Hypothetical question.

Let's say that I plan to install a ceiling fan/light in the future, but only have a light for now. Can I run 12/3 from the switch to the unit with white and black connected and the red simply taped off for now (to be connected in the future when I get a fan unit)? If not, what does need to be done by code?

Similar hypothetical;
Would have been really nice to have 12/3 for a project, but I only have 12/2. Can I just use the black of the second 12/2 and tape off the ends of the ground and white?

Thank you.

 

First off why 12? Is the circuit protected by a 20amp over current device? The first scenario would be fine assuming you have a feed in the switch box now, not sure what you are trying to accomplish with the second scenario.
Geo

 

Since he doesn't have any three wire cable he's asking if he can use 2) two wire cables instead.
You can but it gets confusing. You would connect the ground wires in both cables and cap off the spare conductors.

 

In the ceiling fan scenario, yes you can run 12-3 and cap off the red. I do this all the time. You should also make sure the ceiling box is fan rated and mounted according to the manufacturer instructions.

In the second scenario you can never leave a ground unconnected, but the others can be capped in some situations. More details would be important.

 

12-3 or 12-2 because that's what I have lying around.

Even if all switches and receptacles are grounded, I cannot have "spare" grounds loose?

In this hypothetical, I have;
Originally;
12-2 from breaker to kitchen receptacle.
12-2 from receptacle to further receptacles.

Replaced receptacle with a receptacle/switch to another receptacle, so now (hypothetically)
Original 12-2 from breaker wasn't long enough to work with in old receptacle box, so...
12-2 from breaker to new receptacle
12-2 pigtailed from that to old receptacle (outlet and switch)
12-2 from outlet to further outlets
12-2 (black only) from switch wire back to new outlet

To put it another way
Whites and grounds pigtailed for;
Breaker line
Feed between breaker and outlet/switch
New Outlet

Whites, Blacks, and grounds pigtailed or screwed at receptacle for outlet/switch.

Switch at outlet/switch is what allows Black to send power back up the the new receptacle.

 

That's correct, no spare grounds. All grounds are part of the grounding system.

In your second situation, no. The hot and neutral would have to run together in the same raceway (cable). Separating them can cause inductive heating due to the current imbalance.

 

I find it odd that even though everything is grounded, I cannot have loose (or clipped) "spare" grounds. But, I do believe in code.

Good thing this was only a hypothetical.

On an unrelated note, I'm going to Big Orange today anyway...

 

Well if it's a plastic box and there's no device (receptacle or switch) or other cable in the box, you can leave the ground hanging. If you have two cables and a switch, the ground wires need to be connected to each other and to the switch. If it's a metal box, the incoming ground wires must also be bonded to the box.