"Wired for DCC"...What am I missing?.....

[Jacktal]

OK...maybe I'm dumb,but don't really think so.At home,I have wired a layout for DC operation,with multiple turnouts and block control,etc...and everything worked just fine.For a while now,I've been a member of a local club and am very much involved in renovating the layout,creating new lines,installing and/or replacing turnouts (all Peco of both Insulfrog and Electrofrog) and even created a return loop at one end.Since the club layout runs on DCC,an automatic reversing module takes care of the loop and block control isn't present anymore.

However,I never really cared about "wiring for DCC" and simply install turnouts,wiring,etc...just as I'd do for DC...with great care and no problem has showed up yet,amazingly maybe,but isn't DCC a two wire act like DC?Or even AC?I don't really understand that "wiring for DCC" thing.In my book,a short is a short,whether DC,AC or DCC.Do I have a sword over my head waiting to strike me some day?

[cacole]

To me, wired for DCC just means that you have no control panel with block toggle switches.

I wired the Cochise & Western Model Railroad Club's 20 x 40 foot HO scale layout so it could be ran either way because we have some members who cannot afford decoders. If it's wired for DC block control, switching to DCC is just a matter of flipping a switch to feed the DCC signal through the block control panel.

As you say, if there's no short with DC block control, then there's not going to be a short with DCC.

[Texas Zepher]

QUOTE: Originally posted by Jacktal
However,I never really cared about "wiring for DCC" and simply install turnouts,wiring,etc...just as I'd do for DC...with great care and no problem has showed up yet,amazingly maybe,but isn't DCC a two wire act like DC?Or even AC?I don't really understand that "wiring for DCC" thing.In my book,a short is a short,whether DC,AC or DCC.Do I have a sword over my head waiting to strike me some day?

Short answer - No, the few issues that occasionally pop up have gotten much more press than the many instances where there are no problems.

Long answer - Yes, assuming the simplest situation a straight DC system the two wires go to a track with a locomotive on it - 1 amp. Even normal tiny telephone wire will work fine. With DCC if you have the same one feed to the track with every locomotive on the layout being powered through it. The wire becomes the current limiting factor and can not only be a safety issue because they are too hot, but also cause performance problems. On the other hand if you have LOTS of tiny wire feeders they might share the current load enough to even mitigate this problem.

There are even longer answers that get increasingly more technical and detailed.

[rrinker]

Exactly. The only real difference is that in a DC multi-cab system, if you derail your train and shortout your cab, only YOUR train stops (not counting the blocked track tha no one can get past). In a DCC system, thre is a common power supply even if there are a dozen seperate cabs - any train shorts the track, they ALL stop. This is more annoying than anything else, but this is why you need to be careful with the wiring and with turnouts. It is also why the concept of 'power districts' was invented. By breaking the layout up into multiple power districts, you limit the scope of any short-causing derailment.
The other concern is voltage drop. Voltage drop over a fixed length of wire varies directly with the current being passed. If you have a run fromt he control panel of 50 feet, and run a single 1 amp DC loco on it, you'll have X amount of voltage drop. If that same 50 foot wire now carries DCC power to various parts of the layout, and you have 5 locos each drawing 1 amp running, you now have 5x the voltage drop on that wire. With DC you might get away with using telephone wire from the panel to a block, but that doesn't fly with DCC because the freedom from block limitatons means any section of track can easily have more powered locos in it that even remotely possible with DC control.
Good solid wiring, heavy enough gauge for the distance, plenty of feeders, good soldered joints of feeder to rail, etc. are important for ANY layout, DC or DCC.

--Randy

[pcarrell]

Visit Allen Gartners site at

http://www.wiringfordcc.com/

It will answer most any question you have.

Hope that helps!