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Vitesse Wiring Specs


paulday
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Hi all just a quick question I'm about to rewire the various bits of wiring in my bonnet which is an odd collection of different size colours and types of wiring after 50 years of various owners 'fixes'. What was the original specs for the wiring, size/rating and any recommendations for sourcing wire and connectors in the UK.

Many thanks

Paul

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Hello Paul,

Thinwall wire is the way forward these days - smaller gauge wire but handles higher current compared to the old style wiring found in classics. Thinwall is used in moderns because of its advantages.

I get my wiring from ALM Electrical Solutions via eBay and here is their link: http://www.ebaystores.co.uk/ALM-Electrical-Solutions

Kevin is the chap that owns the business and is very helpful indeed. He has every wire colour combination that has been used and is currently used; in addition his "wire" pages provide the max handling current for the wire in question.

I have also added the current Lucas wiring reference pdf which provides the correct cable colour for the electrical requirement.

Others on here will recommend other providers who will be equally as good - ALM just happens to my choice due to excellent customer service.

Good luck.

Richard.

 

BS-AU7-LUCAS-WIRE-COLOUR-CODES.pdf

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I used alm for cable supplies when I rewired the indicators and headlights on the vitesse, I used their main site for the bulk of the stuff, it was cheaper than ebay, and then the bits I missed I orders via ebay. Customer service was helpful and responsive to queries

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Hi

Interesting reading the Above. I have been trying to get some perspective on the subject. My first thought was the Copper has a known Conductivity, and most was based on 99.9% pure?. As far as I aware that has not altered?. Therefore I found it hard to see how the "new" thinwall could make a substantial difference to the base metals ability to conduct current?. It appears that this (ability) is a function of the insulation`s ability to cope with higher temperature, thereby allowing the current to be increased?.

This:- https://www.workshopwarehouse.co.uk/advicecentre/Electrical/Thin_Wall_Auto_Cables.html

Was informative

Pete

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10 hours ago, 68vitesse said:

Also a good idea to add relays for the headlights to reduce load on the dashboard and column switches, when I did mine also got a decent increase in voltage at the headlights.

Plenty of posts about this.

Regards

Paul

I`ve done that on several vehicles over time. It`s especially important, when cable runs are long, as when needing to add Trailer Lighting too.

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6 hours ago, PeteH said:

Hi

Interesting reading the Above. I have been trying to get some perspective on the subject. My first thought was the Copper has a known Conductivity, and most was based on 99.9% pure?. As far as I aware that has not altered?. Therefore I found it hard to see how the "new" thinwall could make a substantial difference to the base metals ability to conduct current?. It appears that this (ability) is a function of the insulation`s ability to cope with higher temperature, thereby allowing the current to be increased?.

This:- https://www.workshopwarehouse.co.uk/advicecentre/Electrical/Thin_Wall_Auto_Cables.html

Was informative

Pete

Hi,

 Look at PTFE covered wire if you need high current and small CSA. Alas, volt drop is worse.

As noted above its possible to get more copper for the same major diameter with thin-wall.

Cheers,

Iain.

 

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2 hours ago, SpitFire6 said:

Hi,

 Look at PTFE covered wire if you need high current and small CSA. Alas, volt drop is worse.

As noted above its possible to get more copper for the same major diameter with thin-wall.

Cheers,

Iain.

 

Yes, but in the spec sheet I attached, they are suggesting that (almost; 1.005185mm/2 as opposed to 0.989478mm/2) the same cross section of copper can conduct a higher current?. Which would appear to go against what I was taught? (back in the 50/60`s).

Pete

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11 hours ago, PeteH said:

Hi

Interesting reading the Above. I have been trying to get some perspective on the subject. My first thought was the Copper has a known Conductivity, and most was based on 99.9% pure?. As far as I aware that has not altered?. Therefore I found it hard to see how the "new" thinwall could make a substantial difference to the base metals ability to conduct current?. It appears that this (ability) is a function of the insulation`s ability to cope with higher temperature, thereby allowing the current to be increased?.

This:- https://www.workshopwarehouse.co.uk/advicecentre/Electrical/Thin_Wall_Auto_Cables.html

Was informative

Pete

I agree, stay with copper. The heat in the wire is caused by it's resistance and the current flowing through it. This heat is a power lost in the wire and causes a voltage drop. You don't want heat in the wire in the first place. e.g. Thicker wire gives a lower resistance, generates less heat for a given current and less voltage drop.

Also the increase in resistance of copper wire due to the increase in heat is small enough to have little effect in this application.

If it is better than copper then it will be due to a lower resistance for a given length of wire and not it's insulation..  

Dave

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Hi Pete,

 As you have reasoned copper cables of same conductor diameter/Area. Will perform the same.
The different insulation types differ in their maximum operating temperatures. Allowing a higher current requires different insulation materials. Thinwall insulation is a higher temperature for example. How the cable is mounted affects its ratings also.

Hope that makes sense.

Above applies to DC & not silly currents,

Tinned copper thin-wall is good for outside conditions. A high flexible tinned copper cable would conduct a knats less current I Guess?

The cables that have greater current ratings will also have higher volt drops. Voltage loss is not good on a 12V system.

Cheers,

Iain.
 

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1 hour ago, SpitFire6 said:

Hi Pete,

 As you have reasoned copper cables of same conductor diameter/Area. Will perform the same.
The different insulation types differ in their maximum operating temperatures. Allowing a higher current requires different insulation materials. Thinwall insulation is a higher temperature for example. How the cable is mounted affects its ratings also.

Hope that makes sense.

Above applies to DC & not silly currents,

Tinned copper thin-wall is good for outside conditions. A high flexible tinned copper cable would conduct a knats less current I Guess?

The cables that have greater current ratings will also have higher volt drops. Voltage loss is not good on a 12V system.

Cheers,

Iain.
 

The cable should not be working at a temperature that effects the insulation. If it is then there is likely to be to much voltage drop at 12 volts.

A cable with a higher or greater current ratings has a lower resistance therefore generates less heat and has a lower voltage drop at 12 volts.

Sorry to labour the point.

Dave

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39 minutes ago, dave.vitesse said:

The cable should not be working at a temperature that effects the insulation. If it is then there is likely to be to much voltage drop at 12 volts.

A cable with a higher or greater current ratings has a lower resistance therefore generates less heat and has a lower voltage drop at 12 volts.

Sorry to labour the point.

Dave

Which is how I always approached the subject, If in doubt go bigger.?  I owned until 2102, a 32ft American R-V. When I tried to rig trailer lighting, the voltage drop caused real issues. In the end I got round it by running a separate fused cable, rated 40A from the chassis battery and used that for power, switched by Relays for the various functions.

Pete.

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Which is what I am having difficulty with. The resistance of copper is finite within set parameters per metre?. Therefore IF the Resistance of (say) 1mm dia copper conductor is FIXED. the only thing that can change IS Either Current of Voltage?. so Current UP = Voltage DOWN. and vice versa?. Which brings me full circle, back to HOW can "thin" cable (same nominal conductor size) carry more current?. Yet the TABLES are suggesting just that?.

Pete

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Go back to basic physics. A cable with a greater resistance for a given length will cause a bigger voltage drop at a given current and voltage. Basic Ohms law. 

Two factors that can change the resistance are the material it's made of or it's size. If we say copper is a constant then it's the size that makes the difference. i.e. Increase the size of the cable and you reduce it's resistance.

The resistance should be lower not higher for a cable carrying a higher current to prevent both heat and a voltage drop.

The next factor to consider is if the cable is either solid or stranded (multi core). It has been stated that a solid cable for a given diameter has a lower resistance and will dissipate the heat more effectively than a stranded cable of the same diameter. Therefore the solid cable should be able to carry a higher current. However, my training was that solid cable should not be used where there is any vibration or movement as it could fracture. Only stranded should be used in these applications.

Any advantage in current carrying capability with the solid cable is lightly to be small over the stranded cable. To my mind the disadvantage of a likely fractured cable due to higher vibrations present in a classic car is greater.

The main advantage with the solid cable, in Direct Current use, is that it uses less copper. There are other advantages, skin effect, when used in high frequency, AC, radio applications.

Dave

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Solid conductor cable is not always higher current capacity?

I work for a Mechanical/Electrical Company which have a Panel shop making Switch panels up to 2000 Amp ratings.?

They use extensively what is called Tri-rated cable within these panels, this cable is multi-stranded and more flexible than standard PVC sheathed copper cables, hence easier to install inside panels. It is also rated higher than standard cables for current carrying capacity, it is also rated up to 105 degrees Centigrade (I think?) most normal PVC or XLPE type cables are 70 or 90 degree rated

The higher current carrying capacity is mainly due to the multi-strand copper conductors, If I was at work I could show you the current carrying capacity tables out of my Wiring Regulations book, usually multi-strand Tri-rated conductors carry slightly more current than solid Conductors for an equivalent CSA, also the temperature rating helps too.

When designing Industrial/Commercial buildings Electrical Installation circuits you can get one sometimes two sizes lower in the conductor CSA by using Tri-rated type cables instead of standard PVC or XLPE Insulated, it all depends on various factors though, grouping with other cables, type of Installation methods, Length of cable run, Circuit protection device, Etc? 

Similar factors apply for car wiring although the length of run and voltages are lower, the only really high current circuit on a car is the Starter Motor which can draw 300 to 400 Amps hence the larger CSA Cable from the battery to the Solenoid/Starter.

Hope this helps explaining things

Gary

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Hello Gary, The point is you don't want heat in the cable as this is caused by the resistance and current in the cable, this in turn creates a voltage drop at the load end. The cable should operate at the lowest temperature. At 12 volts these are low voltage circuits hence even a small voltage drop is unwanted.

Dave

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Dave

Yes, heat is not good, neither is voltage drop.

With only around 12 Volts available, any small voltage drop is not good for the correct operation of the car electrics, the Head Lights in particular are much more efficient with the full 12 Volts and the use of relays and larger CSA cables is a good move.  

On my Old TR I was measuring only 10 volts at the PI Pump with the car running  with the original puny wiring, so I.ran larger cables from a dedicated fuse with a separate earth , to the Original Lucas Pump via a relay mounted local to the Pump and used the original wiring to control the relay, I was getting just over 12 Volts at the pump with this modification😊.

A lot of car electrical trouble is due to bad/corroded earth connections and rusty/dirty lucar connectors, good clean, tight low resistance connections all help to keep the volts up!

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There have been several claims that the resistance of copper is a constant. While this is true of pseudo-crystalline pure copper, that's not what wire is made of. High quality wire has better copper than cheap nasty stuff, and far less corrosion than 50-year-old Triumph wiring. Defects in the atomic lattice or even alloyed other metals will affect the resistivity, usually adversely.

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For the purposes of this discussion we are saying copper is a constant as that is the point of increasing the size of the wire to handle a larger current.

Agreed there are varies degrees of conductivity as far as copper cable goes. However, there are standards which most manufacturers adhere to.

Dave

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I think that the salient point here about some cables of the same cross sectional area being able to carry more or less current than others is probably down to the temperature specification of the insulation.

There are insulations, such as PTFE and ETFE, that are much more tolerant of high temperatures, so one can carry higher currents in the same cross section of wire.

Likewise, for the thickness of the insulation itself, there are insulations that have much better mechanical durability to abrasions and cuts, so one can get away with thinner insulation.

There are insulations that have much better voltage breakdown characteristics, so again one can get away with thinner insulation - but in a car, the voltage breakdown characteristics are not really a consideration as its all 12V electrics, and not 100's or 1000's of volts (other than the HT leads) 

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I concur Kevin re the insulation. I didn't cover this as we were dealing with a 12 volts system.

High temperature reduces the effectiveness of insulation which becomes apparent when a high voltage is present. If that's coupled with a high current which creates a high energy field then it can make matters worse. Valve radio/TV transmitters or power generation are an example.

Dave

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I've* also run 1000A through a bit of copper pipe with water running through, but at only 12V so any voltage drop mattered! These days we generally don't bother to water cool as we find 400A is enough.

 

* OK, technically it was my brother who ran it, I just designed the electronics at the front end.

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