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Author Topic: Overheating CAT cable  (Read 5967 times)

Tim Steer

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Overheating CAT cable
« on: February 07, 2017, 06:19:51 am »

I work on an international open-air touring production, and I came across a problem I hadn't seen before during a recent show in Australia.

At around 3pm, in the peak heat of the day, several of our 90m Proplex CAT-5e lines between FOH and stage stopped working. Upon inspection, it appeared that temperatures in the cable ramp had reached somewhere between 60-70 deg C. Opening the trap and pouring iced water over the cables brought them back to life, and this became a daily ritual every afternoon on show days.

I realise that the operational temperature rating of this cable is -25 to 70 deg C, but I am still surprised to see heat-related failure of a data cable - I had assumed (I guess wrongly) that the upper temperature rating was the point at which the rubber sheath started to break down.

Certainly I have done plenty of shows in the Middle East where temperatures far exceeded what we were seeing in Perth.

Just interested to know if others have experienced this? Is 70 degrees just asking a bit much from this cable, or is this indicative of some other issue? I have suspected for a while now that we may have been delivered a bad batch of cable, as we have had other performance issues in the past with this multi.

http://pub.tmb.com/ProPlex/CAT5e/pdf/ProPlexCAT5e-A4-web.pdf
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TJ (Tom) Cornish

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Re: Overheating CAT cable
« Reply #1 on: February 07, 2017, 07:17:21 am »

I work on an international open-air touring production, and I came across a problem I hadn't seen before during a recent show in Australia.

At around 3pm, in the peak heat of the day, several of our 90m Proplex CAT-5e lines between FOH and stage stopped working. Upon inspection, it appeared that temperatures in the cable ramp had reached somewhere between 60-70 deg C. Opening the trap and pouring iced water over the cables brought them back to life, and this became a daily ritual every afternoon on show days.

I realise that the operational temperature rating of this cable is -25 to 70 deg C, but I am still surprised to see heat-related failure of a data cable - I had assumed (I guess wrongly) that the upper temperature rating was the point at which the rubber sheath started to break down.

Certainly I have done plenty of shows in the Middle East where temperatures far exceeded what we were seeing in Perth.

Just interested to know if others have experienced this? Is 70 degrees just asking a bit much from this cable, or is this indicative of some other issue? I have suspected for a while now that we may have been delivered a bad batch of cable, as we have had other performance issues in the past with this multi.

http://pub.tmb.com/ProPlex/CAT5e/pdf/ProPlexCAT5e-A4-web.pdf
Something must be marginal - either a short or an open that manifests itself with some heat. I would pull that piece out of service until you can reliably find the problem and then fix it.
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Tim Steer

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Re: Overheating CAT cable
« Reply #2 on: February 07, 2017, 08:00:39 am »

Something must be marginal - either a short or an open that manifests itself with some heat. I would pull that piece out of service until you can reliably find the problem and then fix it.

It happened on several of these cables inside the same multi, including both trunk lines that carry the gigabit LAN backbone which runs a lot of the show. We're aiming to acquire a good LAN tester for the next tour date and test all the lines, as I suspect there may be something else at play (either a bad lot of cable, or the mult has been crushed somewhere and it isn't obvious). We've already had to tack a few lines of CAT-5 install cable to the multi as the Proplex has been hit-and-miss for some applications, including LED video data.
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Keith Broughton

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Re: Overheating CAT cable
« Reply #3 on: February 07, 2017, 09:48:25 am »

We're aiming to acquire a good LAN tester for the next tour date and test all the lines,
[/quote
Should have had one when the system was built, and available on the road! Better late than never. :)
Let us know what the test reveals.
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John Rutirasiri

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Re: Overheating CAT cable
« Reply #4 on: February 07, 2017, 09:55:40 am »

Any PoE or PoCC devices such as personal monitors mixer or digital snake (e.g. Roland S-0808) on the cable?

John R.
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John Roberts {JR}

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Re: Overheating CAT cable
« Reply #5 on: February 07, 2017, 10:21:43 am »

If the wires themselves are generating heat, there may be some unintended ground path current (not good).

Pouring water, cold or otherwise, on electrical cables seems likewise to be a bad idea.

Disregard the fact that it worked(?)...

JR
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Eric Vogel

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Re: Overheating CAT cable
« Reply #6 on: February 07, 2017, 12:22:44 pm »

I work on an international open-air touring production, and I came across a problem I hadn't seen before during a recent show in Australia.

At around 3pm, in the peak heat of the day, several of our 90m Proplex CAT-5e lines between FOH and stage stopped working. Upon inspection, it appeared that temperatures in the cable ramp had reached somewhere between 60-70 deg C. Opening the trap and pouring iced water over the cables brought them back to life, and this became a daily ritual every afternoon on show days.

I realise that the operational temperature rating of this cable is -25 to 70 deg C, but I am still surprised to see heat-related failure of a data cable - I had assumed (I guess wrongly) that the upper temperature rating was the point at which the rubber sheath started to break down.

Certainly I have done plenty of shows in the Middle East where temperatures far exceeded what we were seeing in Perth.

Just interested to know if others have experienced this? Is 70 degrees just asking a bit much from this cable, or is this indicative of some other issue? I have suspected for a while now that we may have been delivered a bad batch of cable, as we have had other performance issues in the past with this multi.

http://pub.tmb.com/ProPlex/CAT5e/pdf/ProPlexCAT5e-A4-web.pdf

Have a look here:

http://www.belden.com/docs/upload/Temperature.pdf

page 7: http://www.belden.com/docs/upload/Understanding_CS.pdf

Your cable is a stranded construction, which one?  TMB  recommends max length of 85 meters, however in practice anything over 200' should be solid BC #24 or #23.

For lengths >= 250' I would used CAT6 or CAT6A solid for extra attenuation headroom.

General rule for structured cabling:
5 m stranded patch < 90 m solid BC link > 5 m stranded patch =100 m channel max
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Tim Steer

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Re: Overheating CAT cable
« Reply #7 on: February 07, 2017, 01:43:03 pm »

Should have had one when the system was built, and available on the road! Better late than never. :)
Let us know what the test reveals.

Hindsight is a wonderful thing! Afraid there were a lot of other things that needed to be bought first - it's a young tour, but it's starting to find its feet. I'll try and remember to report back with my findings.

Any PoE or PoCC devices such as personal monitors mixer or digital snake (e.g. Roland S-0808) on the cable?
John R.

The eight cables in the loom are only used for IP-based data connections. Mostly for gigabit links between Luminex Gigacore switches (which I believe have PoE enabled on the front ports by default, if you think that would make a difference).

If the wires themselves are generating heat, there may be some unintended ground path current (not good).

Pouring water, cold or otherwise, on electrical cables seems likewise to be a bad idea.

Disregard the fact that it worked(?)...

JR

Pouring icy water down the cable tray was the last-minute bodge we had to go with in order to get the show up and running with about 30 minutes to spare before doors. Certainly not the ideal situation, and not one we aim to repeat! That said, our multicores are used to being used and abused at festivals, buried in mud etc.

Have a look here:

http://www.belden.com/docs/upload/Temperature.pdf

page 7: http://www.belden.com/docs/upload/Understanding_CS.pdf

Your cable is a stranded construction, which one?  TMB  recommends max length of 85 meters, however in practice anything over 200' should be solid BC #24 or #23.

For lengths >= 250' I would used CAT6 or CAT6A solid for extra attenuation headroom.

General rule for structured cabling:
5 m stranded patch < 90 m solid BC link > 5 m stranded patch =100 m channel max

Thanks for the links Eric - interesting reading. So in your opinion, 90m of stranded Cat5E is already pushing things a bit (and for gigabit, especially so)? It sounds like the temperature increase in our case possibly derated the cable just enough to make it unusable.

We'll test the lines properly on the next job. I believe all the kit is sat on a cattle ranch somewhere in the USA at the moment.
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John Rutirasiri

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Re: Overheating CAT cable
« Reply #8 on: February 07, 2017, 03:23:57 pm »

The eight cables in the loom are only used for IP-based data connections. Mostly for gigabit links between Luminex Gigacore switches (which I believe have PoE enabled on the front ports by default, if you think that would make a difference).

Even if you plug into a PoE-enabled port, a PoE switch detects presence of downstream PoE device by turning on a low voltage (< 3VDC) for a few hundred milliseconds.  Since you don't have any PoE devices, the switch will not detect a signature current draw, and never turns on the "real" (48V) PoE voltage.  So I think you're fine.

I don't know if the PoE switch polls each port regularly and keeps trying to detect a PoE device  (I would assume), but we're talking less than 1 mA of current during detection.  Hardly enough to heat up the 24AWG conductors of a cat5e.

John R.
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Tim McCulloch

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Re: Overheating CAT cable
« Reply #9 on: February 07, 2017, 03:46:25 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?
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Re: Overheating CAT cable
« Reply #9 on: February 07, 2017, 03:46:25 pm »


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