Multiple feeders vs Ground Loops

Don Vollrath
 

This subject comes up every once in a while in various forums.

The whole purpose of providing multiple connections to model RR track rails is to provide a preferred low electrical resistance path for current to flow instead of relying on potentially poor electrical connections at rail joiners or even that of the rail itself (copper vs steel/brass/nickel rail). Providing rail feeder drops at each piece of rail connected to adequately sized DCC (or even DC) bus feeder wiring back to the power booster (or DC throttle) does just that. This gives the best possibility of problem free operation of our trains.

'Ground loop' problems are somewhat different whereas multiple electrical paths, each with a different amount of electrical resistance, exist and tends to allow or force unwanted electrical currents to flow in the wiring between common or 'grounding' connections supposedly of the same potential. It is the unwanted current flow in those paths, and the difference in voltage drop due to the electrical resistance (& impedance at higher frequencies) that causes a disturbance of the voltage signals available at any given point along the wiring. ie - The signal ghosting problem of multiple paths as Mark Gurries explains... For DCC, a long continuous loop of track and/or bus wiring can form multiple signal length timing connections and become a problem for DCC signaling reception at a given point, but only after the loop starts to exceed several hundred feet in total linear circumference. [Somewhat wiring style dependent.] Simply breaking up the track into typical isolated power or booster or even AR section districts and providing DCC bus wiring as a 'T' from the booster rather than a continuous loop tends to avoid those issues.

DonV  

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