Measurement Of Ducts; Air And Flue Duct Length; Vertical Flue System - Worcester 28Si Installation And Servicing Instructions

4. Measurement of Ducts

4.1 AIR AND FLUE DUCT LENGTHS - NO OFFSET
For a flat roof measure the distance from the appliance top
panel to the outside edge of the hole diameter marked on the
inside surface of the roof. This is dimension 'E
For a pitched roof, measure the distance from the appliance
top panel to the highest point of the hole diameter. This is
2
dimension 'E '. Refer to Fig. 9.
Determine dimension 'F' which must not be less than 300mm.
Duct Length = H — 92mm
Derivation: Dimension G= 1100 — Fmm
Dimension H= E — G
Refer to 2.2 for maximum duct length.
Fig. 9. Vertical flue system (No offset)
E
1
Measure from
appliance
top panel
1 ' Refer to Fig. 9.
F
300mm minimum
G=1100-F
Height of
terminal assembly
1100mm
H
Measure from appliance
top panel
Appliance
Air inlet flange
Weather sealing collar
(Secure with screw provided and
seal with silicone sealant)
Roof flashing (not supplied)
Flue terminal assembly
(106mm) diameter
Fire stop spacer
Air and flue duct
extension kits (750mm)
Vertical flue adaptor
front
6
Flat roof
E
2
Measure from
appliance
top panel