My Service Panel is a Murray 200amp. House is in California.

There is one regular 20 amp breaker in it that is connected to a 12g line that travels through a 1/2" EMT pipe to a junction box in my Laundry room ceiling.

There the line terminates with a wire nut. It is not used for anything and is just sitting there in the Junction box for potential future use. In the Panel I labeled it "Spare."
I also put a label on the Junction box cover saying "spare wire to breaker #12"

Does the NEC 2011/2008 code allow me to keep the Spare breaker and line installed for use in the future as long as I keep it off? Plus as noted - the line is capped off in the junction box where it terminates.

thanks

One problem with the old Murray panels is that MECHANICALLY all kinds of non-Murray breakers "fit" easily--e.g. all type "BR" CBs from Bryant, GE, Siemens, etc.--but very few are UL LISTED for such. You sound like a very meticulous person, so check for "alien" breakers in your Murray panel.

The Murray panels I have experience with are early 1960s models, with ALUMINUM buss bars, making correct LISTED CBs all the more important. With correct breakers, they seem to be fine panels, with no flagrant safety issues.

history:
The Murray 200Amp panel is only about 1.5 years old. And all the breakers in it are less than 2 years old. The Panel is an upgrade from a 100amp Murray (which itself was only maybe 3 years old but the 100amp was too tiny for our needs). A new Kitchen remodel by itself needs 9 circuits if you include Island, GD, DW, Range, hood, fridge., etc...

I'm pretty sure they are all Murray breakers as you are only allowed by code to use same brand breakers in a Panel. And this 200 amp panel got the Rough-in green light to be activated. Inspector came out - looked at panel without cover on, and put Green sticker on it. At that time though - nothing needs to be labeled really.

Now that I went to label the whole box - I found this one dead end breaker. The orig. electrician who did the panel moved out of state. And I am doing the finish up work which is not much - labeling, putting in outlets, switches, cover plates, etc... But I want to get everything perfect before final inspection.

I believe we are still on NEC 2008 (slightly modified) in California with the addition that we must use CO2 smoke detectors in certain areas and the Title 24 Energy stuff we have to follow for lights/dimmers/CFL use. But otherwise it is pretty much 2008 NEC.

So basically it is one leftover unused Black 12g wire that is connected to a 20amp circuit breaker in the Main Panel, and then goes all the way to a junction box in the laundry room ceiling where is is terminated with a wire nut and hidden away.

Am I allowed to leave this or do I have to pull the black wire out of the Main Panel. I believe by NEC code I can leave the spare 20amp circuit breaker and label is Spare - but can I leave the wire attached to the breaker?

Thanks

The far end of a dead wire is not as much of an issue.
If thee is no voltage available in the box (no other circuits) on the end a bare wire would be just fine.

Turns out it is awesome we have this extra line in the EMT conduit because we can use it to pull in a new 12g white and black line for the outlets. It is great as a sacrificial pull line.

New question:
1/2" emt pipe has 3-10awg (red, blk, white) for 240v. Also has 2-12awg (blk,white).
By the code book - looks like it has room for the 2 more 12g thhn lines we want to run. Can anyone please verify? I know that 1/2" conduit has a max capacity of 9 lines, BUT if they are conducting lines there is some deprecation that is needed and you can't fill with 9 if you have 3-10g.

Summary: 1/2" conduit - can it hold these conducting lines:

3 - 10awg (for 30amp circuit 240 dryer plug which is "unused" presently as we have gas dryer)

4- 12awg (for 2 circuits: 1-20amp & 1-20ampAFCI)

Thanks

Problem with Inspection:
Floating wall on 2nd floor (6ft. length, 8ft. tall, open on all sides but beam on top that we can not drill through by code). Inspector says I need one outlet on each side AFCI protected and I can not use the laundry circuit which is directly below it b/c (a) it is on gfci (b) not code.

What I ended up doing was running 12G romex through the bottom 2x4 plate into the Garage ceiling. I punched a couple holes in the garage drywall ceiling, then fished romex 10ft. through garage ceiling to an 8"x4" Junction box. I then joined it up with an existing 20amp AFCI circuit line that was feeding a 2nd floor Bedroom plugs & lights.

Basically, we now have 2 outlets in a small 2nd floor living room partition wall that is powered by a 20amp AFCI circuit which also supplies power to one 2nd floor bedroom plugs & lights. All outlets to both rooms have all 12g romex. From the junction box to the service panel is 12g THHN black & white going to the service panel AFCI breaker.

I can not find anywhere in the Code that would not allow 2 different rooms not adjacent to share the AFCI circuit. Unless there is something I am missing - can anyone confirm?

I only see where Laundry & Baths can not share circuits with non-laundry or non-bath rooms, but it seems like you could share circuits with any other rooms in a house. Even rooms on different floors? Is this a correct reading?

thanks