Reply
 
Thread Tools Search this Thread Display Modes
 
Old 08-08-2016, 02:09 PM   #29
3 Rivet Member
 
2015 28' Flying Cloud
Newtown , Pennsylvania
Join Date: Jan 2015
Posts: 105
Quote:
Originally Posted by cwf View Post
Bruce, to achieve 220/240 you use opposite phases "power legs" as we call them down in the swamp..

Here is a more professional but easy reading explanation.. I ignore the math...as it is not necessary for your question.

http://www.allaboutcircuits.com/text...power-systems/
A 50 amp RV socket is wired with a 220/240 branch. Each leg is 120 volts. You said not to wire it with 220 volts. Why not? That is my question.

Bruce
__________________

__________________
50 amp, Awning package
2015 Ram 2500 6.7 TD, Blue Ox 1000 lb.
4 Lifeline AGM, Trimetric 2020
PD9160 converter, Prosine 1800 inverter
2x eu2000i Propane
AstroBruce is offline   Reply With Quote
Old 08-08-2016, 02:19 PM   #30
Overland Adventurer
 
AtomicNo13's Avatar
 
1991 34' Excella
2009 34' Panamerica
Telluride , Colorado
Join Date: May 2012
Posts: 1,718
The way you get 220 is to omit the neutral and wire across l1 and l2. Otherwise its simply 2 110 volt legs sharing a heavier common neutral.
__________________

__________________
AtomicNo13 is offline   Reply With Quote
Old 08-08-2016, 03:40 PM   #31
Site Team
 
, Minnesota
Join Date: Aug 2003
Posts: 6,645
Images: 59
Quote:
Originally Posted by AtomicNo13 View Post
The way you get 220 is to omit the neutral and wire across l1 and l2. Otherwise its simply 2 110 volt legs sharing a heavier common neutral.
Why would it need a heavier neutral? You can use a neutral the same size as one of the hot legs.

The proper term for split phase power is 120/240 VAC, not 220/240.
__________________
markdoane is offline   Reply With Quote
Old 08-08-2016, 04:17 PM   #32
Rivet Master
 
TG Twinkie's Avatar
 
1974 Argosy 26
Morrill , Nebraska
Join Date: Nov 2009
Posts: 4,825
Images: 2
Blog Entries: 5
Because the neutral carries the accumulative current of both legs when used for 120 volt devices.
__________________
Knowledge: "A gift to be shared. A treasure to receive."
TG Twinkie is offline   Reply With Quote
Old 08-08-2016, 04:33 PM   #33
Rivet Master

 
2007 22' International CCD
Corona , California
Join Date: Jul 2013
Posts: 2,384
30 Amp or 50 Amp?

Uh, not quite.

The neutral carries the difference in current between the hot legs of a 220 circuit. If there is exactly zero current in one hot leg it's the worst case, and the full current is in the neutral. That's why NEC says it only needs to be the same size as the hot legs.

The phasing between the two hot leads is 180 degrees out. That's why this works.

This is why I was the go-to engineer on power distribution issues in our labs. Done this before, more than once. 50 amp connection is actually 220 volt with a neutral and safety ground (safety earth). That's why it's 4 wires. That's also why you need to be darn sure the neutral is properly connected. If it's not, serious issues ensue.

Lew? Amiright?


Sent from my pocket Internet using Airstream Forums
__________________
KE4GNK/AE
'The Silver HamShack' (2007 International 22FB CCD 75th Aniversary model)
Multiple Yaesu Radios inside and many antennae sprouting from roof, ProPride hitch
2012 shortbed crewcab 4x4 Toyota Taco TV with more antennae on it
rmkrum is offline   Reply With Quote
Old 08-08-2016, 05:26 PM   #34
Agent 86
 
J. Morgan's Avatar
 
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton , Arkansas
Join Date: Mar 2013
Posts: 4,364
Images: 11
You are right.


Gradiens super tenui glacie.
__________________
The fact that I am opinionated does not presuppose that I am wrong......

J. Morgan is offline   Reply With Quote
Old 08-08-2016, 05:28 PM   #35
Agent 86
 
J. Morgan's Avatar
 
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton , Arkansas
Join Date: Mar 2013
Posts: 4,364
Images: 11
But your answer wont be understood by all.

They will tend to misunderstand the 240v thing that really is not used as 240v.


Gradiens super tenui glacie.
__________________
The fact that I am opinionated does not presuppose that I am wrong......

J. Morgan is offline   Reply With Quote
Old 08-08-2016, 05:30 PM   #36
Rivet Master
 
TG Twinkie's Avatar
 
1974 Argosy 26
Morrill , Nebraska
Join Date: Nov 2009
Posts: 4,825
Images: 2
Blog Entries: 5
It's a matter of somatic's I guess.
Since we are talking about the 120 volt legs and not the 240 volt.
When you connect a 120 volt device to one hot leg the current flows between that hot leg and the neutral. Not the other hot leg. When you use a 30 amp adaptor you are using one hot leg and the neutral. If there is 20 amps required that 20 amps is read on both the hot leg and the neutral with an ammeter.
When you use both hot legs for individual 120 volt service they both use the same neutral as the return path. If both hot legs draw 20 amps each the neutral current will be higher than a single leg but not double because of the phase shift. Thus my use of the word accumulative.
__________________
Knowledge: "A gift to be shared. A treasure to receive."
TG Twinkie is offline   Reply With Quote
Old 08-08-2016, 05:34 PM   #37
Agent 86
 
J. Morgan's Avatar
 
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton , Arkansas
Join Date: Mar 2013
Posts: 4,364
Images: 11
30 Amp or 50 Amp?

Imagine that one leg is +120
The other leg is -120
The neutral is -0-

The trailer will make a single circuit out of the +120 and the 0

And another circuit out of the -120 and the zero.

And that is all.

There is a potential at the plug to make 240v by making a circuit out of the +120 and the -120 (=240), but the trailer does not use this.

This is pretty much how it all works, except the +120 and the -120 switch places sixty times a second.

(Technically the neutral is not Zero, but it will work as a zero for the illustration)

Gradiens super tenui glacie.
__________________
The fact that I am opinionated does not presuppose that I am wrong......

J. Morgan is offline   Reply With Quote
Old 08-08-2016, 05:44 PM   #38
Rivet Master

 
2007 22' International CCD
Corona , California
Join Date: Jul 2013
Posts: 2,384
Exactly.


Sent from my pocket Internet using Airstream Forums
__________________
KE4GNK/AE
'The Silver HamShack' (2007 International 22FB CCD 75th Aniversary model)
Multiple Yaesu Radios inside and many antennae sprouting from roof, ProPride hitch
2012 shortbed crewcab 4x4 Toyota Taco TV with more antennae on it
rmkrum is offline   Reply With Quote
Old 08-08-2016, 05:50 PM   #39
Rivet Master
 
Wingeezer's Avatar
 
2005 30' Classic
Burlington , Ontario
Join Date: Sep 2008
Posts: 2,458
I would get a price for both in order to decide. I don't think 50 amp RV outlet would cost a great amount more and would give more flexibility in case one day you move to a motorhome or a large fifth wheel trailer, or have friends with a motorhome / fifth wheel visiting you.

If you are pretty sure neither of these things will never happen, then just stick with 30!

As for your trailer, it should be have a 30amp breaker built in it and you shouldn't be doing anything to modify it to try to draw more I don't think.

You can however plug into your 50 amp circuit (if that is what you go for) with a 50-30 adapter and you will still have the protection of the trailer's 30 amp breaker.

Brian.
__________________
Brian & Connie Mitchell

2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.
Wingeezer is offline   Reply With Quote
Old 08-08-2016, 07:27 PM   #40
Rivet Master
Commercial Member
 
lewster's Avatar
 
Currently Looking...
Naples, FL , Hood River, OR
Join Date: Dec 2005
Posts: 7,130
Quote:
Originally Posted by rmkrum View Post
Uh, not quite.

The neutral carries the difference in current between the hot legs of a 220 circuit. If there is exactly zero current in one hot leg it's the worst case, and the full current is in the neutral. That's why NEC says it only needs to be the same size as the hot legs.

The phasing between the two hot leads is 180 degrees out. That's why this works.

This is why I was the go-to engineer on power distribution issues in our labs. Done this before, more than once. 50 amp connection is actually 220 volt with a neutral and safety ground (safety earth). That's why it's 4 wires. That's also why you need to be darn sure the neutral is properly connected. If it's not, serious issues ensue.

Lew? Amiright?


Sent from my pocket Internet using Airstream Forums

RIGHT-O!!!!!

But grid voltage is presently rated for 120/240 VAC in the US, but is rapidly approaching 125/250.

If you measure any grid-supplied outlet with a quality RMS digital volt meter, you will see over 120 VAC every time.

I now see 122-123VAC on a regular basis.

Higher voltage allows for more amps to be pumped thru the same wires with no issues.

Tricky, those power folks are!!



Lew Farber
__________________
Lew Farber...ABYC Certified Master Marine Electrician...RVIA Certified Master Tech ...AM Solar Authorized Installation Center...AIRSTREAM Solar & Electrical Specialist
lewster is offline   Reply With Quote
Old 08-08-2016, 08:29 PM   #41
Rivet Master

 
2007 22' International CCD
Corona , California
Join Date: Jul 2013
Posts: 2,384
30 Amp or 50 Amp?

I paid attention during the electrical power classes. AC and DC...

That knowledge is circa 1966-1967. Hasn't changed much.

Sent from my pocket Internet using Airstream Forums
__________________
KE4GNK/AE
'The Silver HamShack' (2007 International 22FB CCD 75th Aniversary model)
Multiple Yaesu Radios inside and many antennae sprouting from roof, ProPride hitch
2012 shortbed crewcab 4x4 Toyota Taco TV with more antennae on it
rmkrum is offline   Reply With Quote
Old 08-08-2016, 10:33 PM   #42
Rivet Master
 
TG Twinkie's Avatar
 
1974 Argosy 26
Morrill , Nebraska
Join Date: Nov 2009
Posts: 4,825
Images: 2
Blog Entries: 5
I misspoke in my comment above. Meant to type one leg as having a load of 10 amps and the other 20 amps. In this case the load is not balanced and the neutral carries the difference.
In a perfectly balanced system there would be no current flow on the neutral.
Unfortunately this is not the case when we look at an RV. Since most only use one hot leg and one neutral.
The reason the neutral wire doesn't have to be larger than either hot leg is it never has to handle more current than the maximum current of one leg.
Typically RV's that require a 4 wire 240 volt system are not wired to balance the load. They are wired so one can run 1 A/C unit and all other AC devices on 1 hot leg and 1 neutral. The second leg is used for the second A/C unit.
If this were not the case you could not use adaptors and have all systems working except for the second A/C unit.
__________________

__________________
Knowledge: "A gift to be shared. A treasure to receive."
TG Twinkie 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Service snafu $&!&& and which battery is which amirm Sprinter and B-van Forum 25 07-04-2016 09:19 PM
Magnum MMS1012 1000W Pure sine Wave Inverter w/50 Amp Charger & Remote exallen Airstream Classifieds 0 06-05-2016 03:25 PM
Goucho couch,original am/fm 8 track & lots of wood & aluminum from interior remodel gquailhunter Airstream Classifieds 0 09-19-2015 04:25 PM
Samsung tv goes on & off & on & etc jump Electronics & Connectivity 22 03-03-2015 06:01 PM


Virginia Campgrounds

Reviews provided by



Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 02:43 PM.


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.