INSTALLING
A POWERED ROOF ATTIC FAN:
A roof-mounted attic fan should be positioned as near as possible
to the center of the attic. Place it on the back side of the roof
so it is not seen from the front of the house. Here are the basic
steps to follow:
Placement-
Assemble the fan and carry it to the roof near one of the gables.
Using a straightedge or a piece of wood as a guide, set the fan
assembly so the top of the fan is level with the roof ridge. Measure
this distance from the ridge to the center of the fan.
In
the attic, locate the central part and measure down from the roof
peak (on the back side of the roof) to a point that corresponds
to the location of the fan. Locate this point halfway between the
rafters. Drive a nail up through the roof at this point so it can
be located from the top of the roof.
Cutting
the opening-
On the outside of the roof, locate the marker nail. Using it as
a center, draw a circle about 4 inches wider than the size of the
hole specified in the instructions usually provided by the fan manufacturer.
Wit a utility knife, remove the shingles and underlayment down to
the wood sheathing underneath, using the guideline of the circle
you drew on the roof.
Using
the nail as the center point, draw another circle. It should be
the size specified in the instructions. Cut a hole in the sheathing
(or battens) along this circle, using a saber saw or a keyhole saw.
The specified hole size may be larger in diameter than the distance
between the rafters. If so, do not cut the rafters. Instead, saw
along the inner edges of the rafters.
Installing
the housing-
About 6 inches above and below where the fan flashing will cover
the roof, hammer 4 nails into the roof to mark the location of the
rafters. Remove any shingle nails within the area above the hole
that may prevent insertion of the fan flashing underneath the shingles.
Apply
a liberal amount of asphalt roofing cement to the exposed sheathing
and underside the fan flashing. Slip the fan housing sheathing under
the shingles above the hole. Line up the opening of the fan housing
with the hole cut in the roof. Using the rafter marks as a guide,
drive galvanized roofing nails through the flashing at the top and
along the sides at 4 to 6-inch intervals. Then use roofing cement
and place a tad under any shingles that have been lifted. Seal any
cut edges and exposed nail heads. Do not seal the bottom edge of
the flashing.
Adding
soffit vents-
Calculate the vent area you will need for the attic and install
soffit vents, according to the information given in this article.
For every 150 square foot of attic space, install 1 square foot
of net fee vent area.
Connecting
the wiring-
Fasten the fan thermostat to a rafter so that the dial is easily
accessible and the temperature-sensing element is exposed to the
air.
Make
sure the element is not in the fan's direct air stream when the
fan is operating. A 120-volt circuit using a junction box in the
attic powers the fan. If there is no junction box available, run
a 12-gauge copper cable through a wall to a junction box in the
room on the floor below.
Turn
off the power at the service entrance before making any electrical
connections. If you are not familiar with wiring techniques, call
in a pro to do the job. All electrical connections must be in accordance
with local codes, ordinances, and National Electrical Code.
Drill
a 3/4-inch hole in the top plate above an inside wall and directly
above the receptacle junction you want to tap. Recheck that the
power is off and remove the junction box. Fish the cable through
the hole in the plate to this receptacle. Clamp the cable to the
receptacle, run it from the plate in the attic along the side of
a ceiling joist, up the side of a rafter, and connect it to the
thermostat. Hold the cable in place with staples.
Connecting
the fan thermostat-
After you have extended cable up to the fan, connect the two leads
in the thermostat wiring box to the two power leads, matching wire
color and fastening with wire connectors. Wrap the connectors tightly
with plastic electrician's tape. Connect the ground wire from the
power cable to the ground screw, usually green in color, in the
box, You may want to turn the power on or off manually in order
to bypass the thermostat, to turn the fan on and off manually or
to wire in a humidistat. With the last installation, you get automatic
operation triggered by temperature and humidity, or manual operation
bypassing the thermostat and humidistat, and the convenience of
easily turning the fan on or off.
CAUTION:
When you work on the roof outside, be sure you wear rubber-soled
shoes. If the roof is steep, please let a professional install the
attic fan for you. He has the necessary equipment that is too costly
for you to purchase for a 1-shot fan installation
