BK739 Page 13
Holborn Stove User Guide
5.1.4 Secondary Air Control
The control has an internal rotary plate with slots, housed inside the body of the appliance
and is located below the left hand corner of the fire door assembly, when looking at the
front of the appliance.
Sliding the control knob to the right, as far as it will go, achieves the fully open position, see
figure 3. Sliding it to the left will shut down / reduce the air as shown in figure 4.
NOTE : If your stove installation is within a smoke control area, it will be fitted with a
restrictor plate acting as a mechanical stop for the secondary air control. This will not fully
close, thus allowing a bleed of air to the fire box to reduce smoke emissions.
5.1.5 Tertiary Air
All models have tertiary air supply that can be seen working during certain conditions during
the burning period. The outlet for the tertiary air, is at the rear of the fire box chamber, just
below the throat plate through a series of small holes within the rear liner brick
(See page 6).
Tertiary air is employed, to provide additional air to the upper areas of the fire box to
promote additional burning of the unburnt combustion gases and thus ensuring a cleaner
burn emission.
There is no user adjustment required for the tertiary air, as the required air supply is factory
set during the production process.
Fig. 4. Closed / Reduced Position Fig. 3. Fully Open Position
