Using 4 core telephone cable for accessory decoder cabling

[KPJunk]

Hi everyone

I would like to use 4 core telephone  cable to connect the points motor to the accessory module in an attempt to keep the cabling tidier.

Apart from having to cut the unwanted 4th cable both ends and using different colours to the traditional Red Green black cables , can anyone see any problems with wiring this way .

Any help appreciated 

Keith 

 

[Bahnhof Mersch]

Hi Keith

 

I've never used phone cable as I find the single strand a bit fragile.  I succesfully use 6 and even 12 core alarm cable, which has the advantage of being able to use one cable to supply several points close to each other.  The only challenge is remembering which colours were used at either end for which point!

[Teedoubleudee]

That's a good question. I have just completed wiring my points to decoders and I did use single strand copper telephone cable for the frog switching but NOT for the solenoid motor connections for which I used multi stranded wire. I also used the phone cable for short droppers from each rail section to below baseboard DCC bus.

It would be interesting to know what current that cable can take safely - it looks thicker than 15 amp fuse wire so might be OK.

[KPJunk]

Looking at the cable again , I think that 6 core alarm cable would be better especially as most of the points will be in pairs, re colours 3 are red , green & black so that only leaves the other 3 to ensure I translate the colours correctly . Thanks for the suggestion

Re the current the cable can take , it appears to be the same thickness or slightly bigger than the cable I am using already so unless anyone says not a good idea , I shall go ahead

Keith

 

[Pete172]

 Hi,

If your point motor is only about a foot away from your decoder, thin wire may be ok - also depends on which model of point motor, as some demand more current than others. On a reasonable sized layout, the norm is to use multi strand wire at a minimum of 16x0.2 (16 strands) x (0.2mm). This type of wire should usually be able to carry the 4 or 5 AMPS that the typical solenoid point motor demands ...over distance.....

Best to use this type of wire to avoid those frustrating instances when the motor doesn't move reliably.

[tony_forward]

I've used single strand 4 or 6 core telephone cable for years without any problems. Having been given a reel of both by a friendly telephone engineer (yes there are some) some years ago it seemed churlish not to use it :)

 

[Yelrow]

Good for you tony, my papa was a telephone engineer, and its also, been good enough for me. Never had a problem. john

[Flashbang]

Hi

This is always a subject that receives many replies and various answers.

But best practice says use a wire of the largest conductor size possible or practicable. In general the minimum wire size recommended for 100% solinoid operation is 16/0.2mm or 0.5mm2  This will allow fault free operation over a reasonable operating distance switch or decoder to motor.

If your solinoide motors work on damp string, phone wire, alarm wire, bell wire or three lengths of 22mm dia copper pipe that's fine. But the idea is always to offer best practice advice as this ensures the item will work without any issue.

[37lover]

Very well said Flashbang & Pete172. At times it worries me that so many people are willing to take risks with their wiring, and others are offering advice based on something that has worked for them without any "proof". TWD; you have completed your wiring and state "it would be interesting to know what current that cable can safely take". Don't you think you should have established that before wiring?

Anyone know a telephone Engineer who can provide technical specification on telephone cables?

[2e0dtoeric]

Long lengths of very fine wire lose more amps than the same length of thicker wire. (It can also overheat and melt the insulating sheath!)

Single-core wire is more brittle and prone to snapping than multi-stranded wire.

In the final verdict, use whatever is to hand, and suffer the consequences!  :-)

[96RAF]

Given that your point motors are solenoids and they are only powered for milliseconds I doubt the wiring would have time to heat up, unless there was a fault situation such as power being applied for a long time in which case the motor would wrap it's hand in as well.

take a look at the cable size on a Hornby surface mount motor, it's very thin although stranded.

i use double strand network cable for solenoids and single strand for LEDs. I agree single strand wire is prone to inflexibility but then once installed and clipped it should be ok.

[Teedoubleudee]

............................. TWD; you have completed your wiring and state "it would be interesting to know what current that cable can safely take". Don't you think you should have established that before wiring?

Anyone know a telephone Engineer who can provide technical specification on telephone cables?

I did say I'd finished, but I also said I didn't use it for the high current solenoid motors for which I've used 16/0.2mm stranded cable. Should be ample for my point frogs which are powered by miniature latching relays.

 

BTW  Google searching tells me that Farnell rate their 'phone cable limits at 80v and 0.25A.

[Teedoubleudee]

............................. TWD; you have completed your wiring and state "it would be interesting to know what current that cable can safely take". Don't you think you should have established that before wiring?

Anyone know a telephone Engineer who can provide technical specification on telephone cables?

I did say I'd finished, but I also said I didn't use it for the high current solenoid motors for which I've used 16/0.2mm stranded cable. Should be ample for my point frogs which are powered by miniature latching relays.

 

BTW  Google searching tells me that Farnell rate their 'phone cable limits at 80v and 0.25A.

Sorry, meant to say that the 'phone wire should be OK for the frogs.

Here's another interesting link:

http://ce.superioressex.com/uploadedFiles/docs/pdf/technical-guidelines/TG31-Telephone-WireCable.pdf

[37lover]

I did say I'd finished, but I also said I didn't use it for the high current solenoid motors for which I've used 16/0.2mm stranded cable. Should be ample for my point frogs which are powered by miniature latching relays.

 

BTW  Google searching tells me that Farnell rate their 'phone cable limits at 80v and 0.25A.

You certainly did and apologies if it sounded like I was questioning that. I used the 24/0.2 for my Seep motors but only because I was powering via a remote mimic panel which lengthened the cable route. I bought several 100 m rools of different colours of the cable and I think the 24/02 was only marginally more expensive than the 16/0.2. 100m goes a long way round the layout! Fortunately I've managed to sell some of the left over surplus cable!

Interesting info about phone cable, thanks. 0.25A doesn't seem very much. I'm aware that a modern loco might draw that much once running so if two are running does that mean the phone cable on your frogs will be getting warm?

[Teedoubleudee]

They would only get warm when they were passing current which would mean a loco sitting on them for any length of time which I would have thought unlikely. I also used the single strand for the droppers as it was easier to hide them under the rails, but my logic for that one is much the same as they wouldn't be passing current continously and many of them combined with the rails themselves and the heavy duty bus wire would mean it most improbable that one dropper would be passing a large current for any great length of time. It's early days yet so I hope I'm not proved wrong!

Having read your last reply I've just realised it is in fact 24/02mm and not 16/0.2,mm wire that i've used for the solenoids like yourself. I got mine from Maplin and as, like you said, the price difference was negligible.

[96RAF]

In an old thread I posted that a PO engineer had told me telephone wires have a 75v standing current. A response from another PO engineer said more like 90v when live carrying a call As confirmed by his bald head touching a cable up a telephone pole.

so 80v @ 0.25a would give a reasonable current capability of over well over 1.3a continuous @ track 15v, more @ 12v.

ref the frog links the wire used on points by manufs isn't that heavy gauge. Also Hornby points clips are springy wire and springy wire usually doesn't usually mean current friendly.

[37lover]

In an old thread I posted that a PO engineer had told me telephone wires have a 75v standing current. A response from another PO engineer said more like 90v when live carrying a call As confirmed by his bald head touching a cable up a telephone pole.

so 80v @ 0.25a would give a reasonable current capability of over well over 1.3a continuous @ track 15v, more @ 12v.

ref the frog links the wire used on points by manufs isn't that heavy gauge. Also Hornby points clips are springy wire and springy wire usually doesn't usually mean current friendly.

RAF96,

I had gone completely vacant about current capacity inverse relationship to voltage [just thinking 0.25a at all voltages], too much Christmas cheer!

To try and keep my few brain cells active could I ask you what happens to the current flow path as a loco goes around the layout? I assume the current travels though the path of least resistance and therefore could pass through different droppers as the loco moves around. However, the rail must have very low resistaqnce so presumably there may be some current passing through all droppers, in effect load sharing? I'm just trying to understand how lighter duty cable could function as droppers.

[96RAF]

You've got it 37lover with your path of least resistance analogy, think water running downhill, it takes the easiest route. Hence short circuits.

For track droppers I use the sleeved wires stripped out from 1mm twin and earth mains cable, with 2.5mm mains cable wires as the bus wires. Maybe a bit over capable but the wire was what I had spare at the time.

[PJ_model_trains]

You've got it 37lover with your path of least resistance analogy, think water running downhill, it takes the easiest route. Hence short circuits.

For track droppers I use the sleeved wires stripped out from 1mm twin and earth mains cable, with 2.5mm mains cable wires as the bus wires. Maybe a bit over capable but the wire was what I had spare at the time.

 

Excellent way to describe the flow/downhill 'short circuits' RAF

 

I have used 2.5mm for the DCC Bus (twisted), and stripped 2.5mm for the droppers. Over the top but it was easiest and saved buying two sizes.

 

PJ