Section 7: Flue System and air Supply
Page 20
7.1 air Supply
The Grant External Vecta wood pellet boiler draws air for combustion
from the surrounding atmosphere. The combustion air inlet to the
boiler is provided by the gap along the bottom edge of the hinged
front door. This opening must not be blocked off or obstructed in any
way. Refer to Figure 7-1.
Figure 7-1:
Boiler air inlet
7 Flue System and air Supply
7.2 Flue terminal Position and Clearances
The Grant External Vecta wood pellet boilers have high operating
efficiencies and low flue gas temperatures. Only the Grant ‘Biomass’
insulated twin-wall flue system can be used with the Grant External
Vecta boiler.
the flue installation must be in accordance with the
requirements of the Building Regulations approved Document
J – Section 2: appliances burning solid fuel.
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The following points MUST be taken into consideration with regard to
the design and installation of the flue system:
•
The flue system must include the Inspection Pipe (product code:
WPBOM/IP) , which should be fitted directly to the flue outlet of
the boiler. This incorporates both a combustion test point and a
flue inspection hatch. Refer to Section 7.4.5.
•
Grant recommends that the flue is vertical for a minimum
distance of 600mm (measured from the top of the boiler) before
any elbow. However, this is not essential for the operation of the
boiler.
•
There must NOT be any change of direction greater than 45°
from the vertical, e.g. two 45° elbows must NOT be used
together to form a 90° elbow.
•
The flue system must NOT include any horizontal sections of flue.
•
Grant recommends that an adjustable flue extension be fitted in
the flue system as close to the boiler as possible, to enable the
flue system to be disconnected from the boiler flue connection,
as and when required, for future boiler maintenance.
•
The weight of the flue system must NOT be carried by the
boiler, but must be supported using the various support options
available in the Grant ‘Biomass’ flue system. Refer to Section
7.4.4.
•
The minimum distance between the outer surface of any part of
the flue system and any combustible material is 60mm. Refer to
Section 7.3 for flue system designation. A minimum clearance of
25mm around the flue is required for the fitting/removal of locking
bands.
•
The flue terminal should be located in a downdraught free area,
i.e. above the roof, where it can discharge freely and not present
a fire hazard whatever the wind conditions. The flue outlet
positions shown in Figure 7-2 (from Approved Document J) can
meet this requirement.
•
The heights and separation distances shown in Figure 7-2 may
have to be increased in particular cases, e.g. where high wind
exposure, surrounding tall buildings, or adjacent trees can cause
adverse wind effects.
•
No other appliance can be connected to the boiler flue.
•
Any condensate in the flue can run back into the boiler. A
condensate drain at the base of the flue system is not required
as the flue system is designed to allow the condensate to run
back into the boiler.
Boiler air inlet
