# What size junction box do I need?

I am running a long 20 amp circuit out to a stock watering tank from the barn. Given the length of the run (280 ft), I will need to use 4AWG. Midway, I will place a junction box and have an outlet pigtailed from the junction box as well as an outlet at the end of circuit.

What size and type of junction box should I have? The wire will run in buried plastic conduit and the junction box will be mounted outdoors. Both conduits will enter the box from the bottom (one conduit to barn, one to the end of the circuit at the stock tank).

• It looks like you did your voltage drop calculation correctly. The problem when you get to #4 wire is there is not a standard multiplier like with #6 wire. The box size depends on the size of your conduit at minimum you will need 1". You are going to do what is called an angle/ U pull Both conduits going out the bottom of the box. The minimum size is 6X the size of the conduit + the size of the 2nd conduit or 7" box minimum. This information can be found in NEC 314.28(2). – Ed Beal May 2 '16 at 19:45