Can I plug my 50amp cord from my class A into a dryer outlet?

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DonTom

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You will never convince him. Don Tom has made that pretty clear.
What is it that makes those on the NEC committees more knowledgeable than the best technical people here in this forum?

I could be convinced by some good well proven facts, but not just because somebody says so.

And FWIW, I am already a little convinced when the guy in the video mentioned gas lines--something I never thought about before. But to be 100% convinced, an issue that actually happened would have to be shown, such as a house blowing up all because it has a 3-prong instead of 4-prong drier outlet.

-Don- Phoenix, OR
 

xrated

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240VAC doesn't just float around.

The potential needs to find it's way back to the source. In the case of a WYE transformer you have 2 X 120V legs and a neutral.

The ground is intended for a path like a lightning strike. It is also a path of least resistance back to the source should the neutral leg fail.

I suggest you watch this video all the way through. It made a lot of things clear for me when I went to wire up my mobile home.


Note that when he demonstrates the potential on the neutral and ground legs he purposefully makes an imbalance load.

You've stated over and over that a 50amp service is 2 X 120V. It's actually a misnomer because at the pedestal it is 2 hot legs, a neutral and a ground.

RV loads can get extremely imbalanced depending on what is running off of each 120V leg. If the A/Cs are split and only one is running you could have a 15amp split right there.

I'll back up NY-Dutch on the 4-prong as you have both a neutral path and an EGC path.
I've never see a WYE transformer with only two legs of voltage! The reason they call them a WYE is because the configuration resembles the letter "Y".....as in three hot legs....plus the neutral of course.
 

Ex-Calif

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I've never see a WYE transformer with only two legs of voltage! The reason they call them a WYE is because the configuration resembles the letter "Y".....as in three hot legs....plus the neutral of course.
You are right - I misspoke

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People make too much fuss about the so called imbalance. At a homeowner level the imbalance is not going to cause problems because at a maximum, the current will exceed the CB limit and trip. I think the imbalances tend to be more of a problem for the power companies. I may be wrong on this , but in my mind that is the way it works.

The point of showing the imbalance is to educate on where the potentials can exist and shows how a lot of current can be carried on the EGC because effectively on a sub-panel it is a parallel path to N which is in the main panel.

What is it that makes those on the NEC committees more knowledgeable than the best technical people here in this forum?

I could be convinced by some good well proven facts, but not just because somebody says so.

And FWIW, I am already a little convinced when the guy in the video mentioned gas lines--something I never thought about before. But to be 100% convinced, an issue that actually happened would have to be shown, such as a house blowing up all because it has a 3-prong instead of 4-prong drier outlet.

-Don- Phoenix, OR

It isn't the fire hazard. He was showing that a metal gas line is a very low resistance path to ground and can be lower than the circuit back to the ground stakes.

With a 3 prong 240V plug there is no EGC.

As an ex-aviation safety guy I think we are bantying the word safety around quite a bit.

No one is dying every day from 3-prong outlets.

The original poster wants to wire a 50amp dryer male end to a 50amp RV female end.
 

Pedro Dog

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Before folks on here get freaked out by the video about currents flowing via pipes and gas lines, his situation does not apply to service panels in the majority of homes.

His home is situated on acreage and his type of set up is common in the country as folks have sub panels on wells and shops as well as the main residence.

What he is dealing with is a "sub panel" situation. His main panel is at a distance away next to the power drop and meter. At his main panel he does have the ground bonded to the neutral.

If you have your house panel wired directly from the transformer and meter, then his video does not apply to you. If you have a garage or a shop with a sub panel from your main panel, then his video applies to those sub panels.
 

xrated

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Dom-Tom wrote: "The 4-prong dryer cord is comprised of two hot wires, a neutral wire and a ground wire. This creates a separate return path for unused current."

There is no such thing as "unused current" in the context of this discussion. If there is current flow in the ground wire, it is because of a circuit fault....however large or small that current might be.
 

xrated

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And a clarification about a "ground" in a car or truck. No, there is not an earth ground, but yes, many folks refer to a 12V ground.....which is nothing more than a "frame" or "chassis" ground, where by the metal frame of the vehicle is used as a conductor for the current return path back to the source or battery.
 

SeilerBird

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So where is the safety issue?

-Don- Phoenix, OR
When you get a "master electrician" like cavie doing the work. I sure miss him. He hasn't been around here for over a year. If you want a good laugh read this thread:

"here we go again. confusing the newbie with the 100 amp BS."

 

Kirk

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lmao-haha.gif
 

DonTom

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here we go again. confusing the newbie with the 100 amp BS."
But as you know, it's not BS. But would it be less confusing if we used watts? 12,000 watts at 240 VAC and 6KW per line at 120 VAC for a total of 12KW on the 50-amp RV service but always 3,600 watts max on the RV-30 no matter what.

As long as nobody tried to use above 6KW on a 120 VAC line of a 14-50R, all would be fine and clear.

Perhaps the 3-prong dryer outlet makes it even more confusing because it is wired differently (and much better) than the 30 AMP RV service. Only the drier outlet can do the 60 amps total at 120 VAC, yet both it and the RV-30 have three prongs.

-Don- (Middle of Nowhere, CA--40 miles east of Crescent City in those ugly redwood trees).
 
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DonTom

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Dom-Tom wrote: "The 4-prong dryer cord is comprised of two hot wires, a neutral wire and a ground wire. This creates a separate return path for unused current."
Who wrote it (the last sentence) what message number?

I don't see why a path is needed for "unused current". I cannot make any sense out of that, so I hope I didn't post that one! If I did, I must have typed something I didn't mean!

-Don-
 

DonTom

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The concern is when the ground lug is used in lieu of a neutral.
Not sure what you're trying to say there. I don't expect a ground to work as a centertap (neutral) of a transformer for 120 VAC, but there is nothing dangerous about it. A grounded dryer is a grounded dryer. Just no 120 VAC without a neutral.

-Don- Crescent City, CA
 

Boat Bum

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I thought this was settled, soo, can I do this safely or not; what's my risk exposure?. I would not keep it plugged in for any length of time, rather to get the coach charged up and cooled down before a trip.
 

DonTom

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I thought this was settled, soo, can I do this safely or not; what's my risk exposure?. I would not keep it plugged in for any length of time, rather to get the coach charged up and cooled down before a trip.
Yes, you can do it as safely as your own wiring or whatever. Since you're using a 50-amp RV plug, you will be in-between the 30-amp RV Service and the 50-amp RV service. You will have two lines of 30-amp 120 VAC on your drier plug, total capacity will be 60 amps at 120 VAC. That is twice as good as an RV-30 (30-amp RV service), but not as good as a 14-50R that is the 50amp RV service, 40 amps below.

Always use watts to compare total power:

RV park 30-amp max watts=3,600 watts
RV Park 50-amp max watts=12,000 watts
Clothes dryer outlet max watts=7,200 watts.

I wish they would remove all the 30-amp outlets at RV parks and start using 30-amp drier plugs! Much better idea! But then they will have to run another hot for the 30-amp service.

I am stuck with 30-amp service right now, so I need to unplug my electric motorcycle to use my A/C or MW oven. The drier outlet would have enough for both.

The ground lug is a different fit. But a 50-amp RV plug will work fine if you can take care of that issue.

So go for it!

-Don- Crescent City, CA
 

DonTom

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You had the right answer on post #3.
I do not consider it correct as there will then be 60-amps total available instead of 30-amps. A clothes dryer is a 240 VAC outlet.

An RV-30 is 120 VAC ONLY. No 240 VAC in it at all!

So the clothes drier outlet has two 30-amp 120-VAC lines to use for a total of 60 amps.

-Don- Crescent City, CA
 

NY_Dutch

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I wish they would remove all the 30-amp outlets at RV parks and start using 30-amp drier plugs! Much better idea! But then they will have to run another hot for the 30-amp service.
The largest segment of the RV industry is towables. And the majority of towables sold are equipped for 30 amp 120 VAC service per the RVIA.
 
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