Can I zip tie network cable to EMT?

No. NEC 725.143 prohibits Class 2, Class 3, and PLTC cables from being strapped, taped, or attached by any means to the exterior of a raceway as a means of support.

Is there any case where conduit can support low voltage cable?

Yes, one. NEC 300.11(C)(2) permits a raceway containing power supply conductors for electrically controlled equipment to support Class 2 conductors that connect solely to that equipment's control circuits.

Can I use ceiling grid support wires to hold low voltage cable?

Not the wires supporting the ceiling itself. NEC 300.11(B) requires independent support wires identified as suitable and secured at both ends.

Can low voltage cable be supported from conduit?

No. Tie wrapping thermostat wire, security cable, or Category 6 to the outside of an EMT run is one of the most common violations on a rough in, and there are two separate sections that prohibit it. It fails whether you use zip ties, wire ties, tape, or bridle rings clamped to the pipe.

Section 725.143 is the direct rule

Section 725.143 of the 2023 NEC states that Class 2, Class 3, and PLTC cables shall not be strapped, taped, or attached by any means to the exterior of any raceway as a means of support. That language is absolute. There is no exception for short runs, for light cable, or for raceways that happen to be feeding the same equipment. Similar prohibitions appear for other limited energy systems, including Section 760.143 for fire alarm circuits and Section 770.12 for optical fiber, so the rule is consistent across the low voltage articles.

Section 300.11(C) is the general rule

Section 300.11(C) of the 2023 NEC covers raceways used for support. Raceways are permitted to be used as a means of support only under three conditions. First, where the raceway or means of support is identified as a means of support. Second, where the raceway contains power supply conductors for electrically controlled equipment and is used to support Class 2 circuit conductors or cables that are solely for the purpose of connection to the equipment control circuits. Third, where the raceway is used to support boxes or conduit bodies in accordance with 314.23, or to support luminaires in accordance with Part IV of Article 410.

The second condition is the one worth knowing. If a conduit carries the power conductors to a piece of control equipment, that same conduit may support the Class 2 control conductors going to that same equipment. It is a narrow allowance for control wiring, not a general permission to hang a building's structured cabling on the pipe.

Support the cable properly instead

Section 725.24 requires Class 2 and Class 3 cables to be supported by the building structure in such a manner that the cable is not damaged by normal building use, and it points to the 300.4 and 300.11(A) methods. Use independent J hooks or bridle rings anchored to structure, cable trays, or a dedicated support wire installed for that purpose. Section 300.11(B) also prohibits using the ceiling support wires that hold up a suspended ceiling to support raceways or cables unless the support wires and the means of attachment are identified as being suitable and are secured at both ends.

Bundling and heat

While you are up there, Section 725.144 covers the ampacity of Class 2 and Class 3 cables that transmit power and data, which is the power over Ethernet rule. Large bundles of PoE cable get temperature limits based on bundle size and conductor gauge, so a giant loose bundle hanging off a J hook can also be a problem for a different reason.

Field takeaway

Never strap low voltage cable to a raceway. Hang it on independent J hooks fastened to structure. The only exception is Class 2 control conductors landing on the same equipment that the raceway feeds, which is permitted by 300.11(C)(2).