Any electricians out there?

I wired my barn to the house load center with 12-2 UF romax. Everything works, but any tool I use bogs down quickly when put under load. Examples are angle grinder (5 amp rating), miter saw (12 amp rating), sheep shears ( ?? rating).

I plan to start over and run either 8-2 or 10-2 out to the barn. Because of the 12-2 wiring in the barn I believe I'm still restricted to a 20 amp circuit which is ok with me. It's an animal barn. I don't plan to be doing any HD stuff out there. Do I need the 8-2 or 10-2?

With those in mind, I'd suggest burying a 2-1/2 or 3" PVC conduit, and pulling in 5 or 6 pull strings (poke a hole in a ping-pong ball, thread the string thru, use the shop-vac to suck it thru) for 'future expansion' (telephone, computer cable, cable TV coax) and run at least 2- #2's and a #4, and breaker it at 100 amps at the supply end; at the business end, put in a 12 or 16-space panel and you will be set for at least a year or so, then you can go back and pull in another pair of # 2's and set up a second panel if necessary.

use 100 amp breakers at the supply end, because 'odd' rated ones (120, 140, etc) cost a bunch more than 100's (economy of scale in manufacturing them, I guess).

My shop is 140 ft (conduit feet) from the service panel, I have 4-#2's and two # 4's in a 3"conduit, one set for the 'normal' stuff, the other for a 10 kW and a 6 kW electric furnace (no way I'm running pilot lights with the possibility of spilled gasoline) plus water heater. Total draw on the 'normal' circuit is about 60 amps with welder, compressor, hot tank for soaking transmission cases, and all lights on; the other one runs about 90 amps with both furnaces going full-bore and using hot water(Illinois Power loves my account!!)

I also buried 3-1" conduits at the same time for cable TV, phone, computer, and other cables, plus a 4" drain and a 2"pipe in which I ran a 3/4 inch water line (all the comforts of the house, in the shop, OR 'you clean yourself up out there before you come in the house !!!')

This may be 'overkill' for your requirements, but should give you some ideas.

• voltage drop calculater

The electrical code suggests shooting for a max voltage drop of 5%, or 6 volts on a 120 volt circuit. For a 15 amp load out in the barn, you need a max resistance of 6/15 or 0.4 ohm.

(Remember that it is the total load. So if you have the lights on to the tune of 3 or 5 amps then that subtracts from the 15 amps otherwise available.)

For a 500 foot total distance you need a resistance per foot less than .4 / 500 or .0008 ohms per foot. From tables readily available on the net (Do a yahoo search for "Copper wire resistance").

12 AWG wire is .00187 ohms per foot
10 AWG wire is .00118 ohms per foot
8 AWG wire is .000739 ohms per foot

By this calculation, 8 AWG wire would support a 15 amp total load with a 5% voltage drop.

Hopefully you are actually using 12-2 with ground, and providing a separate equipment ground.

A fully code compliant "animal barn" is also supposed to have special provisions for bonding and grounding, and sometimes dust and corrosion resistant wiring measures.

Caveat: I am not an electrician.