How deep must concrete cover be for flat top underfloor raceways between 4 to 8 inches wide?

For flat top underfloor raceways that are between 4 to 8 inches wide, the required concrete cover is 1.5 inches. This specification comes from electrical codes and standards that ensure adequate protection and support for the raceways. A cover of 1.5 inches strikes a balance between providing sufficient mechanical protection against potential physical damage from overlying concrete and maintaining an appropriate depth to prevent issues related to the thermal properties and heat dissipation of the conductors within the raceway.

Having less cover may not provide enough protection, and having more could introduce unnecessary complications in installation and lead to increased costs without any added benefits. Thus, the code specifies 1.5 inches as the optimal depth for adequate safety and compliance in instances where raceways are located in underfloor concrete installations.