Size of layout and size of command station: Are they closely related?

[tstage]

Greetings everyone!

I have a DCC power-related question for you all. I have recently come to understand that, the size of your command station (i.e. maximum current rating) has more to do with the amount of locos you would be able to run on your layout at any one time vs. the actual size (i.e. amount of total trackage) of your layout.

Someone stated that even a small Bachmann EZ Command system (rated a 1 amp maximum current) could "power" a far larger layout than most of us could reasonably build. Is this an accurate statement? If not, how big of a layout could one reasonably expect to run 2-3 locomotives just using the Bachmann 1amp system?

Thanks for your answers.

Tom

[Anonymous]

Tom,

I think the biggest issue is current draw per locomotive. Presuming 1/4 to 1/2 amp per the new plastic steam or diesel you should be able to run up to three locos using one amp (or more or less, depending on the current draw per loco). Older brass and BLI draw more amperage, newer plastic steam/diesel - less amperage. The other issue is line voltage drop over long distances which one may encounter in larger layouts... I presume that you are following Joe F.s clinic on DCC . He has addressed line voltage drop already....

I would presume that one could power a very large layout within the limits of line voltage drop and amperage draw per loco....Does the system allow for the addition of extra/more powerful boosters??? As the layout gets bigger the presumption is that more locos will run at the same time, I'm not sure this is true unless there are multiple operators or automated systems involved.

Usually the system is split into two components: the command station and the power supply/booster system . It is my understanding that a single command station can send signals to several boosters, powering a larger layout with many locos using only one command station....I'm not sure how the Bachmann system is set up in this regard.

[rrinker]

It depends on how many people are going to be running how many trains. Size doesn't really matter. If I fill up my basement, but I'm the only one ever runnign a train, I won't need much power. Conversely, a small 6x10 HO traction layout could have DOZENS of trolleys running all over the place - and you'd need quite a bit of power to run them all. Those may be the exceptions - normally as your layout gets bigger, you have the capability to run more trains and have more operators. How much you actually need depends on the locos, too. I've had 8 running (just power, no trains) on my Zephyr. The other night I tried again, and had 6 running. One was pulling a 25 car train, another a 6 car train, and the other 4 running light. That was a Stewart F7 with 25 cars, a P2K SW-9 with 6 cars, a P2K SD7, and 3 P2K GP7's. All headlights were on, and the caboose of the 6-car train was a lighted P2K model. I didn't keep it up too long, without any extra throttles all but one of those locos is just rolling along on it's own with no control. But the Zephyr never blinked. Maybe I don't need any extra power, not for along time.

--Randy

[selector]

Gee, that makes me feel good. I have the Digitrax Super Empire Builder with the 5 amp booster, but only one controller paddle (throttle). So, with 5 amps, my limit seems to be between the number of locos I have (2), and the number of throttles. Am I correct in saying that if I were to have, say, four guest operators, each with a throttle, and running two locos each, I would still be safe with the 5 amps. I would think so, but will the throttles add a 'draw', or just the locos?

[Anonymous]

Crandell,

I would say that you are probably fine... 8 locos at 1/2 amp each is 4 amps, still within the margin. I don't think the throttles will add any load here...Randy is the Digitrax guy, so he may have a more informed opinion. On my CVP system I have a five amp booster and have run four locos (by myself) around my loop no problem I will have to try consisting and run eight...

Now the other side to your question is: Will any of your operators screw up and run through a switch and throw the breaker, causing everything to come to a halt?....Then you might want two districts (or more), each with their own booster to keep things running. Another option if you don't need the power is to use the circuit breakers being sold by Tony's to break up the districts...

I think the pressure of knowing that if an operator biffs, the whole layout knows it, provides good incentive to be on top of your game as an operator. Noting gets a razzing from the other operators like throwing the breaker (great fun as long as its not you). I may change my mind as the layout moves along....

[selector]

Thanks, Guy, I understand you. I am generally a solitary person, wife knows it, so my question was somewhat rhetorical. Thanks for confirming that I have lots of poop for my setup. It would be nice, some time in the future, to have a more substantial layout to which I could apply districts and use the boosters as you have described. Of course, if there were any 'biffs', the razzing would come from me!

[rrinker]

I had a nice reply but the (&$@ database crashed when I hit the POST button. Oh well....

Basically,t he throttles DO draw power, but not enough to really matter, unless you have dozens of them. ANyway if you have more than a couple, or the jacks are some distance from the command station, you should apply external power per the Digitrax manuals. Since the Loconet uses phone wiring, it doesn't take much load before you have a voltage drop, and the throttles start acting wierd, or running off their battery until it drops too low and they start acting flakey. This is more an issue with the DT throttles with displays and backlighting than with the UT throttles.

As for power districts, if 5 amps is enough power, you can get away a lot cheaper using electronic circuit breakers like the Tony's PowerShield instead of buying an extra booster. I prefer the Powershields to others like the Digitrax PM42 because the PS is all solid-state instead of relays liekt he PM42.

--Randy

[cmrproducts]

Tom

With my fairly large layout (25 x 75 with 2600 ft of track) we have run over 20 engines plus the lighted cabooses with a single 8 amp command station/booster.

And this was done just this past Saturday. I had 50 operators throughout the day, which lasted from 9:00am to 9:00pm.

We used a combination of plug-in throttles and radio units with the majority of them being radio.

Although the layout does not have any circuit breakers (so everyone knows some one ran a turnout) it ran without any problems. We did not run any sound units as 3 engines start causing too many shutdowns.

So your layout should be able to run a lot more than what you have planned. One thing most owners forget is that if you have multiple operators is that not all trains are using the same amount of power. Some are accelerating as others are slowing down and still others are not moving at all.

This is how I was able to get 20 plus engines/trains running at once. On the average there probably would only be 10 at the most using power at one time.

BOB H – Clarion, PA

[tstage]

QUOTE: Someone stated that even a small Bachmann EZ Command system (rated a 1 amp maximum current) could "power" a far larger layout than most of us could reasonably build. Is this an accurate statement? If not, how big of a layout could one reasonably expect to run 2-3 locomotives just using the Bachmann 1amp system?

All good information to know but...I"m still waiting for someone to answer my last question. With a 1 amp command station, and everything wired properly (i.e. 12 ga. power buss + feeders every 3 feet), how big of a layout can I reasonably expect to build running 2-3 locomotives? I more than likely will NOT stick with the Bachmann EZC forever but it's good to know what my limitations are. Thanks!

Tom

[Bruce Macdonald]

Hello Tom.

I'm a newbie, so don't know a lot, but I have found a reference source from the National Model Railroad Association I would recommend you at least look at. Find it at http://www.nmra.org/beginner/wiring.html. The author there provides a method of determining the power needed based on number of locomotives, and suggests 2 amps for a second power pack that runs accessories.

The author, however, doesn't address the ultimate size of layout you can support.

[tstage]

Bruce,

Welcome to the forum! Good to have you aboard! [:)]

Thanks for the reference. I'm familiar with that NMRA site. I pretty much understand the power needs for the locomotives in relation to the maximum output of a command station. (0.25-0.5 amp for each new locomotive; 1amp for an older locomotive) The question is, can a small-size command station (e.g. like the Bachmann EZ Command system with 1 amp maximum output) run a large layout? If not, what would be my limitations - besides the number of locomotives I could run at one time? Is it clear what I'm asking?

Tom

[rrinker]

Well, with #12 wire you could probably manage 100 feet or so in each direction before you start getting noticeable voltage drop. Get some REALLY heavy wire and you can run it further, but you get into diminishing returns as the wire cost starts increasing above the cost of just adding a second booters and running shorter but cheaper wires.
Theoretically, a layout the size of Northlandz could be run with a 1 amp power supply, if only 2-3 trains were running.


--Randy

[jfugate]

As Randy points out, the greatest limiting factor on how BIG a layout you can run with DCC is not the booster amps, but the gauge of your track feeder bus wire.

From my DCC FORUM CLINIC over in the general discussion area:

QUOTE:
Basically, make your power bus wire guage larger rather than smaller to avoid voltage drop at the extreme far end of your power bus. You want a voltage drop of no more than 5% from end to end on your power bus. Here's a simple table that assumes 12 volts and 5 amps going through copper wire:

Length of run for no more than 5% voltage drop
16 guage – 20 ft
14 guage – 35 ft
12 guage – 50 ft *
10 guage – 80 ft

You can find voltage drop tables and calculators on the Internet – just use one of the search engines and type in “wire guage voltage drop” as your search phrase.

If you're wire is big enough, you can run the layout with only one 5A power booster, assuming you don't run more than 8-10 locos at a time.

However, for things like making your DCC layout more impervious to shorts, you need to consider more than one booster.

My preference is for more low amp (3.5 - 5 amp) power boosters and more power districts as opposed to one or just a few high amp power boosters (8-10 amp) and power districts. More boosters and hence more power districts helps you keep the layout up if something shorts, and lower amps mean less damage to things if you do get a really bad short somewhere.