Harsh Environment Cat5?

Hi,

I'm helping select a Cat5 cable for use in a new house on a small island, which definitely qualifies as a marine environment. I've used Belden Direct Burial Cat5 in this application before and it seems to hold up well (except where the silicone grease has been wiped off the ends of the wires and they have been left out in the sun), but I'd like to check if there's something better available.

This is for inside a single dwelling, so it won't actually be used for direct burial, but it's a really harsh environment and I'd like it to last for many decades...

I'm assuming Cat5(e?) will be good enough for as far as I can see into the future, and the builder really doesn't want to spend a ton of money putting in (say) fiber in the hopes that he choses the right one and it becomes useful sometime eventually...

Thanks!

Reply to
William P. N. Smith
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I believe that for a house, where you are unlikely to get near the 100m requirement, that Cat 5 is fine for gigabit.

Cat5E has slightly better attenuation and related characteristics which are length related.

My guess would be that Cat5 should be fine to about 80m, where you would want 5E from 80m to 100m.

Though as far as I know, the gigabit standard was written for Cat5 without the E.

Except for the price and how hard it is to install, DataTwist is a pretty nice cable. Variations in wire spacing within the pair cause variations in impedance which, over a long cable, mostly increases attenuation. DataTwist has the wires in the pair bonded, similar to the two wires in ordinary lamp cord, so the spacing stays much more constant.

Two effects increase attenuation with frequency, skin effect and impedance variations.

-- glen

Reply to
glen herrmannsfeldt

Unfortunately, this isn't the way they wire houses here, it's all the flexible conduit cast in cement, and I really doubt there'll be any way to pull something new or replace it later.

I was thinking of dielectric grease around the connectors too. Would I be better off with FEP cable insulation or 'direct burial', which is essentially flooded with dielectric grease?

[Also, kinda of a rathole, but is it worth going to Cat5E, Cat5E+, Cat6, or something else exotic, or is Cat5 really all that's required to go all the way up to gigabit ethernet? I was getting all interested in Belden DataTwist 600e till I found out it's $752/1000ft!]

Thanks!

Reply to
William P. N. Smith

Gigabit was designed around CAT5, but there were some requirements that nearly all existing CAT5 met that weren't spelled out on the CAT5 standard--that's why CAT5E is "enhanced" instead of CAT6--it's CAT5 that has been tested for the additional requirements. 5E is sufficient for gigabit--it appears at this time that some higher grade will be required for 10 gig. Still, if the environment is as harsh as you say, going to CAT6 might give you a little more service life--if it starts with more headroom then it should, all else being equal, take longer for it to deteriorate to the point that it is no longer usable.

You might find of interest.

Reply to
J. Clarke

Pull in pvc conduit so cable can be easily replaced later. regular cat

5 cable should be fine. By the time the cable has started to go south, the wall jacks will have corroded and need replacing as well. You can use some potting compound or dielectric grease to protect bare metal in the back after you install it.

--Dale

Reply to
Dale Farmer

There's a tool at

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for only $6.82 for splitting the pairs apart, I had assumed that that tool and the usual punch-block 110 tool would be all I'd need for installing the cable.

I've guesstimated the longest run is about 150 feet, maybe I'll dive back into the Belden catalog for Cat5e-ish DataTwist FEP cable...

The failure mode is likely to be corrosion of the wire, 110 terminals, and jacks, or disintegration of the insulation, which is why I'm looking at FEP-insulated or silicone grease flooded (direct burial, or outside plant) cable.

Thanks!

Reply to
William P. N. Smith

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I have never tried it, but the tool should help. Still, it is at least one extra step.

I believe that 110 terminals are supposed to be gas tight, though maybe that still isn't good enough. Bell was always good at doing things right so that they wouldn't have to come back and fix them later.

-- glen

Reply to
glen herrmannsfeldt

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I think you are right, but the phone companies must have a solution for this, as they do supply phone lines to such houses. Maybe they do use grease on the 110 blocks.

-- glen

Reply to
glen herrmannsfeldt

They're gas tight, which is fine for light corrosion, but if you're getting the kind of heavy stuff that occurs in a marine environment then the contacts can be attacked from the exposed surfaces. Or the wire may simply corrode through--used to have a very nice electronic organ that died that way, and that wasn't a particularly bad environment, just waterfront (not even beach-front--it was on a tidal estuary about 12 miles inland from the beach) property in Florida. I finally gave up on replacing the transistors on the frequency synthesizer boards when their leads corroded through-it was a regular occurrance. In retrospect I should have potted them in epoxy, but that was a long time ago when I knew a lot less about certain things than I do today. Salt spray gets into _everything_. You don't realize how much it gets into stuff until you move inland.

Reply to
J. Clarke

You shouldn't expect any cable to last decades. The plastic will harden and crack over the years, etc.

Reply to
James Knott

Only if it was crap to begin with. The electric power cabling in my house has not hardened or cracked in more than 30 years, and the cable in my parents house was fine last time I looked at it, at which point it had been in place for over 50.

The conductor may corrode but without UV exposure the insulation on any cable that meets any reasonable electrical code will not "harden and crack" in just a few decades.

If there _is_ UV exposure then you should be using a cable rated for such use.

Reply to
J. Clarke

That's pretty much why I went with the FEP insulated cable, even though I don't need the plenum rating for fire. I'm going to pick up a few tubes of silicone grease for corrosion protection as well. The CFO said to go with the DataTwist 600e cable, as it's the best stuff that will function today and have the best chance of future-proofing.

Ask me again in a couple of decades and I'll let you know how it holds up. 8*)

Thanks for all the input, gang!

Reply to
William P. N. Smith

I've seen decades old power wire insulation that's crumbling. The aging of plastic is a fact, in that the plasticizers that make it flexible, evaporate with time, even without UV. As an example, take a look at some food storage containers that are a few years old. They're not as flexible as they were originally and will eventually crack.

Reply to
James Knott

How old, and what kind of plastic was used? If you go back far enough then there is no plastic of any kind in the insulation--it's varnished cambric. That in general _is_ crumbling now. After that rubber was used--it also is crumbling now. Some of the early plastics may not be holding up either. But any wire installed in a building in the US that is less than 4 decades old that is "crumbling" is just plain _crap_ that should never have passed inspection.

So? It appears to have escaped your notice that there are many kinds of plastic and the kind from which food storage containers are made is generally not the kind used to insulate electrical wiring.

This is true for some kinds of plastic but not for all. The hardening mechanism is usually crosslinking, not "evaporation of plasticizers" and the reason that UV accelerates aging of plastics is that it increases the rate of crosslinking. Most modern electrical insulation is already heavily crosslinked, so that ceases to be an issue.

Now, please explain to me why I can take a piece of wire installed in a house in 1968, more than three decades ago, and bend it back and forth until the copper inside the insulation work-hardens and breaks, without any cracks or any other kind of indication of failure appearing in the insulation, if such insulation will "crumble" in "decades".

Reply to
J. Clarke

Compare that insulation with new cable and see if it's as flexible.

Reply to
James Knott

If it is it's not enough for me to be able to tell the difference. But even if it is a little stiffer after 30 years, so what? That's a _long_ way from "crumbling". Now the cheap Rat Shack cable on my antenna rotor _is_ a bit stiffer than new (I inspected it a while back while I was putting up a DirecTV dish)--not _much_ stiffer but some. It's been sitting out in the sun for more than 30 years. Still doesn't crack when flexed.

Reply to
J. Clarke

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