P38420
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| posted on 8/12/02 at 03:41 PM |
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Current (Amps) Consumption
Hi,
I am designing a wiring harness lto fit a V6 as a unversity project. I am not changing the ECU harness but completely starting from scratch for the
rest of the car. Does anyone know of a website or have any other literature that would list the current draw from each electrical component on the car
so I can work out cable thickness and fuse ratings.
Thanks
Dan.
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stephen_gusterson
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| posted on 8/12/02 at 07:16 PM |
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these things will all vary depending on car type.
Why dont you get hold of a Haynes manual? You can get all the fuse values there!
Your wiring should always have a greater current rating than the fuse - as a guide.
atb
steve
PS - if you are cheap, why not take a look in a scrap yard - but it might be hard to verify which fuse does what. some cars are dumped with original
owners guides in em.
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David Jenkins
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| posted on 9/12/02 at 09:08 AM |
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It's not too complicated - most cable suppliers divide their range into size and usage: For example, look at:
vwp-cables
It tends to spilt into
Thin stuff - indicators, warning lights, brake lights, etc.
Thick stuff - horns, headlights, etc.
Very thick stuff - battery to alternator links.
An over-simplification maybe, but not far off!
Also look at
premier-wiring
They sell the most modern thin-wall cable that will carry more current for a smaller size - makes the loom smaller! Their site is a bit vague, but it
is really worth getting their catalogue, as it has recommended sizes, colours, etc. plus lots of switches, connectors, etc.
Have fun!
David
(who's busy making his own wiring at the moment)
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P38420
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| posted on 9/12/02 at 11:37 AM |
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Thanks for your help. I'll give them a go.
Dan.
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stephen_gusterson
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| posted on 9/12/02 at 09:30 PM |
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it gets a lot more complicated, David.
Thick stuff isnt always as good as thinner stuff.
I have used something called tri-rated cable on my car. it carries - guess - 3 times more than a std type.
You cant really guage capability on size that well.
1mm cable could do say 3a or 11a depending on type.
take a look on
http://rswww.com
or
www.farnell.co.uk
or get vehicle witing product's brochure.
modern cars have really really thin wire. If you use that as a model without the high rated cable, you might have a barbeque rather than a car!
I think from memory most of my wire is tri rated, carrying either 11a or 20a.
atb
steve
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David Jenkins
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| posted on 10/12/02 at 08:54 AM |
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OK Steve, I know I over-simplified!
I hadn't chosen the cable purely on size - I looked at the rating and matched them to the task. What I was trying to say was that places like
Lightning Looms sell the "traditional" cable which is quite thick. Does the job, but takes up space.
Other places like Premier Wiring are now selling the "thin" cable, which has thinner and better PVC sheathing. The wire inside can be thinner
because it can lose heat faster than in the traditional stuff. The new sheathing is also tougher, more resistant to abrasion and tolerates a higher
temperature (105C, I believe).
As most establishments sell their cable at roughly the same price, I thought that I'd go for the higher-spec stuff! It is remarkably small for its
rating.
rgds,
David
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stephen_gusterson
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| posted on 10/12/02 at 08:12 PM |
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agreed David
it must be ok, but that really thin stuff on cars nowadays makes me worried its gonna chafe and short out.
Funny thing about tri rated cable is its actually thicker walled than the standard stuff!
atb
Steve
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Alan B
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| posted on 10/12/02 at 08:18 PM |
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I could be missing something here, but I though tri-rated meant it complied with Euro, US, and Canadian standards...ie: 3 ratings in one cable.
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stephen_gusterson
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| posted on 11/12/02 at 09:54 PM |
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quote:
Originally posted by Alan B
I could be missing something here, but I though tri-rated meant it complied with Euro, US, and Canadian standards...ie: 3 ratings in one cable.
As far as I know, its called tri rated cos of the load capability.....the stuff in the UK I use is marked as UL (USA spec) certified.
You could be right, and I could be wrong.
But it still stands that tri-rated has a much higher capacity than 'standard' cable.
wouldnt it be 'tri approved' or 'tri standard' - tri-rated sounds a lot like load capability to me.
whatever it its, we use it on everything at work!
convenient that.
Now if I could only build old conveyor systems into my car i would have a real gold mine
atb
steve
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Alan B
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| posted on 13/12/02 at 05:32 PM |
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Not that it matters, but I did some research after my post just to see if I was dreaming.
http://www.concordia.ltd.uk/tri_rated/
Seems to concur with me, although I'd agree your names for it would make more sense.
I think many companies use it so they can sell machines almost anywhere in the world because having the multiple approvals.
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stephen_gusterson
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| posted on 13/12/02 at 08:01 PM |
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Its quite often that UL approval on its own is good enougth, as is the Canadian CSA standard.
But you are right - using cable with as many approvals as possible is a good thing.
atb
steve
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Highcost builder
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| posted on 14/12/02 at 04:51 PM |
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No i think the point alan was making was that your wrong about tri rated not being three times greater at carrying current, i thought you were meant
to be an electrician
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bsilly
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| posted on 14/12/02 at 09:23 PM |
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red ter red.....black ter black......blue ter fxxxk
mainly digger drivin me
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stephen_gusterson
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| posted on 15/12/02 at 12:12 AM |
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quote:
Originally posted by Highcost builder
No i think the point alan was making was that your wrong about tri rated not being three times greater at carrying current, i thought you were meant
to be an electrician
You thought wrong.
An electrician deals with cables, control gear, power distribution, motors,etc.
I am an electronics engineer. I design computer ELECTRONICS from component and pcb level and write software for them. I deal with microprocessors,
ICs, digital electronics and the like.
Cable specification isnt my role or domain.
Read the thread again.
I didnt disagree with Alan. Where did you get that from?
"You could be right, and I could be wrong. "
"But it still stands that tri-rated has a much higher capacity than 'standard' cable. "
Both of the above are true.
The link Alan points to backs his theory. I will accept that, as the person who originally told me the meaning (an assembly tech) was obviously
wrong.
The question wasnt about tri-rated cable - although I mentioned it - but Alans useful input has taught me something too. The question asked, and the
point I was re-enforcing, is that physical sheath size, and internal core size, do not neccesarily imply a higher (or lower) rated cable. And the
original question was related to current not CSA, UL, TUV, BS, VDE, and the like standards.
If you have the current catalog from vehicle wiring products, its shows how the current capacity of wire varies. On one page they have a 1mm cable
carrying 8.75A and lower down, the auto cable David spoke of is also 1mm and carrying 16.5 amps. The 16.5A wire is smaller in overall size......
Cable must be very important to you to make such an agressive response!
atb
Steve
[Edited on 15/12/02 by stephen_gusterson]
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bsilly
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| posted on 15/12/02 at 09:59 PM |
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cable is important to me........i weighed in so much copper in the late 80's.......that i paid off me mortgage...........but regardless of yer
wirings capacity......theres nowt really on a locost....headlights.horn.on a relay....bit of thick wire off the batery.......bobs yer uncle...and
fanny's yer uncles live in lover....sorted
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Ian Pearson
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| posted on 16/12/02 at 08:12 AM |
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Handbags at dawn!
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Highcost builder
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| posted on 16/12/02 at 07:48 PM |
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well steve when i completed my electronics at uni i seem to recall being taught all about current carrying capacity after all without cables we would
struggle to get power to the PCB's, unless im wrong again.
Trouble is there are to many smart arses and not quite enough knowledge to fill them all.
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stephen_gusterson
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| posted on 16/12/02 at 08:51 PM |
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thats true, hicost.
But, when we design industrial machinery (and Im 43 and a bit past uni days when tri-rated probably wasnt around) we do it as a team. I and the other
design engineers specialise in the microelectronics side. As Technical Director, I cant be involved in all aspects.
Someone else wires up the machines and does the control side. Usually the technicians on a project.
So as far as i'm concerned, if the wires carry the signals to my boards, are approved for the market we are selling in, and carry the current
needed, thats all I PERSONALLY need to know! Other people are paid to know and take account of these areas.
Do you have an RS catalog? I found out something interesting today.
Look at the tri-rated cable sized at 1mm. Carries 17 amps.
Look at their normal equipment wire at 1mm size. 6 amps.
Thats just about 3 times the rating isnt it?
If you look in the same catalog, it tells you that the tri rated cable is approved to multiple standards. In fact, far more than three.
Confused?
I should have been.
atb
steve
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David Jenkins
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| posted on 17/12/02 at 08:36 AM |
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Getting back to the topic (rapidly!  ), one thing puzzles me...
...the whole point of the new-style cable is that the PVC covering is tougher, more heat-resistant, and thinner. It's thinner so that it can lose
heat quicker, and therefore carry more current - but then it gets bundled up in a loom, which cancels that out!
It's a puzzle - but I'm not planning to lose sleep over it.
Back to the original question!
If using 'traditional' cable (normal thickness of insulation), the following ratings have been suggested:
0.30/14 (14 strands of 0.30mm wire) for the low-current stuff - sidelights, indicators, connections to the low-current side of relays.
0.30/28 (28 strands...) for high-current use - headlights, horn, fan, etc.
There's also a cable that I think is around 0.30/60, for the connection between the alternator and the battery - often doubled up for extra
capacity.
Does this sound reasonable, Steve?
cheers,
David
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jollygreengiant
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| posted on 17/12/02 at 08:59 AM |
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David, yes it sound pretty reasonable a defintion as ive heard. As reguards the bundling of electric cabling in cars you are right but remember that
it is all done by a university graduate who has never in his life worked on a car in a profesional maner, so you end up with something that works and
as a rule these days works very well --- But have you every tried changing a front side light bulb on a new rover 75, or changing headlamp bulb on a
new type beetle that done lots of miles. and ICME recons that on some cars you can change a wheel bearing in 6 minutes!
one day I will meet one of these new car designer types  
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stephen_gusterson
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| posted on 17/12/02 at 10:37 PM |
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Im sorry that this thread has gotten the way it has over a simple naming misunderstanding, but there ya go - and I learnt something too!
Cable ratings ARE confusing. When I checked today for 1mm cable, in the RS catalog, I got THREE different ratings! 6a, 10a and 17a!
I have seen the thin stuff on cars and it obviously works. It makes me a little suspicious tho - i'd rather have nice thick insulation.
The PVC covering on (some if not all) cables is radiation treated to make it harder and tougher. So I am told. (In case anyone else says otherwise!).
Perhaps the auto cable is the same?
Now, you's think, using logic, that tri-rated cable would have a thinner wall to help it cool.
Not the stuff I have seen! It has a wall thickness thats pretty substantial - moreso than the 6a stuff!
I basically used two types on my car.
1mm for 'general' things like runs to individual lights, panel wiring, etc. I used (I think) 1.5mm approx with a rating a shade over 20a for other
things, such as the main feeds from the fuses to the light switch, abs pump, fuel pump (efi), horn, and the like.
This was all Tri rated cable, having multiple approvals and a 3x in most cases power capability over the std cable  Pleases everyone I hope
I dont recall any of my fuses being over 20A.
Then there is wire colour. If you look at the pics of my car, its all yellow. When I worked at a company that did MOD work, it was pink! All the
wiring in a C130 herc I could see exposed was white I think (scutter?) In my experience of industrial machinery, there tends to be standard colours
for things like mains wire, + power rails and ground rails. Low voltage control wiring (24vdc) tends to be all in one colour. So you get a whole load
of cables one colour. There isnt a lot of colour combos to make every wire unique, so its normal to number the ends. You can get cable marker kits, or
'wrap around' cloth sticky numbers, that let you number each wire uniquely. So my car has a whole lot of yellow wires with numbers at each end so I
know where they go. I also cheated by putting masking tape with a name of where it went or what it was for. This is removed after finsihing.
2 cable sizes with markers worked for me.
As far as the cable from the alternator is concerned, that can carry a lot! On my XJS the alternator was rated at 130 amps!
I would suggest that you take a visit to a scrappy and liberate a ready made wire from a car. A mk3 granada has a wire from the alternator to the
battery thats a good 4 foot long. Why go to the hassle of buying new when a bit of white spirit makes it look new? Its hard to make off those high
current ends without a proper tool. I think even a std ford has a 70a+ alternator.
"0.30/14 (14 strands of 0.30mm wire) for the low-current stuff - sidelights, indicators, connections to the low-current side of relays."
Thats about 9a cable. Each 5w bulb consumes less than half an amp, and a 21w bulb just under 2 amps. So thats fine - but keep fuses 10a max on those
lines.
"0.30/28 (28 strands...) for high-current use - headlights, horn, fan, etc."
thats 18 amps approx.
your choices are just about the same as mine! Keep fuses 20a or less on these lines.
When you wire up the lights - especially headlights - try and use independent fuses - like have the dipped on one line, and the mains fused from
another. If all the lights go it it could be hairy! Its also a good idea to have 2 fuses to the back - one for a lhs sidelight and another for rhs and
numberplate - makes sure there is at least some light at the rear if a single fuse fails!
I also used two 5a fuses under the dash to fuse the dial lights, and to provide an 'always on' (when ignition is on) supply for the panel indicators
(oil, etc.)
My system needed 18 fuses - but if you have non efi and non abs that puts it back to 16.
If you are interested I could get post what I used and what the ratings were.
Hope that helped David.
ATB
Steve.
Perhaps one day I can write up electrics for my site - with decent drgs - try to do a page a week but there isnt always time!
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David Jenkins
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| posted on 18/12/02 at 09:44 AM |
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quote:
Originally posted by stephen_gusterson
Hope that helped David.
Sorry - you have been misled!
I wasn't the one looking for help - that was the originator... the whole thing escalated...
My loom has been designed, and I'm in the process of laying it out - going well so far, but the scuttle part is daunting due to me designing my own
instruments (still doing that, before anyone asks).
First I have to design my own dashboard (and I intend to have fun with that), then I shall wire it up - which should be the easy part, if my dashboard
is laid out properly.
I also had the problem of having all the wire I needed, except for one colour, which I had to send off for...  ...serves me right for wanting to use
the official colour scheme - looks pretty though, and it's nice to pick up a wire and know what it should connect to.
Still, thanks for the offered help - perhaps the originator picked up some tips along the line!
cheers,
David
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Hasse
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| posted on 20/12/02 at 08:38 AM |
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Comments, cables and currents
Hello All,
Some comments wich may be to some help?
PVC, most common insulation on automotive cables, are good for use in aprox -30 to +100 degC. Some qualities may stand for aprox 110 degC, but not
more.
The "newer" thin wall insulation types were developed to save space, and the PVC quality is normally a bit better than the older "thicker" cables,
but temperature range is the same.
The current rating is the same independant of the insulation thickness in the automotive industy.
The fuses are ment to protect the cables/installation if/when a short circuit appears.
Guide for a robust design:
5A fuse protects 0.75mm cable, 7.5A fuse for 1mm, 10A fuse for 1.5mm, 20A fuse for 2.5m and a 30A fuse protects 6mm cables.
Design the circuits so than the fuses in normall use is exposed to max 80% of their ratings.
Unfused cables:
I would go for 16mm cable between battery and starter, and 10mm between starter and alternator.
All the rest depending on load.
I hope this can be to some help.
Regards
/Hasse
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David Jenkins
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| posted on 20/12/02 at 08:44 AM |
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Hasse,
That all looks very sensible.
Thanks,
David
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