10 amp or 20 amp a/c for dedicated layout line?

I've not heard of a 10A breaker? Perhaps you meant 15A? In any case, for the minimal extra cost I'd run #12 Romex from a 20A breaker to a double duplex outlet. You never know when you might want to run a high-draw item such as an electric space heater. Even a shop-vac or circular saw draws about 7A with much higher starting current.

Thanks for the correction Geyser,.  ( I don't know how I got 10 amp in my head.) 15 amp is right.

Mannyrock

Code probably requires a GFCI protected outlet/circuit in a basement.  Go 20 amps as the cost difference is negligible for one circuit close to the box.  

Brendan

I'd go with the 20 Amp as well.

Mannyrock,

The difficulty with putting in just the right amount is that you might be surprised what you may want in the future in your train room, i.e.  TV, computer, stereo, mini fridge  etc.   The cost for the upgraded cable is only a few dollars a foot, the costs for the additional breaker and disconnect box is nominal and you don't want to have to do it all over again after you built your layout.    You should also put in a couple of outlets on both sides of the layout.  You will not regret it.

When you amortize the cost over the time you will be using it, especially with a friendly licensed electrician, the difference will be not worth the time to think about it.

By the way, imho,  all mannys rock.

Manny Levin

Agree with 20A circuit with #12 wire. Unless a real problem I would put in more than one outlet; at least one on each wall. You would want one near your control panel and as Lew said might do a duplex.  One on the other wall. Since in a basement, you would want your plugs a little higher on the wall. I'm sure your neighbor can provide you all the code info.

Just saw Manny's response - agree with him

Lets see, never will run more than two trains, no more than 4 or 5 accessories, never bigger than a ZW, no more than 60 FT of track, you sound just like all of us when we started. Run 20 Amp dedicated line and breaker for sure, and never look back. . .

He did say he was right next to the panel and had empty breakers. That should help with the future. 

You have to think in terms of watts, not amps.

A 20-amp circuit can deliver more than 2,000 watts. That’s five Z4000s running constantly at full, maximum output.

Yeah...a 20 amp circuit should be enough. 

Even with that one outlet you will find as I did you will be running extension cords as you start soldering wires, getting out a vacuum cleaner to clean up debris, plugging in a dremel to do various tasks, etc. So what I did is run the twenty Amp line to numerous outlets around my layout eliminating the use of the extension cords. Now here is where I depart from the the others on this thread. Reread Rich Melvin post. You said you will be running two maybe three trains simultaneously. At most that would take two large transformers even including accessories and any command control boxes. Rich mentions five Z4000's could be run with a 20 Amp circuit. You aren't close to that. After wiring twenty Amp circuits to my shop and layout and 15 Amp circuits with the recommended outlets based on distance between. I can guarantee that after wiring a number outlets with 12 AWG wire versus being able to use 14 AWG wire for a 15 amp circuit, you will be using language your mother will wash your mouth out for using. I therefore suggest the use of a 15 Amp circuit. 14 AWG romex is infinitely easier to work with versus 12 AWG required for a twenty Amp circuit. Besides I would bet that your extention cords are 14/3 which is you ever do draw 20 amps won't carry the current.

My two cents. 

If you are having an electrician doing this, "go for broke" that is more outlets than you ever think you will need.  As said above, you avoid extension cords or long ones.   To add luxury have a 240V line run and split so one 120V phase feeds two sides of wall and other 120V phase feeds other two walls, assuming this is a large room (basement?) and not just a small bedroom.

In this picture I have inserted you can see an example of my placement of an outlet in my table.  I had hoped this picture would have shown it better but in the second table just before the middle leg is the outlet.  This is an expansion I am doing to my 12x20 layout.  I use 1x4 stretchers along the top.  I cut an appropriate size rectangular hole in the stretcher.  I then use an "Old Work" box.  As someone mentioned the first outlet in a circuit, whether one or many, is a GFCI type outlet.  In some localities, they are now also requiring outlets to have an arcing prevention capability also.  In my entire layout I probably have installed 8 to 10 outlets.  There is no set limit to the number of outlets in a circuit.  The operative requirement is outlets are spaced at 8 foot between them when installed in partitions.  This is due to the normal length of cords for devices so for instance a Lamp can be placed anywhere within the 8 foot area and not be beyond its cord length.   If there is a limiting factor to the number of outlets in a circuit is the size of the room.  Based on the 8 foot distance more outlets would be made available in a larger room than a smaller room.  Someone else mentioned raising the height of the outlets in a basement setting.  This is generally a good rule as basement flooding is a risk that must be considered.  Behind my tables one can see a couple of outlets in my wall just barely visible at table height.  I appreciate the height rule in the basement but I set mine at about 38 inches above the floor.  This height is advantageous for us older folks and reduces the amount of bending over to plug a tool in.

The problem with installing lots of outlets is that my foundation is  built with those interlocking huge lego type, prefab, concrete panels, which are 8 inches thick, four feet wide and 10 feet tall.  Meaning, that all of the walls of my basement are basically 8 inches of thick concrete.   No fun trying to install rigid conduit down the wall, to run the wire down from the joists, connect it to the outlet box, and drill all of those holes in the concrete, to attach it all.   Every outlet would have to have the rigid conduit.  

I do everything myself, except hooking the line in the breaker box, so for now, I think  one outlet is all I can stand.  :-)

Mannyrock

I would do the 20 amp circuit, just remember you will need to use the 20 amp rated receptacles.  The standard cheap ones are rated for 15 amp use.  Otherwise the receptacle will be the weak link.