Difference between commercial and automotive wiring?

[farm boy00]

I will be planning on running one, maybe 2 led lights on 12ga wire (what I have for free)
12 ga wire rating is 20 Amps.
From what I know- watts ÷ volts = amps
If I use 2 led lights which are 27watts at 12v.

Watts = w
Volts = v
Amps = a
27w × 2 = 54w
54w ÷ 12v = 4.5a

4.5 amps is way under actual wire rating.

 

[farm boy00]

It’s hard to connect a big wire to a little light wire especially if it’s solid conductor but besides that I don’t see a problem.

Sorry didn't see your post while replying. I was either going to use a butt connector or spade connector.
Spade connector would allow different wire sizes to connect.

 

[jaxs]

" I'm not worried too badly about flexability because this is bent hard in electrical boxes all the time and used in flexable tubing for line sets to rooftop units. "
That's not the type flexibility automotive wire require's. The ability to bend,straighten,bend,straighten,bend repeatedly without breaking insulation or conductor is flex I'm referring to. Repeatedly bend a THHN and automotive wire of same guage and THHN will break long before automotive. 10k viberations can equal 1 hundred sharp back and forth bends when it come's to work hardening and fracturing. This is turning into a debate,your question has been answered.

 

[wagne223]

In a building normally solid wire is used, the assumption is that once it's placed it will never move. In a vehicle normally stranded wire is used, the assumption is it will be subject to vibration and flexing. Solid wire will crack if it is repeatedly flexed.

Vehicles are typically 12 volts, buildings are typically 120 volts or more (in the US). Power is volts times current, so to transmit the same power vehicle wiring has to carry ten times as much current. On 120 volt household wiring a 500 watt light needs 4 amps of current, which can easily be carried by an 18 gauge lamp cord. The same 500 watt light on 12 volts needs 40 amps of current, which would require an 8 gauge wire.

This is a great explanation!

To bad to OP is rebutting everyone's answer and opinion. Not sure why people ask a question, then when they receive well thought out opinions along with facts, they choose to debate.

 

[Birdhunter1]

I have used THHN wire alot in trucks and tractors, if I have to buy wire for a truck or tractor wiring project I will typically buy extension cord wire and use that. It gives me three conductors that are flexible that are insulated with a protective jacket. It has held up well on my tractor and in pickup trucks.

On your Ranger I would run the 12 gauge for your lights and go get some 18 gauge thermostat wire to run to switches in the cab to relays under the hood. There is plenty of room for your relays under there, I put the relay box on my last one near the brake booster. The reason I said 18 gauge thermostat wire, you can get it in 2, 4, 5 or 8 conductors in the outer jacket, control wiring uses practically no amperage and its thin and flexible enough to go into alot of places.

 

[wagne223]

Or you can get 100 ft of actual automotive wire that has the correct size strands for 12 volt applications for $13

14 GAUGE WIRE RED & BLACK POWER GROUND 50 FT EACH PRIMARY STRANDED COPPER CLAD 14 GAUGE WIRE RED & BLACK POWER GROUND 5 FT EACH PRIMARY STRANDED COPPER CLAD - - Amazon.com

 

[oosik]

I can tell you of the VERY DEFINITE difference in wiring between brands of Ham Radio Transceivers. I have two - one is a Collins, the other is a Kenwood. Both are considered - top of the line in the Ham Radio field.

The Kenwood has normal exposed wiring and standard push/click connections. The Collins has EVERY SINGLE WIRE in the entire transceiver run inside a braided stainless steel outer shielding. Every connection is a screw type connection.

Collins is considered to meet military specifications in the configuration. This configuration reduces spurious transmissions and makes the entire unit almost totally rodent proof.

This configuration, of the Collins, makes it very expensive.

 

[Coolerman]

As a side job, I build wiring harnesses for old Toyota FJ40 Land Cruisers. A lot of research went into figuring out what wire to use.
Besides the obvious things like wire gauges, number of strands, strand gauges, and tinned copper (marine wire) the next big thing is what coats or protects the wire. Early automotive wire used a type of coating called GPT for General Purpose Thermoplastic. Worked well, but was very sensitive to heat (would melt), and over time, get hard and brittle. To address that issue modern automotive wires are almost without exception cross link polyethylene (XLPE). This wire will withstand high heat and is immune to gas and oil. In addition it is a very flexible coating even at low temps. This wire comes in types labeled SXL, GXL and TXL. SXL has a thick coating, GXL a medium coating and TXL a thin coating. Depending on what you are wiring, you first determine the gauge wire needed, then choose the type of coating. For example a starter wire might need to be 2ga, but because of movement of the motor, you would want to use GXL coated wire to make it more flexible.

On a tractor I would not use any type of building wire unless you can absolutely prevent it from moving due to vibration or motion. Due to its stiffness, it will fatigue and break MUCH faster than say GXL wire in the same application.

Someone also mentioned it will be more difficult to join the bigger wire to the smaller wire. You can buy reducer crimp on butt connectors (something else I don't recommend on anything that moves) but the best way to join two wires permanently is to solder and heat shrink with glue lined heat shrink. For wires that must sometimes be unplugged like lights. I always use the Weather Pak, Metri-Pak or equivalent connectors. Totally water proof and can carry large amount of current. They do require a "special" set of crimpers that can crimp the wire and the seal. The better ones both at the same time.

 

[farm boy00]

I have used THHN wire alot in trucks and tractors, if I have to buy wire for a truck or tractor wiring project I will typically buy extension cord wire and use that. It gives me three conductors that are flexible that are insulated with a protective jacket. It has held up well on my tractor and in pickup trucks.

On your Ranger I would run the 12 gauge for your lights and go get some 18 gauge thermostat wire to run to switches in the cab to relays under the hood. There is plenty of room for your relays under there, I put the relay box on my last one near the brake booster. The reason I said 18 gauge thermostat wire, you can get it in 2, 4, 5 or 8 conductors in the outer jacket, control wiring uses practically no amperage and its thin and flexible enough to go into alot of places.

So if THHN wire is bad to use why would you recommend something like thermostat wire? It is a solid wire that is easy to break which almost everyone says is bad to use.

 

[farm boy00]

This is a great explanation!

To bad to OP is rebutting everyone's answer and opinion. Not sure why people ask a question, then when they receive well thought out opinions along with facts, they choose to debate.

I thought this forum was for asking questions and trying to figure out answers and gaining knowledge but I guess I must be wrong on that.