1.6 amps to run how many engines?

jessenoah Aug 29, 2015

  1. jessenoah

    jessenoah New Member

    Hello everyone! I have a question about DCC...I have 11 engines and an MRC DCC controller that puts out 1.6 amps, I'm not much of an electrical guy, but is having 10 engines idling while 1 runs an ok thing? All the engines have sound and DCC decoders, and I usually only run one engine at a time, is it an issue to have some many engines sitting idle for power consumption kind of reasons?

    thanks for your expertise!
    - Jesse
  2. gatrhumpy

    gatrhumpy TrainBoard Member

    Ten idling? Hmm, that might trip the circuit breaker.
  3. MRLdave

    MRLdave TrainBoard Member

    You're probably close to the limit if all the locos are idling (sound) and have lights on, but if you want to test, power up a few more and see how many you can actually run before the breaker trips. My guess is if your pushing the limits of your supply, it will get pretty warm, and heat is never a good thing for electronics. If it's NOT getting hot and/or you can actually run 2-4 locos while the others idle, you're probably OK for now.
  4. Gats

    Gats Staff Member TrainBoard Supporter

    That depends on a few factors. I assume HO locos here. Spitballing a few thoughts...

    1. Modern locomotives have better efficiency than those of years back. Your Genesis and Proto 2000 are examples of those using better motors at around 0.15-0.2A draw. Older locomotives will pull around 0.5A (give or take) whilst running.
    2. Sound decoders at idle. Are they actually making noise or are they set to quieten after a short period (if function is available)? These will pull around 0.1A. Lights alone will be around .02-.03A (20-30mA).

    You'll possibly be looking at 1A with 'idling' (sound on) locomotives alone plus the lone running loco. Likely within the 1.6A you have available but sailing too close the maximum and not allowing for any continguency.
  5. jessenoah

    jessenoah New Member

    thanks guys! I'm in N scale with an MRC prodigy...pairs of kato GS4s, Intermountain AC cab forwards, atlas SD9s, I guess I have more engines than I know what to do with! a good problem to have!
  6. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

    For N scale, I have about 20 idling units at all times plus two or three running, with sound. Never get above 1.2 amps
  7. subwayaz

    subwayaz TrainBoard Member

    Being new to DCC; I found this thread very informative on a aspect of DCC not a lot published on that I know of.
    Thanks for sharing your insight folks
  8. DCESharkman

    DCESharkman TrainBoard Member

    The other thing to consider is that the moving locomotives will increase their current draw if they are going up a grade or around a curve. A 24 inch radius180 degree curve has the same increase in drag as a 2% grade. A good number for loco power budget is 20 mA for DC/DCC only and 50 mA for a sound unit, stationary.

    The numbers when moving are about the same, meaning the 20 - 30 mA for motion is the same for DCC or DCC sound. Some sound decoders use more power than others.

    So looking at the numbers, 10 stationary locomotives would be either 200 mA plus 50 mA for the runner for just DCC for a total of .25 Amps with no sound being pessimistic.

    If they are all sound decoders you are looking at 500 mA plus the 80 mA for the motion locomotive. That gives you a budget of .58 Amps used.

    There used to be a sticky that somehow got lost where I provided the way to calculate the power needed for both the DCC layout, and the accessories that may be used. But the power utilization calculation is needed. After all, even with an 8 Amp booster, you are only dealing with 96 watts of power using N scale. That is almost a 100 watt incandescent bulb dissipation.

    You always need to be a bit overly conservative because many things factor into the power consumed by the moving locomotives. As said earlier curves and grades will have an effect on how much current is used, but also the weight of the train being pulled will also have an effect. Always allow a margin of safety. In all power calculations you want to makes sure you are not too close to the full rated power of the controller. As you get closer and closer to the full power rating bad things can happen like random current spikes etc.

    Because of these and other factors I always use only 75% of the rated power of my controller or booster. That way there is some extra power available in the event it is needed.

    For my N scale modular layout I use three 8 Amp boosters and an 8 Amp controller. This allows me to have almost as many locomotives as I want.

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