What is common practice or code when running new electrical lines in a home(15 amp/20 amp) in a basement that feed up to the 1st and 2nd floor of a home?
Is there a rule on how many wires can be run down the same floor joist overhead? In other words, If I need to run 10 new 15amp/20amp lines, can they bunched together and secured to the floor joist overhead safely, or is there a rule on how many cables can be together? And what is the rule if these wires need to cross a metal gas line?
Best Answer
Bunching together is a serious issue. For instance, in EMT conduit, you are allowed only 9 active conductors regardless of pipe size, unless you derate (use larger wire than normal). That means four circuits, or three 3-phase circuits. I notice the multi-cable racks only hold 4 cables.
The reason is heat, and you have to design for worst case, you can't armwave it with "it's residential, they'll never all be used at capacity at once." At least it isn't for you to armwave; Code decides which corners may be cut based on a lot of research and experience. Even then, Code is a bare minimum- common sense also applies. I wish a Code expert would speak up.