What is the minimum size required for secondary conductors if a transformer has no secondary conductor protection?

The minimum size required for secondary conductors, particularly when there is no secondary conductor protection in place, is determined primarily by the NEC (National Electrical Code) guidelines regarding transformer installations. In this context, if a transformer has a secondary with no protection, the conductors must be sized to safely carry the load without overheating or risking damage.

When a transformer is involved, size requirements for conductors depend on the rated output of the transformer. A critical factor is that secondary conductors must be able to handle a higher amount of current than what might typically be expected for a circuit of lower amperage. For secondary conductors with no protection, the NEC stipulates that these conductors should be sized to handle at least 125% of the transformer's rated output.

For example, if the secondary circuit connected to the transformer carries a load that could potentially reach up to 40 amperes, then conducting wire must be selected to safely manage this current, factoring in any potential peaks. Therefore, the minimum size that must be used to safely support the current flow under this condition is 40 amperes, making it the correct answer in this scenario.

Considering the nature of electrical work and safety standards, selecting a conductor too small could lead to overheating