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When choosing a DCC decoder, how important is the amp rating?

Decoders are definitely not all the same, they have different numbers of pins, can control different functions, come in different shapes and sizes, and often, have different amp ratings. But how important is the latter?
Well, it is both very important, and not very important all at the same time. Decoders have two ratings, a continuous rating, and a peak rating. A continuous rating is the maximum amount of amps the decoder will safely support for prolonged periods, a peak rating, is the amount of amps it can tolerate in the event of short spikes in power. If either are exceeded in their relevant context, the decoder will likely be permanently damaged.
The above is clearly the reason why amp ratings are very important, having said that, how likely is your locomotive to draw more amps than even the lowest rated decoders can handle?
Well, that depends on the engine itself, the length of your trains, the gradients encountered, and the number of functions used. A layout featuring a humble tank engine shuttling up and down between fiddle yard and country station is unlikely to be greedy with the amps. On the other hand, a display layout with steep gradients, locos with sound, lights, whistles and bells, and long consists to please the spectators, may well have locos that require decoders with more heavy-duty capabilities.

If you have an ammeter, you can always do a quick test to see how many amps your loco is drawing at maximum power, just don't forget to really put it under some strain when you take your measurement. If you do not have an ammeter, you can either play it safe and install a decoder with a higher amp rating, or check on your decoder's manufacturer's website to see if your decoder is suitable for use with your loco.

Posted in: Model Railway

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