HAMWORTHY HEATING LTD
6
SHAFTESBURY HE
500001049/N
6.5
Disconnection
Provisions should be made for disconnection of the flue
pipe for servicing. It is advisable that bends are fitted
with removable covers for inspection and cleaning as
appropriate.
NOTE!
The flue system must be self
supporting and not present a risk to people in or around
the building.
See
Section 13:
SERVICING
for further information
.
6.6 Flue Discharge
The flue system must ensure safe and efficient
operation of the boiler to which it is attached, protect the
combustion process from wind effects and disperse the
products of combustion to the external air.
The flue must terminate in a freely exposed position and
be situated so as to prevent the products of combustion
entering any opening in a building. Consideration should
be given to the fitting of a flue discharge terminal or grille
to stop the ingress of birds etc.
The flue system should be designed such that the
flue terminates at least 1 metre above the roof
surface, or above the level of any nearby structure
which is within 2.5 metres of the flue.
6.7 Surface Temperatures
Combustible materials in the vicinity of the boiler and
flue shall not exceed 65 °C during boiler operation. The
flue shall not be closer than 50mm to any combustible
material, except where it passes through such material
with a non-combustible sleeve when the air gap may
not be less than 25mm.
6.8
Flue System Location
The flue system must not be placed or fitted where
there is undue risk of accidental damage to the flue pipe
or undue danger to persons in the vicinity.
NOTE!
The
flue
MUST
be self supporting. Check that the flue and
chimney are clear from any obstruction.
6.9 Condensate Discharge
When designing the flue system, care must be taken
to ensure that any condensate which may form
within the system, can be safely drained to a
suitable waste point and, that the flue material used
is resistant to the corrosive effects of that
condensate.
7.0 AIR SUPPLY
Detailed recommendations for air supply are given in
BS 6644
. The following notes are intended to give
general guidance. In all cases there must be provision
for an adequate supply of air for both combustion and
general ventilation, in addition to that required for any
other appliance.
7.1
Air Supply By Natural Ventilation
The boiler room must have, or be provided with,
permanent air vents directly to the outside air, at high
level and at low level. For an exposed boiler house, air
vents should be fitted preferably on all four sides, but at
least on two sides. Air vents should have negligible
resistance and must not be sited in any position where
they are likely to be easily blocked or flooded or in any
position adjacent to an extraction system which is
carrying flammable vapour. Grilles or louvres must be
so designed that high velocity air streams do not occur
within the space housing the boiler.
The air supplied for boiler house ventilation shall be
such that the maximum temperatures within the boiler
house shall be as follows:
1) At floor level (or 100 mm above floor level)
= 25 °C.
2) At mid-level (1.5 m above floor level)
= 32 °C.
3) At ceiling level (or 100 mm below ceiling level)
= 40 °C.
Where both low and high level openings are used, the
grilles shall have a total minimum free area of :-
Low Level (inlet) 540cm
2
plus 4.5cm
2
per kW in excess
of 60 kW total rated input (gross).
High Level (outlet) 270cm
2
plus 2.25cm
2
per kW in
excess of 60kW total rated input (gross).
7.2 Air Supply By Mechanical Ventilation
Air supplied to the boiler room by mechanical means
should be as follows :-
1)
Mechanical inlet and mechanical extract can be
utilized providing design extraction rates comply with
Figure 7.1.
2)
Mechanical extract ventilation with natural inlet
ventilation
MUST NOT
be used.
NOTE:
For mechanical ventilation systems an
automatic control should be provided to cut off the gas
supply to the boiler, in the event of failure of air flow in
either inlet or extract fans.
Forced Draught
Boilers
Inlet air
(Combustion
Ventilation)
Extract air
(Ventilation)
m
3
/s
m
3
/s
Volume
0.9
0.6
Flow Rate per 1000 kW
total rated heat input (gross)
Figure 7.1 Mechanical Ventilation Flow Rates
