DMX vs Cat6

RonHebbard

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Waterdown, ON, CA
From my perspective, every high-bandwidth connector you don't have to terminate yourself is one you can't screw up. But yes, if you're pulling long enough runs, or enough of them, connectors are going to be a pain. It may be worth borrowing one of the Fluke network bandwidth testers for a day once everything is done to make sure you're getting the full expected performance of the cables. The day you suddenly find yourself needing to run 4k video over an HDbaseT transceiver you'll be very happy you did.
@Eleanor Saitta Borrow? The company I was free-lancing for owned one of the Flukes; fully testing each and every cable was a standard part of every installation, along with including 10% spares.
Toodleoo!
Ron Hebbard
 
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Finland
@Eleanor Saitta Borrow? The company I was free-lancing for owned one of the Flukes; fully testing each and every cable was a standard part of every installation, along with including 10% spares.
Eh, I'm just saying that if you're in-house at a single venue and worried about whether it's worth pulling CAT5, you might not want drop $1500 on a cable bandwidth tester for a use case you don't currently have for those cables. :)
 

ACTSTech

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Nov 13, 2019
Location
USA
There is a point in all tech where DIY is a distant 2nd to hiring Pros!
You also have to look at cost. I’d love to bring in some pros, but when it comes to bringing in one pro or having enough money to have programs and tickets printed, you bite the bullet and pull the wire yourself. Or you get on ControlBooth and ask for help from people who understand that sometimes you do these shows because you enjoy it even when you don’t get paid.
 

mbrown3039

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Mar 20, 2018
Location
vegas, baby..!
Run as many cables as the conduit (or raceway/J-hooks if "temporary" or plenum-rated) will hold; Cat5e is good for most things today, but shielded Cat6 is a must for high-quality video. Check around with local electricians and data installers -- you'd be surprised how many partially-used spools of cable they throw away (generally, anything under 250-300' is tossed). As for crimping, the Belden connectors for shielded Cat6 are universally accepted but a major PITA to install. I have been using the Platinum EX series connectors (and tool, which has interchangeable dies for Cat5 v. Cat6) for a couple of years now with just one failed crimp (and now I always wear my glasses when terminating, lol).

Not sure exactly where you're located, but there may be a couple of CB members willing to lend you a hand. m
 

DIYLED

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Feb 5, 2016
Location
Palm Springs, California
I usually use cat5e with molded RJ45's. Bestlinknetware has a variety of lengths. In some situations it can be pulled with l-com brand covers taped over the connectors, and hardware stores have electrician's lubricant. But it is easier to pull non-crimped cat5e over long distances, tight openings, and turns. Another trick is cut one end off a pre-made cable. That reduces number of DIY crimps by 50%. Code requires data be separate from power in conduits. If it's not, it must be shielded to work, and shield connected to DMX ground at at least 1 end of each cable.
 

RonHebbard

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Jun 12, 2004
Location
Waterdown, ON, CA
I usually use cat5e with molded RJ45's. Bestlinknetware has a variety of lengths. In some situations it can be pulled with l-com brand covers taped over the connectors, and hardware stores have electrician's lubricant. But it is easier to pull non-crimped cat5e over long distances, tight openings, and turns. Another trick is cut one end off a pre-made cable. That reduces number of DIY crimps by 50%. Code requires data be separate from power in conduits. If it's not, it must be shielded to work, and shield connected to DMX ground at at least 1 end of each cable.
@DIYLED You definitely wouldn't want to pull your shielded cables in with power AND bond both ends to ground.
Induced circulating currents would burn / fuse the shield connections, likely fusing at the point of highest resistance / greatest voltage drop.

In a multi circuit, 120 / 208 volt house light installation where most of the 96 outputs of a Strand CD80 dimmer rack were routed from the basement dimmer room to an attic junction box via three parallel runs of 2.0 or 2.5 inch I.D. rigid steel conduits; both ends of all three pipes were fitted with threaded on "Grounding bushings."
Years later, the attic J-box was opened to facilitate an alteration. Surprise, surprise, surprise:
Each of the three pipes contained the outputs of dimmers from one of the three phases. (no interphase cancellation of currents) Each pipe had contained one single 10 gauge TW, green jacketed grounding conductor. The grounding conductors had been bonded to their respective grounding bushings at both ends. ALL three of the green jacketed #10's had fused (burnt) at the attic ends melting as much of their green insulation at we could expose / see. The opposite ends were in the basement in a J-box within the poured concrete slab outside the dimmer room. I never ventured within the basement ceiling J-box to examine the lower ends of the three 10 gauge bonding conductors.
Toodleoo!
Ron Hebbard
 

DIYLED

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Feb 5, 2016
Location
Palm Springs, California
I had meant signal common, not earth ground. The DC ground, not the AC ground.

That is odd that the shared ground was on the same phase and I'm guessing the same gauge as the hots and neutrals. Even more strange that the green wires were carrying current and nobody noticed that something was wrong. At least they used a J-box and metal conduit. Otherwise would have burned down the whole building.
 
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RonHebbard

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Waterdown, ON, CA
I had meant signal common, not earth ground. The DC ground, not the AC ground.

That is odd that the shared ground was on the same phase and I'm guessing the same gauge as the hots and neutrals. Even more strange that the green wires were carrying current and nobody noticed that something was wrong. At least they used a J-box and metal conduit. Otherwise would have burned down the whole building.
@DIYLED The building was built from its sub basement foundations on up beginning in late 1971 and approved for occupancy / final construction clean-up during the summer of 1973. All of the work was by union contractors including members of my local / home IBEW local.

Whether by spec' or pure coincidence, the ou puts of all phase A dimmers were routed from basement to the attic within one 2 or 2.5 inch I.D. conduit.
Likewise all phase B dimmers and phase C dimmers.

At the basement / source end, all neutrals were connected to the common neutral buss.
All conductors were 10 gauge TW to partially offset voltage drop over the length of runs.

A suitable quantity of neutrals were included within each of the three conduits.

Each of the three conduits were fitted with threaded grounding / bonding bushings on both of their ends.

Each of the three conduits contained a single, TW10 gauge grounding wire bonded to the ground bushing at either end.

The ground wire was NEVER intended to carry current except during fault conditions.
When you (for whatever reason) enclose all of the conductors from the same phase, in the same conduit, with a random assortment of neutrals, you've created essentially an 'air core' transformer.
Air cored transformers are more commonly employed at RF frequencies and transform FAR less power at 60 Hertz.

None the less, transformer action / eddy currents / whatever, resulted in a ground loop comprised of the single TW10 gauge insulated conductor within each conduit looping back via the appreciably larger / much lower resistance threaded rigid steel conduit surrounding the insulated grounding conductor.

In the survive the battle of the transformer coupled ground loop currents, the single 10 gauge was predictably the loser.

Only trouble was: Apparently no one had troubled themselves to assess the odds.

Go figure / who'da thunk. Only another of the many things innocently overlooked during inspections.
Nobody was opening the basement box overhead within the poured concrete slab of the basement ceiling / 1st level floor.

Had we not decided to utilize a spare dimmer, via spare conductors, NOBODY'D have ever noticed the flames that erupted and burned themselves out within a 16 x16 or 24 x 24 inch J-box anchored to a poured concrete attic wall approximately 8' above the attic floor.

Upon opening the J-box we simultaneously saw the charred insulation, smelt the fumes AND felt the heat rising by convection and escaping from the attic ends of all three conduits. With all three conduits ending in the same box, the heat build up was appreciable.
None of the other conductors were showing any evidence of overheating since they were loaded well within their ratings.

At the time, I was a very junior IBEW member in my fourth or fifth term catching calls with Hamilton's IA 129. My boss within Hamilton Place was Head Electrician Tom Taylor; Tom had an excellent relationship with the IBEW foreman who'd built the building from undisturbed soil to the roof.

Rather than call in an electrical inspector, Tom chose to contact the IBEW foreman who visited the next time he was passing.

Post much humming and stroking of beards, the decision was nade to replace the supplied solid cover with a cover band-sawed from from a sheet of heavy gauge expanded metal to simultaneously bar access to nosy fingers while leaving adequate open space for rising heat to escape.

Years later, another CD80 / 48 slot / 96 x 2.4 Kw rack was installed in the attic, on the floor and anchored to the poured concrete side wall immediately below our infamous J-Box; a 3.5 or 4" run of conduit was installed up the wall of a nearby, 84 step, spiral stair to supply a 400 Amp, 3 phase, 5 wire feed to power the newly installed attic rack.
To the best of my knowledge, the CD80 rack is still there, comfy and undisturbed in its happy little attic nest.
Toodleoo!
Ron Hebbard
 

DIYLED

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Feb 5, 2016
Location
Palm Springs, California
That's quite a story. Could you explain what the mistakes were? AC is not my specialty. It sounds like they should have used a thicker green wire if unbalanced and only grounded the conduits on 1 end. And maybe it's standard practice to balance phases through large conduits?

I would have guessed that the magnetic fields of the hots would somewhat cancel the magnetic fields of the neutrals, and the voltage generated in the green wire would somewhat cancel that of the conduit. Maybe it's the random alignment of wires with imperfect cancellations that generated the transformer effect?
 
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RonHebbard

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Location
Waterdown, ON, CA
That's quite a story. Could you explain what the mistakes were? AC is not my specialty. It sounds like they should have used a thicker green wire if unbalanced and only grounded the conduits on 1 end. And maybe it's standard practice to balance phases through large conduits?

I would have guessed that the magnetic fields of the hots would somewhat cancel the magnetic fields of the neutrals, and the voltage generated in the green wire would somewhat cancel that of the conduit. Maybe it's the random alignment of wires with imperfect cancellations that generated the transformer effect?
@DIYLED I'll kick this can one more time and employ CB's 'Bat Call' to summon a few likely knowledgeable regular posters.

Putting all of the outputs from any one phase in a conduit WITHOUT any of their out of phase mates equates to maximal accumulation of currents with essentially ZERO out of phase cancellation.
Selecting neutrals at random meant they all came from one common neutral bar in the basement, which is normal and NO problem.
When, once you're in the attic J-box, they were connecting 250, 500 and 1Kw loads to dimmers, keeping track of the hots but choosing any neutrals for their loads; some neutrals from one pipe serving as returns for hots in a neighboring, rather than the same, pipe.

Bonding the single TW 10 gauge green jacketed grounding conductor was common practice but it was forming an insulated ground loop within the MUCH more conductive rigid steel conduit. With all of any given phase's live conductors in one conduit, induction would've been EXTREMELY high within the conduit itself leading to creating an excessively high induced voltage over the lengths of the conduits: Bonding each conduit's ends together with a single TW 10 gauge conductor was akin to shorting a butch battery / AC transformer with a single conductor not even close to being able to safely conduct the currents induced.
Envision shorting your 12 volt car battery with a length of 18 gauge copper wire; you wouldn't want to be holding said wire in your fingers when you shorted out your car's 12 volt battery.

If you own a pair of jumper cables, the wire gauges chosen aren't accidental. 'nough said.

Perhaps I'll summon @Jay Ashworth @Ancient Engineer @FMEng @TimMc @tjrobb and @MNicolai to explain the inadvertent conspiracy of coincidences. (Possibly more commonly referred to as a "Cluster Phuque)
Toodleoo!
Ron Hebbard
 

FMEng

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Tacoma, WA
I think the mistake was not keeping the neutrals paired with the hots in the same conduit. There is no issue with having all the loads from the same phase in one conduit, as that is commonly done. The vector sum of all the currents flowing through the conduit has to be zero to cancel the magnetic field and thus not inducing high current in the "one turn coil" made by the conduit and ground wire.

The National Electrical Code basically says all of the wires for any given load have to be kept in the same conduit. There is an exception for paralleling large conductors in multiple conduits, but there has to be one of each phase and neutral in all the conduits. So if the current code were correctly applied to that work, the melted ground wire would not have happened. The NEC makes wiring very safe when it's followed.
 

DanAyers

Member
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Mar 6, 2003
Location
United States
There's some great responses above. I'd like to clarify a couple things I noticed which may help.

Typically, All cabling between network ports, jacks, patch panels, and equipment must utilize prefabricated CAT6a, or better as required by the application, patch cables of appropriate length. Pre-fabricated cables are not run through conduits, only between devices.

When the cable is not simply between devices, and it goes through a conduit, you would not want to pull terminated cables through so the contractor will utilize a standard testing procedure. The contractor will test the cable to prove compliance with ANSI/TIA-568.2-D they will do so with the criteria specified in ANSI/TIA/EIA-568-C. That's a lot of jargon to say they will use a Fluke DSX-5000 or similar which will produce a report verifying the cables.

As far as whether or not it's appropriate for your facility depends on how you will use your systems. For a new construction 750 seat theater I designed recently, I did install DMX from FOH to Stage and Electrics mainly for convenience but I also installed Cat6A cable for every foreseeable use (Sound, Lighting, Video, and IT) plus spares and extra empty conduit to add more.

At the end of the day there are no wrong answers, just be sure you're thinking through the application. I recommend a drawing, even if it's on a napkin. It's much easier to identify your needs when you can visualize the space. It's much easier to install during construction than retrofit.
 
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BillConnerFASTC

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Location
Clayton NY 13624
also installed Cat6A cable for every foreseeable use (Sound, Lighting, Video, and IT) plus spares and extra empty conduit to add more.
I urge caution in installing infra structure for "future". I've seen and renovated many facilities with provisions for things that never materialized, not in the 25-50 years since installed. It may happen, more often in worship or pro than hs or university. And Cat6 whatever probably is not what you'll want in 10 years. Some spare conduit maybe.
 
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DanAyers

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United States
I urge caution in installing infra structure for "future". I've seen and renovated many facilities with provisions for things that never materialized, not in the 25-50 years since installed. It may happen, more often in worship or pro than hs or university. And Cat6 whatever probably is not what you'll want in 10 years. Some spare conduit maybe.
You bring up a great point. My goal was to ‘be intentional’ about infrastructure.

And you’re right we’ve already moved from cat5e and fiber is getting cheaper every day; we don’t want to abandon infrastructure before its used.
 

RonHebbard

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Jun 12, 2004
Location
Waterdown, ON, CA
I urge caution in installing infra structure for "future". I've seen and renovated many facilities with provisions for things that never materialized, not in the 25-50 years since installed. It may happen, more often in worship or pro than hs or university. And Cat6 whatever probably is not what you'll want in 10 years. Some spare conduit maybe.
Posting in FULL support.
Empty conduits (with labelled pull lines); they're NEVER cheaper to install than when they're routed and tied down to re-rod within poured concrete slabs.
Conduits installed in poured slabs during initial construction are extremely fast to install, time truly IS MONEY.
Conduits ran in slabs normally run point to point by the shortest, most direct, routes possible.
COMPARED TO:
Surface mounted conduits requiring skill and FAR MORE TIME to install them "pretty", parallel, plumb, ninety degree bends, offsets and saddles, conduit straps, anchors, anchoring holes individually hammer-drilled into concrete, dust to be vacuumed up, yada, yada; so MUCH MORE time and labor.
WORST CASE EXAMPLES: Adding conduits to floor boxes under seating in finished auditorium floors equates to labor, LABOR, MORE LABOR, down time, overtime and lost revenue.
'nough said, I hope.
Toodleoo!
Ron Hebbard
 

ggooch

Member
Joined
Dec 5, 2019
Location
West Lafayette, IN
Unfortunately when you are talking about installs, terminating yourself is the only way to go. Thank manufacturers can't screw up terminations? Think again. I routinely run into DMX and ethernet terminations with manufacturer issues.

Geoff