Small back story:
This is a Philly row home, so the long wall are solid brick. original outlets were non-existant or embedded in baseboards. While most of the home is being wired with romex, I am chiseling out boxes and conduit paths for switches and boxes which need to be in these walls. I have much less experience with conduit.
One of these is a three gang box, with 1 1/2" piece of conduit extending through the floor to the basement and a second to interstitial space between floors. My concern is not overloading the conduit. My supplier couldn't get three gangs with 3/4" so it was the best I could do.
The three circuits are two lights and a 3-way switch. They are on the same leg coming from the floor. So far I have been running grounds in the conduit. I'm pretty sure I do not have to but I was just being cautious. With this setup, I would have 10 wires (14 ga) going through a piece of 1/2 If I didn't omit the grounding wires.
What is the best way to do this? Can I just bond everything to the boxes in the floor and ceiling and omit the grounds?
Best Answer
Yes, you can omit the ground as (properly assembled) steel conduit is an acceptable ground path (bonded in at both ends, as you stated.)
Given that the max fill for #14 in 1/2 EMT is 12 wires, you also need to.
You may also be able to reduce wire count (same circuit, so you only need one neutral wire - which will not be how you think "naturally" if used to running NM-B.)