If a electrical enclosure containing only terminals (terminals are rated Ex II 2 G D) is located in an area classified Zone 2, does the enclosure itself need a zonal rating?

 

In general, I'd say yes. You will need to check the compliance documents for the terminals for details, but if they are (for instance) Ex e terminals they will be certified as components and not as a complete unit - this will be indicated by a suffix -U on the end of the certificate number.

Terminals will be safe only under specified conditions of clearance and creepage distance, and any moisture or dirt could compromise these values and render the terminals non-compliant. Sop Ex e terminals must be installed in an Ex e box with specified ingress protection requirements.