Johnson & Starley 42-451-15, Installation, Commissioning & Servicing Instructions

Page: 6 / 36

www.johnsonandstarley.co.uk
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26
VENTILATED Low level grille 627cm
2
(97in
2
)
FROM INSIDE
BUILDING High level grille 314cm
2
(49in
2
)
VENTILATED Low level grille 314cm
2
(49in
2
)
FROM OUTSIDE
BUILDING High level grille 157cm
2
(25in
2
)
Table 1
Minimum Effective Areas
4. DUCT SYSTEM
4.1
RETURN AIR
4.1.1 All return air shall be POSITIVELY ducted from outside the compartment to the top of the unit via a return air
duct, and mechanically secured. It is recommended that the return air duct be not routed directly from the main
living area, but from a convenient central area serving the remainder of the dwelling.
4.1.2 The return air system should be constructed of fire-resistant material. The flue shall not be run through an area
serving as a return air path. It is extremely important that the correct size of return air grilles and ducting is used.
For heaters on maximum output the return air duct size should not be less than the equivalent of 400mm x 300mm
(16" x 12"). If flexible duct is used the duct diameter should not be less than 406mm (16") dia. The return air
grille should have a free area of not less than 2118cm
2
(328in
2
).
4.1.3 An adequate and unobstructed return air path is essential from areas not served by a directly ducted return and to
which warm air is delivered. All such rooms should be fitted with relief grilles which have a free area of
0.0088m
2
/kW (1in
2
/250Btu/h) of heat supplied to the room. The only exceptions are kitchens, bathrooms and
WC.’s.
4.1.4 The return air duct should allow for ease of removal for access to the flue.
4.1.5 All duct work in the room or internal space in which the heater is installed shall be mechanically secured, and
sealed with ducting tape.
4.2 WARM DELIVERED AIR
4.2.1 All duct work, including riser ducts, should be fully insulated with 50mm (2in) fibreglass or similar. If short
extended duct runs are taken below floor level these should be similarly insulated, and in addition wrapped with a
sound vapour proof barrier, and protected from crushing.
4.2.2 The duct system should be carefully designed (as given in the guidelines in the British System Design Manual) to
suit the needs of its specific heating requirements and building layout. The type of duct system, (i.e. radial/
extended plenum/stepped) should be installed using the least number of fittings to minimise airflow resistance.
5. INSTALLATION REQUIREMENTS
5.1 FLUES (see British Standards BS 5440 Pt.1 Flues)
5.1.1 All joints shall be soundly sealed.
5.1.2 The flue should be kept as short and warm as possible.
5.1.3 Sufficient support brackets shall be installed to bear the weight of the total flue system.
5.1.4 The spigot connection of the heater draught diverter will accept internally the spigot end of a non-asbestos flue
to BS567 or twin wall metal flue to BS715 of nominal 125mm (5in) diameter.
5.1.5 A split collar should be fitted to provide for flue maintenance or inspection.
5.1.6 The flue shall be in accordance with the Building Regulations and British Gas Materials and Installations
specification 3rd edition) with regard to clearance and shielding from combustible materials.
5.1.7 All materials shall be in accordance with Building Regulations requirements.
5.1.8 The flue should run as vertically as possible. Horizontal runs should be avoided if at all possible and any
directional change should be as gentle as possible. If there is any doubt about the flue configuration, the
equivalent flue height should be determined (see 5.1.11).
3
Fig. 6b, non-MODAIRFLOW FUNCTIONAL DIAGRAM
5.1.9 If the appliance to be fitted is a replacement, the old appliance should be checked for signs of spillage prior to
commencement of the installation and appropriate action taken, (i.e. check flue system and renew as necessary).
5.1.10 It is recommended that at least 600mm of vertical flue should be provided from the top of the draught diverter
(for new installations this shall be incorporated into the flue design). However, when carrying out replacement
installations, an existing flue system may be encountered, where the vertical flue above the appliance to the first
bend is less than 600mm. In the first instance, the installer must judge whether this distance can be achieved
practicably by some means. Where this is not practicable, the existing flue system may be used, providing there is
no evidence of spillage from the old appliance (see 5.1.9 above). Every effort must be made, however, to ensure
that the existing flue complies in every other way to BS 5440 Part 1, including the visual inspection, flue flow and
spillage test described in 4.3.2 of the above standard. Flue configurations may be assessed in terms of equivalent
vertical height - details are given in 5.1.11. For air heaters, the minimum equivalent vertical height is 1 metre. The
installer must make a judgement based on his knowledge and experience and the examination and testing
described above as to whether an existing flue system can be used.
Note: Ventilation of the compartment, room or internal space in which the appliance is to be installed must be checked
for compliance with the requirements of BS 5440 Part 2 ( Ref. Section 3 of these instructions) and upgraded as
necessary.
5.1.11 Calculation method for flue sizing: ( from BS 5440: Part 1, Appendix A)
a. This appendix provides a procedure for estimating whether a given flue design is likely to ensure full
clearance of combustion products.
b. The procedure is based on calculating the ‘equivalent height’ of the flue under consideration, i.e. that
height of the straight vertical circular flue pipe of specific size which will produce the same flow rate as
the flue under consideration. The equivalent height is calculated from the formula:
(K
i
+ K
o
)
e
H
e
= H
a
x ____________________
(K
i
+ K
o
)
a
- K
e
H
a
+ Sum K
where:
H
e
is the height of the equivalent flue;
H
a
is the vertical height of the actual or proposed flue;
K
i
is the inlet resistance of the flue;
K
o
is the outlet resistance from the flue;
subscript e refers to the equivalent flue diameter;
subscript a refers to the actual or proposed flue diameter;
K
e
is the resistance per unit length of the equivalent flue;
Sum K is the resistance (other than the inlet and outlet resistance) of the actual or proposed flue.
Note: K and Sum K are obtained from Table 2. K
o
and K
i
are obtained from Table 3.
c. Table 2 gives resistance factors for common flue components for use in the formula. Table 3 contains the
appropriate inlet and outlet flue resistances, ( the flue is likely to be satisfactory if its equivalent height
exceeds 1m ).
4 25
Fig. 6a, MODAIRFLOW FUNCTIONAL DIAGRAM