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Participant

Join Date: Apr 2009
Posts: 4

DMX Lighting Control

12/17/2010 10:47 AM

Hi folks-I have a question about combining 120V power wiring with DMX control wiring in the same conduit. We have 9 building columns spaced at 40' with flexible strip light bands on them. We have only one conduit (360 ft total) the connects to all of the columns and then goes into the control room. If we put the 120V power wiring in the same conduit with the DMX control wiring, will it work?

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Guru

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#1

Re: DMX Lighting Control

12/17/2010 11:16 AM

NEC codes cover requirements for running various wiring.

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Participant

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#3
In reply to #1

Re: DMX Lighting Control

12/17/2010 11:37 AM

Thank You for your response. If the NEC permits combining, I still need to be concerned about the magnetic field of the power cable interfering with the DMX signal

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Power-User

Join Date: Jun 2010
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#2

Re: DMX Lighting Control

12/17/2010 11:35 AM

Standard requirement is to run the cables separately. But provided if you do not have an option as a last resort select concentric and shielded cables.

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Join Date: Apr 2010
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#4

Re: DMX Lighting Control

12/17/2010 12:09 PM

Not only is there a high probability that combining these runs will cause "anomalies" in your lighting control but this may become a warranty issue as in NO WARRANTY.

Best to check with the manufacturer rather than an internet forum on this.

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Guru

Join Date: Feb 2009
Location: West Coxsackie, NY
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#5

Re: DMX Lighting Control

12/17/2010 11:07 PM

You mention you have 1 conduit. Is this cable tray,or is it conduit?

If this is ladder type cable tray, what is the width and depth?

I have run many shielded cables on sensative sensor equipment for all connections from the main control cabinets to the sensors and in the same cable tray I have 120V, 480V 1Ph and Cat5E cables with 0 issues in regards to the sensor equipment or any other equipment issues.

These cables are seperated in the cable tray. That said, the shielded cable is a braided overall shield with drain connected at the controller cabinets only.

Depending on the width and depth of your cable tray, you might be able to run them as long as your DMX is a properly shielded cable. If you truly have closed metal or pvc conduit my answer wold have to be no. In that case, run a parallel conduit.

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#6

Re: DMX Lighting Control

12/17/2010 11:50 PM

To continue with #5's question:

You mention you have 1 conduit. Is this cable tray,or is it conduit?

If this is ladder type cable tray, what is the width and depth?

If this is a tubular conduit, is it EMT, Galvanized, or Non-Metralic Tubing, and what is it's size?

I recommend an isolation transformer for the 120V to prevent a grounding-loop.

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Participant

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#9
In reply to #6

Re: DMX Lighting Control

12/20/2010 2:58 PM

Hello, thank you for your response. The conduit installed is 3/4" PVC underground.

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Participant

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#7

Re: DMX Lighting Control

12/18/2010 12:31 AM

As long as your cables are shielded you'll be fine - I do this day in, day out in real world situations in controlling led arrays without incident.

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Join Date: Dec 2010
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#8

Re: DMX Lighting Control

12/20/2010 12:45 PM

The DMX lighting conductors are typically powered by a Class 2 power supply. They may be shielded, but all of these cables/conductors will have a voltage rating. The line voltage conductors are typically rated as 600 volts. The NEC (National Electric Code) covers the installation of Class 2 conductors in Chapter 725.

725.136 Separation from Electric Light, Power, Class 1, ... "Cables and conductors of Class 2 and Class 3 circuits shall not be placed in any cable, cable tray, compartment, enclosure, manhole, outlet box, device box, raceway (this would be your conduit), or similar fitting with conductors of electric light, power, Class 1, non-power-limited fire alarm circuits, and medium-power network-powered broadband communications circuits unless permitted by 725.136(B) through (I)."

The permission list is extensive and should be consulted, but in general there must be a barrier between Class 2 and power wiring; or physically 2" of space between.

If you must use the conduit for both systems, it is permitted-- if the wiring of the DMX is upgraded to equivalent voltage protection. The change in wiring method makes this now a Class 1 circuit and it may be installed in the raceway with power conductors. This may not be possible if the DMX wiring has special requirements (shielding for example).

Consult the local electrical inspector as he is the authority having jurisdiction.

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