Reply
 
Thread Tools Search this Thread Display Modes
 
Old 03-21-2013, 11:53 AM   #1
Rivet Master
 
1973 25' Tradewind
Beautiful , Oregon
Join Date: Sep 2009
Posts: 548
Running Additional Circuits help keep me out of trouble.

Hi folks,

I am hoping to get some needed advice. I am hoping while I have the bathroom tour up and replacing univolt to also add a couple of AC circuits.

Is it as straight forward as I think it should be to add a couple of circuits to a 1973 Tradewind? It currently has a two 20 amp breaker box.

Is it just a matter of getting a four breaker box and changing out and then run the circuits? I want to run two additional 20 amp lines one for the microwave under the kitchen lower cabinet and another that would be used for an electric milk house type heater. The microwave will be dedicated.

My other question: What is the best way to run the circuits outside the walls. My plan is from breaker box around back of toilet and shower ( before put back together) and against wall above wheel well, which is under the twin bed, and into surface mounted box above water heater in the kitchen lower cabinet.

I suspect running #12 Romex exposed is not going to meet some kind of RV electric Code. Should I not use Romex and put in some kind of flex cable?

Anyway any help would be appreciated.

Tony

Rogue River, Oregon
__________________

__________________
Tony S is offline   Reply With Quote
Old 03-21-2013, 12:08 PM   #2
Rivet Master
 
1974 Argosy 20
2014 20' Flying Cloud
Kooskia , Idaho
Join Date: Jul 2009
Posts: 4,591
You might be able to swap the existing circuit breakers for half size ones, assuming that the originals are full size breakers. That would keep you from having to change out the entire box. Half size breakers are pretty common, although when heavily loaded for long time periods, like AC use they do have a tendency to heat up and trip out for no reason.

If I were adding the new circuits you propose, I probably would put them in some kind of flexible conduit to protect the wire from mechanical abrasion over time. Take a look at Home Depot or Lowe's at what is available. You may be able to run the two new circuits in the same conduit for most of your run, if they are going to the same area in the trailer, then use a J box to branch to your specific new locations.
__________________

__________________
idroba is offline   Reply With Quote
Old 03-21-2013, 02:37 PM   #3
2 Rivet Member
 
1973 27' Overlander
East Tawas , Michigan
Join Date: Jan 2012
Posts: 61
Tony don't forget that you are still only drawing 30 amps. You may have additional outlets for plugging things in but if the draw exceeds the service you will be popping breakers at the least. Try to time the use of heavy draw appliances.
__________________
baylito99 is offline   Reply With Quote
Old 03-21-2013, 04:35 PM   #4
Rivet Master
 
1973 25' Tradewind
Beautiful , Oregon
Join Date: Sep 2009
Posts: 548
Thanks for the replies.

Is it correct that I can't use romex in any kind of conduit by code?

Yes, I will have to watch the draw. I can't image going too crazy but the microwave and the coffee pot or electric heater is a combination I have been known to use simultaneously.

Tony
__________________
Tony S is offline   Reply With Quote
Old 03-21-2013, 04:57 PM   #5
3 Rivet Member
 
2006 25' Safari FB SE
Merkel , Texas
Join Date: Nov 2012
Posts: 139
By code romex, or NM cable, cannot be exposed. The suggestion by idroba is a good one. Home Depot or Lowes will have BX cable which is electrical conductors already installed in flexible metal conduit. It is available in different configurations but if you get 12-3 with ground you can take both circuits in the one raceway if they are going to the same general area. I think it would 3/8 conduit and would have red, black, white and bare conductors. Use the red for hot on one circuit, black for hot on the other, white as a common neutral and bare as a common ground for both circuits. That will work unless either is a GFI circuit as they cannot share a neutral. Hope this helps.
__________________
afneill is offline   Reply With Quote
Old 03-21-2013, 09:20 PM   #6
Rivet Master
 
1973 25' Tradewind
Beautiful , Oregon
Join Date: Sep 2009
Posts: 548
Afneill Thanks. If I may ask a follow up do you know what I should do if I am using a GFI Circuit. Being under the sink I suspect a GFI would be the way to go. I have some 20amps that no longer meet residential code here in Oregon because they are not tamper proof that I thought I would use.

Tony
__________________
Tony S is offline   Reply With Quote
Old 03-21-2013, 10:21 PM   #7
Rivet Master
 
1974 Argosy 20
2014 20' Flying Cloud
Kooskia , Idaho
Join Date: Jul 2009
Posts: 4,591
Quote:
Originally Posted by afneill View Post
By code romex, or NM cable, cannot be exposed. The suggestion by idroba is a good one. Home Depot or Lowes will have BX cable which is electrical conductors already installed in flexible metal conduit. It is available in different configurations but if you get 12-3 with ground you can take both circuits in the one raceway if they are going to the same general area. I think it would 3/8 conduit and would have red, black, white and bare conductors. Use the red for hot on one circuit, black for hot on the other, white as a common neutral and bare as a common ground for both circuits. That will work unless either is a GFI circuit as they cannot share a neutral. Hope this helps.
No, on a 120 volt only 30 amp input system such as is used in the Airstream, you cannot use a 3 wire system for two circuits. The reason for this is that the neutral could potentially be forced to take the return current from both circuits, totaling more than the 20 amps allowable (assuming you are using #12 wire). It works on a 120/240 volt home panel as in that case the neutral is taking only the difference current between the two hot legs, which can never be more than either hot line will carry. It gets a bit complex to explain simply, so I have to say "trust me" on this one.

I happened to be in West Marine today and they have boat NM cable which is made of stranded wire and very flexible. It is expensive, but might be another possible way to go. I still would put it in conduit.

I do not think I would use BX type cable either. The metal sheath has a tendency to rust and we do know that Airstreams get water in unusual places now and then....lol.
__________________
idroba is offline   Reply With Quote
Old 03-21-2013, 10:43 PM   #8
Rivet Master
 
TG Twinkie's Avatar
 
1974 Argosy 26
Morrill , Nebraska
Join Date: Nov 2009
Posts: 5,140
Images: 2
Blog Entries: 5
It is not legal to run Romex inside of conduit. It restricts the heat dissipation capabilities.
If you are going to use a conduit. Individual conductors such as THHN should be used.
__________________
Knowledge: "A gift to be shared. A treasure to receive."
TG Twinkie is offline   Reply With Quote
Old 03-21-2013, 11:54 PM   #9
Rivet Master
 
1974 Argosy 20
2014 20' Flying Cloud
Kooskia , Idaho
Join Date: Jul 2009
Posts: 4,591
Quote:
Originally Posted by TG Twinkie View Post
It is not legal to run Romex inside of conduit. It restricts the heat dissipation capabilities.
If you are going to use a conduit. Individual conductors such as THHN should be used.
Yea, I know that is true, but really silly as you can run Romex in a cavity of an insulated wall covered up with insulation, or in a ceiling. I think the physical protection is better than the possible heating issues. Not code, but realistic.

Yep THHN is the legal wire in conduit.
__________________
idroba is offline   Reply With Quote
Old 03-22-2013, 09:57 AM   #10
3 Rivet Member
 
2006 25' Safari FB SE
Merkel , Texas
Join Date: Nov 2012
Posts: 139
Unless there is a difference between residential code and RV electrical code, and there may well be, the explanation for why you cannot run two circuits as I described doesn't hold water. For years in residential construction circuits were run with 12/3 romex and split into separate circuits at the end away from the panel, with no differentiation as to whether both came from the same phase or not. It is not as commonly used since the advent of arc fault breakers being code required in bed rooms but still is done that way on some circuits, to save money. They use one neutral, one ground and two hots to make two circuits. Again, RV codes may differ.
__________________
afneill is offline   Reply With Quote
Old 03-22-2013, 10:06 AM   #11
3 Rivet Member
 
2006 25' Safari FB SE
Merkel , Texas
Join Date: Nov 2012
Posts: 139
As an addendum to my previous post, BX cable is available in aluminum conduit in addition to galvanized and may be even more commonly used. If you decide to use BX, just make sure you get aluminum BX if you are concerned about the possibility of it rusting.
If you are using this circuit in the kitchen area, residential code probably would require GFI protection on the circuit, most easily provided by using a GFI receptacle.
__________________
afneill is offline   Reply With Quote
Old 03-22-2013, 10:06 AM   #12
Rivet Master
 
TG Twinkie's Avatar
 
1974 Argosy 26
Morrill , Nebraska
Join Date: Nov 2009
Posts: 5,140
Images: 2
Blog Entries: 5
There are a lot of things in the CODE that don't make sense. To me anyway.
There are plenty of places in the trailers that one could route Romex where it would not get damaged. For example: In my trailer, there are storage areas under the twin beds. The bottom of the storage compartment is 5" above the floor, leaving a dead (wasted) space that I use when I want to run and extra AC or DC circuit. It makes a good wire trough.
If one takes a close look, I think you will find this to be the case. Where there is a space behind or below the cabinetry etc that could function as a wire way.
If one is concerned about damage occurring. You could use the direct burial type of Romex. It has a really tough outer cover that would stand up to anything inside a coach.
__________________
Knowledge: "A gift to be shared. A treasure to receive."
TG Twinkie is offline   Reply With Quote
Old 03-22-2013, 10:17 AM   #13
3 Rivet Member
 
2006 25' Safari FB SE
Merkel , Texas
Join Date: Nov 2012
Posts: 139
I think the area you are describing probably would qualify as the romex not being exposed. All the code is trying to do is protect it from physical damage by being exposed to that possibility. I think what all of us want, including the code committee, is a safe installation that will not cause danger or damage.
__________________
afneill is offline   Reply With Quote
Old 03-22-2013, 12:43 PM   #14
Rivet Master
 
1974 Argosy 20
2014 20' Flying Cloud
Kooskia , Idaho
Join Date: Jul 2009
Posts: 4,591
Quote:
Originally Posted by afneill View Post
Unless there is a difference between residential code and RV electrical code, and there may well be, the explanation for why you cannot run two circuits as I described doesn't hold water. For years in residential construction circuits were run with 12/3 romex and split into separate circuits at the end away from the panel, with no differentiation as to whether both came from the same phase or not. It is not as commonly used since the advent of arc fault breakers being code required in bed rooms but still is done that way on some circuits, to save money. They use one neutral, one ground and two hots to make two circuits. Again, RV codes may differ.
It is not a code issue of RV vs residential, it is an issue of how much current can travel through the neutral wire on a 3 wire circuit. The only way that the residential 3 wire two circuit system was code legally wired was if each circuit came from different legs of the panel (not phases, the household system is all a single phase system with a two leg center taped transformer secondary provided by the power company).

A 30 amp 120 volt RV outlet is connected between one leg of the center taped system and the neutral.

Inside the RV, the hot wires are all connected to the incoming hot line (30 amp max) via circuit breakers and the neutral wires are all connected to the neutral bar and neutral in the incoming cord. Those incoming wires are #10 with a 30 amp capacity.

Now for simplicity sake, lets say you had two 15 amp circuits running through two 15 amp breakers leading to a 3 wire #14 line to your loads. Lets further assume that both 15 amp circuits were fully loaded, that is 15 amps is being drawn from each one. The circuit breakers would each supply 15 amps, loading the panel up to the 30 amp capacity of the incoming line, but all would be well there. However the entire load of 15 amps + 15 amps would have to go back through the neutral line, which in this case would be 30 amps running through a #14 wire, overloading it by double it's capacity. Once back to the panel, the 30 amp #10 neutral supplying the trailer would take the load fine. But the poor #14 neutral line in the 3 wire circuit would not.

In a household 120/240 volt panel, with the two 15 amp circuits connected to different legs of the panel, the two 15 amp 120 volt loads look like a single 15 amp 240 volt load to the system, and there would be 0 amps in the neutral line of the 3 wire system.

So, if both hot lines are connected to the same leg as in all 30 amp RV systems, the neutral in a double circuit 3 wire setup takes the sum of the currents in the two circuits. In a properly wired 120/240 volt two leg plus neutral system such as a house, the neutral only takes the difference current between the circuits. Lets say one has a 10 amp load the other a 15 amp load, the neutral would take 5 amps, the difference, not the sum of 25 amps.

Any code inspector seeing a 3 wire household system would check to be sure the installer had the circuits on different legs or it would not be approved or code legal, now or in the past.

Also as mentioned the GFIC's and Arc Fault systems have made the use of 3 wire two circuits pretty rare in today's household wiring, so the problem of double neutral current is little understood.
__________________

__________________
idroba 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 01:15 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.