Layout power requirements

[GaryHinshaw]

I'm not sure if this is the best place to post these questions or not, but I'll give it a shot.  I'm in the process of renovating my 25'x25' basement for a new N scale layout and I have 2 dedicated 20 A circuits available.  At present I am planning to divide power for the room lights between the two circuits: one circuit for the back half and one for the front half of the basement.  Each half will have about 800 Watts of daylight fluorescent lighting , but these circuits will also have to supply train power.  I figure I have an additional ~1000 Watts per circuit available for other needs (with a bit of margin). So my questions are:

1) How much power should I budget for trains?  The layout will be large enough to accommodate roughly 4-6 trains running at once with a typical consist being four 6-axle Kato units pulling a ~12-15' train (25-40 cars) up 2% grades.  I really have no experience with how much juice a single such train might draw, but I sure hope 10 amps is overkill for the whole shebang.

1a) As an aside, what would you recommend as an appropriate sized DCC system for this kind of operation?

2) How much power for accessories such as signals (pretty low I imagine) and maybe, in the future, a SurroundTrax type sound system?

3) Any other power hogs I'm not thinking of?

4) Do you recommend putting the layout power outlets on a switched circuit or just leave them unswitched?

Note that other services like a/c, laundry, etc. are on separate circuits.

Thanks in advance!
Gary

[ednadolski]

I have the 5A  NEC DCC system and have had no problems running three 4-loco trains at the same time.  But I believe the rule of thumb is to go by the maximum possible draw -- isn't that based upon the stall current for the motors?  I'm not sure what that is offhand for N scale diesels.

I run it all on a single 15A house circuit, which includes ~ 500W of fluorescent daylights (not just the train area).  But I'd think you need to figure on the # of boosters that you want, and the power consumption (not the power delivered) of each one.

Will you have to factor in added capacity for sound decoders?  I understand these use more current, but again I don't know how much for N scale.

To me, two 20A lines sounds like plenty.  I think I'd put all the lights on one circuit tho -- would allow more headroom on the other circuit.

[ednadolski]

four 6-axle Kato units pulling a ~12-15' train (25-40 cars) up 2% grades.

Gary, have you tried this to see if 4 locos can do it?  I generally get about 8 cars per loco, tho my grades are a bit steeper and tightest curve is 16" r.  You might need a 5th loco to get to 40 cars.   I've found it helps to speed-match, so that the locos don't fight each other.  (If you use BEMF, you have to tune them so they don't fight each other).

[GaryHinshaw]

Thanks Ed.  5 A is a useful number to know, and it's probably a good point about separating the lights from the layout power.  I'm going to build the back half of the layout first - and only install the back half of the lighting for now - so I can get some experience with it before I commit on how to feed the second half.

I have not tried a 40 car train on 2% yet; that's why I want to go in stages.  In my drawings I have been very anal about limiting the grade to 2% and the curves to 20" with easements, but that's only part of the equation.  If necessary I'll go with shorter trains, but the sidings are sized for ~16' right now.

Cheers,
Gary

[wm3798]

My MRC Prodigy Advance is rated at 3.5 amps, and I regularly have a yard switcher, two road consists and a mill switcher running simultaneously.  That's anywhere from 6-8 locomotives.  It's also all spread out in one power district, although I will be adding a second in the process of the yard build out.

4-5 amps should be plenty.

Lee

[Bob Bufkin]

Lee:

Just how do you put in another power district in DCC.  I've got one place where I want to do this (a long seperate siding) and am not sure how.

[GaryHinshaw]

Lee:

Just how do you put in another power district in DCC.  I've got one place where I want to do this (a long seperate siding) and am not sure how.

Ditto  (and thanks for the previous input).

[John]

I run two 5 amp boosters .. of course I use digitrax, and each of the boosters feeds a power management module, which allows me to split the layout into 4 sections. That way, each section gets 2.5 amps .. the last time we ran trains, I must have had 6 or 7 going at one time, all with multiple locos..

don't over engineer this .. but use #12 buss wires, #18 or #22 feeders, and make sure no buss run is longer than about 50-75 feet, and you should be alright ..

[ednadolski]

Here is the power supply I am using with my 5A NEC DCC system:

http://www.dccspecialties.com/products/mf615.htm



This is rated @ 5A, 15VAC output.  The input voltage is 120VAC.  It doesn't say what the actual power consumption is, but with an output of 5A 15VAC,  I'd think that the load on a 20A, 120VAC line would be nothing to worry about, even for several of these.

[dclyde]

I'm also using Digitrax and have 2 8amp Command Stations.  I don't have any power management modules...yet.  I have however, split my 64 foot layout in half with one command station controlling one half and the other command station set to booster mode and powering the other half of the layout.  I'm using a 14 guage harness and haven't had any power issues.

I have had loconet power issues as I currently have 18 DS64s and a need to add another 8, 13 UP-5s, a UR91 and 4 throttles.  These issues were overcome by powering all the loconet devices off of a 12VDC bus rather than track power and/or loconet power.

Dave

[John]

Lee:

Just how do you put in another power district in DCC.  I've got one place where I want to do this (a long seperate siding) and am not sure how.

Making a siding a "power district" is not what you want to do .. you can however, isolate the siding with rail gaps, then run a separate feeder to it from your power buss .. 

When we talk about power districts, its really dividing the layout into sections, such as a yard might be a power district, and the rest of the mainline another.

The M&O is divided into 4 districts .. the lower level is divided into 2, and the upper level is also 2 .. I use a PM-4 to do all this

[Bob Bufkin]

My problem is I used DC so long I still think that way on wiring a layout.  I really need to get a book on DCC to show me what to do. 

[John]

My problem is I used DC so long I still think that way on wiring a layout.  I really need to get a book on DCC to show me what to do. 

It does take a little getting used to .. if your layout is not too large, like Lee's, you can actually get away with just one power district .. most modern loco's don't draw all that much power .. and you can run quite a bit of trains on a 5 amp system ..

[GaryHinshaw]

Great feedback gents.  On the subject of power districts, how is the power hand-off managed when a train crosses a district boundary?  (Ditto for a reversing loop.)  Since these are just basic DCC questions, and I'm a DCC newbie, maybe someone could recommend a good DCC primer for me.  I'm definitely aiming to keep this as simple as possible.

Cheers,
Gary

P.S. Ed, unless that unit is dissipating a lot of heat, it should only be pulling ~0.5 A from the house line at full load.

[John]

The decoder in the loco will adjust itself when crossing a power district .. you just need to make sure that the voltage is relatively the same, otherwise you will see a little slow down or speed up. Reversing loops require a "reverser" or they can be wired with a toggle switch, just like DC reverse loops ..