# Wiring question



## mopac (Feb 24, 2011)

I am STILL in the planning and thinking stage for my next and I hope
final layout. Let me state the plans and then ask some questions. The
layout is to be around the walls layout. 2 separate railroads on layout.
Not connected. Each railroad a double main. So basicaly 4 main tracks
around the room. The mains of each railroad will be connected. I am
serious about this as I have already spent a bundle for a dcc set. Digitrax.
I have read your guys comments on PM42s and AR1s. I am brand new to 
dcc but I liked what I read about these products. Ok, here comes the questions. Correct me if I am wrong and please add to it. Oh, and I forgot to add, I want a "Y" on each railroad to turn engines. Are PM42s mainly for
short protection? PM42 will service 4 sections of layout. Should I wire from
command station to the PM42, 4 sets of wire from there , one to each main?
Now, what to do about the "Y"s, is that auto reversing stuff? Should I use
2 AR1s for the "Y"s? Should there be insulating rail joiners between each set
of mains to keep the PM42 sections apart? Any other wiring tips would be appreciated. Thanks, Al

I was a little disappointed I will have to buy these other products. I thought I had spent enough on the digitrax set.

One more question. A single dcc system will run what I have planned won't it?


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## Brakeman Jake (Mar 8, 2009)

The power of your system is dictated by the expected current consumption (number of locos) more than by the layout size.You didn't specify the Digitrax set you have but a five amps. set will power most home layouts without a sweat and an eight amps. set is big power.However,though quite sufficient for most home layouts (3-4 locos,even more in N),the Zephyr might need the addition of a booster if you want to run more.

The PM42 has four "sections" that can be used for either short protection or polarity reversing,the four sections being independent from the other.Used as short protection,only the shorted section of the layout will shut down not the whole layout.You could go without it,but then a short shuts the whole layout off since the command module is short protected.Having power entering the PM42 from your command then go separate ways to your mains is indeed the way to wire it.

Yes,the Y's need polarity reversing,wich you could use an AR1 or one of the PM42 sections for.Now you can get away with one AR1 for two or more Y's as long as no two Y's are used at the same time.

Finally,yes you'll need to isolate your mains from eachother,otherwise it would defeat the purpose of the PM42.

There are a few ways to dividing a layout,and another option is the use of boosters.They are used when you need more power than what your command station can deliver,but they are also used to power sections of large layouts that are far from the command station.


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## mopac (Feb 24, 2011)

Thanks Jake. System is a super chief 8 amps so should be plenty of amps.
I figured I needed it cause I could see with 4 mainlines I might run 4 3-engine
consists at one time. That would be 12 engines and some with sound. The command station will shut down with a short, but maybe not in time to not fry a decoder? I 
guess. Its my understanding the PM42 can be set to shutdown easier and faster
than the command station. Plus it breaks up layout in 4 sections to help detect shorts
faster. At least you know which section has a problem.It does sound like a worthwhile
gadget. Thanks for letting me know the AR1 can work on 2 or more sections as long
as only 1 section is used at a time. I really don't need to turn 2 engines on "Y"s at
the same time.


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## mopac (Feb 24, 2011)

Just thought of this. With the 8 amp system will each of
the 4 sections from the PM42 have 8 amp service?


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## Brakeman Jake (Mar 8, 2009)

When used as circuit breakers the four PM42 sections have I think 2 or 3 adjustable levels of amperage they'll allow to go through before they trip.These are user adjustable and if my memory serves me well,the instructions say that they come preset at the low amps. level or 1.5 amps.And yes,it probably can be set so that you have the full eight amps. on one circuit tough I have serious doubts...the PM42 is not an amperage multiplier...if you use eight amps on one main,nothing left for the other mains.


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## mopac (Feb 24, 2011)

I understand. You use 3 amps on one main you only have 5 amps
left total for the other 3 mains. Average of 2 amps per main. Ate 
those 8 amps quick. May have to use some dummy engines if I
start to run out of juice. Thanks for info. Probably not a good idea
to max out your command station either.


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