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Topic: Will this setup cause a fire? (Read 3 times) previous topic - next topic


ignoring the law, can that setup 'technically' work without overheating?


Feb 05, 2013, 04:14 am Last Edit: Feb 05, 2013, 04:18 am by PeterH Reason: 1

I can already draw 12V, 7A DC through a 6ft length using one twisted pair just fine..

That seems to me about ten times too much current for a CAT5 cable. If you were planning to use RJ45 or similar connectors, I'm sure you'll find they have a very low current rating too.

I think you're also exceeding the rated voltage by about a factor of two.

Bottom line is that this is the wrong cable for the job.

ignoring the law, can that setup 'technically' work without overheating?

Ignoring the law, it's unsafe. Given that you clearly aren't familiar enough with electrics to understand that for yourself, I recommend that you stick to using cables within their rated capacity and aim to comply with building standards in your area. Not necessarily because it would be necessary for your work to be legal (although that's a good reason) but because it means that you can know that what you're doing is safe.
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For what it's worth, this Wikipedia article says it's good for .577 A per conductor and 125VDC. Seems there are 8 conductors per wire so that gives you under 5A per wire; your 7A is asking for trouble.

I'm not able to comment on the VDC vs VAC thing....

But I'll go with lefty (as usual  8) ) and others on this: don't mess with stuff like this when you don't understand it. It's not worth the risk.

Have to ask: why are you asking?- you have lots of surplus wire?

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Why would you even want to do this? Cat5 isn't any cheaper or easier to use. If you're looking for a power over Ethernet solution for 12v, many already exist.
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Without knowing what you exactly looking for, but have an idea (individual PoE) I would NOT do it in the way you asked.

IF you consider some sort of PoE for devices that are kind of "energy hungry", your first thought in principle is right: the higher the Voltage, the lower the current on wire, the lower the voltage loss on the cable (you will not see anything close to 12V at the end if you input 12V and having a 100ft cable).

That's (and staying in the "safe voltage region) why they use 36 / 48V for PoE. It allows for enough loss on the cable with still enough input Voltage to make a step down regulator do the propper job for your application. You should also consider this path.

120V AC directly on a cat cable is defo out of specification and could cause significant trouble from a law and responability side! Keep in mind that not only the specification of a cable counts, also the usecase and the surrounding! In many countries, you will not be allowed to use a 120V AC cable sitting directly attached to a PELV using cable.

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