How many power packs are needed?

Model Railroader General Discussion (Model Railroader)
1

I don’t use DCC so my question is based on DC w/control panel. I have 2 older MRC Tech II’s, which I got real cheap, brand new in their boxes, never used. Once I get this layout under way and start adding lights to buildings, crossings, signal lights, street lights, etc. how many additional power packs (power supplies) should I expect I will need? One MRC II has three outputs; variable DC (to 14VDC), 18.5VAC and fixed 15VDC with a total of 17VA. Now if I understand Volt-Amps (VA) you must divide the VA by the input voltage (i.e. 17 divided by 115) which gives me aprox. **.**15 amps continuous load.

I read here on MR forum that some power packs are 2.5 to 5.0 amps. Is this really VA or are these ratings true continuous load amperage? Is this only the variable output or total output? If it is true continuous load amperage then do I not have enough power to run 2 locos on a large consist? Will I need to buy additional power supplies to run the signals, crossings, lights, etc.?

2

just to be safe and not drain power from my locos, I DID.

3

“Will I need to buy additional power supplies to run the signals, crossings, lights, etc.?”

Yes, as ec says above, you do not want to run accessories with the power pack running your trains.

But, there is no reason use a model railroad power pack to run lights, switch machines, etc. Plug in wall transformers work fine. See: http://dkc3.digikey.com/PDF/T033/1095.pdf

4

Hi dhuff

To get the correct Amperage you have to divide VA by the OUTPUT voltage which is about 14 volts ; a 14 VA would give about 1 amp, a 28 VA would give 2 amps and so on.

Martin
Québec City