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Thread: Warning: Power Cables Are NOT The Same! (4K)

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    Supporting Member tsbrownie's Avatar
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    Warning: Power Cables Are NOT The Same! (4K)

    Power cables on common electrical appliances from TVs to computers use C-13 type cables, BUT those cables have a very wide range of power carrying capabilities and the markings can be very misleading! Using a too small cable on a device can lead to a damaged cable or fire! Unfortunately, manufacturers of both cables and devices do not make it easy for the average consumer to know which plugs can be used safely with what devices.



    ===========================
    For more info google: Ampacity Charts for your country/state/region

    VDE cable: Verband der Elektrotechnik, Elektronik und Informationstechnik aka VDE in English is the Association for Electrical, Electronic and Information Technologies.

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    Supporting Member BuffaloJohn's Avatar
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    Not surprising, not much info here, repeating the same thing three times.

    Is there a single chart or reference that fits all? NO... Wish it were so, but it is not.

    Wire of a particular gauge has a particular rating for differnt situations. For example, wiring has a rating based on it's type and shield temperature properties but also the spacing between conductors and how the bundle is constructed and the types of loads involved and if the wire is contained. Those are SIX independant variables.

    Here is a wire chart for in house wiring:
    Warning: Power Cables Are NOT The Same! (4K)-ampacity.jpg

    Seems simple enough, copper versus aluminum, temp rating of shields. This chart though is not the maximum rating of the wire to when it becomes a fuse, these ratings are the rated usage full time 24/7/365.

    What are the fail ratings? See this chart:
    Warning: Power Cables Are NOT The Same! (4K)-wireguagesizeresistancecurrent.jpg

    Lots of things in the chart, but look at the column for FuseCurrent. That 14 gauge wall wire rated at 15A has a 166A FuseCurrent, so your breaker should trip WAY before the wire gets in trouble. Even the smallest wire he had (0.75 sq mm) is about 18AWG and that has a fuse current of 82 amps.

    That chart has lots of other columns and what you do with the other columns requires more experience and knowledge than can be explained here.

    Here is another chart I used when designing equipment on 24v vehicles, in particular I was concerned about loss of voltage if a module was some distance away from the power source (once you plug in resistances, spreadsheets let you blow out a bunch of numbers):
    Warning: Power Cables Are NOT The Same! (4K)-wire-sizing-chart-24-volt-system.jpg

    Cords are rated generally by the conductor size and sometimes they care about how the wires are packed in the cord. It is unlikely that this guy's smallest cord would have failed, even in the situations he showed, but it is always better to have more copper than not, so go with what is bigger...

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    Quote Originally Posted by BuffaloJohn View Post
    Here is another chart I used when designing equipment on 24v vehicles, in particular I was concerned about loss of voltage if a module was some distance away from the power source (once you plug in resistances, spreadsheets let you blow out a bunch of numbers):
    Click image for larger version. 

Name:	Wire Sizing Chart 24 Volt System.jpg 
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    Great info. But isn't that 24v chart voltage independent? Like it could be <insert voltage here> with 5% drop.

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    Supporting Member BuffaloJohn's Avatar
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    Quote Originally Posted by nova_robotics View Post
    Great info. But isn't that 24v chart voltage independent? Like it could be <insert voltage here> with 5% drop.
    Yes, you are correct, but it was from a particular project and sometimes you have to label charts for the non-engineers - if you know what I mean...

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    Supporting Member Frank S's Avatar
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    I get into this argument with truck drivers all the time about them adding too many lights on their trailers
    Why do my lights seem dimmer than they used to be and go bad so frequently?
    Because you have too many lights for the wiring harness to be able to handle.
    But they are all LED and only draw 20% as much current.
    Yes but you have added 10 times as many lights as the trailer had from the factory. Your trailer is 53 feet long it takes 240 feet of wire to reach all of the marker lights and all of that current is traveling on a 12 ga conductor with a 15 ft long pig tail connecting the tractor to the trailer which is also only 12 ga. You want the lights to be brighter and stop going bad due to low voltage remove half or them or more, Or run a second dedicated pigtail splitting the load between more than a single wire
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    Quote Originally Posted by Frank S View Post
    I get into this argument with truck drivers all the time about them adding too many lights on their trailers
    Why do my lights seem dimmer than they used to be and go bad so frequently?
    Because you have too many lights for the wiring harness to be able to handle.
    But they are all LED and only draw 20% as much current.
    Yes but you have added 10 times as many lights as the trailer had from the factory. Your trailer is 53 feet long it takes 240 feet of wire to reach all of the marker lights and all of that current is traveling on a 12 ga conductor with a 15 ft long pig tail connecting the tractor to the trailer which is also only 12 ga. You want the lights to be brighter and stop going bad due to low voltage remove half or them or more, Or run a second dedicated pigtail splitting the load between more than a single wire
    Whadda ya mean I can't put LEDs on my truck?




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