Is there a rule of thumb of how powerful your transformer should be? Say for a lay out of of over 100 feet of Fast track O gauge? Just wondering. Right now I'm getting by on a MTH Z1000 transformer 100 watts. My whole system needs to be wired better. Just trying to save for certain things. Open to suggestion Thank You all!
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Power requirements probably depend more on your wiring and what you are running on the track than just track length alone.
Better to have too much power than not enough, IMHO. You can always throttle back. 
There are people that will put a Z4000 on a 40x60 loop and swear by their decision. In reality it depends upon what you're running. If you operate at 18VAC (for example) and see a draw of 2.5 amps it doesn't matter if it's a Z1000, Z4000, or a ZW-L for that matter. Amps are amps.
As for a rule of thumb; put one power feeder for every 6 joints on your FasTrack. The loss is in the joints, not the rails. Again there are folks with 100 feet of track that try to power it with a single 18 ga. feeder.
Another rule of thumb? When in doubt, run bigger wire. While it is counterintuitive (and I have been vehemently argued about this) but larger wire (12 ga. for example) has lower resistance per foot than 18 ga. wire.
Want to pull 15-20 passenger cars with incandescent lighting with three powered engines blowing smoke? Start saving up for your bigger transformer.
BTW, Paul I think it's safe to say that you have enough power there for any O gauge layout ever built.
Gilly@N&W posted:
Another rule of thumb? When in doubt, run bigger wire. While it is counterintuitive (and I have been vehemently argued about this) but larger wire (12 ga. for example) has lower resistance per foot than 18 ga. wire.
Current travels on the surface of the wire, so that is correct. The larger the wire, the more surface area, thus less resistance.
Simon
Simon Winter posted:Current travels on the surface of the wire, so that is correct. The larger the wire, the more surface area, thus less resistance.
Simon
Correct. Yet one of our club 'experts" continues to insist that 22 ga. wire has lower resistance than the 14 ga I have been using for wiring for our club modules. It does tick me off. I'm an electrical engineer.
Gilly@N&W posted:Simon Winter posted:Current travels on the surface of the wire, so that is correct. The larger the wire, the more surface area, thus less resistance.
Simon
Correct. Yet one of our club 'experts" continues to insist that 22 ga. wire has lower resistance than the 14 ga I have been using for wiring for our club modules. It does tick me off. I'm an electrical engineer. He sells toys.
Every club has to have an "Einstein".
Amazing, huh?
Gilly@N&W posted:Correct. Yet one of our club 'experts" continues to insist that 22 ga. wire has lower resistance than the 14 ga I have been using for wiring for our club modules. It does tick me off. I'm an electrical engineer. He sells toys.
Good Lord. He obviously doesn't read, so maybe a picture would help...
And here.
DDAVE,
There is “NO RULE OF THUMB”!
Its called “CALCULATION”!
Just saying !!
FREDSTRAINS
Simon Winter posted:Gilly@N&W posted:
Another rule of thumb? When in doubt, run bigger wire. While it is counterintuitive (and I have been vehemently argued about this) but larger wire (12 ga. for example) has lower resistance per foot than 18 ga. wire.
Current travels on the surface of the wire, so that is correct. The larger the wire, the more surface area, thus less resistance.
Simon
Skin effect at 60hz in copper wire is 8.5mm, so skin effect is not a factor with any wire we'd be using. In case anyone is keeping track, that means unless the wire conductor is more than about 2/3" in diameter, skin effect isn't a factor.
Yes, 12ga wire has lower resistance than 18ga wire for the same length, that's simply because there's more conductive material in the 12ga wire, not because of skin effect.
Anyone wiring their layout with 0000 wire?
BTW, the published wire tables are for acceptable voltage drop for a 120 vac circuit 100 feet in length. The acceptable voltage drop for an 18 vac circuit of the same current and wire gauge would be about 0.15 times 100 feet, or 15 feet. For example, the drop for a 12 gauge wire at 100 feet with 20 amps is 6+ volts. Obviously too much of a drop for a circuit that is only 18 vac. Limiting the length to 15 feet, same gauge and current, limits the drop to less than a volt. Acceptable and a typical length for most home layouts as it happens.
My rule of thumb is a low number in wire gauge and a high number in transformer wattage. Consequently, I find that 12 and 360 work fine for me.and be sure to use fast acting breakers or fuses.
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