Reply
 
Thread Tools Search this Thread Display Modes
 
Old 05-04-2013, 05:16 AM   #1
Rivet Master
 
VeggieBullet's Avatar
 
1973 31' Sovereign
2007 20' Safari SE
Vintage Kin Owner
Wesley Chapel , Florida
Join Date: Oct 2011
Posts: 879
Can a 30AMP 240v provide 2 30AMP 120v??

Hi guys, looking for some enlightenment from the electrician here in the forums.
just wondering is based on the same concept that:
1) 50AMP 240v provides 12000W (50A x 240 V) We see very often the Y adapters for 2 30Amp 120V
2) Can a 30Amp 240 that provides 7200W (30A x 240V) be used to split 2 30Amp 120V??
According to our obvious limited knowledge in the electrical field isn't the same principle?
thanks for your time!!
__________________

__________________
Still One Nation under GOD
2 chronicles 7:14
VeggieBullet is offline   Reply With Quote
Old 05-04-2013, 07:31 AM   #2
2 Rivet Member
 
1984 31' Sovereign
Currently Looking...
charleton , Illinois
Join Date: Mar 2010
Posts: 42
Images: 3
Not sure where your going with this but I'll try.
Campers use a 120V / 30 amp hook up OR a 240V / 50 amp.
Have never seen a 240V / 30 amp at a campground, or
a camper wired for 240V / 30 amp.
All 240V systems are two 120V legs to a common "neutral" regardless of amperage.
The adapters that allow a 240V / 50 amp camper to use a 120V / 30 amp outlet has an internal jumper wire that ties both 120V legs together. This allows all the 120V circuits to be powered in the camper, but too much demand will overload the 120V / 30 amp supply and trip the circuit breaker.
__________________

__________________
jerry d is offline   Reply With Quote
Old 05-04-2013, 07:48 AM   #3
Site Team
 
, Minnesota
Join Date: Aug 2003
Posts: 6,940
Images: 59
Many generators have 30a 240v outlets. If you want to run two separate trailers from a single generator, make sure ther is only one N-G connection and you have a good ground at the generator.
__________________
markdoane is offline   Reply With Quote
Old 05-04-2013, 08:10 AM   #4
Rivet Master
 
1981 31' Excella II
New Market , Alabama
Join Date: Sep 2011
Posts: 5,648
I think you can get two 120V 30A connections out of a 30A 220V connection but I am having trouble with the current in the neutral. I would think that two 120V connections would draw 60A through the neutral but I think it is probably 30A. I am having trouble with this. When you are running 220V nothing is going through the neutral. You definately need to make sure the nuetral feeding the recepticle is the same gage as the two hots. Which should be #10. So you would need 10/3 and preferably an independent ground. I run my trailer off a stove outlet in my dad's utility shed by pulling one leg off that. But if you ran two trailers one off each leg, I am worried about running too much current through the neutral.

I know that the feed coming into a house has 3 conductors of the same gage.

Perry
__________________
perryg114 is offline   Reply With Quote
Old 05-04-2013, 09:10 AM   #5
Rivet Master
 
1974 Argosy 20
2014 20' Flying Cloud
Kooskia , Idaho
Join Date: Jul 2009
Posts: 4,591
No, you cannot use a normal 30 amp 120 volt RV cord to supply two 30 amp circuits. There are only 3 wires in the cord. One is the hot leg, one the neutral and the third is the ground.

In a 50 amp cord there are 4 wires. Two hot legs, one neutral and one ground. When wired properly the neutral only takes the difference current between the two legs, not the sum current as in effect the two hot legs are the outside of a center taped transformer and the neutral is the center conneciton. If incorrectly wired, the two legs are connected to the same half of the transformer and the neutral then would have to take the sum of the currents (60 amps) and if the same size, would overheat.

But, in short, the RV cord cannot be used for two 30 amp 120 volt circuits.
__________________
idroba is offline   Reply With Quote
Old 05-04-2013, 09:17 AM   #6
Rivet Master
 
1981 31' Excella II
New Market , Alabama
Join Date: Sep 2011
Posts: 5,648
That is what I was worried about. So to do it right you would need a nuetral that would handle 60A not 30A?

Perry
__________________
perryg114 is offline   Reply With Quote
Old 05-04-2013, 09:22 AM   #7
Rivet Master
 
1974 Argosy 20
2014 20' Flying Cloud
Kooskia , Idaho
Join Date: Jul 2009
Posts: 4,591
Quote:
Originally Posted by perryg114 View Post
That is what I was worried about. So to do it right you would need a nuetral that would handle 60A not 30A?

Perry
Yes, if both hot lines were connected to the same half of the transformer wired to the power supply.

The real point is that you don't have enough wires in a normal 30 amp RV cord.
__________________
idroba is offline   Reply With Quote
Old 05-04-2013, 09:56 AM   #8
Rivet Master
 
1981 31' Excella II
New Market , Alabama
Join Date: Sep 2011
Posts: 5,648
When I had the back off my trailer I put in a 10/4 pigtail going to a 4 pole twist lock with the hopes of upgrading to a dual 30A system running off a 50A RV recepticle.

Perry
__________________
perryg114 is offline   Reply With Quote
Old 05-04-2013, 10:23 AM   #9
Rivet Master

 
Southwestern , Ohio
Join Date: Nov 2006
Posts: 1,669
Quote:
Originally Posted by perryg114 View Post
I think you can get two 120V 30A connections out of a 30A 220V connection but I am having trouble with the current in the neutral. I would think that two 120V connections would draw 60A through the neutral but I think it is probably 30A. I am having trouble with this.
The two hot pins of a 240 V, 30 A outlet (for example a welder outlet) are 180 degrees out of phase, so if you connect two 120 V loads to the outlet the current flowing in the neutral is the difference between the two 120 V load currents.

That's why the neutral line coming into your house is the same size as the two hot lines. The most current the neutral ever sees is equal to the current flowing in one of the hot lines when there is no load on the other side.

So in answer to the original poster's question, there is no reason you couldn't fan out a 240 V, 30 A outlet to two 120 V, 30 A RV outlets, as long as the 240 V, 30 A outlet has a neutral line (a 4 prong outlet). Not all 240V outlets do.
.
__________________
Nuvite-F is offline   Reply With Quote
Old 05-04-2013, 12:05 PM   #10
Rivet Master
 
1981 31' Excella II
New Market , Alabama
Join Date: Sep 2011
Posts: 5,648
I thought there was something I was missing. It has been 25 years or so since I took Circuits 1.

Perry
__________________
perryg114 is offline   Reply With Quote
Old 05-28-2013, 06:20 AM   #11
Rivet Master
 
VeggieBullet's Avatar
 
1973 31' Sovereign
2007 20' Safari SE
Vintage Kin Owner
Wesley Chapel , Florida
Join Date: Oct 2011
Posts: 879
thanks for all the replies, as always Airforums is a great community!!
Well the whole issue here is that we have a generator cord rated 30AMP 240 (4prongs) and we were wondering if we can use that cable & install a 30Amp 240V Outlet to have 2 trailer plugged with full 30Amp.
I see that there is still a split decision whether "yes" and "no".
We are planning on installing a 50AMP 240 and have the "Y" adapter to 2 30Amps 120V but since we have the generator cord that could save us a ton of funds that can be very useful for some aluminum...
__________________
Still One Nation under GOD
2 chronicles 7:14
VeggieBullet is offline   Reply With Quote
Old 05-28-2013, 07:15 AM   #12
Rivet Master
 
SteveH's Avatar
 
2005 39' Land Yacht 390 XL 396
Common Sense , Texas
Join Date: Sep 2007
Posts: 5,311
Quote:
Originally Posted by Nuvite-F View Post
The two hot pins of a 240 V, 30 A outlet (for example a welder outlet) are 180 degrees out of phase, so if you connect two 120 V loads to the outlet the current flowing in the neutral is the difference between the two 120 V load currents.

That's why the neutral line coming into your house is the same size as the two hot lines. The most current the neutral ever sees is equal to the current flowing in one of the hot lines when there is no load on the other side.

So in answer to the original poster's question, there is no reason you couldn't fan out a 240 V, 30 A outlet to two 120 V, 30 A RV outlets, as long as the 240 V, 30 A outlet has a neutral line (a 4 prong outlet). Not all 240V outlets do.
.
Nuvite-F has it correct.
__________________
Regards,
Steve
SteveH is offline   Reply With Quote
Old 05-28-2013, 08:35 AM   #13
4 Rivet Member
 
2008 16' Safari
Destrehan , Louisiana
Join Date: May 2009
Posts: 395
You should have an electrician check the wiring of you 240/50 amp circuit.
Not all 240 circuits were provided with a neutal line that was large enough to carry the 120 neutral. What you need is a 4 wire circuit. Two 120 hot leads, one neutral and one ground circuit.
A 50 amp circuit would be a 8 AWG wire. You need at least a 8 AWG neutral and a ground wire (usually green or bare wire).
Some 240 vac circuits only provide two hot leads and a ground. This would not be suitable to split for two 120 vac circuits.
Have it checked out.
And,yes, I am an industrial electrician.
__________________
dlb435 is offline   Reply With Quote
Old 05-28-2013, 08:46 AM   #14
Rivet Master
 
dznf0g's Avatar

 
2007 30' Classic
Oswego , Illinois
Join Date: Jul 2010
Posts: 9,407
Images: 5
So, I have a 4 prong 240V outlet for an electric stove (unused, I have gas) right on the other side of the garage wall. What do I do to convert it to a 30 amp, 120V RV outlet if I moved it through the wall?
__________________

__________________
-Rich-

"If the women don't find you handsome, they should at least find you handy." - Red Green
dznf0g is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 05:18 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.