15A, 15A split receptacles, 20A... What do I use in my train room?

[craigolio1]

Hello all.  I'm planning the wiring for the train room so I can get that done this week.  I'm looking for input on how many circuits I should run and what they should be rated for.


First some information:

Room lighting and electrical will be on a separate circuit.

To give you an idea of the size of the layout, the room is about 20ft x 20ft and is described here.    https://www.therailwire.net/forum/index.php?topic=35666.0

It will be a two deck around the wall type design.

I plan to divide the layout into sections either with boosters or circuit breakers, how many is to be determined but if one power supply can handle my whole layout I'm thinking of three circuit breakers, one for each level in the main room, and one for all of the track in the smaller room.

The layout is N scale.

Turnout control will be manual.

I plan to use extensive LED lighting as a feature on the layout.

There may be up to 12 N scale locomotives in use at once.

I currently own a Digitrax Zephyr but will eventually upgrade to a system (perhaps a Zephyr Extra) that accesses all of the features.  I bought the Zephyr quite a while ago to experiment in DCC but since my layout will be a walk around design, I also plan to add a couple of wireless controllers. 

I currently own a 4.5-15v, variable, 25A power supply with short and overload protection so I figured I would use this to power my layout.

I'm running a dedicated circuit to power the train layout.  In theory this would be used for anything on the layout which includes the DCC system as well as any accessories and lighting, but not for the valance lighting as it will be on the same circuit as the room lighting.


Questions:

Would I be OK with the standard 15A circuit or should I run something larger, or maybe more than one circuit?  My thinking is that one 15A circuit is enough as that's all I need to run my power supply, and it will be running the layout.  I have the 12-2 so it's just a matter of getting a breaker and a receptacle.  Not a major expense. I'm leaning towards running a 20A circuit.

My planned workbench/work area will have my computer as well.  This is where I will do my decoder programming and may in the future play with some computer control for the layout.  I figured I would locate all of the DCC infrastructure here and home run my track buses back to this location for connection. Additionally, all layout accessory wiring will be home run here as well and most likely run off of my 25A power supply, as I'm sure it's large enough. Having all of my layout wiring home run to one central location will ensure I can simply add an extra power supply, or more DCC stuff as needed without rewiring.  Naturally I plan to locate the layout's dedicated receptacle here as well, but should I include receptacles on the dedicated circuit elsewhere along the layout as well?  I can't see why but you never know.  Perhaps I should run a length of 14-2 to a junction box in my ceiling (drop ceiling so it'll be accessible and meet code) so I can add to this circuit on an as needed basis.  Honestly, if I'm home running all of my layout's DCC and accessory wiring I can't see why I would need more than one receptacle.

That's it for now.

Thanks for your input!

Craig

[C855B]

I recommend 20A for convenience outlets and 15A for lighting-only circuits. You need to think beyond just your layout. If you are wired with 12/2 to the outlet, then your own or future owners' addition of more outlets to the circuit won't be compromised or require rewiring to the panel for 20A capacity. First outlet in the chain will need to be GFCI (also 20A capacity, obviously) since you're in a basement. Yes, include at least one more outlet on the convenience circuit, located for a DCC booster, a wall-wart for a UP5 panel, or power tool access.

One of the reasons I stress 20A capacity is this is a utility area, not a living room or a bedroom. High-power consumers like power tools are more likely to used in basements and garages, so the extra headroom is called for.

A single circuit for the layout, etc., and a single lighting circuit should be plenty. Absolutely make them separate circuits - you trip a breaker, say, running a power saw while the air compressor kicks-in, and your lights are on that circuit... OOPS!, you have a spinning blade near your hand and you are suddenly in the dark. Very bad.

20x20 is fairly large, which is why I mentioned the DCC booster, and you also might want to consider a second power supply for accessories and lighting. Your wiring life will be easier if you don't try to make everything a home run in that large a space. Even if you're running wireless, if you plan to use the Digitrax handheld throttles (versus, say, a smartphone on WiFi) don't dismiss having a couple of UP5 panels. Even the new duplex system gets hung-up from time to time and you would need to plug in.

[Scottl]

I did 15A split pole with 14/3 wire so I have dual circuits at each plug.  It has proven to be overkill, but may come in handy at some point.  Looks completely normal if we ever sell the house.

[peteski]

You could approach this scientifically. each 15A circuit should continuously be able to supply around 10A.  That is around 1200W.  How many watts will your boosters, lights and computers consume?  I suspect that 2 15A outlets (each on separate breaker) will be way more than enough.  Of course, 20A outlets in a basement, like C855B mentioned, would be nice for possible heavy-duty power tool use.

[craigolio1]

Scott,

 I was thinking split recepticals as well. Mike brought up a good point about power tool use. In my first house I constantly had issues with the breaker tripping in the garage when my compressor would come on and another tool was in use. I rewired my current house a few years ago (Aluminum, gremlins, ugh. I had a permit and inspections.) and when I did the garage got it's own sub panel with separate circuits for lighting, the door openers, a heater, and two 20A circuits for receptacles. So good call, the convenience outlets will either be split 15A or 20A.

Now about the layout circuit. I don't like the idea of having components all over the layout. I build home theater system and whole house audio systems as a part time gig. One thing that is a staple in that industry is home runs. Having every cable run to a central location makes installation, repairs, trouble shooting, and future reconfiguration so much easier.  Having everything accessible in a rack or whatnot makes trouble shooting easy vs. having components in hidden or awkward spots. I just don't see how this can't benefit a DCC system. The location I have chosen is in an area that is central to either side if my layout. If I do three sections, with a 12awg bus, the run would be about 6ft to the start of the first section, 12ft to the second and 15ft to the third. Considering the size of some larger layouts I don't feel that this extra length would hurt. This would allow me to locate all of my DCC components, including power supplies, boosters, circuit breakers, or whatever in the same spot. So I'm going to home run for sure.

Mike, you make another very good point about the UP5 though. I've never used one and I didn't know they need a power supply for some applications. Because of this I would locate a couple of extra recepticals to service them for sure. At this time the locations are to be determined so I will run the layout circuit to a closed junction box in the ceiling. I can pull wire to locations that need recepticals once I know where they'll be. Fishing isn't a problem.

So as it stands the plan is:

15A room lighting circuit with feeds to wall mounted junctions for future addition of valence lighting on each level. Valences will be on their own switch. 
20A convenience outlet circuit (I have loads of 12-2)
20A layout circuit to one receptacle and ceiling mounted junction for future expansion.

Thanks again guys. Please make more suggestions or make me feel stupid for my current design if needed.

Craig. 

[craigolio1]

Peteski you are absolutely correct, except that I don't know enough about my future DCC system (or any DCC system for that matter) to calculate the power requirements!!  Haha. My out of the box Zephyr has powered anything I've ever built so I havn't had to learn anything bigger yet (and won't be at that stage for a while.

I looked at the specs of Digitrax's PS2012, 20A power supply. They don't post its power draw. Same with the other accessories but I've found that sort of thing to be common unless the item has a huge power draw (some of the amps I've installed in home theaters needed their own dedicated circuits!)

So really I'm planning to fish with dynamite here, and build my infrastructure bigger than it will ever need to be. I have loads of 12-2 so it's no problem to run 20 amp circuits.

Craig

[C855B]

Scott and I were chatting in the background about split circuits. While they were standard practice in some jurisdictions, AFAIK they aren't allowed in the more recent code revisions, so you might want to check what code applies to your area. Also - and probably more important, anyway - if you are installing GFCI in your outlet chains (which, again, I think you should), split circuits no longer work.

Split circuits work by splitting 240V into a pair of 120V legs, with devices (loads) connected in series, and sending any difference in load down the neutral. Example: if you have a 6A/120V load on one leg, then an 8A/120V load on the other, you have 6A across the 240V, and then 2A back down the neutral. Pretty nifty! Unfortunately, GFCI works by comparing the current carried by the hot leg against the neutral, and if they're unequal it shuts the power immediately. Split circuits... well... if there's any load, it's unequal against the neutral all the time, and GFCI just won't work. It is technically possible to run a 12/3 from the panel but then split the circuits at the first box into separate GFCI chains, but I'm not up on this detail of the recent codes and don't know if it's still OK. [Frankly, I get the heebie-jeebies with 240V in a single box of "ostensibly" 120V circuits. I do it all the time, just try not to think about it. ]

[craigolio1]

It's been a while but I think I recall that when I wired my kitchen, my electrician friend who was helping me advised to do 20A circuits, which we did, for the reasons you state.

I've opted for 20A in the basement and I'm going to consult with my friend again as to whether the GFCI is required by code. I don't know if it is in my area.

Thanks again for your input! Where are you located?

Craig.

[peteski]

DCC will not consume more than few hundred watts.   For example, a 15V DC 20A supply can supply 300W of power on the DC side (15 x 20).  So, it needs to consume at least that on the AC side. There is some power loss in the power supply, so to be safe let's say that it will consume 400W of AC power.  But that would be at a full load.  I doubt that your N scale home layout will consume anywhere near 20A of current on DCC.  So the 20A supply would only be at a partial load, consuming less that 400W of AC power.  Probably closer to 100W

A home computer consumes probably around 150W and an LCD monitor around 50W (or less).  As for the lighting, you would have to figure that out yourself.

I also recommend staying away from split circuit.   Couple of years ago I had my house upgraded from 100A to 200A service.  This involved replacing the breaker panel.  I had couple of split circuits in the house (it was wired that way before I bought it). The electrician forgot to wire the neutral in one of those circuits and soon I found several items in the house (lights, TV and some other electronics) acting real funny and eventually couple items smoked!  It got fixed and I was reimbursed, but I still don't like the concept.

[C855B]

I'm in downstate Illinois, Craig. Our city hasn't ratified the newer codes so I can still do things like split circuits if I wanted to, but I don't.

When you're doing new work (like I am with the layout building), running two 12/2 lines to the same location isn't that much more work than one 12/3, and it only saves a few bucks in wire. Besides, Pete's experience points to the main weakness... a broken, loose or otherwise mis-connected neutral can put 240V at the outlet and fry things instead of just failing into an open circuit.

[craigolio1]

I didn't know that could happen with split receptacles. I just figured they would be dead if the neutral broke away. At any rate, I don't have any 14-3, and I do have lots of 12-2.

Now Peteski your detailed info is very interesting. I guess I really don't need to bother with a 20A circuit for the layout then.

Craig

[peteski]

I didn't know that could happen with split receptacles. I just figured they would be dead if the neutral broke away. At any rate, I don't have any 14-3, and I do have lots of 12-2.

I never really thought about this until the problem occurred. The problem will not occur until there is a load put on both sided of the split circuit.  Otherwise nothing bad is happening.   If you turn on devices (loads) on only one branch, they will appear dead (Since with no neutral, there is no path for current to flow).  That is exactly what I did. After the electrician left, I started discovering that some of my outlets  were dead (not powering up devices plugged into them).  Without even thinking about whether these outlets were on one of the split circuits, I started turning more electric devices on to see the extend of the problem.

Once I got to some devices which were on the other phase of the split circuit, suddenly the items which seemed dead on the other phase came to life!  Because now there was a path for the current to flow between the phases (220v).  The devices turned on in each branch were now connected on series.  In this type of connection the current will be constant but the voltage across each device will depend on its internal resistance.   In m example I had some low wattage (high internal resistance) devices on the first branch. Then I turned on a 100W light bulb (which has low internal resistance).  This resulted in the light bulb glowing very dimly (which means there was small voltage across it). with the brunt of the 220V ending u across the low-wattage electronics (which promptly fried).

Now Peteski your detailed info is very interesting. I guess I really don't need to bother with a 20A circuit for the layout then.

Craig

20A circuits are usually used for appliances such as the ones in a kitchen (microwave, toaster, etc.) or in other rooms (such as window AC units).  Also on outlets which will be used for larger power tools. But if you will be running new wiring anyways, you could to make them 20A.  You just won't be using the full available power for your layout.  OTOH, 14 AWG wire is easier to deal with when hooking things up (less stiff).

[Scottl]

For what it is worth, my experience is from the Ontario electrical code and dating to c. 2005-6.   I pulled out my code book after this discussion and confirmed (from that time) that this is the normal usage for a split pole, and it advised the use of 14/3 or 12/3 rather than dual wire runs.  It made reference to very specific sections where the latter was permissible but my version did not have those sections.

All of these scenarios have risks if not implemented carefully or if a fault develops.  A bound breaker with separate wiring runs is the functional equivalent of a combined wire run but with two neutral lines. Both bring 240V into the gang.  A more likely wire failure path is to fail to the bonding line (ground).

Craig, I'm sure your electrician friend will set you right on the current code.  BTW, I suggest copper rather than aluminum wire

[craigolio1]

I've decided to use aluminum cans taped together with foil tape. Coke Zero for hot, and Diet Coke for neutral and then all of my unused Micro Trains trip pins soldered end to end for the ground. I've decided that due to slin effect, the hollow cans will be better conductors and I don't need breakers. I'm just going to jam some nails across the connections as the foil tape will act like a fuse.

Craig

[Scottl]

I'll start saving beer can tabs for you- no need to thank me