2006 New York Code - Permits.

 
    §  27-4190  Permits.  a. For purposes of this subchapter, refrigerants
  shall be classified  by  safety  groups  in  accordance  with  reference
  standard  RS  13-6 of the building code. Except as otherwise provided in
  this subchapter, it shall be unlawful to maintain or operate  without  a
  permit  any refrigerating system that uses a group A1, A2, A3, B1, B2 or
  B3 refrigerant or that is  mounted  on  or  suspended  from  a  roof  or
  ceiling, except a refrigerating system of less than five horsepower that
  uses a group A1 refrigerant and that is not mounted on or suspended from
  a roof or ceiling. Such permit shall be posted adjacent to the system or
  kept on the premises in a location where it can be produced upon request
  of any representative of the department.
    b.  Permits  shall not be required for refrigerating systems installed
  in the residence portion of any building; installed in vehicles, vessels
  or railroad cars; or employing water or air as a refrigerant.
    c. The  system  capacity  of  a  refrigerating  system  with  multiple
  compressors shall be the aggregate of all the individual compressors.
    d. If the department finds that the system creates a hazard to life or
  property  or  for  other  good cause, it may order the system to be shut
  down until the corrections required by the department are made.