ethernet and AC in conduit

Other than it being in violation of NEC (National Electrical Code), it will probably work if you have some spacing between the AC wires and the ethernet cables, and if the AC wires are parallel, as in Romex. Loose wires in conduit are going to be a problem.

The failure mode is 60 Hz pickup by the ethernet transceiver. Most of the 60Hz will be rejected by the intentionally lousy frequency response of the typical ethernet transformer. The CAT5 cable and ethernet input circuitry also has very good common mode rejection, which is mostly what's keeping stray signals out of your ethernet transceiver. Under ideal conditions, the amount of AC pickup by the CAT5 wiring should be identical in each wire and therefore cancel.

That's fine if there is some distance between the AC wiring and the CAT5. Past about 4 wire diameters, the pickup on each wire is essentially identical and your ethernet will work as advertised. However, when the AC wire are at different distances from the CAT5, you're going to get different signal levels on each CAT5 wire. Since they're different levels, the common mode rejection of the input xformer can't get rid of the crap.

The worst case situation happens when the wires are right next to each other. Although the wire spacing is small, the differences in wire spacing is large. Therefore the induced voltages are large.

Realistically, it takes a considerable length of parallel run AC and CAT5 before there will be any noticeable problems. My guess(tm) is that the problems start at about 25 meters with loose wires. Romex will probably work over a longer distance.

The real danger is safety from electrocution and induced power line glitches. I'm sure you put the convenience of sharing the conduit, over having your insurance company invalidate your fire insurance and the potential risk of electrocution. Therefore, I won't suggest that perhaps the NFPA has a clue and that your safety might be worth considering.

Reply to
Jeff Liebermann
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Be careful of attibutions of statments in this tread. several have been presented as coming from me that are not. could well be those tagged to John N and others are fake as well.,

Reply to
NotMe

In the extreme the permitting authority and or the utility will 'condemn' the property requiring a complete, detailed and expensive reinsertion and permitting.

Good example are folk that by pass the transfer function for emergency gen sets. More than one, in my personal experience, used a modified dryer pig tail and inadvertently caused a live back feed to the mains. (people have been known to die for this game).

Power company WILL set the property on a black list and the property owner will pay hell and a ton of money getting the power reconnected.

:
Reply to
NotMe

The ultimate PoE?

It's not the 60Hz, it's the noise, spikes, and glitches on the line that cause problems.

I inherited a customer that had CAT5 running parallel with about 100ft of Romex. That's what happens when you get an electrician to run the residential network wires. They were getting erratic errors on this ethernet connection and were wondering why. I tested it (using SNMP to collect errors and stats) and didn't find anything unusual. However, I did it on a weekend, when nobody was around. During business hours, there was some heavy machinery running on the same AC circuit that was producing large power line glitches, spikes, noise, etc, which were being induced onto the CAT5. Although there was probably no 60Hz coupling, and the common mode rejection should have prevented the glitches from being a problem. That wasn't the case as the distances between the various AC conductors and the CAT3 were different, therefore, different induced voltages.

Incidentally, they also had POTS phone service shared on this run of CAT5. There was 60Hz hum, but only on some instruments.

I'm wondering about the safety issues. Run enough AC and ethernet wires in parallel, and eventually, it becomes a transformer. I'm not sure how much voltage it would induce in unterminated CAT5 wires, but I wouldn't want to find out the hard way. It should be easy enough to test the worst case. Take a length of CAT5 and apply 117VAC to one pair. Measure what appears on the other pairs. Try different lengths.

Reply to
Jeff Liebermann

: >Unlikely to have technical problems BUT should there be a fire/injury and : >the insurance company finds out they will void your coverage. : : I don't know about your insurance policy, but mine has no such : exclusion.

the usual process:

Insurance company denies liability/coverage Someone sues.

Court upholds the denial of coverage/liability

Home owner gets no money or the injured party gets a judgment against the home owner.

Does it always happen this way? No, but it does happen often enough that a prudent man takes the necessary steps to avoid the exposure.

Reply to
NotMe

Yep. Some, not all, WRT54G and BEFW11S4 have internal switching regulators, that allow a wide range of applied voltages. As I recall,

3.5VDC to about 18VDC. There's a photo (somewhere) of my BEFW11S4v4 running 3.5VDC. The problem is that I have consistent or accurate way to determine which of the various Linksys mutations will run on this range of voltages. There's already been one disaster, where someone applied more than 5VDC to their Linksys WRT54G v1.1, and blew it up. For now, I know that v1 and some v1.1 models will NOT work. Everything else up to v4 will run a wide range of voltages. No clue on v5 thru v8.

No problem. I've done both DC and AC version of your arrangement without much difficulties. The limiting factors are the current handling abilities of the RJ-45 connectors (1A max per pin), resistive wire losses in the CAT5 (17.2 ohms/100m per conductor), shock hazard, and heating (use a fuse). The calculations are trivial, but you neglected to supply anything I can use.

  1. Make and model of equipment?
  2. Actual measured equipment voltage and current consumption.
  3. Ratings on stock wall wart.
  4. Length of CAT5.
  5. Anything else in the circuit or powered with this device?
Reply to
Jeff Liebermann

In comp.dcom.lans.ethernet Jeff Liebermann wrote: (snip)

It is required to run the hot and neutral wires through the same metal conduit for a good reason. If you do, then the net current through the wires should be zero. If not, it will try to induce current into the conduit, or into other wires in the conduit.

-- glen

Reply to
glen herrmannsfeldt

Yeah, right, tell that to the plaintiff when they get a summary judgement and you end up homeless because you've lost all your assets fulfilling your obligation.

Plenty of folks want to whinge about the legal system.... until they actually need what it provides.

As offensive as the other garbage?

And if you can't stick to one argument without trying to prop it up with other, even weaker ones, you're just pathetic.

Reply to
Bill Kearney

On Sat, 3 Jan 2009 21:20:24 -0600, "NotMe" wrote in :

Bill is just being Bill.

Reply to
John Navas

Yep. First of all, with insurance, you are betting on disaster. If nothing happens, then you lose. If, after paying for years, something does happen, you are gambling that the company you paid all along to protect you when disaster arrives, will follow through in your time of need. They usually do, but not always ! And it's often a fight to get back what you put into it.

Worst of all is the effect on society. Personal responsibility and direct feedback on the actual cost of things is lost. Anything insured (auto bodywork/ health care) becomes ridiculously expensive because the consumer is insulated from the real costs- even though they still pay for them, with a profit added for the middlemen.

I don't take offense myself, and can agree somewhat. There are some aspects that are much better in a more free (less supervised, regulated) country like Mexico, but the effect of anarchy and chaos is often just as Bill says. Driving is very scary here. 16 year olds who never learned any rules of the road, passing on blind curves.

10 foot drop offs 12 inches from your wheels due to construction or road failure. No warnings, just watch out for everything.

Ah, we are getting very philosophical, and I can agree to some of this. Though size of burgers and sides of road is just cultural.

Agreed! US is a crazy society- but then which one doesn't have it's faults?

Reply to
seaweedsl

Multiple single conductors are allowed in conduit, so yes the US still allows single-strand.

Jerry

Reply to
Jerry Peters

Yup! using the exact numbers I came up with 3.08V drop for 120' - should be no problem.

Assuming you are using a wrt54g_v4, I have noted a heat related situation. I have a wrt54gs_v4 which uses the same pcb with more memory - the cpu/ethernet controller is a BCM5352.

With the case removed & the AP operating in a 86°F room I have measured 130°F temp at the center of this chip. This is with nothing connected to the AP, ie no data being moved. The cpu was not overclocked.

On my unit I am in the process of installing a small heatsink on this chip, & then adding or enlarging the oem vent holes.

Probably a good idea to think about this - heat kills :)

Cut the tamper label on the bottom, the front will "pop" off & you can see for yourself. Might have to gently rock the front some but it will "pop" off eventually.

I got concerned after I noticed the top of the case was getting quite warm. I couldn't hold my finger on this chip for 5 seconds, which is my standard test for overheating.

Seems everything past the first vs 1.0 & 1.1 devices will work in this situation. I just looked at a v6 & it appears to be the same design.

Of course I'm using dd-wrt.

Oh, the internal antenna switch &/or the transmit/receive switch can blow from static. my v6 only works well on one antenna, I forget which. see:

formatting link
But I think you will be very happy with the overall performance!

Good Luck

kc

Reply to
Kim Clay

Thanks Jeff. This is exactly what I wanted to know. See my other posts about insurance and fire safety, if you care! I'm considered over safe by most anybody I work with, but do make my own estimates on risk. I believe that the NFPA does a good job, but standards are meant to work across many situations, and my 120 feet of conduit in a ditch going from an exterior box to an exterior box gives almost zero possibility for shock other than digging hazard.

Reply to
seaweedsl
  1. Make and model of equipment?
  2. Actual measured equipment voltage and current consumption.
  3. Ratings on stock wall wart.
  4. Length of CAT5.
  5. Anything else in the circuit or powered with this device?
Reply to
seaweedsl

In fact, it's the only thing allowed in high voltage (110 and up) conduit by the NEC as I understand it. Romex as some call it, or Non- Metallic Sheathed cable is NOT to be run in conduit. There's nothing wrong with running single wires that I can see. Often the temp rating etc availible is better for their insulation.

Steve

Reply to
seaweedsl

Great info, thanks. We are in a similar humid environment as the poster, I will watch out for that type of failure. Eventually, I think I'll go over to the Ubiquiti weatherproof CPEs and APs as things fail here. They claim to have ESD protection and should have the heat thing worked out as well as possible, for the price!

Anyway, in this case, the WRT54G is mounted in a Rootenna box with the top half of the case removed. It will get hot, but what the heck. Here on the coast, everything goes within a couple years no matter what. Ideally, the electronics will fail from heat right around the time they corrode. No point in strengthening one link in the chain.

Thanks, Steve

Change of topic #4: I'm running DD-WRT on my Linksys/Buffalos also. I wonder about underclocking the CPU to lower heat. Any thoughts? Looks like I can take it down from 200 Mhz to 183...

Reply to
seaweedsl

Well, since I now have the v6 opened up, I looked into the problem.

Didn't take long - the "dead" antenna was the one that had the coax connection (left from front) to the pcb. There are unused pads for a (missing) matching network & the pads for the last capacitor (cap to gnd. at the antenna connection) were bridged with solder. Must have happened when soldering the coax to the pcb as I had to cut the tamper seal when I opened the case.

After removing the solder bridge all is fine with both antennas.

So I have yet to find a defective antenna switch in my collection.

kc

Reply to
Kim Clay

Using numbers provided - 120 foot of 24 AWG carrying 1 amp may mean a 7 volt drop. To provide 12 volts from a single chip regulator means a DC power source at the other end of that cable would be 22 volts DC minimum and less than 35 v. Single chip regulator is a classic 7812. Example of that single chip power supply, located adjacent ot the AP, is in the datasheet:

formatting link

Reply to
westom1

Yes I have underclocked all my linksys APs. I have never noticed any slowdown in any of its actions, but none are really loaded with multiple clients or connections.

I have not done any temp measurements with it underclocked but from normal experiences underclocking does decrease operating temps. So I consider it a good idea.

kc

Reply to
Kim Clay

You underestimate how a misused fish tape can neatly slice through just about anything short of BX armored (aka greenfield) cable jacketing. Some idiot tries fishing a new line through it at some later point and uses a bit of electrician's fish tape with a hook bent into the end of it. After strenuously pulling on said tape he manages to force the new wire in there. Not realizing the tape was stuck as it was cutting a gouge into the insulation of the wire already present. Only by the grace of the 'god looks after idiots' rule does he not get himself electrocuted in the process. Perhaps days/minutes/hours/whatever time later that ripped insulation decides to put live AC onto the other conductors in the conduit. Oh, and the installer bypassed the old ground lead since there wasn't enough room in the junction box any more. The voltage simple waits until some poor soul handles what they think is a safe connector (RJ45 network, RJ11 phone or even bare bares). They meet their maker after a puff of smoke and a brief bit of voltage-induced flailing about.

So, really, it's worth doing the job well.

Reply to
Bill Kearney

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