I have been using my NCE SB3a power booster to run my 5' x 12' HO layout (approx. 30' run of code 83 track). I have been running the system for about 1-1/2 years without any problems. However, the system has never shut down because of a short even though I have had derailments and other shorts occur. Anytime a derailment or some other short happened, I would quickly shut off the power. My bus wire is a closed loop of AWG 14 with AWG 22 & AWG 26 feeders at every 3' track section. After reading the August 2012 DCC CORNER Article by Mike Polsgrove, I tested my layout after removing all locos from the track, by shorting the rails together with a metal file. SB3a booster circuit breaker did not trip after 1 full minute. Does anyone no why the circuit breaker does not trip? Is it because the bus is a complete loop?
I would appreciate any comments.
Ed
First test I would make is right at the booster outputs. Disconnect the track bus and short the two outputs. If it doesn't trip the booster immediately, suspect either the booster's short circuit protection malfunctioning or the power supply not supplying the needed volt/amps to create an overload. I suspect the power supply may be the trouble. Your complete loop would actually help the circuit breaker to trip.
If the booster does trip immediately, you will need to find the problem in your bus and/or feeder system. Best way to do this is use the divide and conquer method. Cut the bus at its half way point and test each half separately. If the problem is only found in one half you only need to look at that half. Continue the divide and conquer method until solved.
Martin Myers
NCE does not recommend that the bus be in a loop, but should be open ended. That may have something to do with it.
The standard NCE system should trip, but I am not sure about the SB3a. However, it has been recommended by DCC experts that you should not rely on the circuit breaker qualities of the DCC system, but should have a separate external circuit breaker. The EB-1 by NCE would do the job at a small price.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
I concur with Elmer, that you should undo the closed loop. Then try it.
Ken G Price My N-Scale Layout
Digitrax Super Empire Builder Radio System. South Valley Texas Railroad. SVTRR
N-Scale out west. 1996-1998 or so! UP, SP, Missouri Pacific, C&NW.
Why not try the logical approach that Martin has outlined? If the problem is in the DCC unit itself doing all of the disconnecting under the layout will be a lot of work and won't give you the answer.
Joe
Closed loop should not have a bearing on short circuit protection. NCE recommends not closing the loop to prevent data crashes. That would happen on very large layouts with bus runs of 30+ feet in each direction. Hook a DCC system up to an oval of track using only one set of feeders. The rail creates a closed loop and it still works.
mfm37 First test I would make is right at the booster outputs. Disconnect the track bus and short the two outputs. If it doesn't trip the booster immediately, suspect either the booster's short circuit protection malfunctioning or the power supply not supplying the needed volt/amps to create an overload.
First test I would make is right at the booster outputs. Disconnect the track bus and short the two outputs. If it doesn't trip the booster immediately, suspect either the booster's short circuit protection malfunctioning or the power supply not supplying the needed volt/amps to create an overload.
I agree. That's where I would start my troubleshooting in such an instance.
Rich
Alton Junction