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Re:I Ripped Out a £6k Lighting System by WalterBright on Sunday November 15, 2020 @06:15AM (#25100246)
Crosstalk is when two wires are close together, one induces a voltage in the other (it's how transformers work). The trouble with house wiring is if you run a phone line parallel and close to an A/C line, it will induce a 60 cycle hum in the phone line, which will drive you utterly mad.

The electrician was installing the cat3 phone wires in the same holes as the A/C wires. It was guaranteed to induce a hum.

The correct approach is to keep the low voltage wires as far from the A/C as you can, and if they cross, keep the crossing at 90 degrees. Don't run them in parallel unless they are separated by feet (plural). If you have to, you can run them in grounded metal conduit as a shield.

I probably went overboard on this, but doing it inadequately meant 60 cycle humming on the phone lines and an utterly ghastly bill to rip the walls up and fix it.

He also was installing cat3 (POTS cable) and R59 cable (1970's cable TV stuff). I pulled that all out and threw it in the trash, putting in cat5 (cat5e and cat6 are better, but weren't available then) and quad-shielded RG6 cable.

Getting the best cable available cost maybe 20 or 30 dollars more, so it's crazy not to do it. The network and cable speeds have all increased dramatically since I installed it, and the cables have all worked like a champ.

Even the cat5 cables are happily carrying gigabit Ethernet.

I have a couple plugboards in the basement where all the wires terminate.

I did the whole thing for less than a grand. If an electrician had done it, it likely would have been 10 or 20x more.

Re:I Ripped Out a £6k Lighting System by stinos on Sunday November 15, 2020 @07:15AM (#25100578)
Sorry should have been more clear; I'm an eletronics engineer so I know what crosstalk is, it's just that I didn't understand how this would be an actual problem with CAT5. Phone line, that's something else though.

If an electrician had done it, it likely would have been 10 or 20x more.

Hmm, that is like twice the amount one would typcially pay here. Still, don't froget the working hours you put in there :) plus the fact that usually technicians get their materials for cheaper than you do (also because in my case it's only 6% VAT instead of 21%). I did many such calculations when renovating and for some things it was actually cheaper to get a technician.

Re:I Ripped Out a £6k Lighting System by petre on Sunday November 15, 2020 @10:42AM (#25101998)
That's an easy one. Switch on the light, network disconnects. We had this happen at our office. There's obviously much more happening on an electrical network other than 50/60 Hz, like transient response to switching loads on and off, RF noise from spark loads, dimmers etc.
Re:I Ripped Out a £6k Lighting System by Thlom on Sunday November 15, 2020 @04:41PM (#25105167)
In digital cinema the projector and the playback server does a handshake and key exchange before you can play encrypted content.The rest of this story might not be entirely correct, I've been out of the business for a few years and this happened maybe 5-6 years ago, but it's a bit fun and kind of relevant.

This usually works without any issues, but on one type of projector they had used a non-shielded network cable internally in the projector and if the projector lamp was lit juuuust at the right moment, the handshake would fail and the film would not play. Normally it wouldn't be a huge deal as the handshake happens just before the film and the lamp is usually lit on the beginning of the show long before the film starts. HOWEVER, there was this one cinema chain that had standardized their playlists in such a way that they for some stupid reason turned of the projector lamp in between the trailers and the film (I think to "introduce" the film) and then turned it on again just before the film with the result that the handshake failed 3 out of 10 times or so.

Long term solution was to replace the shoddy cable. Short term solution was to change all their playlist templates to blind the lamp instead of turning it off. Like they should have done to begin with.

Re:I Ripped Out a £6k Lighting System by stinos on Monday November 16, 2020 @03:43AM (#25109505)
Never had this myself for network, but I can imagine if the wires are close enough together and the light switch sparks enough (or draws enough power) it could happen. Actually this is our 'standard' way of intentionally messing up serial or USB communication: place wire next to the serial line, then try to generate as much transients as possible to induce errors in the bit stream. Still doesn't always work.
Re:I Ripped Out a £6k Lighting System by baybal2 on Sunday November 15, 2020 @08:55AM (#25101187)
Indeed, UTP5 is more or less crosstalk immune within for practical uses, STP5+ moreover so.
Re:I Ripped Out a £6k Lighting System by WalterBright on Sunday November 15, 2020 @06:26PM (#25105993)
> technicians get their materials for cheaper than you do

Sure, they buy materials wholesale, but they bill you full retail for it. I installed around a mile of wiring :-)

But I also got it exactly the way I wanted, the wires run where I wanted, and I bought professional quality tools to do the work, and still have/use them. I like working with my hands now and then, it's viscerally satisfying in a way a keyboard never is.

Re:I Ripped Out a £6k Lighting System by ur-whale on Sunday November 15, 2020 @08:33AM (#25101048)
They're maybe getting it for cheaper than you do, but if you think that's what they're actually charging you, you're deluded.

The typical electrician gets it indeed for cheaper than market rate, then charges it to you retail rate plus 20% to account for the "trouble" of sourcing and purchasing it.

Re:I Ripped Out a £6k Lighting System by stinos on Sunday November 15, 2020 @10:42AM (#25101992)
if you think that's what they're actually charging you,

I never claimed that.

The typical electrician

Maybe you rather mean 'the typical electrician I met' or so because I know for a fact the rest of that sentence does not apply to the ones I met myself.

Re:I Ripped Out a £6k Lighting System by parliament32 on Monday November 16, 2020 @01:37PM (#25115290)
From my experience in trades, you just double the price of all materials.. which conveniently is roughly the same price homeowners will see if they spot-check at Home Depot.
Re:I Ripped Out a £6k Lighting System by WalterBright on Sunday November 15, 2020 @06:31PM (#25106031)
> I didn't understand how this would be an actual problem with CAT5

I know that twisted pair is supposed to be resistant to that, but I wasn't going to risk it and didn't have a good way to test it. I didn't want even a teensy bit of hum, and there isn't any :-)

Re:I Ripped Out a £6k Lighting System by hondadriver on Sunday November 15, 2020 @06:36AM (#25100371)
Here in The Netherlands and probably other parts of Europe, you are not allowed to run electricity and network or phone cables through the same tubes. Also the number of wires allowed in a single tube is limited.

Many houses have concrete walls, floors and ceilings, so you don't run extra tubes easily...

Reconfiguring switches is next to impossible and via existing switch wires you can dim/switch the lights but not change colour(temperature).

So here the original switches are removed and the connection is bridged (always on) and battery/kinectic powered ZigBee switches control the lights directly, even if the gateway is down.

Re:I Ripped Out a £6k Lighting System by shawnz on Sunday November 15, 2020 @10:50AM (#25102053)
> Here in The Netherlands and probably other parts of Europe, you are not allowed to run electricity and network or phone cables through the same tubes.

Presumably that is not because of interference concerns but because of the danger of mixing high voltage and low voltage circuits in the same conduit, right?

As others have noted, conduit isn't usually used in houses in the west.

Re:I Ripped Out a £6k Lighting System by hondadriver on Sunday November 15, 2020 @02:57PM (#25104218)
Yes, it is for safety reasons.
Re:I Ripped Out a £6k Lighting System by bhickey on Sunday November 15, 2020 @06:51AM (#25100453)
Conduit isn't very common in US residential construction. Electricians will generally cut a hole in the drywall, drill a hole in the floor plate and tack the cabling to the framing.
Re:I Ripped Out a £6k Lighting System by quickthrowman on Sunday November 15, 2020 @11:58AM (#25102601)
Even if you aren’t using conduit you cannot use the same pathways for line-voltage and low-voltage wiring. You need to drill separate holes thru the studs to run NM in one and Cat6 in the other. You also need a divider in a multi-gang box if it contains line-voltage and low-voltage wiring.

Source: US National Electrical Code

Re:I Ripped Out a £6k Lighting System by ur-whale on Sunday November 15, 2020 @08:42AM (#25101096)
In houses than are typically built with a wooden frame. From a European pov, that sounds like a recipe for fire.
Re:I Ripped Out a £6k Lighting System by michaelt on Sunday November 15, 2020 @09:53AM (#25101620)
Americans love building single-storey detached houses on big lots. And when they build an upper floor, they love complex roof systems where almost every upper floor window has a first floor roof or porch below it.

This means problems like fires spreading to adjacent buildings and fires trapping people where they can't escape are much reduced; you'd never see a repeat of the great fire of London in an American suburb because there's practically a fire break between every single home.

This is made affordable by America's vast tracts of land and high rates of car ownership.

Re:I Ripped Out a £6k Lighting System by maxerickson on Sunday November 15, 2020 @02:41PM (#25104077)
I'm curious how you'd compare the Great Chicago Fire (that happened ~200 years later)?

https://en.wikipedia.org/wiki/Great_Chicago_Fire

The same day, a forest fire ravaged a number of small towns:

https://en.wikipedia.org/wiki/Peshtigo_fire

Re:I Ripped Out a £6k Lighting System by ComputerGuru on Sunday November 15, 2020 @10:03AM (#25101695)
I think that is very location dependent. Here in the Midwest, Romex still isn’t a thing and most residential construction still requires (effectively or otherwise) 1/2” electrical conduits for all high voltage wiring. Older construction might be the horrible BX/AC instead.
Re:I Ripped Out a £6k Lighting System by mindslight on Sunday November 15, 2020 @10:32AM (#25101917)
You said Midwest, but are you sure you don't just mean Chicago? Chicagoland is the single place I've heard about residential work requiring conduit.

I had a house with mostly Armored Cable and came to appreciate it. Especially after I opened up a floor and found an exposed conductor on some Non-Metallic that had been chewed by a squirrel.

Re:I Ripped Out a £6k Lighting System by quickthrowman on Sunday November 15, 2020 @11:59AM (#25102609)
NM wiring is extremely common in every state (except for Illinois) and NM is allowed without restrictions in multi-family stick-built housing up to four stories. You must live in Chicago or some other restrictive AHJ.

There are still existing functional knob and tube wiring systems that are 100 years old

Re:I Ripped Out a £6k Lighting System by Shebanator on Sunday November 15, 2020 @02:41PM (#25104082)
I still have some knob and tube wiring in my home (which is 96 years old). I've ripped out most of it over the years, but it is amazing how reliable it actually is.
Re:I Ripped Out a £6k Lighting System by jdeibele on Sunday November 15, 2020 @07:28PM (#25106484)
Were you able to do that without digging into the walls? My house had a bathroom and the kitchen upgraded by the previous owner and we did the basement but most of the house remains on knob-and-tube.

I've gradually added GFCI outlets to each circuit. They're not grounded, unfortunately, but they do trip if something were to go wrong. And it allows us to plug in 3-prong plugs without using those horrible 2-to-3 adapters.

We had to change home insurance companies because Amica blacklisted us the instant they heard there was knob-and-tube wiring. A few other companies have the same approach. But it's not like homes are spontaneously combusting everywhere because of it.

Re:I Ripped Out a £6k Lighting System by Shebanator on Wednesday November 25, 2020 @02:48PM (#25213455)
We ripped open the walls. This was done in the context of a larger remodel and then a rebuild of the back of the house after a fire.
Re:I Ripped Out a £6k Lighting System by ComputerGuru on Sunday November 15, 2020 @02:02PM (#25103714)
> (except for Illinois)

Guess where I am ;-)

(Not in Chicago/Cook, though.)

Re:I Ripped Out a £6k Lighting System by shawnz on Sunday November 15, 2020 @10:31AM (#25101903)
> if you run a phone line parallel and close to an A/C line, it will induce a 60 cycle hum in the phone line

Isn't twisting the pairs supposed to prevent that? Isn't that what makes it feasible to run telephone lines on the same poles as electricity, thus allowing the POTS system to be practical?

Re:I Ripped Out a £6k Lighting System by TheOtherHobbes on Sunday November 15, 2020 @02:58PM (#25104234)
Yes, it is. Also true for data. The problem is that common mode rejection is limited for unshielded pairs, so it works - but not perfectly.

POTS is legacy now, so I'm not sure how much of a consideration it is for modern builds.

There are safety issues with running network and power cables close to each other, but generally on small domestic systems crosstalk between data and power shouldn't be a serious problem.

The exception is if you have a lot of hash on the power lines from USB chargers, unfiltered noisy motors, or white goods that generate both digital and analog noise.

Ferrites or other kinds of filtering can help. So can using shielded cat cable.

Re:I Ripped Out a £6k Lighting System by bleepblorp on Sunday November 15, 2020 @12:00PM (#25102617)
I would seriously question the overall competence of any electrician who ran any low voltage cable in direct contact with AC power cables. This practice is not permitted by the electrical code. An electrician who does not respect that code requirement might be cutting corners with the code in other areas, too.

While the level of knowledge among electricians regarding network wiring is gradually increasing, the conventional wisdom for anyone who wants network wiring installed professionally is to hire a contractor that specializes in low voltage wiring.

Re:I Ripped Out a £6k Lighting System by WalterBright on Sunday November 15, 2020 @06:40PM (#25106096)
This was 20 years ago and the general contractor thought I was nuts to pre-install all this cabling. This all changed a year later, and network cables pre-installed became normal.
Re:I Ripped Out a £6k Lighting System by tinus_hn on Sunday November 15, 2020 @07:31AM (#25100684)
Although that hum is annoying on analog signals, it has no effect on digital high speed communications.

Still I agree it isn’t worth the headache of issues to save $20 and it’s more futureproof to use better cables.

Re:I Ripped Out a £6k Lighting System by ficklepickle on Sunday November 15, 2020 @08:09AM (#25100892)
It has no effect unless it lowers the SNR too much and errors can't be corrected. Try wrapping RG6 a few times around a thick, active AC line. I saw that a few times back when I was a field tech.
Re:I Ripped Out a £6k Lighting System by hnarn on Sunday November 15, 2020 @07:34AM (#25100702)
Just out of curiosity, would shielded cat-cables help in a situation where you have it next to A/C wires?
Re:I Ripped Out a £6k Lighting System by walshemj on Sunday November 15, 2020 @03:39PM (#25104610)
It would have to be a very noisy line and probably not the average house ac - this is from what my CCNA instructor commented.

They also said that stp is a lot harder and expensive to install.