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Power districts, blocks, and gaps

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JRP
  • Member since
    November 2006
  • From: Upland, CA
  • 255 posts
Power districts, blocks, and gaps
Posted by JRP on Tuesday, July 22, 2008 12:31 AM

Hi All,

I have the Zephyr DCC system and have been reading many of your notes on gaps and blocks, but also reading MR books.  The "Basic Wiring for Model RR's" (2001 Rick Selby) suggest that if you want blocks, even with DCC, you must install gaps in both rails at all locations to completely isolate the blocks and prevent a short circuit.  He also says you "must supply power to turnouts from the point end and still cut gaps in order for them to operate properly".  His diagram shows gaps cut on straight track between feeder wires and turnouts.

In "DCC Projects & Applications", Mike Polsgrove talks about power districts and the big advantage in finding and isolating short circuits by adding this. He also says you need to have isolated gaps between districts. 

Questions?:   What is the difference between blocks and power districts?  Are they the same thing?  Do I need to cut gaps on both rails on all my turnouts with DCC? (my turnouts are all  Atlas).   Is it difficult to add districts after I have already installed my main bus lines (14 gauge) and connected all my feeders?  And last, what do you all look for with a short circuit beyond the obvious? (IE: metal object on track, wheel flange in the turnout, etc.)?

Thanks for all your input.

JRP  

  • Member since
    July 2006
  • From: Vail, AZ
  • 1,943 posts
Posted by Vail and Southwestern RR on Tuesday, July 22, 2008 1:15 AM

Rather than trying to answer your individual questions, I'll point you at this:

http://siskiyou-railfan.net/e107_plugins/content/content.php?content.13

In this example, Joe Fugate shows Power Districts broken into what he terms "Train Blocks".  (I don't think there are any standard terms here, but these make sense.)

 

Jeff But it's a dry heat!

  • Member since
    February 2002
  • From: Westchester NY
  • 1,745 posts
Posted by retsignalmtr on Tuesday, July 22, 2008 8:13 AM

for your question lets suppose you have a 4'x8' layout with two ovals of track connected to your zephyr. if you get a short on the inside oval any train running on either track will stop until you find and clear the short. if you install separate power districts on each track with circuit breaker protection only the train in the shorted track will stop. you will have to run a separate buss for each track to do this. also when you do this you will have to install insulated joiners on any switches between the inner and outer loops on both rails to isolate the districts from each other. the only reason to install blocks with dcc is if you want to have signals or occupancy detection. gaps should be cut into both rails at each end of the block. also if you are going to run anolog locos on dcc you will need a siding where you can layup the dc loco where you can shut off the track power so it will not be buzzing and overheat when not being operated.

using atlas switches with insulated frogs it will not be necessary to feed the rails from the point end as they will pick up power from the rails they are connected to. it may be good to place a pair of feeders on any siding or industry track past the switch just to assure continous power through the switch. the only time you realy need gaps with dcc is to isolate power districts from each other.

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