National Electrical Code Articles and Information

1. It applies to any heater mounted in the airstream of a forced-air system where the air-moving unit is not provided as an integral part of the equipment [424.57].

2. Use with elevated inlet air temperatures [424.60], use with heat pumps and air conditioners and mounted closer than 4 ft to them[424.61], and use with air conditioners or other air-cooling equipment that could result in condensation [424.62]

3. It has to be energized any time a heater circuit is energized. But a time or temperature controlled delay is permitted [424.63].

4. It must be provided with an approved, integral, automatic-reset temperature-limiting control (or controllers) to deenergize the circuit(s) [424.64].
   
5. Sufficient clearance must be maintained (this is an owner and occupant issue, not just an installer issue) to permit replacement of controls and heating elements, and for adjusting and cleaning as necessary [424.66].