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Cable sizes for a basic DC layout


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I have finally managed to aquire all the electrofrog points that I need, so I am ready to start my layout, the problem is I am uncertain about which cable size(s) I should be using. I am assuming that something like Thinwall  11 amp, 0.5mm sq. 16/0.20, or 16.5 amp, 1mm sq. 32/0.20   will be more than adequate. Most of the wiring information I have found on line, and though the forum search, has been about DCC wiring which I am not using, I also have no plans to install point motors, Most of the information I have found about DC wiring has added to my confusion, with advice ranging from solid core vs. multi core, and very fine telephone cable to heavy 4mm sq. cable, so I am hoping that some helpful people on here can help. My experience of 12v wiring is limited to boats and so I only really understand standard and thinwall vehicle wiring specs, rather than AWG, most of which have no equivalent readily available in the UK. I do understand about resistance, and voltage drop, and the ampereage of modern loco motors is so low that they are unlikely to contribute anything noticeable on such short runs. The planned layout is an end to end one with a through station and sidings all within a length of about three metres, I would welcome some advice.

 

Oh, and one other thing, the term BUS seems to come up a lot, is it merely an abreviation of Bus Bar Wiring , or does it mean something else?

 

 

 

 

 

 

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For a good introduction try  https://www.brian-lambert.co.uk/Electrical_Page_1.html

He also has a book which some of our club members have found very useful.

Most of what you require for a layout of the size you propose  will be 7/0.2mm for individual track circuits fed by 16/0.2mm from the controllers, this will leave some margin if you later consider DCC. Thinwall insulation is fine.  A good source for this stuff if required is CPC-Farnell. check pricing and quantity carefully because they can have bargains , especially if you are not to concerend with the insulation colour

https://cpc.farnell.com/search?st=7%2F0.2mm hook up wire

For connections soldered to the track I use a solid strand 1/06mm wire. This is easier to solder neatly to the rail, then under the baseboard transfer to the flexible wire for the main run.

'Bus' is much as you suggest and applies particularly to DCC layout where the track (and sometimes) accessory power is distributed. This can become a 'mine is bigger than yours' event but depending on the perceived and actual loads and size of the layout. A common value here would be 2.5mm2, cheaply obtained from house wiring cable a pair of wires running the length of the baseboard and branched where needed to the track with smaller wires.

One use of a similar 'bus' in DC installations will be where 'Common return' wiring is used. Again Brian Lambert's site ref above will describe this better than I can.

In relation to wires: There is an increasing tendency for aluminium wire to be used in small sizes, telephone, 'bell wire' and thin alarm cables are common sources. This stuff should be avoided like the plague. It is frequently (and correctly) described as 'CCA', Copper Coated  Aluminium. It can be a swine to solder but breaks when you look at it. The copper version will be more expensive, but worth it.

AWG wire size equivalants to swg and mm2 can be found on line.

 

From a safety point of view, avoid mains electricity on the baseboard  -  keep it safely in it's own box away from the layout.

Have fun and welcome to the world of magic smoke transmission

 

 

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If you're using DC, then in effect you're really only needing to power 1 loco in each section of the layout. If you want to run multiple locos, they have to be in different sections, separately supplied and controlled. Modern loco motors typically take no more than 1.0A (OO gauge and below) and so this is the current that you need to supply to each section. This is different to DCC where there is the potential for multiple locos running off the same supply.

 

I always recommend using multi-core ("stranded") cables. They are much more flexible than solid core and are easier to solder, when you have the need. 0.5mm2 wire is rated to 3A (this is equivalent to 20AWG or 16/0.2) and this should suit your needs. You can buy reels of this wire, although my approach is to buy mains flex of this size, since it is relatively cheap, colour coded and easily available. The only reason to use anything larger is if you have very long runs of wire and where voltage drop might become significant.

 

The term "bus" in relation to wiring really applies to DCC rather than DC. In DC layouts, it is necessary to run separate wires from the control panel (or whereever your control switches are located) to each track section. In DCC, a single pair of wires can in principle be laid around the layout and short droppers taken from these wires to the track where required. This pair of wires is termed the "bus" since it serves many places on the layout - and yes, it is kind of equivalent to bus bar wiring.

 

Yours,  Mike.

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AWG + American Wire Gauge & is one of the more bizarre units Americans are needlessly clinging on to rather than using something more meaningful.

Having just tried to read up on it, the gauge has to be calculated in a rather weird way. It seems to make things complicated just for the sake of it. It is also some sort of "denominator scale": the bigger the number, the smaller the wire.

 

The rest of the world has switched to metric for wire gauge because it actually means something: 7/0.2 being 7 strands of 0.2mm diameter wire.

 

Thicker wire (with the same conductor) will always give less resistance, which is desirable, but there are always compromises; weight, cost, tidiness & workability. On a model railway, weight is the last of these to become an issue, but because of the last 3, I agree with Steve W; 7/0.2 for droppers to track & 16/0.2 where you feel you need something a bit more substantial. Farnell's prices look really good too.

I would avoid telephone cabling. It is designed to carry low current signals, not layout power. I could not even find a current rating for it.

 

Use as many colours as you can justify. It will make tracing connections much easier.

 

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Thanks for very helpful information gentlemen, I have loads of 0.5mm2 multicore cable in my spare cable box, so from what you are saying I should be OK with that without having to buy any.

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