Installing Air Conditioning Units

Before Purchasing or Installing

  • Calculate the size of room to be cooled so that you buy an AC unit with enough capacity.
  • Obtain permission for installation from building management.
  • Make sure that electrical service is adequate. AC units should have dedicated outlets.
  • Ensure that the window and frame where the unit will be installed are in good condition.

Installation Guidelines

  • Follow the manufacturer's instructions.
  • Make sure the unit is installed securely. Support the unit from underneath, or firmly fasten it from inside with angles. You may use metal brackets, mounting rails, etc.
  • Supporting metal brackets, interior angles, etc. should be structurally fastened to the building and must be strong enough for the size and weight of the AC unit.
  • Objects or shims used to adjust the position of the AC unit must have an independent source of fastening or attachment.
  • Secure leveling objects to prevent movement and shifting due to vibrations from the AC unit, wind and other weather conditions.
  • Install the AC unit so it remains in place when the window is opened or affix it so that the window can't be opened accidentally.
  • Tilt the unit slightly to provide water drainage, but don't over tilt.
  • Do not use loose objects - such as wood blocking, bricks, telephone books, gypsum board or cans - to support the leveling of the AC unit.
  • Do not place anything (TV antennae, satellite dishes, plants, etc.) on top of the AC unit.
  • Do not block fire escape windows or other exits with the AC unit.


A work permit or equipment use permit is generally not required to install a common window AC unit, unless the unit exceeds three tons/36,000 BTU/hr. For more information see the NYC Building Code.


It is important to periodically check on the position of the AC and the condition of the window frame to make sure that the AC remains supported and secure.

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