Sirius FS
36
GB/IE
The following table can be used as a guide when calculating the flue outlet resistance,
please refer to flue manufacturers instructions where possible :
Worked Example:
An FS525 boiler is to be installed on a B
23
type flue. The installation would require:
1 x T-piece, 2 x 1m Straight lengths, 3 x 45
O
Elbows, 1 x 90
O
Elbow, 8m of flexible flue liner
and a flue terminal. The calculation would be as follows:
The total resistance is over 250 Pa, so this 180mm flue system would not be acceptable.
Therefore a larger diameter flue system is required.
This system is still restrictive
(see flue resistance table page 33)
but the total resistance is
under 250 Pa, so this 200mm flue system would be acceptable.
If the same calculation was applied to a 250mm diameter flue system, the total resistance
would be 70.1 Pa, which equates to an output increase of 10kW, from a 180mm flue system.
Model: FS525
Item
Quantity Pa each Pa Total
T-piece boiler outlet
1
45.3
45.3
45º Elbow
3
10.1
30.3
90º Elbow
1
17.6
17.6
1m Straight lengths
2
5.0
10.0
Flexible flue liner (m)
8
13.9
110.8
Flue Terminal (H/D 1.0, Zeta 1.0)
1
50.4
50.4
Total Flue Resistance (Pa)
264.4
180mm Flue outlet size
Flue diameter
180mm
Flue diameter
200mm
Straight (1m)
3.0
1.8
T-piece boiler outlet
25.5
16.7
90º elbow
9.9
6.5
45º elbow
5.7
3.7
Flue terminal (Zeta = 0.05 conical)
1.4
0.9
Flue terminal (H/D = 1.0, Zeta = 1.0)
28.3
18.6
Flue terminal (H/D = 0.5, Zeta = 1.5)
42.4
27.8
Flexible Flue Liner (per meter)
7.4
4.7
Flue diameter
180mm
Flue diameter
200mm
Flue diameter
250mm
Straight (1m)
5.0
3.0
1.0
T-piece boiler outlet
45.3
29.7
12.2
90º elbow
17.6
11.6
4.7
45º elbow
10.1
6.6
2.7
Flue terminal (Zeta = 0.05 conical)
2.5
1.7
0.7
Flue terminal (H/D = 1.0, Zeta = 1.0)
50.4
33.0
13.5
Flue terminal (H/D = 0.5, Zeta = 1.5)
75.6
49.6
20.3
Flexible Flue Liner (per meter)
13.7
8.9
3.5
Resistance Pa
M
od
el
:
FS
40
0
Item
M
od
el
:
FS
52
5
Resistance Pa
Item
Model: FS525
Item
Quantity Pa each Pa Total
T-piece boiler outlet
1
29.7
29.7
45º Elbow
3
6.6
19.8
90º Elbow
1
11.6
11.6
1m Straight
2
3.0
6.0
Flexible flue liner (m)
8
9.1
72.8
Flue Terminal (H/D 1.0, Zeta 1.0)
1
33.0
33.0
Total Flue Resistance (Pa)
172.9
200mm Flue outlet size
