Kitchen range hoods usually come equipped with a fan that can suck away any smoke or smells produced beneath it. It is possible though to install a more powerful fan on the outside of the house that can achieve the same results but in a quieter fashion. In addition, unlike some range hood fans that simply filter the air and spit it right back out into the kitchen, and an external blower fan will shoot anything it pulls in directly outside. The steps below explain how an external blower can be installed.
Step 1 – Cut a Hole for the Blower
Using a circular saw, cut a hole in the wall or roof where the blower will be mounted. The hole should be around 14-inches wide and 18-inches long. If going through the roof, shingles may need to be first cut away with a utility knife.
Step 2 – Mount the External Blower
Place the blower against the hole that was cut in the roof or wall. The discharge vent, or the portion of the blower with the screen on it, should be facing the ground and, ideally, in the direction opposite of prevailing winds. The flange that surrounds the blower unit must be positioned carefully so that no water can enter the unit. If the blower is being installed on a roof, the top-most piece of the flange should be tucked beneath the row of shingles above it and the bottom portion of the flange should be overlapping the row of shingles below. If doing a wall installation, do the same with the siding. Secure the unit into place with a drill and the weather resistant galvanized mounting screws that came with the unit. Once secure, generously apply roofing sealant around the edges of the unit where the flange meets the wall or roof.
Step 3 – Connect the Exhaust System
The ductwork that comes off of the blower is usually round and 10-inches in diameter. A round 10-inch adjustable elbow may be connected to the back of the blower in order to change the direction of the ductwork so that it travels in the correct direction towards the range hood. Any ductwork added to the external blower must remain round and 10-inches in diameter until it has passed through the wall or ceiling of the house. However, after it has passed through either the roof or ceiling bracket, a 10-inch to 8-inch reducer will need to be installed to make the ductwork compatible with the exhaust hole provided on the range hood (the exhaust may be different, but range hood exhaust ports are generally 8-inches). From this transition, additional lengths of 8-inch ducting may be connected to reach the range hood, but plan carefully – for the blower to work properly, the 8-inch ducting cannot run more than 5-feet before it reaches the range hood. Once all the ducting is connected, run a small screw through each of the joints to ensure they cannot separate. Then, tape them with copious amounts of heat resistant tape.
Step 4 – Wire the Blower to the Range Hood
Remove the cover of the external blower to access the wiring. Conduit must be run from the blower down to the range hood. Once the wires are pushed down through the conduit, to the range hood, wire the blower to the range hood following local electrical code. Remember to always turn off the power before attempting any electrical work. Replace the cover of the external blower and it is ready for use.