How much power do you need? DC and DCC

Model Railroader Layouts and layout building
1

At this point I have around 170 feet of rails, when done I would guess I will have around 270 to 350 feet. I like big.

Track will use 2 power supplys so I can run DCC and DC Blue boxes. I would guess not worth the cost to up grade them to DCC.

With the uses of rubber joiners and electical swithes I should be able to run either main line or whole track DC or DCC.

Here are my goals.

1 Be able to run three Blue boxes at the same time DC.

2 Be able to run 5 PKs at the same time.

My current DC power supply is a MRC 1440 and if I done the math right only 0.96 amps. It will run 2 blue boxes but gets warm, added a 3rd one and shuts down pretty quick. It handels 3 PK2’s with no problem but they will be DCC so that does not matter.

My first DCC unit will be a Bachman E-Z . Before you tell me it is a waste and I wont like it I am buying from Tstage at a prices I cannot say no to. More than likely I will out grow it like Tom did but you got to start some where. If I am right it has 1 amp of power. Do you think it will power between 4 to 5 PK’s?

Do you need more power when you added more rail? I will have power taps (is that the right term) about every 10 feet of rail and 80% is flex. I was ready to buy a nasty power supply for the HO slot cars then I learned a easy way to do power taps for them. (way harder than rails) and found the little wall warts and good Parma hand controler I was hitting sMph of 486. Coverd 160 feet of track in around 11.5 seconds.

On the DC side, would the MRC Teck IV 2600 or 2400 handle 3 Blue boxes? I was hot and heavy after a MRC 2500 II but I am not sure I want to spend that kind of money to run 3 blue boxes.

Thank you for the answers that are coming.

Idiot Ken asking questions again.[:D]

2

It will be a stretch to run 5 P2K locos with the EZ-Command, but moreso if you have them tow good sized trains. The locos, themselves, won’t draw much power if they are straight DCC, and not also sound-equipped. But, put them to work, and add a grade or two, and you will up the pressure on your EZ-Command considerably…possibly too much. If you have sound, I would suggest that somewhere around three locos would be your max.

So, it is the work, in physical terms, that makes the motor draw amperage, and too many locos working too hard will cause your circuit to overload, or to trip its protection.

The length of the rails won’t necessarily demand more “power”, but the length will impart resistance to the circuit. What I mean is that the voltage to the track will drop as you get further out from the actual power supply. This happens in all wired systems. The way around that is to break up long rail lines into districts that each get their own power supply. Also, you would use heavier gauges of wire right at the power supply and taper down to thin wires, like telephone gauge, from the bus, or sub-bus if you have one, to the rails. Those thinner wires will be short, so the voltage drop will be negligible.

An analog to this phenomenon is like the pressure to the main water line in your home. You would have a 3/4" pipe leading into the home, but only 1/2" to each fixture. That way, you have the pressure from which to draw through the thinner pipes, and each fixture keeps a reasonable flow. If you had only a 1/2" main into your house, and tried to open three or four taps, your pressure at each one would be very low. The same applies in wiring. Voltage “flows” downhill, so to speak, and downhill is further along the lines of wires. As it descends, it loses potential…the voltage drops and your locos can’t get the juice that you want them to use to pull your trains. So, thicker wires “uphill”, nearest the input (power supply), and thinner wires further along.

3

No reason not to DCC those Blue Box Athearns. It’s even pretty easy to do, Digitrax sells a special harness that makes it really easy. You can use the harness with Digitrax or other decoders. The trick with the Athearn motors is proper lube (a speck on the end of a toothpick on each motor bearing) and cleaning the commutator. The gold colored motors anyway will run very nicely when cleaned up. No they aren’t super-efficient can motors, but they aren’t 5 amp power hogs, either.
The Bachmann DCC won’t run any more than your current MRC pack, they both have approximately the same rating. One of the next level up systems with 2-2.5 amps would be able to handle what you expect to run. If you want to retain a DC pack to switch over to, you will need one of the slightly bigger MRC packs to provide enough power. Rememebr DC and DCC cannot be connected to the same track at the same time, so it’s one or the other.
Power requirements depend on the number and type of locos you intend to run at one time. You could have 10 feetof track or 500, if you only ever run 3 locos that’s allt he power you need. You do need to use adequate wiring standards on a physically larger layout to prevent voltage drop at the far ends, but it doesn’t take more power to handle that.

–Randy

4

The amount of power you need depends on the load yo’ll be running, not on the size of the layout. It’s not the number of trains or engines on the track, but the number that are in motion at any one time. Most people greatly overload their DC power supplies. I suspect that the DCC power supplies are overloaded less often.

Some numbers I’d use, which I’ve measured. Some of these loads are worst case, but it’ll get you along the way. Remember, power supplies usually overheat, even when powering their rated load for very much time.

Locomotives - 0.75 amps each

Passenger cars - 0.06 amps each

Building lights - 0.06 amps each.

A passenger train of mine with 12 cars and three locomotives pulls 2.5 amps going up and over the grades I have. My double-headed coal trains pull close to 1.5 amps each. Remember, these are currents at 12 VDC, and NOT 120 VAC line currents! 1 amp at 12 VDC equals 12 volt-amps.

Hope this helps!

Mark in Utah