3) Part FDHB6:
a maximum 636 C.F.M. blower with a variable speed motor, 2 noise reduction collars, a blower
speed control and a mounting bracket and a back draft damper.
NOTE: the 3 parts FDHC6, FDHC6-1, FDHB6, must be used together for this system. Use of any substitutes will
de-certify the system.
The 8” back-draft damper prevents hot air from travelling into the ‘C’ vent (single wall) ducting unless the Central
Heat Blower (FDHB6-1) is operating. When the thermostat calls for heat, the blower turns on and opens the one-
way valve. At the same time, the room air is drawn through the upper and lower louvers, which mixes and reduces
the overall temperature of the forced air that travels through the ducting.
WARNING: If the back-draft damper is not installed, the central heat ducting may become too hot for the
surrounding combustible materials. Any substitute for the FDHB6-1 kit will void all warranty coverage by
RSF Woodburning Fireplaces.
Installation
1. Remove the cover to the left or the right of the flue outlet on the Onyx AP.
2. Cut the insulation to the size of the opening and remove the cover plate underneath (it is taped in place).
3. Install the back draft damper crimped side up, making sure it is pushed all the way down. Bend out the tabs on
the lower edge of the damper at 4 places inside the fireplace with a pair of pliers, so the back draft damper can-
not be pulled out again.
4. Before proceeding with the installation of the blower, make sure that the electrical service to the blower is in the
"OFF" position. All wiring should be in accordance with local ordinances and the National Electric Code.
NOTE: The blower can basically be
installed anywhere in the home.
However, some thought should go
into the planning, to ensure that the
blower noise does not affect rooms
you would like kept quiet. If the cen-
tral heating system ductwork is
passing through an area in your
home that you do not wish to be
heated, then the ducting should be
insulated. Length of runs should be
as short as possible to conserve
ONYX AP Owner's Manual
RSF Woodburning Fireplaces
22
Figure 25: Central heat blower kit: FDHB6
Back draft
damper
2 noise reduction
collars
Central heat variable
speed blower
Blower speed
control
Mounting
bracket
Ideal blower thermostat location
Hot air
Cold air
Central heat
blower
Warm air
registers
Air circulation through fireplace and home
with central heat blower in the ’off’ cycle
Figure 26: Central heat ducting options (single floor)
Air circulation through fireplace and home
with central heat blower in the ‘on’ cycle
(blower thermostat calling for heat).
