Wiring House (Cat5e) -- have a question..

[Chumster]

Fellow Anandtechers,

I'm wiring my house with Cat5e and have all of the necessary materials (cable, jacks, punchdown tool, etc) but was wondering if running the shielded Cat5e cable next to electrical wire would cause performance to drop. Anyone know?

TIA,
Chum

 

[ScottMac]

It should be a moot point: shielded Cat5/5e/6 is useless in nearly all cabled environments, and if not installed properly, with all components specifically made for shielded cabling, is worse that standard (non-rated) phone cabling.

The new generation cabling, along with much better transceiver technology are more than enough to tame common mode noise (like 60Hz fields).

FWIW

Scott

 

[cmetz]

Chumster, the best thing to do is to keep your data cable as far away from your twisted pair as you can. This is often not possible. The next best thing is to make sure where they are together they are either perpendicular or parallel - it's late and I forget my EM Fields but one way in theory you get no EM coupling and the other way in theory you get the same EM coupling with both sides of the pair, and it gets subtracted out. The key is that funky angles aren't so good.

As far as shielded cable goes, make sure to properly ground exactly one end. Otherwise your shielded cable will be worse for noise than an unshielded cable. The shield should help with noise from power cables.

My personal experience is that I haven't ever had problems with power coupling onto data lines causing performance problems. I'm somewhat paranoid about it when running cables so that I don't have to deal with it later.

 

[Chumster]

Originally posted by: ScottMac
It should be a moot point: shielded Cat5/5e/6 is useless in nearly all cabled environments, and if not installed properly, with all components specifically made for shielded cabling, is worse that standard (non-rated) phone cabling.

Scott

Thanks for the reply -- though I now have more questions. Isn't all Cat5/5e/6 cable shielded? If not, and assuming that I don't have shielded cable (purchased 1000ft Cat5e from the local CostCo), will electrical cables cause problems?

Originally posted by: cmetz
Chumster, the best thing to do is to keep your data cable as far away from your twisted pair as you can. This is often not possible. The next best thing is to make sure where they are together they are either perpendicular or parallel - it's late and I forget my EM Fields but one way in theory you get no EM coupling and the other way in theory you get the same EM coupling with both sides of the pair, and it gets subtracted out. The key is that funky angles aren't so good.

As far as shielded cable goes, make sure to properly ground exactly one end. Otherwise your shielded cable will be worse for noise than an unshielded cable. The shield should help with noise from power cables.

My personal experience is that I haven't ever had problems with power coupling onto data lines causing performance problems. I'm somewhat paranoid about it when running cables so that I don't have to deal with it later.

It appears I may be confused.. see question above.

Thanks again for the responses.

Chum

 

[skyking]

keep it at least 2 feet away when running parallel to the power. That is not too hard to do. It is OK to cross it, but try to make it a large angle, near 90 degrees.

 

[Isezumi00]

Originally posted by: Chumster

Thanks for the reply -- though I now have more questions. Isn't all Cat5/5e/6 cable shielded? If not, and assuming that I don't have shielded cable (purchased 1000ft Cat5e from the local CostCo), will electrical cables cause problems?

All Cat5/e/6 cable is not shield...hence why its called UTP Unshielded Twisted Pair.

If you check the check the cable it should saw whether its UTP or STP or ScTP on the jacket.

However you mentioned that you are wiring a house...and my first question is, is this a single or multi store house??

Also the general rule is

2 inches from 110v lines.
2 feet from branch circuits.
2 meters from 220/440 branch circuits
Run parallel and perpendicular as necessary to lines that would cause interference.

And a bunch of other useless ANSI EIA/TIA standards!!!!

 

[Chumster]

Originally posted by: skyking
keep it at least 2 feet away when running parallel to the power. That is not too hard to do. It is OK to cross it, but try to make it a large angle, near 90 degrees.

Hmm.. well, 2 of the drops are run parallel to electrical wire (within close proximity, ie < 2 inches) so I might have a problem. They happen to be behind a wall that was recently drywalled, so pulling them out isn't an option. Hopefully I won't see too much performance loss. :frown:

Originally posted by: Isezumi00
{snip} However you mentioned that you are wiring a house...and my first question is, is this a single or multi store house?? {snip}

The house is a one story ranch with an open attic. I have dropped the cable from the top with all wires leading back to a central location.

Thanks for the help,

Chum

 

[azev]

Can someone please explain the rule for crossing power cable again ?? I dont really understand.

Thanks

 

[cmetz]

Chumster, normal UTP - unshielded twisted pair - is unshielded. It's four pairs of 24ish gague wire, twisted together, with a nylonish strength member in there and a plasticky jacket around it. (deliberately going a little vague because cables vary). There is also "shielded UTP" (a misnomer, but used to differentiate from the STP that other networking technologies use... Token Ring?), which has a foil shield around the stuff inside. This normally costs about double what the unshielded version cost AND limits your choices significantly because it's a bit of a specialty product. If you didn't go looking for and paying for shielded cable, you didn't get shielded cable. Don't worry about it, you should be able to do fine with what you have.

chumster & azev, as far as running parallel to power wire, the short rule is to keep as far away as possible. Avoid crosses where possible, if not possible, try to separate them (if you're perpendicular but at least put an inch or two of depth between the cables, that's better than right on top of each other). The 60Hz from the AC power isn't as big a deal as the noise on the power line and the current going through it. So for example, the power line that powers your refrigerator or a flourescent light is a particularly bad one to have to cross, both are devices that use a good bit of power (i.e., current) and also generate a good bit of noise at different frequencies. Contrast with a wall outlet that powers a 60W lamp, that's reasonably tame, or a wall outlet that isn't expected to power anything, even better.

azev, this comes from electromagnetics. Wire with current flowing through it generates a magnetic field normal (perpendicular) to the wire. A magnetic field normal to another wire generates an electric field in that wire. Hence, EM coupling - a current in one wire will appear, at a greatly diminished strength, in a parallel wire. In theory, if the wires are parallel and the twists are good, the field will couple into both wires twisted together into a pair more or less equally, and since the data signal is the difference of the two, the equal noise should subtract out. Even if they mostly but not completely subtract out the noise is thereby diminished.

All - just do the best you can and relax. I think we're getting a little too deep into this for a home network. Keep as far away from power as you can. But in a home wiring scenario, there's only so much you can do, and beyond that... well, just try and see. Luckily (unluckily if you have to debug it!), Ethernet is able to work in all sorts of marginal environments well enough.

 

[ITJunkie]

Thanks for the info cmetz :beer:

 

[azev]

Thanks alot for the info Cmetz, the reason I asked is that the wire contractor that did my house make a lot of crossing with the power cable. There is a way to go around the power wire, but that would be too much turning and they just go aheand and cross the power wire. Well, they are at a final step now (installing all the jack) and hopefully everything will still works fine.

 

[cmetz]

azev, most of the home wiring contractors don't really know what they're doing. Also note that there is a minimum bend radius - 1m I believe - and so right angle turns or tight turns are actually bad too. Home wiring is kinda tough because it's far from an optimal environment and the other subcontractors rarely coordinate with you, so I give the wiring guys just a little bit of slack just because they're often put in a position where they're no real way to do things 100% correct.

 

[Chumster]

cmetz - Thanks for all of the information. I'll be able to fix a number of the drops, though not all. I just put finished putting up the drywall with a number of mistakes behind it:

- all wires are run within 1 inch of electrical wires that are feeding outlets.
- there's a 90 degree corner that the wires pass through

Oh well, I'll be sure to run some tests once I terminate the ends and hook up my switch.

Again, thanks for the help.

Chum

 

[ScottMac]

Minimum bend radius is ~1.5 to 2" for UTP.

The cable must not be stretched.

The cable must not have had more than ~14 pounds of pulling tension.

The cable jacket must not be compressed.

The cable jacket must not be deformed (knotted, kinked, twisted, or otherwise displaced).

The cable should have proper strain-relief at the termination point.

The individual wires should not have more than 1/2 inch exposed (out of the jacket).

The individual pair must not be untwisted more than a half inch (total, included in the half-inch exposure).

For Cat6, recommended exposure / untwist is more like 3/8" total.

Cables should no less than 18" long (3 feet is recommended).

The end-to-end span acquires the rating of the lowest rated component. If you use unrated connectors, you have an unrated span ... just like junk phone cable (by the book).

The cable plant is a system and (ideally) should be matched components (same vendor, same class - connectors, panels, inserts, etc).

Category X certification is more than "how many twists per foot;" the materials used for the jacket, the insulation of the individual wires, the ratio of twists from one pair to another, the lay of the pairs within the jacket, and other factors determine the cables transmission characteristics.

... and about another couple dozen basic rules. Any violation will degrade the performance to some degree.

Pulling tension may vary from vendor to vendor. Cable characteristics vary from vendor to vendor. Component characteristics vary from vendor to vendor. Using vendor "A" cable with Vendor "B" components may cause an imbalance of some transmission characteristics and degrade performance.

FWIW

Scott

 

[azev]

Minimum bend radius is ~1.5 to 2" for UTP.

The cable must not be stretched.

The cable must not have had more than ~14 pounds of pulling tension.

The cable jacket must not be compressed.

The cable jacket must not be deformed (knotted, kinked, twisted, or otherwise displaced).

The cable should have proper strain-relief at the termination point.

The individual wires should not have more than 1/2 inch exposed (out of the jacket).

The individual pair must not be untwisted more than a half inch (total, included in the half-inch exposure).

For Cat6, recommended exposure / untwist is more like 3/8" total.

Cables should no less than 18" long (3 feet is recommended).

The end-to-end span acquires the rating of the lowest rated component. If you use unrated connectors, you have an unrated span ... just like junk phone cable (by the book).

The cable plant is a system and (ideally) should be matched components (same vendor, same class - connectors, panels, inserts, etc).

Category X certification is more than "how many twists per foot;" the materials used for the jacket, the insulation of the individual wires, the ratio of twists from one pair to another, the lay of the pairs within the jacket, and other factors determine the cables transmission characteristics.

... and about another couple dozen basic rules. Any violation will degrade the performance to some degree.

Pulling tension may vary from vendor to vendor. Cable characteristics vary from vendor to vendor. Component characteristics vary from vendor to vendor. Using vendor "A" cable with Vendor "B" components may cause an imbalance of some transmission characteristics and degrade performance.

FWIW

Scott

Damnn, looking at all these requirements, I think my contractor did a crappy job. I know they pull the wire pretty tight (no way to messure 14lbs or more), I dont think they follow the bent radius, and I know they zipped tied the wired to tight. At least they dont use flat stapler though . Well, they should be putting all the keystone jack sometimes this week and I should be able to test them all next week. I'll post pictures when they are done.

 

[JackMDS]

Quote: "Damnn, looking at all these requirements, I think my contractor did a crappy job. " :brokenheart:

With all due respect!

While specs. are very important, they are drawn with scientific, technological, and heavy commercial use orientation.

The actual surroundings of many private homes can not physically support some of the rigorous demands.

Taken into consideration the number of computers and the amount of Traffic that are Home Network generates, it will functionally tolerate well the Semi- Professional installation.

So do not feel so bad about it.