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7/02 wire has a maximum continuous current rating of 1.4A and a resistance or .1 ohm per metre. While it can handle much higher currents for a very short time the voltage could be a significant factor. For instance, 0.5A over a 2m length will give a voltage drop of 1 Volt; hardly significant for traction. Point motors take much higher currents. However, if you are using a CDU with a reasonably high voltage, there should be no problem unless you are using route switching, in which case, the wire supplying the diode matrix should be heavier duty. Also, you might have problems with a long wire run feeding two points (as in a crossover with linked points switching).

Reference: Model Rail Forum > The Engine Sheds - Community Forums > Tracks, Layouts & Scenery > Wiring for pont (sic) motors, last post 14th April 2008.
 

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Hi Richard.

I note your comments which are, of course, valid as a general statement. However, I was taking into account two things, maybe erroneously. One was that David does not mention DCC so I assumed that he is operating in DC; I know virtually nothing about DCC, my one foray with it being not very satisfactory. Secondly that he is using a small layout. (I ought to add a third to that - namely that his layout isn't going to be subjected to rigours of the exhibiiton circuit.) My experience of modelling is limited; I built several 'layouts' some 50-45 years ago but not having much money none every got finished. I built a layout 20 years or so ago that was 13' x 8' HO and used 7/02 for the track power with no adverse results. I am in the process of building a new Z scale 6' x 2' layout and am, again using 7/02 as all the runs are very short so straightforward resistive drops are not significant and, as it is DC, AC is only present in signalling and lighting circuits. (I note that the Viessmann Z scale semaphore signals work fine on 10Vac, just over half the recommended 16Vac so, at 50Hz, not a problem.

(1) Yes, point taken. I am well used to using a soldering iron on electronic circuits and have an Weller iron that is temperature controlled. So the only time I have a problem is when I solder to track though even there I am getting better at it. Joint resistance could be a problem with dry joints etc. I haven't checked the resistance of my solder joints but I might do that some time to see exactly how much it is (hopefully negligible).

(2) Again, taking the specific layout and assuming the use of DC for all but tasks mentioned above I don't see inductance as being a problem. I understand that DCC works well above 50Hz and inductance would introduce phase shifts as well as increasing the impedance.

(3) From what you say, wiring for point motors should be 8A minimum and take your point regarding sticking switches. With Peco point motors taking 4 amps continuous you might just get away with using 24/0.2 with a continuous rating of 6A as long as the wires were not loomed. (This was dramatically brought home to me when, as a teenager, I used some 5A flex folded back on itself to form a 6 or 8 wire bundle to drive a 2kW fire. When I undid the string holding it all together - pre tywrap days - the whole lot was a solid wadge of insulation. I kept it as a reminder for years. The current flowing through it was 8 amps.) Mind you, how quickly would you no longer have a point motor? Would that burn out first. A while back I deliberately burned out a faulty Marklin point motor. It only took a couple of seconds to do it.

(4) See above. If David had said that he was using DCC I wouldn't even have bothered replying.

I am using 7/02 throughout my Z scale layout. The only exception will be where there is a common cable that could be carrying multiples returns from a number of sources (e.g. the common return buss from the track that could be carrying current from four (unlit) trains in which case I will use 16/0.2). I will also require heavier cable if I go down the route selection system of turnout control just to prevent excess voltage drop.

I hope that shows where I was coming from when I wrote my response above. When I come to build my N scale layout (13' x 12') I will certainly use a heavier wire.

Once again, thank you for your response to my message.

With best wishes,
Chris.
 
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