Terminal Assembly; Nominal Flue Height; Flue With Offset Using Two Flue Bends; Flue Restriction Rings - Worcester 28Si Installation And Servicing Instructions

2.1. TERMINAL ASSEMBLY

The overall height of the terminal assembly is 1100mm.
Note. A minimum of 300mm shall extend above the surface
of the roof. Refer to Fig. 2.
2.2. NOMINAL FLUE HEIGHT (NO OFFSET).
The maximum equivalent flue heights, excluding the flue
terminal assembly are:
Table 2.
24i, 28i, 35CDi II
WR325, WH1
25Si, 28Si, C1
15SBi, 24SBi, 24CDi, 80ic
9/14, 14/19CBi
19/24CBi
28CDi
Highflow 400 Electronic

2.3. FLUE WITH OFFSET USING TWO FLUE BENDS.

A flue offset can be provided using, 2 at 90° (except for WH1
and WR325 RSF water heaters where 90° bends cannot
be used) or 2 at 45° bends.
When using an offset the overall length of the system is
reduced.
A 90° bend is equivalent to 750mm of straight flue.
A 45° bend is equivalent to 375mm of straight flue.
Note: For the 24i, 28i and 35CDi II 2 x 90° bends allows a
maximum straight length to not exceed 800mm or 1550mm
for 2 x 45° bends.
When measuring between the centre-lines of flue ducts an
allowance must be made for the relevant elbow. Refer to Fig. 3.
Fig. 3. Flue Offset
D - 162
1.414D - 60
30
Minimum 76mm
2.3m
2.6m
3.0m
4.0m
3.0m
2.25
3.5m
4.5m
D
30
D
Fig. 4. Example of vertical flue assembly showing
equivalent straight flue lengths
Equivalent
Length 4m
IMPORTANT: The flue terminal assembly must always be
vertical at the roof outlet.
2.4. FLUE RESTRICTOR RINGS
The flue restrictor rings are in the appliance installation pack.
Refer to the relevant Installation/service instructions for the
method of fitting a restrictor ring.
Table. 3.
MODEL
15SBi
24SBi
C1 & Si Series
9/14CBi
14/19CBi
19/24CBi
WR325 RSF
WH1
35CDi II
24CDi
28CDi
3
2m
Equivalent
length 2x750mm
90° = 1.5m
bends
0.5m
EQUIVALENT EQUIVALENT
FLUE LENGTHS FLUE LENGTHS
UP TO 1M 1M TO 4M
79mm NONE
75mm NONE
EQUIVALENT EQUIVALENT
FLUE LENGTHS FLUE LENGTHS
UP TO 725MM 725MM TO 3M
79mm NONE
TERMINAL
EQUIVALENT
ASSEMBLY FLUE LENGTHS
UPTO MAX LENGTH
ONLY
72mm
NONE
79mm NONE
UP TO 2600mm
NONE
UP TO 1m
1m-2.3m
85
NONE
NONE
NONE