Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 146, § 86

A license for a refrigeration technician, refrigeration contractor or a refrigeration trainee shall be classified and limited as to the maximum size of the refrigerating system with which the applicant is familiar in installing or servicing, and the applicant shall be licensed for that particular size of system; provided, however, that any person may make application for and, if found to be qualified, receive a license to engage in the installation and servicing of all sizes of refrigerating systems.