MK9R
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| posted on 29/9/03 at 11:59 AM |
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Wire rating
Just about to start hacking the zx9 loom apart and extending/shorting it where needed. What sort of rating/size wire should i be using. Not worried
about lighting at the moment, just want to get the egine running
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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pbura
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| posted on 29/9/03 at 12:21 PM |
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Handy page about wiring:
http://home.clear.net.nz/pages/phil.bradshaw/car_wiring.htm
BoL,
Pete
Pete
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rell
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| posted on 29/9/03 at 12:32 PM |
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The wire thickness depends on the curent that flows throw it (not the voltage. the voltage governs the insulator thickness).
I can only give rating on house hold wiring hope it helps.
these are for tri rated cable.
1mm - 19A
1.5mm - 25A
2.5mm - 34A
4mm - 46A
6mm - 59A
10mm - 81A
16mm - 109A
I would use tri rated cable because it is nice and flexible and more inportant it can take 90 C beffor the insulator starts to get damaged (insted of
70 C).
quick point thow for exsample if you have a cable is carying 18 A and it is in a big group of cables go for 1.5mm insted of 1mm because of somthing
called grouping factor so if there are lots of cables in a group and it is close to the limit go up a size.
same with engine bay if it run in a place that is going to get hot and it's geting close to the limit go up a size.
Then agane if power is only on for a few seconds and then turnd off and there is a resanable amount of time beffor it is put back on may be go down a
size eg. 20A go for a 1 mm cable.
good look with the loom haven't started mine yet 
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rell
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| posted on 29/9/03 at 12:41 PM |
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Good link pbura
these ratings are for normal 70 c pvc not tri rated i think ?
(posted when i was typing  )
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rell
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| posted on 29/9/03 at 12:56 PM |
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thinking on 70 c pvc is probably ok because of the short time that thing are swiched on (dose not have time for the heat to build up).
save your self some money get normal 70 c pvc.
I would make shore that you get stranded cores (not one solid core) so it bends easy and is less likey to brake
thinking on 16mm dose sound a bit small for your main 100A 
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Stu16v
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| posted on 29/9/03 at 05:50 PM |
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Err, I know (hopefully) that it has only been used as an example, but I wouldnt advise anybody to use household cable in vehicle wiring.....
To put it simply, the higher the voltage, the less work that leccy cables have to do. Obviously there is a big difference between 12v and 240
volts....
Dont just build it.....make it!
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rell
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| posted on 29/9/03 at 06:35 PM |
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what cable do you think i should use for my loom then?
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rell
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| posted on 29/9/03 at 07:06 PM |
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dose pvc react with petrol and the like
if not there is no reason not to use normal 70 c pvc insulated.
as i said beffor the voltage is only the the insulator rating. there is no difference between dc and ac because ac is mesured at a rms value what is
the equivalent dc value.
if a cable of the same crossection can take more current it is because the insulator can take more heat (the more current gose throw the wire the
hotter it gets)
have a look at wiring regs bs 7671 if you can get hold of one ( it's a reference book every electrician should have one)
if there is a wiring regs for cars i would like to take a look at it if eney one has one ?
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Mk-Ninja
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| posted on 29/9/03 at 07:37 PM |
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I was going to use the wires from the donor loom. Not just because Im tight but I should be able to extend the wiring with the correct colour codes,
and I presumed that it must be up to the job since it was doing it before.
I'm sure I've got one, just don't know where I've put it
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kiwirex
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| posted on 30/9/03 at 09:28 AM |
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Ooops, sorry, wrong thread.
Thought it said "wife rating" and got all excited.
I'll get my coat
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Stu16v
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| posted on 30/9/03 at 05:08 PM |
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240 volt 1.5mm cable has a rating of 25 amps.
Ohms law states that volts = amps x ohms.
So, 240 (volts) divided by 25 (amps) means that this wire is capable of running a component with a resistance of 9 ohms.
Now to put that into perspective in a 12 volt system. Using Ohms law above, if we divide 12 volts by 9 ohms, we find that we only need a wire
with a current rating of 1.3 amps. All very simplified, but shows to highlight whats going on.....
So in reverse, for an 12 volt electric fan with a current drain of 15 amps, in simple theory you would need 240 volt cable rated at 300 amps.....
Dont just build it.....make it!
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suparuss
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| posted on 30/9/03 at 05:30 PM |
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whenever ive done electrical stuff on cars (mostly helping me mates do mods on their cars, bloody boy racers ) ive used equipment wire, i think it
is 1mm, cant remember the ratings, but will post later cos im on me back out to the shed now so will ave a look
Russ..
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rell
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| posted on 30/9/03 at 08:05 PM |
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yes stu this is right but it is a mater of power.
for example power (watts)= volts x amps
so for a 16watt fan current would be for 12 volt would be
amps = watts/volts
so
amps = 16w/12A
so
amps = 1.33A
lets try that with 240v
amps = watts / volts
so
amps = 16w/240v
so
amps = 0.067A
there for on 240v for the same power you would need a smaller cable
equipment wire is normaly 70 c pvc wire
when i say 70 c wire i meen 70 degrees c
tri rated is 85 c to 95 depending on who makes it
70 c is the temp the insulator can get up to befor it starts to brake down
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rell
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| posted on 30/9/03 at 08:30 PM |
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RS do cables tayor made for the job.
www.rs-components.co.uk
thay give you all the info you need (graph curent against temp)
thay have some nice green wire this will make a good looking loom with some cable ties
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suparuss
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| posted on 30/9/03 at 08:30 PM |
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yep, the equipment wire i use is 1.5kv rms 6A at 70 c. ive never had a problem with it. i mostly just use it cos i bought a few 100m reels of
varying colours so i need to use unless its gonna go in me will for the grand kids (im 23 btw)
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Stu16v
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| posted on 30/9/03 at 10:41 PM |
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quote:
Originally posted by rell
yes stu this is right but it is a mater of power.
for example power (watts)= volts x amps
so for a 16watt fan current would be for 12 volt would be
amps = watts/volts
so
amps = 16w/12A
so
amps = 1.33A
lets try that with 240v
amps = watts / volts
so
amps = 16w/240v
so
amps = 0.067A
there for on 240v for the same power you would need a smaller cable
equipment wire is normaly 70 c pvc wire
when i say 70 c wire i meen 70 degrees c
tri rated is 85 c to 95 depending on who makes it
70 c is the temp the insulator can get up to befor it starts to brake down
Err yes mate, thats exactly what I have been trying to say. 240 volts has smaller (less capacity) wire to supply the same amount of power (watts) to
operate the component at the other end. To supply the same amount of power with a 12 volt system you need bigger cables.
An extreme example is the reason why overhead power lines carry 40,000 volts+. The high volage means that small(ish) cables can carry enough power to
run the next city, Imagine the size of the cables if they only carryed twelve volts....
Dont just build it.....make it!
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rell
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| posted on 1/10/03 at 07:54 AM |
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I don't see where you get 300A from?
a 300A cable at 240v will deliver 72000 watts
to get this current on 240 you would
need 0.8 ohms load for this current
and at 12v it deliver 3600 watts
on 12v you would need a load of 0.04 ohms
a 300A (thats a 240mm cable) will take 300A at 12v or 240v the only thing that changes is the insulation rating(the thickness of the pvc).
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rell
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| posted on 1/10/03 at 09:14 AM |
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I see where y sliped up.
you put 300A insted of 300 watts
power = Volts X current
power = 12 X 25
power = 300 watts
but still cables have a current rating and a voltage rating not a power rating.
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rell
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| posted on 1/10/03 at 11:08 AM |
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I think i will be useing this cable.
ACW High Temperature Engine Harness Wiring
Back to: All Products | Cable & Connectors | Cables | Automotive Cable | Automotive Cable
Sold in reels of 100m
stock no. price per reel
1-7 8-15
0·5mm2 Black 369-4771 £23.79 £21.78
Red 369-4787 £23.79 £21.78
Green 369-4793 £23.79 £21.78
White 369-4800 £23.79 £21.78
(September 2003 Catalogue page 1-261)
Sold in reels of 100m
stock no. price per reel
1-7 8-15
1·0mm2 Black 369-4816 £32.11 £29.39
Red 369-4822 £32.11 £29.39
Green 369-4838 £32.11 £29.39
White 369-4844 £32.11 £29.39
(September 2003 Catalogue page 1-261)
Sold in reels of 100m
stock no. price per reel
1-7 8-15
1·5mm2 Black 369-4850 £39.73 £36.36
Red 369-4866 £39.73 £36.36
Green 369-4872 £39.73 £36.36
White 369-4894 £39.73 £36.36
(September 2003 Catalogue page 1-261)
Sold in reels of 100m
stock no. price per reel
1-7 8-15
2·5mm2 Black 369-4901 £53.11 £48.60
Red 369-4917 £53.11 £48.60
Green 369-4923 £53.11 £48.60
White 369-4939 £53.11 £48.60
(September 2003 Catalogue page 1-261)
ACW wire is a composite construction with a tough radiation cross-linked fluoropolymer outer layer. This outer layer is bonded to a radiation
cross-linked polyolefin.
Excellent fluid resistance, designed to withstand attack from a range of automotive fluids, including oil, brake fluid, antifreeze and fuels
Designed to function in the hot engine compartment environment
Excellent mechanical strength
Ideal for automotive wire handling
ETFE material performance at reduced cost
Smaller, lighter and more flexible
High level of compatibility with other automotive materials
Reel length = 100m
Note:This is a recommended replacement for Type 62™ automotive Wire.
technical specification
Wire Size CSA Conductor Primary Max. Cond.
(mm2) Strandings Wire Resist @ 20°C
(mm) O.D. (mm) (Ω/Km)
0·50 19/0·18 1·50 37·10
1·00 19/0·23 2·00 18·50
1·50 37/0·22 2·30 12·70
2·50 37/0·28 2·85 7·60
technical specification
Method Typical Value
Operating temp. ISO 6722 150°C (3000hrs)
Voltage rating 50V
Thermal overload ISO 6722 200°C 6hrs
High temp pressure test ISO 6722/WD 150°C 4hrs 1kVa.c. rms
Cold bend ISO 6722 -40°C
Flammability ISO 6722 45° Flame
Hot shrinkage ISO 6722 150°C <2%
Oil resistance ISO 6722 90°C <1% swell
Fuel resistance ISO 6722 23°C <1% swell
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Conditions of Sale | Website Terms | Privacy Policy
RS Web Helpline: 01536 444222 (8am-8pm Monday - Friday)
© RS Components Ltd
Birchington Road, Corby, Northants, NN17 9RS, UK
temp data on attachment
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rell
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| posted on 1/10/03 at 11:27 AM |
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Insted of using different coloured wires use numbers that clip on to the wire
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JoelP
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| posted on 1/10/03 at 01:10 PM |
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i myself will simply use new 12v wire, read the rating and pick an approproate size, and hence avoid the headache associated with equations!
regular size house hold wire that takes 13amps is actually quite thin as it obviously has 3 wires inside, car wire only has the one. As already
pointed, out due to the difference in volts an identical wire running at 12v will supply one twentieth the power of a 240v wire if the amps were the
same. So if you crank it back up to get the same power you have 20 times the current.
so which ever origin of wire you use, the power drain of the appliance will be the same and the current will be the same, as the volts will still be
12. The only problem with household wire is that because it is assumed it will be running at 240 volts, a given max current (say 13 amps) will result
in max power of around 3.25kW. If you try providing 3.25kW at 12 volts it will have a current of 260amps. Bosche.
Is wire rated in amps or watts? I would have imagined it would be in amps, in which case it is a moot point cos the max amps is the same whatever the
volts, it just means that less power can be supplied over all due to the lower volts.
Are both these equations correct? im just quoting those above:
volts= amps x ohms
P=VA
if so power = amps^2 x ohms,
so in stus example above the 240v wire rated at 300amps would be capable of supplying 22MW.
As rell says, voltage only changes the thickness of the insulation.
I must at this point remind everyone that i know nothing about electrics, only A level physics years ago, so please forgive me if im talking bollocks.
made sense when i wrote it...
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A Badger
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| posted on 1/10/03 at 01:45 PM |
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Joel,
You not talking rubbish, you just don't need to worry about resitance as generally any car load is quoted as a power rating, so it's just
power rating/ 12V = steady state current.
I've just started designing the wiring loom and have come up with the following requirements. I am going to use plenty of fuses to help with
identification of problems so will have the following circuits...
Stop/Tail lights 2x21W + 2x5W current = 4.333 Amps.
Side Lights 14W, current = 1.2 A
Fog Light/ Reversing light 2 x 21W current = 3.5 Amps
Indicators 94W current= 7.83 Amps
Headlamps 240W current = 20 Amps
I've yet to rate other items like the horn and the ignition/charging circuits.
The values above don't allow for warning lights etc, but I was planning to group them all together and use 25Amp cable for everything except the
headlights (use 39Amp).
Andrew
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timf
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| posted on 1/10/03 at 02:06 PM |
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house hold wire also tends to be 'stiffer' than auto wire and can run the risk of stress induced breaking in an automotive environment.
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rell
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| posted on 1/10/03 at 02:19 PM |
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Beet me to it badger just about to say the same thing.
and yes cable has a current rating not watts
don't no where you get 22MW from you corectly said
power = amps^2 X ohms
so there for
power = (300 X 300) X 0.8
power = 90K X 0.8
power = 72KW
for a 240V supply to deliver 300A it must have a resistance 0.8 ohms
V = I X R
there for
R = V / I
R = 240 / 300
R = 0.8 ohms
but it's all geting technical againe keep it symple as badger says work the curent out and look on the chart for the right size wire.
do not use house hold wire no one has advised you to use it on this post? i think people think when i said 70 c cable thay thort i ment twin and eirth
the flat gray stuff or flex what you wire plugs up with not the case i ment get a roll of single wire that is stranded so it is flexable.
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JoelP
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| posted on 1/10/03 at 04:15 PM |
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quote:
Originally posted by JoelP
so in stus example above the 240v wire rated at 300amps would be capable of supplying 22MW.
i was in the garage when it dawned on me that this is nutsack anyway, real answer should be 72kW. Got confused!
But yeah, when i get wire i'll walk into the shop (maplins i guess!) and simply ask for wire suitable for automotives, and pick wire to exceed
the fuse for each circuit. i wouldn't use twin and earth!
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