Bus and feeder gauge

[tom mann]

A quick search through the forum shows a number of options that people use. Is there a consensus now? I was going to use 14ga for the bus and 22 for feeders.

Is there a difference between solid and stranded for DCC?

[Philip H]

I think you are in the ball park - though the size of bus wire seems to be related to run distance - i.e. longer runs actually require larger gauge (lower number) bus wires due to resistance issues.

I also think solid versus stranded is a personal preference . . .

[peteski]

Exactly, solid or stranded wire is a personal preference (or whatever is available at the local surplus store).  If you were to use those IDC suitcase connectors then I believe those are for stranded wire.

The gauge used should be based on the length of the bus and on the current going through it. Not the operating current but short-circuit current.  Basically the bus resistance should be low enough that if you place a coin (short) across the rails at the most distant location on the bus, the short should trip the breaker in the booster.

If you have a 10A booster (trips at over 10 amps) or a 2A booster (trips at over 2 amps) the bus wire requirement will be different. 10A circuit will need a thicker wire than the 2A circuit.  But like I said, the bus length also matters.

[jagged ben]

14ga is fine for a 10A booster.  In fact it's generally more than big enough for all considerations, if you're not doing O scale.  But when you consider that #14 wire tends to be cheaply available at any big box store, such that saving money on a smaller gauge wire means more time shopping around than it's worth, that's really all the justification most people should need to use 14 gauge wire.

I disagree with peteski that we should base bus wire on short-circuit current, although it's true that you may have overload problems if you use too small a wire, and then combine that with poor soldering or relying on rail-joiners for electrical connectivity.    The main reason we oversize our bus-wires is to avoid voltage drop, which noticeably effects our train speed.  I think you are more likely to see ill-effects of voltage drop before your overload breaker stops working, although either one could be a warning of the other.   But, see my first paragraph for why you can just use #14 and not worry.

I would say that solid vs stranded is a personal preference, and that one can make a direct analogy to preferring either 'easy-to-bend-smooth-curves' Atlas code 55 flextrack no 'holds-its-shape' Micro-Engineering.

[peteski]

I disagree with peteski that we should base bus wire on short-circuit current, although it's true that you may have overload problems if you use too small a wire, and then combine that with poor soldering or relying on rail-joiners for electrical connectivity.    The main reason we oversize our bus-wires is to avoid voltage drop, which noticeably effects our train speed.  I think you are more likely to see ill-effects of voltage drop before your overload breaker stops working, although either one could be a warning of the other.   But, see my first paragraph for why you can just use #14 and not worry.

I'm not sure you are disagreeing with me.  If the bus wire is robust enough (has a low enough resistance) for a short at the end of the bus to trip the booster's breaker, then the voltage drop under normal operation will be negligible. But if the bus uses a thin wire which has a resistance high enough that even with a dead short at the end of the bus there isn't enough current flowing to trip the breaker then there is a good chance that even during normal operation there will be appreciable voltage drop over the length of the bus.

We seem to be saying the same thing, just in a different way.

[fire5506]

Just a point of information on the Stranded VS solid wire. You should not use crimp connectors with solid wire unless you also solder the connector to the wire. When you crimp the connector on solid wire it also deforms the wire and will seem to have good electrical connection at that time, but down the road you will get a little corrosion in the joint and have problems that will be hard to locate. I have run into this on our club layout, have to find the offending connector by wiggling every wire/connector. We have taken to soldering every solid wire connection as we find them while working in the area.

I use solid wire if I have it on hand, but solder the connectors.

DO NOT use TIX flux for soldering anything electrical. It is an acid flux and in time will eat either the wire or whatever it is soldered to. TIX is fine for soldering brass parts on loco's and such as long as you was it off well with lots of water and a brush.

Richard