/19 04:35pm Link  |  Quote  |  Print  |  Notify Moderator

stevenal wrote:



Sparkydave,

My profession as well, registered in the state I reside in. I won't be stamping the design proposed. In your appliance example, you are plugging your UL listed #18 wire device into a NEMA 5-15 or 5-20 receptacle without an adapter, else you would be violating its listing.

https://rvnerds.com/2017/06/12/power-adapter-101/


True, it's not really up to code, but do the math. Shore power cord "burning up"? Horrors! Pardon me, but that sounds a little like worrying about the fire department getting your carpets wet if your house is on fire.

These seemingly unlikely faults that somehow draw exactly 50 amps and happen to occur between the dogbone and the circuit breakers must be a genuine concern and cause shore power cords to burn up all the time. I should get rid of my 50 amp to 30 amp dogbone right away, because if I'm plugged into a 50 amp pedestal with my 30 amp RV, I can't be violating UL and have my shore power cord rating possibly being exceeded while my RV is burning to the ground.[emoticon] Circuit breakers can and do fail, so plugging a 30 amp into a 30 amp pedestal must be dangerous too. If these faults that can cause a 50 amp fault to happen between the pedestal and the breakers, then it must be equally likely you could have a 30 amp fault in the same place while plugged into a 30 amp pedestal, but we can breathe easy because we won't be exceeding the shore power cord rating and having it "burn up". The RV will only have a 3560 watt problem inside it instead a 5900 watt problem, so the fire in the RV won't be as big [emoticon]

Now do you see what I'm getting at? Focusing on a minor issue instead of the much bigger issue in an unlikely occurrence.

Nah, I think I'll worry more about the condition of the wires and the outlets in the pedestal. I'd also worry more about the chuckleheads who wire RVs such as mine; I had all the ground wires from the 12 volt side jammed under one wire nut. Even the rat's nest of electrical tape couldn't hold it together.

PNW_Steve

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Posted: 07/25/19 05:07pm Link  |  Quote  |  Print  |  Notify Moderator

rk911 wrote:

fj12ryder wrote:

Just get a 50 amp to 30 amp adapter. You plug your 50 amp plug into it and then into the 30 amp pedestal. Easy peasy.

and no, a 50-amp RV pedestal is not 220-volts. it is two separate legs of 120-volts, each leg capable of supplying 50-amps. you can safely connect your 30-amp RV to the 50-amp RV pedestal using the 30-female/50-male dogbone adapter


Thank you for enlightening us.

It's a wonder I passed the Journeyman's electrician's test given that I always thought that a 50amp 240volt circuit actually provided 240 volts.

Learn something new everyday [emoticon]


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2oldman

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Posted: 07/26/19 02:15pm Link  |  Quote  |  Print  |  Notify Moderator

Oasisbob wrote:

So can a 50 amp outlet be 110 volt or are they, or can they be 220 volt? How do you tell?
My choice would be a voltmeter.

rk911

Wheaton IL

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Posted: 07/26/19 03:20pm Link  |  Quote  |  Print  |  Notify Moderator

2oldman wrote:

Oasisbob wrote:

So can a 50 amp outlet be 110 volt or are they, or can they be 220 volt? How do you tell?
My choice would be a voltmeter.

yup. I test each pedestal before I connect. my tester shows the voltage and proper wiring (proper ground, neutral, etc.) for each leg...~115 to 120-volts.

[image]

fj12ryder

Platte City, MO

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Posted: 07/26/19 03:44pm Link  |  Quote  |  Print  |  Notify Moderator

PNW_Steve wrote:

rk911 wrote:

fj12ryder wrote:

Just get a 50 amp to 30 amp adapter. You plug your 50 amp plug into it and then into the 30 amp pedestal. Easy peasy.

and no, a 50-amp RV pedestal is not 220-volts. it is two separate legs of 120-volts, each leg capable of supplying 50-amps. you can safely connect your 30-amp RV to the 50-amp RV pedestal using the 30-female/50-male dogbone adapter


Thank you for enlightening us.

It's a wonder I passed the Journeyman's electrician's test given that I always thought that a 50amp 240volt circuit actually provided 240 volts.

Learn something new everyday [emoticon]
I guess we should all be glad you're not wiring up RV park pedestals.


Howard and Peggy

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