buck boost transformer

[mshields]

I've need to add a buck boost transformer for a 16A, 230V rated piece of equipment in a lab. I'll put the buckboost in the ceiling above the connection point. I don't believe I need any fusing or overcurrent protection at the buck boost. a) is this correct and b) by what code section/paragragh is this exempt from having protection in closer proximity? i.e. for an ordinary dry type I go by the rules in Art 240 which require that the primary and secondary protection not be more than 25 feet apart.

Thanks,

Mike

 

[hurk27]

Because Buck/boost transformers are an auto transformer which is non isolating as an SDS type transformer is, a fault to ground on an auto transformer will provide a line to ground fault current to the primary side, a fault to ground on a SDS transformer will only provide a line to line current at the ratio of the transformer for this reason the primary of an auto transformer is closer fused at the load current on the primaries and will protect the secondaries, see 450.4