NEC Article 725.136(D) and 725.136(I) address the situation you're describing, regarding Class 2 or Class 3 circuits in the same enclosure as power conductors. The important point here is that you generally cannot run Class 2/Class 3 (like Cat5) in the same raceway as the 480V power circuit unless certain conditions are met.Here's a breakdown of why, and what the NEC says: 725.136(D)(1): Separation from Electric Light, Power, Class 1, Nonpower-Limited Fire Alarm (NPLFA), and Medium Power Network-Powered Broadband Communications Circuits. Class 2 and Class 3 circuits shall not be placed in any cable, cable tray, compartment, enclosure, manhole, outlet box, device box, raceway, or similar fitting with conductors of electric light, power, Class 1, NPLFA, and medium power network-powered broadband communications circuits. In your case, the 480V conductors are clearly electric light and power circuits. So, the default is you cannot run Cat5 (Class 2) in the same EMT. 725.136(D)(2): Exceptions to Separation Requirements. There are a few exceptions where you can co-mingle these circuits, but they are specific and probably not applicable in your Big Ass Fan installation: (a) Where the electric light, power, Class 1, NPLFA, and medium power network-powered broadband communications circuit conductors are separated from the Class 2 and Class 3 circuit conductors by a barrier. This means a physical barrier inside the EMT. This is generally impractical. (b) Conductors of electric light, power, Class 1, NPLFA, and medium power network-powered broadband communications circuits are installed in a raceway or cable of the type identified in 300.3(C)(1). This would require the 480V conductors to have insulation rated for wet locations, grounded shield and installed according to article 300. 725.136(I): Class 2 and Class 3 Circuit Conductors with Communications Circuits. This section discusses when communications cables can be in the same raceway, but it's primarily related to data circuits and not to situations where power conductors are involved.

The issue is safety. Low-voltage, limited-energy circuits like Class 2 are designed to be inherently safe. Running them in the same raceway as higher-voltage power circuits creates a potential for insulation breakdown and dangerous voltages appearing on the low-voltage circuit.

Your Specific Scenario

Since you're talking about a 480V power circuit, it is highly unlikely that running your Cat5 control wiring in the same EMT would meet the NEC requirements without adding the specific exceptions mentioned above.

What to Do1. Separate Raceways

The simplest and safest solution is to run a separate* EMT conduit for the Cat5 control wiring.2.

Verify Control Circuit Classification

Make sure the Cat5 circuit you are using is truly a Class 2 or Class 3 circuit and that it meets the voltage and current limitations for that classification.

In Conclusion

It is highly advised to install the Cat5 control wiring in a separate EMT raceway to avoid violating the NEC and to ensure the safety of the installation. Running in the same raceway without special conditions, like a physical barrier or the exception listed above, is a code violation.Consult with a qualified electrical inspector or engineer to ensure your installation meets all applicable NEC requirements and local codes. Flag for review