Can a wire gauge be too large?

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dibbons

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I know too small a wire can melt and even cause a fire under certain conditions, but I always wondered if there were a downside to using a bigger wire or a wire larger than necessary (besides a larger wire will cost more per foot). If a system only needs a 12 gauge wire, for example, what happens if I use a 10, 8, or even 6 gauge? Does the current flow increase, decrease, stay the same? Really curious and don't remember ever seeing this discussed before.
 
Can't hurt anything but your pocket book.

May pose routing issues.
 
I always heard it could hurt to use too large of a wire....maybe over load what ever you're running with the wire.
 
I'm an electrician...using larger wire will not hurt anything or cause any overload. The larger wire will cost more, the pathway or where it has to fit, and the physical size of the connecting means (ie. the size of terminal or clamp it has to fit in), will all be determining factors in just how big is too big. A larger guage wire will carry more current for any given distance than a smaller guage wire will. You should ALWAYS size the wire to the load it will carry. If not sure what size that is...find out, don't just guess. That's how an overload, overheating, and possible fire will happen.
 
I do know that you can have too big of a connector. Father-in-law changed out the blower motor on my wife's car, before we got married. Blower always ran slow. After we got married, I decided to unwrap the bundle of electrical tape he had on it(golf ball size) and see what was going on. He didn't have a solderless connector, so he pulled one off of his lineman work truck and used a large one used to connect overhead power lines! Changed it out and motor ran at regular speed after that. I guess it was a huge resistor.
 
I am far from being a electrician but I have increased the wire gage when rewiring
some cars that's harness was a mess from age, burns and previous splice ins. Mostly just to use up what wire I had available at the time. I jumped up a couple sizes with out any problems at all.
Built a new complete harness front to back using the schematic in the factory service manual.
Put a fresh battery in and a car that has been dead since the 70s all came to life. I cleaned a lot
of contacts and changed bulbs while I went thru the job.
If there is a down side to what I did it was all the wire was the same color due to me working with one roll. So trouble shooting will be more difficult now.
Of course the battery and starter cables were built larger and not from the same spool.
Did a e-body, 56 desoto, and a couple trucks like this. The wire was good quality belden
that was donated from a factory my uncle was employed at. Soldered all terminals.
If there is a reason not to do it this way it has never shown up for me.
 
If I was going to spend extra money on wire (and if you can I think that's a good idea), I would be more concerned with strand count, quality and durability of the insulation, making sure it's designed for automotive use. I don't know what the percentage above max expected current draw should be for selecting the gauge but that and length of run are also things to consider.
 
Bing "voltage drop and wire sizing"

Larger wire have less voltage drop as a smaller wire over the same distance. Look at the improvements my headlight relay kit has over the stock wiring in light output. It's a huge difference going from 16ga to 12 ga wire for the voltage at the light.
 
If I was going to spend extra money on wire (and if you can I think that's a good idea), I would be more concerned with strand count, quality and durability of the insulation, making sure it's designed for automotive use. I don't know what the percentage above max expected current draw should be for selecting the gauge but that and length of run are also things to consider.

X2 flexable fine strands with a quality jacket. Heat shrink rather than butt connectors.
I cut off all the plastic sleeves on the terminals, soldered and used heat shrink tube.
Problem free for over a decade now. Belden makes some quality wire. At least they did
20 years ago.
 
I always go one wire size bigger than stock when I redo circuits....
 
I do know that you can have too big of a connector. Father-in-law changed out the blower motor on my wife's car, before we got married. Blower always ran slow. After we got married, I decided to unwrap the bundle of electrical tape he had on it(golf ball size) and see what was going on. He didn't have a solderless connector, so he pulled one off of his lineman work truck and used a large one used to connect overhead power lines! Changed it out and motor ran at regular speed after that. I guess it was a huge resistor.

Must have been a bad connection...the physical size of a connector would not matter to the blower motor. All you did was fix a bad connection.
 
Don't forget to plan the wire routing and securing to keep from chafing on sharp edges or hot exhaust.
 
It will not change the current that flows, unless the prior wire was a significant restriction in the total path from BATT+ to GND. Besides costing more and taking space, it will add unneeded weight. I have no idea why some people chose to run 0 awg welding cable in their cars.
 
Why... voltage drop, same reason headlights work better on my relay kit and larger ga wire! watts = volts x amps

I guess I'm a knucklehead for running 2/0 battery cable to you, but, my high compression stuff starts without issue. I've been down the 2 and 1 gauge wire route and prefer the beastly heavy 2/0 cable.

Total weight difference between a 20 foot section of 2/0 and 1 ga... 4 pounds! 4.6 pounds to the 2 ga. No thank you. I'll deal with the weight penalty. :)

Pick your parts, pay your money.
 
Extension cords are prime examples of "do your homework" I have a Craftsman air compressor that has a 4 foot power plug, useless. So I haul out my 50 foot green cheepo extension cord and fire it up, well it sounded like a Volkswagon starting with a dead battery..wump-wump-wump-fzzzzz! Blew a 20A circuit breaker in my panel, garage went dark. Then I tried the heavier orange one I have. That worked decent but the compressor never did build pressure and the wire got physically hot. Nix on the extension cords!Maybe I should have read the manual? I then bought 20 feet of stiff 12/2 Romex and wired up a plug on one end and a plastic J-box on the other and installed a receptacle. Now that baby kicks over like it was plugged straight into the wall.
 
Extension cords are prime examples of "do your homework" I have a Craftsman air compressor that has a 4 foot power plug, useless. So I haul out my 50 foot green cheepo extension cord and fire it up, well it sounded like a Volkswagon starting with a dead battery..wump-wump-wump-fzzzzz! Blew a 20A circuit breaker in my panel, garage went dark. Then I tried the heavier orange one I have. That worked decent but the compressor never did build pressure and the wire got physically hot. Nix on the extension cords!Maybe I should have read the manual? I then bought 20 feet of stiff 12/2 Romex and wired up a plug on one end and a plastic J-box on the other and installed a receptacle. Now that baby kicks over like it was plugged straight into the wall.

DITTO ON THE 2 GAUGE battery cable, 4RTH CAR DONE W/ IT NOW, never a problem
 
Extension cords are prime examples of "do your homework" I have a Craftsman air compressor that has a 4 foot power plug, useless. So I haul out my 50 foot green cheepo extension cord and fire it up, well it sounded like a Volkswagon starting with a dead battery..wump-wump-wump-fzzzzz! Blew a 20A circuit breaker in my panel, garage went dark. Then I tried the heavier orange one I have. That worked decent but the compressor never did build pressure and the wire got physically hot. Nix on the extension cords!Maybe I should have read the manual? I then bought 20 feet of stiff 12/2 Romex and wired up a plug on one end and a plastic J-box on the other and installed a receptacle. Now that baby kicks over like it was plugged straight into the wall.

That's because you used the proper guage/length of wire. I'm sure the manual would have listed the appropriate guage of extension cord to use for a given length of cord. A good quality 12ga./20' extension cord capable of carrying 20A would have worked just as well. But those aren't cheap...so most people just use the 16ga. 50' ones they get at harbor freight and wonder what's wrong with my compressor or what ever they are trying to run :banghead:
Lots of lessons here...at least you corrected the problem with running the same wire you would have run in to extend a 20A circuit...so in essence it is plugged into a wall. All the information (voltage/amperage/) is printed on every motor or electrical device made today. If not sure what all those number mean...find out before you connect it.
 
I burned up a cheap electric leaf blower the first time I used it with a long, small gauge extension cord. At first I thought it was poor workmanship, now I wonder if the current was too weak to run it efficiently (something they should have taught us kids along the way).
 
I burned up a cheap electric leaf blower the first time I used it with a long, small gauge extension cord. At first I thought it was poor workmanship, now I wonder if the current was too weak to run it efficiently (something they should have taught us kids along the way).

It's a compound problem...too SMALL a wire guage will not carry the rated current and overheat the cord or connection (plug). Too LONG of a cord will cause voltage drop...(as voltage goes down-current (Amp) draw goes up)...if it's connected to a motor that causes the motor to over heat from the excess amp draw...if it's not thermally protected then it fries:eek:ops:

If it's too long and too small a guage...well...you get a quicker meltdown.
 
I am far from an electrical genius, but it was always explained to me much the same as water running through a pipe. A bigger pipe will flow more water, but lower the pressure. A smaller pipe will not flow as much, but flow at a higher pressure.

Lookin at it like that, a bigger wire will flow more current, but lower voltage. A smaller wire will flow less current with more voltage. whether that's right or not I don't know, but it sounds good. LOL
 
Volts stay the same, but the amp capability is higher.
Bigger wire does not use more volts. (actually the reverse is true but still depending on amps draw)

Take a 100 foot 14 gauge wire and connect 12 volt DC bulb to it and the voltage at the bulb will be much lower than with 100 feet of 10 gauge with 12v DC.

If there were zero amp draw, then both wires would have exactly the same voltage.
 
... it was always explained to me much the same as water running through a pipe. A bigger pipe will flow more water, but lower the pressure. A smaller pipe will not flow as much, but flow at a higher pressure.
Correct that water flow in a pipe is a good analogy. However, many people don't really understand how water flows in a pipe either. You can't always say "bigger pipe = more flow". It depends on the total system. A bigger pipe does have more capacity to flow, but other things may determine the flow. A classic question in beginning engineering classes is since wall friction restricts flow, wouldn't the fluid slow down and thus less flow out the end of the pipe? No, whatever you put in one end must come out the other (conservation of mass, in-compressible liquid).
 
I know too small a wire can melt and even cause a fire under certain conditions, but I always wondered if there were a downside to using a bigger wire or a wire larger than necessary (besides a larger wire will cost more per foot). If a system only needs a 12 gauge wire, for example, what happens if I use a 10, 8, or even 6 gauge? Does the current flow increase, decrease, stay the same? Really curious and don't remember ever seeing this discussed before.




that all depends,what are you talking about?upgrading a 12 wire to a 10 on a 20 amp circiut in a car ? where no distance is applicable?or are you talking about a distance of 200 feet?
 
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