How many amps?

[holshot14]

In theory, how many amps would a layout need to run all 21 heritage units in HO scale? 11 genesis and 10 intermountain. All DCC w sound.

[waltr]

How many Amperes does each Loco draw? Add them up.

[holshot14]

I don't know how many? That's why I am asking? I don't even have a layout built yet.

[Selector]

If they are DCC/sound units, count on up to 2 amps for really hard-working locomotives. That figure is likely to be the maximum rated continuous amperage for any of the decoders anyway, so it's a good planning figure. If each locomotive only pulls maybe 20 cars on the level, you will probably draw between 0.7 and 1.2 amps per locomotive. As you add properly weighted cars, all with good running qualities, and impart grades AND curves to the mix, your amperage draw will rise.

[ncmrdispatcher]

How many do you want to run simultaneously? Certainly not all 21!

Those that are moving are the only ones that matter. All the others draw an insignificant amount of current when just sitting there idling, even if they are making noise.

When I was doing some HO decoder installs a typical, modern HO locomotive drew only about 0.1 amps without a load, and at most 1/2 amp pulling a train. I'm in O-scale these days and 1 1/2 amps at full wheel slip would be normal for a diesel with a large 8xxx Pittman motor.

All the best.

[holshot14]

Actually I did want to run all 21 at the same time in a consist.

[Selector]

Unless you intend to build a large layout, you are highly unlikely to have room for more than the locomotives, themselves, in motion without looking silly. Add the cars to make it prototypical, if such a thing ever happened, would mean you'd need a loop with about 80' of track, and even then it would be chasing its tail.

However, it is your layout. If you really do intend to run all 21 locos, and towing a realistic number of cars for the horsepower 21 locos of the prototype would provide at the rail head, you are still looking at about 12-15 amps for locomotives with sound.