A note on the shorthand used on the drawing might be in order.
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A1a - indicates that the buss segment depicted is coming from
Booster A, circuit breaker 1, and is the first segment so
connected. So B3d is on booster B, circuit breaker 3, and is the
fourth wire segment attached to that breaker.
On 2019-09-21 11:19, Blair & Rasa
(minor responses interspersed below, then read on here:)
The layout room is 52 x 28; the layout is HO. Attached is the
overall DCC plan. The room is basically a double deck, with three
locations where it becomes triple. Some context: the oval at the
bottom is a three tier staging room, 10x28; The three peninsulas
are fed from their bases(points A, B, and C), as are the outside
walls of the room. Be aware, there are more subtleties, but this
gives you the flavor. We have built about 30% of the upper deck,
as well as the branchline on the third level, upper left (i.e.
busses C2 and C3 are in place and in use). We have been operating
with a single DCS100 located at 'C'. The time has come to build
the rest of the upper deck, which requires boosters at A and B,
hence my questions. Once built, A will be the location of the
DCS100, B will be a DB210, and C will be a DB150. Each will have
a quad circuit breaker; yes, this could change, but the basic
topology doesn't change if I add or remove a breaker or two.
- There's around 600' of main line, plus two 120' interchange RRs,
and a 70' branchline.
- the topology of the RR lends itself to the chosen booster
locations. There's just a lot of track in excess of 30' from the
- most bus runs go in two directions from the boosters already.
- Most of those runs are > 30' each way. All busses shown are
planned to be 12 ga. twisted.
- everything installed to date passes the 'quarter' test, and runs
fine, with the exception of two reported instances of loss of
control at the far ends of busses C3a and C3b. These could have
been operator error (i.e. using a DT400, you can end up with the
wrong knob active, and only think you're changing your
- I'm trying to avoid more boosters, as for the operations I plan,
more current is unnecessary based on loco and passenger count; two
5A boosters and an 8A booster are enough. That will service the
three yards, and the long mainline country runs. If I eventually
need more, it's likely that the staging yard room will be the
reason, and it will be easy to separate it out and add a booster
From what I've read, adding snubbers improves performance to the
point where I'll be okay with the longer runs, but how many
snubbers to add is the question. I'm well aware that each one
presents an added current load, though not a lot; most
recommendations list a 1/2 watt 100 ohm resistor. If we assume
1/4 watt dissipation, each resistor draws about 50 ma. (P=I*I*R,
R=100, P=0.25, therefore I=0.05). If I had to install 34
snubbers, I'd be looking at 1.7 amperes just for them.
Sorry for the length of this, but I'm trying to give you all the
info you might need, as you seem to want to help.
On 2019-09-21 8:39, Ross Kudlick
Already sort of done. See plan.
I have 3 thoughts:
"each limiter's output will feed multiple bus segments" my not
be convenient for operations. A short in one segment will stop
trains in all other segments which will be frustrating to your
train crews.. I suggest having each 'circuit breaker' power a
contiguous section so a track short creates minimal train
"each of those runs will exceed 30' " -- Can you relocate your
boosters to avoid exceeding 30' main bus runs? A 60' length can
be powered as 2 30' sections by lacating the booster with a main
bus configured as a 'T." You could power a 60' section on both
levels (120' total) with a single booster without exceeding 30'
main bus length. This will mimiize (and possibly eliminate)
any need for 'snubbers.'
Noted. I have the PM42s, and intend to use them until they annoy
me enough, or are inadequate, at which point PSX is likely where
I'm going, unless there's a newer product available. We'll see.
Circuit breaker selection - consider using 'single' breakers
rather than a 'quad' breaker. Individual breakers can be
located along the main bus creating a 'sub-bus' feeding each
section. This mimimizes the amount of large gauge bus wire
needed (and mimizes the 'spaghetti bowl' of wiring under the
railroad). I prefer the PSX breakers; others may offer other
suggestions. (Note - a PSX4 is actually 4 indiviual PSX
breakers that can be snapped apart for individual installation.)
Yep. Already trying to do that, that's why I asked before I
proceeded. Short of spreading boosters all over the place, I
would have thought "best wiring practices" would include snubbers,
where length dictates. Not sure which "best wiring practice' you
think I'm violating, so please elaborate.
Designing to 'best wiring practices' now will be benficial in
the long run. You may have to think 'outside the box' for the
best solution for your railroad.
But thinking outside the box requires that one actually know where
the box boundaries are...