The only electrical project I did not tackle myself was tapping into the main line and installing a new sub-panel for all the basement electrical runs. I would recommend a dedicated sub-panel in your basement for a few reasons, but we'll get into that in a bit.
When tapping an existing outlet box it will always be OK to extend the circuit from a box with fewer than the maximum wires running to it, as long as the total electrical draw from the other outlets in the circuit don't exceed the ampere rating.
How to add an electrical outlet to an existing line
I know plenty of you can relate to the struggle of not having any 220 volt A/C outlets in your garage space. Same here. The new place we just moved to has only one 220v outlet and it is dedicated to the water heater. This week I am adding in 2 outlets (or "plugs") to the garage. Here's a quick video on how the project went:
Attach the box to the wall and cover with the outlet plate. Repeat for each outlet needed. De-energize the whole electrical panel by shutting off the house’s main breaker. Install an arc volt breaker by attaching white and black wire to the breaker. Attach white wire from the new breaker directly onto the electrical panel’s neutral bar.
Adding an additional outlet to an existing outdoor junction box gives additional outlets for your outdoor power equipment or for lighting. Connecting electrical conduit from the existing outlet box, to a newly installed box, will have your electrical project complete in no time.