I have an electrical outlet in my garage that I want to wire to a switch. Right inside my front door there is a 3 gang switch box/1 switch is not active and I am going to use it. Directly behind the switch box is my garage wall(Drywalled)If i want to run romex from the back of the switch box and through the drywall do i need to mount a junctionbox and enter through the back of the box and proceed to finish the run through flex conduit to the recepticle. It just seems odd to just run the romex through the drywall and straight into flex without a handybox or something.
Also, is it ok to run flex up the inside face of the suds and across and then vertically across the dbl top plates and back down to the receptical box. Instead of drilling holes through all the studs. I suspect so but I'm not sure.
If you are going to install flex 99.5% of the way, why not run the flex those few final inches and go into the box with the swtich? The only thing I can see that would keep you from doing that is if the switch box is plastic. But if you can, I would run the flex all the way.
Now, there's two types of flex I envision you using. One is flex that already has the wires in it (commonly called BX, AC or MC). If you are going to use that, you will need a junction box to convert from the romex to your flex.
The other type, FMC, or flexible metal conduit, does not have any wires in it. You would technically not need a box to convert from one wiring method to another, but romex is not going to be easy to pull into it if you are going any considerable length. And the longer the run and more bends you have, the more difficult it will be to pull the NM in.
If I were given the above choices, I would prefer:
1: MC (with wires already installed) continuious between the two points.
2. MC to a j-box behind the switches if the MC cannot be connected to the switch box. A little more money and time, but insignificant compared to doing it wrong and have problems later.
3. FMC and struggle all day pulling the NM in.
If you use FMC you can pull THHN a lot easier than NM (Romex).
Many 3-gang boxes have a knockout in the back. You could go staright out the back to an LB fitting to a conduit or EMT.
Since you are going to run on the surface in the garage, I would consider using 1/2" EMT with THHN. Most people with tools would bend the EMT at corners but you can buy fittings to do it without bending. If you use EMT you don't need a ground wire but the EMT must be grounded if you have plastic boxes.
In some jurisdictions you might be able to use 1/2" PVC conduit, which is a lot easier to install. The issue is whether the conduit is susceptible to damage.
I have seen a lot of installations where the rigid conduit is connected to a flex at the end to connect to a motor. The connection is made by using a straight flex-fitting to a terminal adapter on the conduit.
Thanks guys. The .5 % is because the switch box is plastic. What do you guys think, since the box is plastic>? if i route out 1/2 hole in the back of the box so that I could connect the flex with a connector(name?)would that be ok or should i stub out the flex in wall or run the flex(FMC) to a small junction box and knock out the rear k/o and just snap in a bushing to protect the romex and run it in to the switch box from there?