What ambient temperature is assumed for wiring located above heated ceilings?

For wiring located above heated ceilings, the ambient temperature is assumed to be 50° C. This assumption is based on industry standards and safety protocols that take into account the increased heat exposure in such environments.

When wiring is placed in areas with heated ceilings, the heat emanating from the ceilings can significantly elevate the temperature around the wiring. Using a temperature of 50° C reflects a cautious approach to ensure that the wiring materials are capable of withstanding this heat without becoming a fire hazard or degrading over time.

This value helps in determining proper wire sizing and insulation requirements to ensure safe operation. It also aligns with the National Electrical Code (NEC) and other relevant safety guidelines which account for the thermal effects on electrical installations in heated spaces.