I have a generator that has two 15A circuit breakers on it. I mainly use it for a welder / compressor for air tools. The welder works fine, but the compressor is rated at 15A, but when it starts up, it draws a bit too much and pops the circuit breaker. So I made this little "adapter" to handle the extra current at start-up.
Be warned if you make this though: If you plug one cord in, and not the other the other cord is electrified, and is therefore extremely dangerous. I suggest if you use it, you hold both plugs in your hands before plugging them in.
Another note: If you use this as a "redundant" plug and the first circuit is shorted, the second one will short along with the first. It would only be good for power failures on one circuit.
Tools and materials you will need:
Step 1: Prepare the conduit box/platic fitting
2. Cut the conduit to the correct length.
3. Glue all the pieces together in the design you want
4. Wait for them to dry for the next step
Step 2: Prepare the electrical components
2. Strip the sheathing away from the inside wires
3. Strip and twist the inside wires
4. Thread both cords into the compression fittings and into the conduit box
5. Twist all like colors together (it is usually a god ides to get the exact same manufacturer / style of extension cords, as some may use different colors)
6. To make this step very easy, plug one of the cords into the outlet that is going in the box, (make sure the other plug isn't touching anything conductive), and use a multimeter to match the wires to the screw then attach. (You may want to take this time to make sure that the wires aren't conductive to each other as well)
Step 3: Final assembly
2. Tighten the compression fittings around the cords (make sure to give some slack inside the box, but not too much)
3. Add the faceplate / markings that you want
In this instructable, I used two 13A cords and a 20A outlet, dues to monetary limitations and of not being able to find a higher amp outlet. This should be well above the current requirements for my compressor, but don't go trying to pull 30A out of this thing unless you have capable hardware to do it.