I have a few dumb questions about how 12v electric works in a trailer. I have read (and re-read several times) my book about RV wiring. If I understand correctly, neutral and ground are sort of redundant systems to make sure that the circuit is safe and there's no voltage difference in the event of a short, yes? So why are trailer lights wired with just positive and grounded to the frame with no neutral wire?
2nd question, how do I tell how many amps small single interior lights require? It's not on the packing material for the lights or on the manufacturer's website, so it must be an obtuse question that everyone knows the answer to (except me :-)). If I understand the chart about wiring gauge and distance the wire runs, I would have about 15 amps on 14g wire for 22'. My farthest away light is about 20' from the fuse panel - I am trying to decide if I should install 12g wire instead of 14g.
To clarify, I will have help hooking up and testing wiring my trailer, but I would like to understand the basics.
Posted 2005-07-12 6:55 PM (#27983 - in reply to #27980) Subject: RE: understanding trailer wiring
New User
Posts: 2
Location: the dakota's
This is not real technical, but basically the trailer IS the ground. The positive side is switched (blinker switch, 4 way switch, brake switch, clearance switch, etc.) to complete or 'close' the circut. That is why the lights 'ground' to the trailer frame or body. 14g should be sufficient for most trailer wiring.
Posted 2005-07-12 7:56 PM (#27985 - in reply to #27980) Subject: RE: understanding trailer wiring
Extreme Veteran
Posts: 378 Location: Nebraska
To figure the amps calulate it this way
AMPS= Watts / Volts
Watts being the size of your light
Volts being the voltage supplied
So if you have a 60 watt light bulb with 12 volts the wire is carring 5 amps. length shouldn't matter in a horse trailer. A 12 ga wire will carry 15 to 20 amps
Posted 2005-07-13 7:05 AM (#27988 - in reply to #27980) Subject: RE: understanding trailer wiring
Expert
Posts: 2958 Location: North Carolina
Originally written by NoSpam on 2005-07-12 5:32 PM
Hi,
I have a few dumb questions about how 12v electric works in a trailer. I have read (and re-read several times) my book about RV wiring. If I understand correctly, neutral and ground are sort of redundant systems to make sure that the circuit is safe and there's no voltage difference in the event of a short, yes? So why are trailer lights wired with just positive and grounded to the frame with no neutral wire?
12 volts is considered low voltage and is safe to touch with normal body resistance. It is my understanding that the neutral wire applies to electric power from the utilities. 115 Volts had enough "push" to kill. So the ground is supplied to provide a low resistance alternate path (Instead of through your body)in a fault condition.
Posted 2005-07-13 9:50 AM (#27996 - in reply to #27995) Subject: RE: understanding trailer wiring
Expert
Posts: 2958 Location: North Carolina
Originally written by NoSpam on 2005-07-13 8:26 AM
Interesting. Then is a neutral wire ever used for DC appliances, or are they all wired with just positive and ground?
I've never seen a 115 volt DC appliance. Some motors are rated 115 volt ac or dc. (like a blender) But if you're talking about 12 volt appliances like a coffee maker... yes.. I would think just a neg and pos.
understanding trailer wiring
