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50 Amp RV Plug to 250V/30A (3 Wire) Dryer Plug


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So as the title says and now I ask, can you safely adapt the two 120V legs of the RV to this particular receptacle say if you created a ground via attachment to the house water pipe? 

"There are No Experts, Do the Math!"

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There is no way to do so because there is no neutral wire to the 3 pin plug. Your RV does not use 240V power but only 120V which means that the two hot legs are split into separate load distribution inside of the distribution box by connecting loads between each hot leg and the neutral that is not available in a three pin, 240V power plug. 

As Darryl has said,  NO!

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
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FWIW here's another huge NOOOOOOOOOOO lol and FYI here's why

A 50 amp two pole 3 wire grounding receptacle has: Two Hots, L1 & L2 and an Equipment Ground,,,,, It DOES NOT have a Neutral (aka Grounded Conductor)  which is absolutely required and necessary to properly and safely achieve 120 VAC from L1 or L2 to Neutral......…The RV DOES NOT use 240, it uses two legs L1 & L2 each of 120 VAC Line to NEUTRAL (which the dryer plug lacks)

A metallic house water pipe may under certain circumstances suffice as a "Grounding Electrode" to which the incoming service entrances Neutral might be bonded ( NEC bonds to all "readily available" Grounding Electrodes)  HOWEVER it is certainly by no means to be used as a Neutral for conducting normal return current.

Neutral (GrounDED Conductor) is NOTTTTTTTTTTTTTTTTTTTTT the same as the Safety Equipment GroundING Conductor. Its purpose is for the dedicated return of FAULT CURRENT ONLY while the Neutral (Grounded Conductor) is to carry normal return current.

NOTE a 50 amp 3 pole 4 wire grounding receptacle CAN BE MODIFIED for a 50 amp 120/240 volt RV use as it has Two Hots L1 & L2, Neutral, Equipment Ground IE 4 wires like the 50 amp RV system.   

To be safe and comply with the NEC NEVERRRRRRRRRRR use Ground for Neutral and NEVERRRRRRRRR use Neutral for Ground.

1 hour ago, NoDirectionHome said:

Thank you Kirk.  I was hoping you, RandyA or OlJohnT would respond.  -Steve

 Keep safe

OlJohn T Longggggggggg retired n rusty power distribution design engineer.

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Actually, most older 30 amp dryer outlets are two hot legs and a neutral, because the neutral and one of the hot legs is what is used to turn the dryer motor, which will be 120 volts.  It is still really not a good idea to use this as a power source for your RV.  You may or may not have a good ground return to the panel through a plumbing pipe.  It would be best to just wire a 50 amp four wire outlet as close to the RV parking area as you can to avoid damage to your RV and house.

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Actually, older 30 amp dryer outlets used 2 hots, and a ground wire. The ground was used as a Neutral conductor, due to a NEC decision. The variance was later removed, to prohibit all ground wiring from being regularly used as a current carrying conductor.

I have been wrong before, I'll probably be wrong again. 

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1 hour ago, Darryl&Rita said:

Actually, older 30 amp dryer outlets used 2 hots, and a ground wire.

THATS CORRECT Darryl & Rita. It was the (often Bare/Green) Equipment GroundING Conductor NOTTTTTTTTT the Neutral. However, since its bonded to the Neutral at the Service Entrance it could (if so wired) carry return current and there actually exists 120 VAC between it and the Hots. That problem was later corrected by using four wires, Two Hots, Neutral, Equipment GROUND. Some equipment/appliances used straight 240 no 120, in which case Neutral wasn't needed so two Hots and Ground sufficed.

AGAIN  Neutral is notttttttttttttttttttt same as nor to be used as the Equipment GroundING Conductor (Dedicated fault current return path ONLY) and the Equipment GroundING Conductor is nottttttttttt the same as nor to be used as the Neutral. Neutral is insulated same as the hots  DUH  as its a live current carrying conductor !!!!!!!!!!!!!  The EGC is often bare and is bonded to the outer conductive metallic frames of some tools and appliances WHICH YOU TOUCH !!!!!!!!!!!

2 hours ago, 57becky said:

You may or may not have a good ground return to the panel through a plumbing pipe

Based on my training and experience Id say there's a better chance there's NOT any proper ground return through any metallic (if used) plumbing pipe (But hey I'm rusty and have been wrong before and open minded and always willing to learn something new). In addition, you should NEVER use plumbing as a return current path to the panel, but instead the normal branch circuit NEUTRAL CONDUCTOR and the Equipment GroundING Conductor to carry Fault current. 

NOTE there may or may not be a bond between metallic home plumbing and the Neutral. The NEC when I practiced power distribution required bonding the Neutral to ALL READILY AVAILABLE GROUNDING ELECTRODES of which metallic pipes was one of such, but often it did NOT get bonded. REGARDLESS I suggest it never be used for conducting Neutral current, use the branch circuits Neutral and Ground instead.........

John T   rusty on the latest NEC but believe all this still holds true

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2 hours ago, NoDirectionHome said:

OK, I'm gonna pull it apart and post a picture....yes, after I turnoff the breaker.

Go ahead and try it if you wish but understand that you have been advised not to do so by both career electrical techs and an electrical engineer. If you burn up your electrical systems in the RV it will be a very expensive lesson. 

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure

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7 hours ago, NoDirectionHome said:

I just want to see if it's a center neutral or ground as there seems to be some question among those techs and experts.

No direction, that's a plan, just open, look see, and trace the wiring back to the panel and let us know.

That being said iffffffffffffffff its a typical older 2 pole 3 wire grounding receptacle and iffffffffffffff it was wired correctly THE THIRD WIRE IS THE EQUIPMENT GROUNDING CONDUCTOR NOTTTTTTTTTTTTTTTTTTTTTTT NEUTRAL. PS don't take my word for it, consult any trained professional electrician or engineer or the NEC and NOT what's posted here including yours truly (although I'm pretty sure I'm correct)

So how to tell ?? Typically (if wired correct) the Equipment GroundING Conductor is Bare/Green

                               Typically (if wired correct) Neutral is a white INSULATED conductor

                                Trace the wire back to the panel and see if its connected to the Equipment Ground Buss or the Neutral Buss

                                HOWEVER in many older main service entrance panels there's a single common Neutral/Ground Buss to which  

                               BOTH White Neutrals and Bare/Green Grounds are attached !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Because at the main service entrance

                                panel Neutral is BONDED to Ground as the utility uses a BONDED not a Floating Neutral like some gensets. So it may be a panel with a single common buss or separate bonded with a cross tie bar Neutral and Ground busses...

 

CAUTION BOTTOM LINE

REGARDLESS if its a Neutral orrrrrrrrrrrrrrrrr a Ground  ITS STILL NOT PROPER CORRECT AND SAFE NOR NEC APPROVED because for a 50 amp RV you need BOTH A NEUTRAL PLUSSSSSSSSSSSS A GROUND AND YOU NEED FOUR WIRES NOTTTTTTTTTT JUST THREE !!!!!

There's just no safe proper and NEC approved method to power up a 50 amp RV with ONLY three wires PERIOD so it doesn't matter if that third wire is a Ground (which it is if wired correct) orrrrrrrrrrr a Neutral (which is NOT correct for a 2 pole 3 wire grounding receptacle)

A persons RV and life safety is his or her own choice so do as you please but if my training and experience as an engineer of forty nine years and the NEC matters I have to go on record as advising NOT power a 50 amp RV with only three wires !!!!!!!!!!!!!!!!!

PS I don't consider there's disagreement  among "techs and experts" because if they are actually EITHER they would agree a two pole 3 wire grounding receptacle (iffffffffffff wired correct that is) is connected to two hots and an equipment ground NOTTTTTT Neutral but hey if Billy Bob or Bubba not trained not electricians wired it there's no telling how they did it lol so NO ONE here can say for certain not having examined the wiring BUT THREE WIRES IS NOT ENOUGH REGARDLESS

PS Noooooooooo PLEASE don't use a water pipe for Ground or Neutral, its neither !!!!!!!!!!! It's NOT not a safe proper or heaven forbid NEC approved Equipment Ground Conductor and its certainly NOT a safe or proper or NEC approved Neutral DUH. It can in certain situations be used as a Grounding Electrode...…..similar to driven copper rods or foundation steel etc. 

John T  Retired Electrical Power Distribution Design Engineer but rusty and not up on current NEC so no warranty, wire as one pleases..   

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https://i.imgur.com/Lq9ZT6H.jpg 

https://i.imgur.com/LL0Ewod.jpg

https://i.imgur.com/fGlES5R.jpg

So yes I have a neutral with no ground which was common back in the 1960's for an appliance.  

"There are No Experts, Do the Math!"

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1 hour ago, oldjohnt said:

it was wired correctly THE THIRD WIRE IS THE EQUIPMENT GROUNDING CONDUCTOR

It is your RV so do what you want but it would cost far less to pay a licensed electrician to install a proper, 4 pin, 240V outlet than it will to repair your RV when you finish saving money. '

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure

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Yes, and that is what I will do.  My curiosity just had to get this fully defined first, for both myself and those that have posted.  
I don't think anyone likes the OP to just go away after having asked a question and others take the time to discuss it.

As always, many thanks to all!

"There are No Experts, Do the Math!"

2014 Freightliner Cascadia DD16 600hp  1850ft-lb  18spd  3.31  260"wb
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I've been trying to imagine what would happen to a PLUMBER who tried to work on a pipe that some idiot was using as a conductor.  I imagine if he died, the person who did it would not only be looking at a MASSIVE civil suit, he'd also be looking at an involuntary manslaughter charge.

Regards

John

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17 minutes ago, NoDirectionHome said:

Think about it...All plumbing is a ground path. 

As long as the pipe is intact, yes.  Consider a situation where the pipe in question was leaking, and he decided to cut the bad section out and splice a new piece in.  Once the part of the pipe connected to the outlet is no longer making a connection to the whole plumbing system, I could see how current could flow through him if he touched it.

Regards

John

DON'T FEED THE VULTURES!

My Body is a Temple!  Ancient, Crumbling, Probably Cursed . . .

I Don't Like to Make Advanced Plans.  They Cause the Word "PREMEDITATED" to Get Thrown Around in Court!

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5 hours ago, NoDirectionHome said:

Yes, and that is what I will do.  My curiosity just had to get this fully defined first, for both myself and those that have posted.  
I don't think anyone likes the OP to just go away after having asked a question and others take the time to discuss it.

Thanks for the feedback, yes it helps when the OP keeps us informed and I for one appreciate it. If you help us we can better help you

The picture you posted appears the third wire in that receptacle was connected to the White conductor, which if all's correct ????????????is Neutral instead of a Bare/Green Equipment GroundING Conductor as typical on a 240 Volt 2 Pole 3 Wire Grounding Receptacle. Of course (if that's indeed a Neutral) there's still no safety Equipment Grounding Conductor which is there solely to carry fault current and save a life and which is required for a 50  Amp RV    IE    YOURE STILL ONE CONDUCTOR SHORT  its just NOT gonna work to correctly and safely supply a 50 amp  RV. Again a 240 Volt 2 pole 3 wire grounding receptacle IF WIRED STANDARD AND CORRECT would have two Hots and Ground and could supply straight 240 volts for a tool or appliance that uses say 240 volt motors or heat strips etc plus has the safety third wire Ground. 

ALSO it looks like 30 amp 10 gauge wire but you need 6 gauge 50 amp 4 conductors for a 50 amp RV !!!

 

4 hours ago, NoDirectionHome said:

Think about it...All plumbing is a ground path. 

If indeed the plumbing is metallic conductive and assuming its buried, it is a conductive current path to "Mother Earth" but SO WHAT ??

If it was incorrectly used as a live current carrying conductor (such as a Neutral) and if it was touched by a plumber, he is placing his body and heart in a parallel current path and it only takes like 0.030 to 0.050 amps to cause the heart to fibrillate WANNA TRY IT OR LET YOUR GRANDKIDS TOUCH IT ?????????????????????????? Ever notice the Neutral in your outlets and wiring IS INSULATED unlike the bare equipment ground hmmmmmmmmmmmmmmmm that's because its a live current carrier and if you touch it subject to other factors you can get shocked !!!!!!!!!! But you are touching the Bare/Green equipment grounding conductor if its bonded to the outer metal case/shell of a tool or appliance which can save your life  !!!!!!!!!!!!!!  NEUTRAL IS  NOT SAME AS GROUND !!!!!!!!!!

BUT if done correctly buried conductive pipes can be used as a Grounding Electrode to which the services incoming Neutral gets (along with other electrodes) bonded  BUT ITS  NOT CARRYING NORMAL RETURN CURRENT FROM A TOOL MAKING IT HAZARDOUS AS OUTLINED ABOVE  

Try as I may I'm not a good enough teacher to explain to non electricians the difference in Ground and Neutral grrrrrrrrrrrr my bad lol

Neutral Ground BONDING is  nottttttttttttttttt the same as Earth Grounding of the Neutral (HV Primary and LV Secondary) for lightning and surge suppression and to keep the grid at a common low voltage reference IE MOTHER EARTH

But that's NOT bad against lay persons, if you haven't been trained in it and worked with it and the NEC most wouldn't understand it either.  

Hope this helps, I try my best but its impossible to put in a paragraph that which can take entire books and years to understand

 

John T

 

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I was raised in a home that didn't have a ground prong on any plug.   No one that I knew had a smoke alarm or seat belts in their car or ground prongs.  We survived but now my home has grounds and smoke alarms.  We use our seat belts.  A 3 prong plug will work if wired correctly but the safety factor is not there.  In addition the grounding plugs in the R will be an increased danger as these are wired and engineered for grounds.  I wouldn't even think of wiring for my RV without a ground but you and others might survive without it.  In fact you probably would survive but is it worth it?

Randy

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Yeah, even thought of driving in a copper ground bar but, I'm too old to have come this far and survived to be knocked off by a chafed wire.  I'm gonna trench a line and put in an RV pedestal.  Ya can't eat the money, especially if you're dead.

"There are No Experts, Do the Math!"

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