HAMWORTHY HEATING LTD
48
WESSEX MODU
MAX
100 SERIES
500001123/C
APPENDIX D - VENTILATION
D1.1 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.
Combustion air for the boiler is drawn through the slots in the rear edge of the side panels. The air inlets
must
be
kept open and free from blockage at all times.
D1.2 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 the 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 100mm above floor level) = 25°C
2) At mid-level (1.5m above floor level) = 32°C
3) At ceiling level (or 100mm 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) - 540cm² plus 4.5cm² per kilowatt in excess of 60kW total rated input (Gross)
High level (output) - 270cm² plus 2.25cm² per kilowatt in excess of 60kW total rated input (Gross)
D1.3 Air Supply by Mechanical Ventilation
Air supplied to the boiler room by Mechanical means should be as follows:
1) Mechanical ventilation must be interlocked with the boilers to prevent operation in
the event of ventilation fan failure
2) Mechanical inlet and mechanical extract can be utilised providing the design
extraction rate does not exceed one third of the design inlet rate.
3) Mechanical extract ventilation with natural inlet ventilation
MUST NOT
be used.
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.
Figure D1 Mechanical Ventilation Flow Rates
Flow rate per 1000kW
total rated heat input (Gross)
Inlet air
(Combustion
ventilation)
Extract air
(ventilation)
m³/s.
m³/s.
Volume
1.10
0.45
Atmospheric
Boilers
