What is the maximum fill percentage allowed for a 1" rigid metal conduit with four current carrying conductors?

The maximum fill percentage allowed for a conduit is determined by the National Electrical Code (NEC), which aims to ensure safe and efficient installation of electrical wiring. For a rigid metal conduit, the fill capacity takes into account the number and size of conductors within it, as well as whether those conductors are current-carrying.

When four current-carrying conductors are placed in a 1" rigid metal conduit, the NEC stipulates that you can only fill the conduit to 80% of its total capacity to maintain proper heat dissipation and to prevent overheating. This fill ratio helps ensure that the conductors have enough space to allow for air circulation and avoids excessive heat buildup, which can occur when too many conductors are crowded into a conduit.

The maximum fill percentage of 80% applies to scenarios with more than three conductors. Therefore, the answer is based on supporting safe electrical installations, ensuring that electrical systems operate efficiently within their thermal limits.