How to Do a Duct for a Microwave

Installation

• 1

  Select a location for your microwave oven that is large enough to accommodate its width. Check with a stud finder to ensure that there is a stud behind the location to support the microwave's weight.

• 2

  Turn off the electricity to the kitchen. Cut an opening in the cabinets sized to the ducts you will use above or behind the microwave installation site with a rotary tool saw attachment, being sure to avoid studs and wiring. Cut a corresponding opening into an existing oven duct, or directly through the kitchen wall or ceiling.

• 3

  Insert a straight length of metal duct into the space between the new openings. Select a duct that is the appropriate width as noted in the microwave's installation guide -- 3 1/4-by-10-inch rectangular or 6-inch round ductwork is common. Add duct elbows and adapters to create a path between the site for the microwave and the opening in your kitchen wall or ceiling. No more than three 90-degree elbows are recommended. Crimp the joints between duct components with a metal crimper to seal them together.

• 4

  Fit and crimp a roof cap or wall cap outside your home where the duct exits through a finished exterior surface. Seal around the cap with caulk to prevent air and moisture from leaking into your home.

• 5

  Measure the space where you want to install the microwave with a tape measure. Mark the wall with a pencil based on the manufacturer's installation instructions. Screw in the microwave's mounting brackets using a screwdriver.

• 6

  Slide the microwave into position and attach the interior end of the duct as you lock it into position. Attach a damper adapter, if necessary, so the microwave's vent leads directly into your microwave's duct. Plug in the microwave and test it by running the heat function for a few seconds. Check for loose duct components or installation problems if you feel warm air coming from the microwave.