Honeywell Central Heating Cooker Natural Gas - Manual (Page 20)

20
INSTALLATION
1.1 The supply pipe from the cooker is 3/4” BSP threaded male.
An isolating gas valve must be fitted adjacent to the cooker and
the gas installation pipe work must be installed, inspected,
tested for soundness and purged in accordance with BS 6891
Nominal inlet gas pressure 20mbar
Maximum gas pressure 25 mbar
Minimum gas pressure
with both burners running
17 mbar
2.1 To evacuate the products of combustion safely and
thoroughly, the cooker must have an efficient flue system.
Reference should also be made to BS 5440 Part 1 & 2 if
further information is required on conventional chimneys.
2.2 This unit is designed to work on a conventional flue system
with a draught of 0.05” +/- 0.02” W.G (12.45 +/- 4.98 Pa or
0.124 +/- 0.498 mbar).
2.3 The chimney should rise as vertically as possible and terminate
at a point not subject to down draughts or wind eddies.
2.4 Brick and masonry chimneys must be lined with a moisture
and acid resistant liner of the same diameter as the boiler
flue outlet.
2.5 A factory made insulated chimney complying with BS 4543
Part 3 may be considered as an alternative to a structural
chimney both for new and existing buildings.
2.6 The in-built flue gas resistance of the appliance is such that it
allows the boiler to operate reliably over the wide range of
chimney draughts encountered from typical domestic
chimneys. The use of a flexible stainless steel liner is a convenient
method of lining an existing chimney and this should be back
filled with ‘vermiculite’ or similar insulating material to retain
heat. A flexible liner should also be used in chimneys fitted
with large diameter clay liners to reduce the flue bore and
improve the thermal insulation.
2.7 The use of a draught stabiliser should not be necessary nor it
desirable since it allows flue noises to be emitted into the
room.
Notes:
1. In view of the appliances high terminal efficiency it is
important that a liner is fitted, otherwise condensation
problems could result.
2.Before fitting a liner, the chimneymust be thoroughly
cleaned free from all traces of soot and scale.
1. GAS SUPPLY
3.1 There are four basic chimney/vent systems that can be used
with gas fired appliances.
These are:-
Twin Wall Gas Vent.
3.2 A metal twin wall flue system incorporating an air gap of
between 6 mm and 20 mm constructed in either all
aluminium for external use or aluminium inner and
galvanised or stainless steel outer skin recommended for
internal use only. Such products shall be certified to BS 715.
Stainless Steel Lined Prefabricated Chimneys.
3.3 These chimney systems consist of two skins of stainless steel
or a combination of stainless steel and galvanised steel
incorporating high quality insulating materials. Depending upon
the materials of combustion, these products can be used internally
and externally. Such products shall be certified to BS 4543.
Ceramic or Concrete Lined Prefabricated Chimney.
3.4 Similarly, constructed to the previous category except that
the inner liner is fabricated with either lightweight fireproof
concrete or ceramic material. These products shall be
certified by the British Board Agreement.
Concrete Block/Masonry Chimneys.
3.5 These can be divided into three different categories:-
(i) Conventional brick or masonry construction with either
clay to BS 1181 or refractory concrete flue liner manufactured
from a kiln burnt aggregate and high alumina cement.
(ii) Prefabricated chimney block systems
(iii) Gas Flue blocks.
3.6 Category (i) is the conventional chimney and in the majority
of installations where used with a gas appliance it will be
necessary to utilise a stainless steel flexible liner. The second
category (ii), prefabricated block chimney systems are designed to
accommodate quite a range of heating appliances, gas
appliances included. In some cases they may need to be
lined with a flexible liner. The appliance manufacturer and
chimney manufacturer should be consulted for guidance.
The final category (iii), gas flue blocks consists of a narrow
rectangular flue way within a building block normally used as
part of the internal or external construction of the house.The
flue way is usually very narrow, and the systems are often
linked with twin wall gas vent to which they are “adapted” in
the roof space, after which the gas vent completes the chimney
run through termination. Such systems should be carefully
inspected for soundness before being used. If they are
incorrectly constructed they can contribute to operational
difficulties and in particular condensation within the chimney
system as a whole. If any doubts should arise as to the
condition of such chimney systems they should be carefully
checked and possibly replaced with a new flue system.
2. FLUE & CHIMNEY REQUIREMENTS
3. TYPES OF CHIMNEY AND FLUE SYSTEMS