Confused about dcc cable

[AdeRail]

Hi,

 

Sorry that this question has probably been asked trillions of times ☹️

 

But I'm a little confused about dcc cable size for my layout.

 

From what I can gather from good posts on this forum, with my layout being approx 12 feet square, I will need 1.5mm2 bus cable.

 

However I'm not sure if this should be flex or solid cabling.

Plus being on a tight budget I'm hoping to get it cheap from toolstation, so if possible could anyone point me to the right choice from this link.

 

http://www.toolstation.com/shop/Electrical/d190/Cables+%26+Flexes/sd2730

 

Any help is good,

Thanks

Ade

[Chrissaf]

Ade,

 

You really know how to open a 'can of worms'. Many 'in the know' will recommend 'multi-strand' cable (what you are calling 'flex). Just as many will say I use 'solid' conductor and it is fine. I'm in the 'stranded' wire camp.

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The main pros and cons.

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• Stranded wire is less prone to fatigue induced breakages.
• Stranded wire size for size is more flexible than 'solid' wire so easier to route and install under a baseboard.
• Solid conductor wire in the form that you have identified with your posted link is easier to obtain over the counter.
• Stranded wire more often or not needs to be ordered from a specialist cable vendor for which minimum length order quantities may prevail.
• Stranded wire comes in all sorts of colours for colour coding their function.
• Solid wire stripped out of electrical Twin & Earth (UK colours) as you have proposed is limited to Brown & Blue.
• Personally, I feel that your proposed 1.5mm2 is too thin and needs to be 2.5mm2 as a minimum and twisted around each other to form a twisted pair to reduce susceptibility to induced interference.
• Solid conductor wire is probably a little easier to remove a length of insulation to make a soldered joint to a thinner dropper wire.

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PS - Above is just my personal view. Other's are bound to be in disagreement hence my 'can of worms' comment.

[AdeRail]

Yup if ya want a hard to twist cap off can of worms opening, I'm ya man 😇

 

Anyway 

Any recommendations for the best place to get "the right" 2.5mm2 single or multi strand cable from, online or high street?

[westernwill]

I have always found Railway Scenics good. They have a wide range of cables and connectors and provide quick and reliable service.

[Chrissaf]

I bought all my cable from "rapidonline.com" but there again I was buying in bulk on 100 metre reels. A low cost per metre, but a significant cost overall because of the quantity (the number of different coloured reels I purchased). You can however, buy per metre lengths via ebay. Search 32/0.2mm wire for main distribution bus and 7/0.2mm wire for droppers.

[96RAF]

For the track bus cables I have used 2.5mm ex mains twin and earth ring main cable. Stripped of the outer grey sheath it is easy to work with and strip insulation from to attach droppers for which I use more regular stranded cable as stated earlier.

Rob

[RDS]

I have also used 2.5mm T&E stripped of the outer sheath for my DCC Bus.

[2e0dtoeric]

Don't be too fussed about how thick is thick enough!

Within reason, the thicker the better, as there is less voltage drop on a thick wire, rather than a thin one! It is also structurally stronger. The main considerations are - what you can get hold of, - and physical weight.

In my unwanted opinion, stranded wire is better than single-core, because, as Chrissaf put, it is less prone to fatigue breaks. which always seem to occur INSIDE the plastic sheath, and are a devil to find!

BUT - thick single is easier to solder than thick stranded!

I use an old curly microphone wire, to connect my Elite to the BUS, because it doesn't end up in an almighty tangle, and I've run the power cable from the transformer down the centre of the curly wire, thus keeping that under control at the same time.

[Bulleidboy]

I bought my 2.5mm2 from B&Q  - cost about £10 for a 25m roll - solid core.

[AdeRail]

I bought my 2.5mm2 from B&Q  - cost about £10 for a 25m roll - solid core.

So would this be similar to what you bought?

http://www.diy.com/departments/prysmian-25mm-twin-earth-cable-reel-l50m/33842_BQ.prd

[spursnz]

I'm afraid you have all missed the point of the discussion. When choosing suitable cable for any instalation we are primarily concerned with current carrying capability. Therefore most DCC Installations 12 ft by 12 ft as example would only draw a maximum of 2 amps or so. As I haven't got the relevant  code standards at hand but from experiance 1.5 would eat 2 amps in fact 10 amps would still be within its capability. Any noise interference on the system should be dealt with at the source as it quite simply should not be there.

[96RAF]

Just remember when talking about flex wire spec that the second number (e.g. 0.2mm) is the per strand diameter but it is cross sectional area (2.5mm2) of each core we are talking about with the ex-main cable. Hence if you go for a flex wire with twice the diameter then you get rather more than just twice the area. Compare πD to πR2. Current carrying capability is relative to cross sectional area as stated above by spurnz.

[Rog RJ]

I'm afraid you have all missed the point of the discussion. When choosing suitable cable for any instalation we are primarily concerned with current carrying capability. Therefore most DCC Installations 12 ft by 12 ft as example would only draw a maximum of 2 amps or so. As I haven't got the relevant  code standards at hand but from experiance 1.5 would eat 2 amps in fact 10 amps would still be within its capability. Any noise interference on the system should be dealt with at the source as it quite simply should not be there.

The reason for using such heavy gauge cable is to keep the voltage drop caused by resistance to a minimum, not just to allow full voltage to reach the locos but also to ensure that the DCC command station or booster shuts down IMMEDIATELY if there is a short circuit. This is essential to prevent damage to tracks and models.

It is often suggested that a check is made that the command station/controller/booster shuts down properly by doing the "coin test".  That means deliberately creating a short circuit by placing a coin (or other conductive object such as a screwdriver) across the rails to make sure that an instantaneous shut down happens.  The coin test should work from any point on the track without hesitation.  It is best to remove all locos from the tracks while doing the coin tests to prevent accidental damage.

 

[Chrissaf]

Regarding the comment "Any noise interference on the system should be dealt with at the source as it quite simply should not be there." twisting the DCC signal pair is a lot more than just rejecting induced noise from external sources.

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Mark Gurries is a member of the NMRA, here is an extract from his website relating to this topic. Granted, more relevant to larger layouts and longer DCC bus wiring, but an Insurance Policy for peace of mind is still worth having on smaller layouts.

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https://sites.google.com/site/markgurries/home/dcc-general-best-practices/wiring-planing/twisted-pair-wiring/twisted-wiring-dcc-background

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And in addition to the overview above, this page from Mark's website:

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https://sites.google.com/site/markgurries/home/dcc-general-best-practices/wiring-planing/twisted-pair-wiring/technical-discussion