Project specifications typically distinguish between hvacr control wiring, which is specified in Division 15 and often installed by the controls contractor, and equipment power supply wiring, which is provided by the electrical contractor under Division 16.
In spite of our tendency to consider the control wiring systems common to temperature control and energy management systems as harmless and somehow separate from “real” electrician’s work, they are considered electrical wiring under the National Electrical Code (NEC) and subject to requirements that you should be aware of. Specific sections of the NEC applicable to modern control system installations include Article 725, “Class 1, Class 2 and Class 3 Remote-Control, Signaling, and Power-Limited Circuits,” and Article 800, “Communications Circuits.”
Requiring compliance with the NEC and applicable Division 16 sections is usually adequate definition of these requirements within the temperature control specification. However, basic knowledge of how the NEC treats these installations can assist the hvacr engineer in design coordination, cost estimating, and construction inspection activities.