17
- Installation & Servicing
INSTALLATION
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FLUE RESISTANCES
CONCENTRIC FLUE SYSTEMS
For concentric flue systems with elbows fitted, use the table to
correct the maximum flue extension capability. Alternatively
use the table to design the flue system, deducting the
individual resistance of components from the maximum
pressure drop allowed in the flue for that boiler.
The maximum pressure drop allowed in the flue is given
below.
Note: The resistances are given in Pa and also the equivalent
length of straight concentric pipe. Equivalent lengths are not
an indication of the maximum flue length as terminal
resistance must be deducted from them, plus any elbows.
W45: 100Pa = 16m 80/125 = 40m 100/150
W60: 140Pa = 11m 80/125 = 26m 100/150
W80: 150Pa = 24m 100/150
TWIN AND OPEN FLUE SYSTEMS
For twin or open flue systems with elbows fitted, use the table to
correct the maximum extension capability. The table shows the
equivalent length of either air or flue tube for the elbow required.
Concentric Flue Systems
Pressure drop per component Pa m Pa m Pa m
Terminals
Vertical Roof flue kit 80/125mm 40 6.3 62 6.2 - -
Vertical Roof flue kit 100/150mm 21 8.4 32 7.6 50 8
Horiz. Wall kit 80/125mm + 90º elbow 40 6.3 62 6.2 - -
Horiz. Wall kit 100/150 + 90º elbow 21 8.4 32 7.6 50 8
Pipes and elbows
45º bend Ø 80/125 mm 7 1.1 11 1.1 - -
45º bend Ø100/150 mm 3 1.2 5 1.2 7.51.2
90º bend Ø 80/125 mm 10 1.6 16 1.6 - -
90º bend Ø 100/150 mm 5 2 8.4 2
12.5
2
Straight pipe Ø 80/125 mm per m 6.3 1 10 1 - -
Straight pipe Ø 100/150 mm per m 2.5 1 4.2 1 6.3 1
W45 W60 W80
W45 W60 W80
Fitting Air Flue Air Flue Flue
Tube Tube Tube Tube Tube
90º elbow (m) 1.4 2.1 1.4 2.1 2.7
45º elbow (m) 0.4 0.6 0.4 0.6 1.8
Twin and Open Flue Systems
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EXAMPLES OF CALCULATING FLUE RESISTANCES/LENGTHS - EXAMPLE 1
ima5357
Horizontal flue for W45
Resistance (Pa) Resistance (m)
Flue size 80/125 80/125
Horizontal wall flue kit 80/125 40 6.3
2 x 1m extension flue 2 x (6.3) 2 x (1)
1 x 90º elbow 10 1.6
Total flue resistance 62.6 9.9
The total maximum flue resistance for an W45 is 100Pa or 16m
80/125. Therefore this installation is acceptable.
Example 1
FLUE OUTLET
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