TrailManor Owner's Forum - View Single Post

**Bill** · 09-11-2002, 02:39 AM

Bill -

In choosing wire size, you have to consider two issues. One is safety - meaning you don't want the wires to overheat and burn up. The other is how much voltage drop you can put up with.

For AC house wiring, #12 wire is rated for 20 amps, #10 wire for 30 amps, and #8 for 40 amps. For all practical purposes, amps is amps, so these ratings are also good for 12 volt DC distribution, FROM THE POINT OF VIEW OF SAFETY.

On the other hand, a small voltage drop means a lot more in a low-voltage system than in a higher-voltage system. For example, if you draw enough current to cause a couple volts of drop in your wires, this doesn't mean much in a 120-volt household system (it drops 120 volts to 118 volts), but it means a lot in a 12-volt system (it drops 12 volts to 10 volts). For this reason, I would always go at least one size larger than the household standards suggest - 2 sizes larger if you can manage it.

So choose #8 or #6 wire for a 30 amp circuit - anything heavier gets pretty hard to handle. Note that 30 amps at 12 volts is only 360 watts. This is one of the arguments against inverters, BTW - you have to have very short runs of very heavy wire. Put your inverter near the battery, and get out your conduit bender to form the wire!

Hope this helps

Bill

09-11-2002, 02:39 AM	#14
Bill Site Team Join Date: Feb 2003 Location: The mountains of Scottsdale, AZ, and the beaches of Maine Posts: 10,109	Re: Replacement Refrigerator Bill - In choosing wire size, you have to consider two issues. One is safety - meaning you don't want the wires to overheat and burn up. The other is how much voltage drop you can put up with. For AC house wiring, #12 wire is rated for 20 amps, #10 wire for 30 amps, and #8 for 40 amps. For all practical purposes, amps is amps, so these ratings are also good for 12 volt DC distribution, FROM THE POINT OF VIEW OF SAFETY. On the other hand, a small voltage drop means a lot more in a low-voltage system than in a higher-voltage system. For example, if you draw enough current to cause a couple volts of drop in your wires, this doesn't mean much in a 120-volt household system (it drops 120 volts to 118 volts), but it means a lot in a 12-volt system (it drops 12 volts to 10 volts). For this reason, I would always go at least one size larger than the household standards suggest - 2 sizes larger if you can manage it. So choose #8 or #6 wire for a 30 amp circuit - anything heavier gets pretty hard to handle. Note that 30 amps at 12 volts is only 360 watts. This is one of the arguments against inverters, BTW - you have to have very short runs of very heavy wire. Put your inverter near the battery, and get out your conduit bender to form the wire! Hope this helps Bill