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-   -   Basic RV Electrical Question, I think (http://www.airforums.com/forums/f37/basic-rv-electrical-question-i-think-172021.html)

leonot 08-28-2017 05:19 PM

Basic RV Electrical Question, I think
 
Just had someone at an RV parts store say "never plug in to 220, you'll fry your rig". He was clearly not to be questioned, so I'll ask here:

Isn't that exactly what we do when we plug into a NEMA 14-50 (4 prong) socket? (My 2017 SilverCloud 50A comes with that plug, of course.) I've got a NEMA 14-50 in my home, and have even VOM-confirmed that it's 220.

So... are we just pulling 110 off of one half of the circuit, and the other side being ignored?

The reason this came up is that I'm currently parked a few feet away from a NEMA 6-50 welding power socket. It basically looks like a giant 120v plug - 3 prongs. Was hoping to find an adapter for that, but they don't seem to exist.

So ... I'm quite confused as to what's REALLY happening here?

Thanks for anyone who can clarify. :-)

Leo

sgschwend 08-28-2017 05:39 PM

I would think your owner's manual will cover your question. I have heard that the 50A powered trailer has a circuit breaker panel that is setup for 125VAC. The manual or a call to AS should be a safe way to find out.

I do see you state the welder has a three wire plug but the trailer is 4 wire. So the welder does not have the neutral you need.

steve

leonot 08-28-2017 05:41 PM

Quote:

Originally Posted by sgschwend (Post 2000684)
I would think your owner's manual will cover your question.

I should have mentioned that I started there. No real help.

Thanks!

Leo

lsbrodsky 08-28-2017 05:49 PM

This has been answered a hundred times on the forum, do a search.

rmkrum 08-28-2017 05:51 PM

With the NEMA 14-50 RV socket, you have two hot leads, one neutral, and a safety earth (ground)

Its 220 volts across the two hot leads...which is just fine. But there is only 120 volts from Hot to Neutral, which is even better..

The reason is, your AS is wired with all the internal loads between ONE hot lead and the Neutral, thus seeing only 120 volts on the circuit. Only one Air Conditioner is connected to the other side, usually. The 4th lead (safety earth (ground)) is wired to the frame and shell of the Airstream for safety--that's the wire that is supposed to blow the supply breaker(s) if a hot lead kisses the shell of the AS, instead of electrocuting innocent bystanders.

That other NEMA 6-50 three-wire Welder outlet most likely has two hot leads with 220 volts between them and a safety earth (ground). There is NO safe way to adapt that to run your trailer. Don't even think about it. Install the correct socket and proper wiring if you need 50 amp RV service...

The dude at the RV store was correct only in the idea that plugging a 30 amp trailer into a miswired RV-30 outlet with 220 volts between the hot and neutral prong will fry things.

He is probably remembering a miswired 30 amp setup where a supposedly experienced electrician wires the two hots and a ground to a 30-amp 120 volt RV plug, thinking its wired like the welder plug you mentioned. My theory is that they have been doing it so long that they don't bother reading the very clear instructions on the box the socket comes in...

Messed-up wiring that puts 220 volts on a 120 volt 30-amp input to an AS been reported, and it is messy--fries most stuff in the AS...

There is a good reason for the different shapes and sizes and ratings for electrical connections in the US...it prevents a great deal of expense when things are done right, and to code...

rmkrum 08-28-2017 05:53 PM

Quote:

Originally Posted by lsbrodsky (Post 2000688)
This has been answered a hundred times on the forum, do a search.

Hey, in the interests of safety, I am fine with answering this question again and again...it's only a dumb question if it's not asked...

leonot 08-28-2017 05:59 PM

Quote:

Originally Posted by rmkrum (Post 2000689)
With the NEMA 14-50 RV socket, you have two hot leads, one neutral, and a safety earth (ground)

Its 220 volts across the two hot leads...which is just fine.

The reason is, your AS is wired with all the loads between ONE hot lead and the Neutral, thus seeing only 120 volts on the circuit. The 4th lead (safety earth (ground)) is wired to the frame and shell of the Airstream for safety--that's the wire that is supposed to blow the supply breaker(s) if a hot lead kisses the shell of the AS.

This is exactly what I was looking for (and couldn't find by searching the forums, either - apparently my search skills aren't up to snuff).

Not a case where I'm looking to add anything (did that at home with a NEMA 14-50). The place I'm visiting has the welder plug, which I will now avoid even thinking about. :-)

Thanks again,

Leo

rmkrum 08-28-2017 06:05 PM

Quote:

Originally Posted by leonot (Post 2000694)
This is exactly what I was looking for (and couldn't find by searching the forums, either - apparently my search skills aren't up to snuff).

Not a case where I'm looking to add anything (did that at home with a NEMA 14-50). The place I'm visiting has the welder plug, which I will now avoid even thinking about. :-)

Thanks again,

Leo

It's probably not your search skills...the forum search system is not super reliable. Glad to be of help. There are some rather sad stories on the forum of folks blowing out their AS electrical devices with miswired RV-30 plugs. Yet another argument for a smart surge suppressor that checks voltages and polarity before it applies power to the internals...be safe out there!

Seagars 08-29-2017 02:10 PM

That's a mean comment

Seagars 08-29-2017 02:14 PM

I'm capable of asking novice questions all the time.
I would always appreciate the forums advice. It saves a lot of searching for what I hope is the right answer.
Comments from a novice newbie.

lsbrodsky 08-29-2017 02:26 PM

I have developed a pet peeve about people too lazy to spend the time to do a decent search of this forum or the internet. There are 1000's of threads available here with a wealth of information available to anyone willing to take the time. Moreover, there may be a depth of information not available from a few answers in a new thread.
What is the point of having all of the old threads available if they are not used by people seeking information? Maybe it is just a part of the instant gratification problem...just post your question, get an answer and get back to something else.
I have learned a lot from many individuals on this forum, people I have never met and will never meet. You do them a disservice if you just ignore what they have already answered.
If my post is viewed as mean, so be it.
Larry

tjdonahoe 08-29-2017 03:12 PM

Ground, neutral, hot 110, hot 110, the two hot lines are out of phase with each other, that is why're is only 110 volts.....

Wayne&Sam 08-29-2017 03:39 PM

Quote:

Originally Posted by lsbrodsky (Post 2001099)
. There are 1000's of threads available here

Add to that a less than ideal search engine and people can search and still have to ask. I know I have had many unsuccessful searches looking for a thread I had previously read.

There is a lot that is annoying on the internet. It's best just to ignore what annoys you.

rmkrum 08-29-2017 03:46 PM

Quote:

Originally Posted by tjdonahoe (Post 2001110)
Ground, neutral, hot 110, hot 110, the two hot lines are out of phase with each other, that is why're is only 110 volts.....

You will find that using a multimeter to measure voltage, that Hot to Neutral is in fact 110 volts, as you would expect....

Most homes and campgrounds are typically wired so hot to hot measurement will show 220 volts total. That's because the two hot leads are in-phase...

Pretty much USA electrical code bog standard, single-phase power wiring found in pretty much every home. Even my Mom's 1950's glass-fused El-cheapo house can deliver 220 volts for an electric stove across the two hot leads.

Industrial stuff uses three-phase wiring, and that's a whole different story..

For the 50-amp RV connection, unless the RV has 220 volt appliances in it (we're talking huge rigs) the wiring is designed to only deliver 110 volts to the appliance because it is wired Hot and Neutral plus safety earth (ground) to an outlet or appliance.

Not-Quite-A-Disclaimer: I'm not a practicing electrician, but I am a well-trained systems engineer that really does understand electrical power distribution systems, AC and RF grounding systems, and 480 volt three-phase power systems in large manufacturing plants... I made a 50+ year career out of knowing this stuff...(grin).

And I managed not to get killed by the dumb mistakes so-called expert electricians have made in my facilities...that I ended up having to diagnose and correct. A great example was swapping a three phase line and neutral in a power panel!

uncle_bob 08-29-2017 05:39 PM

Hi

How the trailer is wired depends a *lot* on which model it is. The "right" approach with a 50A feed is to balance the loads between the two hot legs. This gives you minimum current back down the neutral. Less current / less voltage drop is the more efficient way to do things.

Hooking 220V onto a line that should have 110V on it is indeed a really bad thing to do. A mis-wired socket on an pedestal could do this (neutral and hot interchanged or open neutral). That's why most of us invest in gizmos (EMS boxes) to check voltages and disconnect if it happens. My guess is that the guy at the store was trying to get you to spend the several hundred dollars that one of these boxes cost.

Bob

rmkrum 08-29-2017 05:44 PM

Not that buying an EMS and surge suppressor box is a bad idea...

Having seen what miswired power systems and voltage brownouts and surges can do to downstream hardware, its a darn fine idea.

There are several threads discussing opinions on hard-wired versus portable, etc., plus the usual gang of deniers that think EMS systems are not worth the money...personally, I'll spend a couple hundred bucks to avoid damaging several thousands worth of hardware and AS...

cazual6 08-29-2017 07:09 PM

Quote:

Originally Posted by rmkrum (Post 2000691)
Hey, in the interests of safety, I am fine with answering this question again and again...it's only a dumb question if it's not asked...

I concur

markdoane 08-29-2017 08:25 PM

Not only am I also fine with answering these questions, I can say pretty confidently that the specific question that was asked (about a 240v welding socket) has not been asked hundreds of times.

There have been lots of threads about 30a 120v receptacles. Plenty of threads about 50a 120v/240v receptacles.

But I don't recall anyone asking about a NEMA 6-50 (50a 240v) receptacle before now.

wahya 08-29-2017 08:58 PM

Quote:

Originally Posted by lsbrodsky (Post 2001099)
I have developed a pet peeve about people too lazy to spend the time to do a decent search of this forum or the internet. There are 1000's of threads available here with a wealth of information available to anyone willing to take the time. Moreover, there may be a depth of information not available from a few answers in a new thread.
What is the point of having all of the old threads available if they are not used by people seeking information? Maybe it is just a part of the instant gratification problem...just post your question, get an answer and get back to something else.
I have learned a lot from many individuals on this forum, people I have never met and will never meet. You do them a disservice if you just ignore what they have already answered.
If my post is viewed as mean, so be it.
Larry

I agree 1000 percent!!!!.

sandollars 08-29-2017 09:37 PM

Quote:

Originally Posted by lsbrodsky (Post 2001099)
I have developed a pet peeve about people too lazy to spend the time to do a decent search of this forum or the internet. There are 1000's of threads available here with a wealth of information available to anyone willing to take the time. Moreover, there may be a depth of information not available from a few answers in a new thread.
What is the point of having all of the old threads available if they are not used by people seeking information? Maybe it is just a part of the instant gratification problem...just post your question, get an answer and get back to something else.
I have learned a lot from many individuals on this forum, people I have never met and will never meet. You do them a disservice if you just ignore what they have already answered.
If my post is viewed as mean, so be it.
Larry

This isn't your thread so why are you bullying the OP? Just close it and move on if it bothers you. There are plenty of us who are reading along with the OP and are learning as people impart their wisdom even if it is sometimes a rehash. I simply do not see what the big deal is?


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