Conventional Flue System - Combi V3 And Combi Max; Combustion And Ventilation Air Supply For Conventional Flue Boilers - Grant Combi 70 V3 User's Installation Manual

Fig. 11 - Combustion and ventilation air supply for conventional flue boilers
Minimum size of air vents required - see Figs. 10 and 11
Combi 70 V3
Vent A 85 cm² (13 in²)
Vent B 171 cm² (26 in²)
Vent C 85 cm² (13 in²)
Vent D 171 cm² (26 in²)
Vent E 256 cm² (40 in²)
5.6

Conventional flue system - Combi V3 and Combi Max

See Figs. 12 and 14
Grant boilers have high operating efficiencies. Care
must be taken to ensure the flue system is suitable for
the low flue gas temperatures.
1 An insulated flue terminating in a down draught
free area, i.e. at least 1 m above the point of exit
through the roof or preferably above the ridge
level, will normally provide the necessary
draught of at least 8.7 N/m
measured close to the boiler connection. If a
draught of 37 N/m 2 (0.15 in wg) or more is
measured, then a draught stabiliser should be
fitted in the flue.
2 The flue terminal must be at least 600 mm from
any opening into the building, and 600 mm above
any vertical structure or wall less than a horizontal
distance of 750 mm from the terminal.
5 - GENERAL BOILER INFORMATION
Combi 90 V3 Combi Max
118 cm² (18 in²) 156 cm² (24 in²)
235 cm² (36 in²) 311 cm² (48 in²)
118 cm² (18 in²) 156 cm² (24 in²)
235 cm² (36 in²) 311 cm² (48 in²)
353 cm² (55 in²) 467 cm² (72 in²)
2
(0.035 in wg) as
Combi V3, Combi Max and Vortex Combi models
Vortex Combi 26 Vortex Combi 36
116 cm² (18 in²) 171 cm² (27 in²)
231 cm² (36 in²) 341 cm² (53 in²)
116 cm² (18 in²) 171 cm² (27 in²)
231 cm² (36 in²) 341 cm² (53 in²)
347 cm² (54 in²) 512 cm² (80 in²)
3 If an existing chimney is used, it must be lined with
a stainless steel liner for use with fuel oil. The top
and bottom of the annular space must be sealed and
the void filled with a suitable insulating material to
reduce cooling of the flue gases.
4 If a rigid flue is used either internally or externally,
it must be of the twin wall type with a stainless
steel inner skin suitably insulated and weather
proofed.
5 The internal flue diameter for all models must
be 100 mm (4 in).
6 The flue must be run upwards following as near a
vertical route as possible. Horizontal runs must be
avoided and no bends should have an angle of more than
45° from the vertical. There should be at least 600 mm
of vertical flue above the boiler before the first bend.
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