Wire gauge on long run

[Darkbreeze]

So, I've got project I'm building and I've already determined that I need to use 10 gauge wire running to this 8.5 amp DC motor, since the run is 20ft long. The run pretty much HAS to be 20ft long. Any shorter and the project is defeated.

So I've configured two 10 AWG OFC power wire runs, one for power and one for ground, which takes care of the supply requirements. The question I have however is that AT the motor itself there is 14 or 16 gauge wire that runs into the motor. I've already removed the motor backplate to see if it was feasible to replace the existing wire from the factory by soldering the ends of my 10 gauge run in place of the existing wiring, but it's not. The way the wiring is configured inside the end cap of the motor there just isn't room for the larger diameter wire.

Will the short, maybe 6-8" of smaller diameter (14-16 gauge) at the motor cause me any major problems? I know the problem is created by resistance per foot when it comes to the bigger numerical gauge vs the larger, small gauge wire in the run, but I am casually concerned as to whether or not less than a foot of smaller gauge wire, that is however what it came from the factory with, is enough to create any problems?

Thanks.

 

[Marctrees]

Pretty safe to think the motor connection wires were chosen by the motor manufacturer, and would be appropriate.

Why are you thinking they are insufficient?

Also, I'm not understanding why you are using such a large conductor for that load, at only a 20' distance?

How did you decide on #10?

Marc

 

[Darkbreeze]

Well, the run is actually closer to 25ft, being just shy counting the length of the existing wire, my run and the length of the jumper style clamps I'm using to connect to the battery power source. Based on 8.5a continuous and a 10a inrush startup current, seemed appropriate based on the closest amperage rating here:

http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

 

[mike93lx]

You do not need to worry abouy changing the motor wiring. The 10 gauge will deliver the current with minimal voltage drop to the factory wiring, which is more than adequate for the task.

 

[Darkbreeze]

I figured that, but it's reassuring to get a second, or third, opinion anyhow. Thanks guys.

 

[EOC_Jason]

Yes, the wiring inside the motor is fine for that short distance even with the overall so long.

 

[mm08822]

Op, what "OFC" ?
At 8.5a with a 12volt dc source you would have 11.5v at the motor. The motor leads do add minimal loss, but attempting to change them may be very difficult and even destroy the motor trying to do so. Leave them alone.

All of your connection points in sum will probably add as much v loss as wire resistance. So do each of them properly.

 

[Darkbreeze]

Oxygen Free Copper. Supposedly. Yada yada yada. I don't want to have a discussion on the merits, or lack thereof, of oxygen free vs non. Doesn't really matter in this case anyhow.


At to the voltage source, it won't be 12v. It will be more like 14-14.6v because this motor will never be running unless the vehicle is running so it will be running off alternator voltage which is actually about 14.5v on this vehicle. Minus any drop in voltage of course.

 

[Bert_]

That short 6" of #16 wire will have almost no effect on the overall voltage drop.

By the way it would be helpful to tell us what voltage this motor operates on. Loosing several volts at 250VDC no big deal while loosing several volts at 12VDC is.

* OP must have been typing at the same time, so ignore the above question

 

[Darkbreeze]

Thanks Bert. And everyone.

 

[nsula_country]

Voltage drop on 12 VDC is very different than AC. Wire size goes up quick!

Also, with DC distance of run needs to be both conductors... At least I know this to be true with welding machines.

CT

 

[Darkbreeze]

Yes, both conductors are 10 gauge except for the last 8" or so at the pump motor. I'm actually thinking that at some point I might simply add a short run at the one off switch by the motor and use an AC to DC converter so I can make my long run using a large gauge extension cord and limit the use of the long DC run to situations where there is no AC power available.