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Author Topic: Overheating CAT cable  (Read 5968 times)

Mac Kerr

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Re: Overheating CAT cable
« Reply #10 on: February 07, 2017, 03:52:27 pm »

I work on an international open-air touring production,

I wouldn't use CAT5 outdoors on the ground at or near the maximum distance spec if the devices I was connection were switches. I'd put the right GBIC in the switch and use fiber. It is more rugged than CAT cable and more reliable.

Mac
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Dan Mortensen

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Re: Overheating CAT cable
« Reply #11 on: February 07, 2017, 07:35:18 pm »

The test that got away - a clamp-around ammeter.  It sounds like there were at least a couple amps of current flowing to create this much temperature.  Mike Sokol?

How would they implement a clamp-around ammeter on CAT cable?

I thought an ammeter could only read on one wire of a multiwire cable, and if it was simulateously around the return for that single wire the two currents would cancel out.

Wouldn't they have to break out the twisted pairs and untwist them in order to get to just one wire? That would have to be a cable adaptor that was put in for the measurement and taken out after, as the untwisting would screw up the CAT rating.

Or am I missing something, like your tongue in cheek?
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TJ (Tom) Cornish

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Re: Overheating CAT cable
« Reply #12 on: February 07, 2017, 07:40:41 pm »

How would they implement a clamp-around ammeter on CAT cable?

I thought an ammeter could only read on one wire of a multiwire cable, and if it was simulateously around the return for that single wire the two currents would cancel out.

Wouldn't they have to break out the twisted pairs and untwist them in order to get to just one wire? That would have to be a cable adaptor that was put in for the measurement and taken out after, as the untwisting would screw up the CAT rating.

Or am I missing something, like your tongue in cheek?
the errant current, of any, would be flowing on the shield, so effectively the cable is one wire.
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Dan Mortensen

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Re: Overheating CAT cable
« Reply #13 on: February 07, 2017, 08:38:27 pm »

the errant current, of any, would be flowing on the shield, so effectively the cable is one wire.

Ah, thanks.

So the thought is that a current is getting into the shield from some source other than the wires inside the shield, and thus the current is taken to ground by the Ethercon at the ends of the cable?

The OP didn't indicate there was AC or other cables in the loom/cable ramp, but he also didn't say there weren't, so I wasn't thinking of some kind of degraded jacket on both CAT loom and AC cable that would allow this errant current.

Or could it be induction? We know the CAT wires are twisted and the shield is effectively a straight cable. So induction could occur into the shield but not the twisted pairs.

If they had Cam-Lok type individual cables in their cable ramp, and if there was significant current flowing in one or more of the phases, could that induct into the parallel shield and create current that way?

If that's possible, what kind of spacing would be necessary to avoid significant induction?

Tim S, you have an interesting problem! Did you have AC cables in the ramp? How long was it, meaning for how much distance were the cables parallel, if there were parallel AC cables?
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John Roberts {JR}

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Re: Overheating CAT cable
« Reply #14 on: February 07, 2017, 09:07:12 pm »

It is unclear what exactly is going on, and how ice water fixes it.

JR
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Mac Kerr

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Re: Overheating CAT cable
« Reply #15 on: February 07, 2017, 09:24:53 pm »

It is unclear what exactly is going on, and how ice water fixes it.

JR

I think the original implication was that the sun shining down on the black cable ramps the cable was in drove the temp of all the cables up.

Mac
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Bob Leonard

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Re: Overheating CAT cable
« Reply #16 on: February 07, 2017, 09:27:39 pm »

I wouldn't use CAT5 outdoors on the ground at or near the maximum distance spec if the devices I was connection were switches. I'd put the right GBIC in the switch and use fiber. It is more rugged than CAT cable and more reliable.

Mac

What Mac says above is the proper way to do the job. There's plenty of multi jacket plenum rated fiber cable to be had, and in the long run (no pun intended) the practicality will far outweigh the additional costs for implementation.

You should also keep in mind that any UTP 3 through 6 will provide accurate and reliable data transmission within it's rating up to 328', so there should be no 200' limit. Also, PoE devices will fail before you can supply enough current to heat the cable, that being unless someone is running lights or a carnival ride on the other end. The heat failure is always associated with jacket compression. The jacket "wilts" under the extreme heat creating an anomaly. When the jacket is cooled, the shape of the jacket/tunnel is restored and so is the distance between pairs. At lower speeds and light loads you may not see the problem, but at high speeds life is more critical. Find a good high temp rated cable and replace what you have, or as was stated, use fiber.
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TJ (Tom) Cornish

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Re: Overheating CAT cable
« Reply #17 on: February 07, 2017, 10:20:22 pm »

I think the original implication was that the sun shining down on the black cable ramps the cable was in drove the temp of all the cables up.

Mac
That was what I presumed the situation was.
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George Dougherty

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Re: Overheating CAT cable
« Reply #18 on: February 08, 2017, 01:31:38 am »

IMO, as others mentioned, stranded CATx cable has no business being involved in long runs.  Patch cable is intended for short patches and flexibility.  Solid conductor cable is the only thing that should be used for runs over ~50ft.  It boggles my mind that cable companies even produce this stuff in longer runs where it was never intended to see use.
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Lyle Williams

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Re: Overheating CAT cable
« Reply #19 on: February 08, 2017, 03:58:52 am »

Solid has no business being repeatedly re-laid either.
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Re: Overheating CAT cable
« Reply #19 on: February 08, 2017, 03:58:52 am »


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