HAMWORTHY HEATING LTD
45
Wessex ModuMax
mk3
Boilers
500001308/C
Figure D1 Mechanical Ventilation Flow Rates
Note * : Where the associated air extraction is also by means of a fan, this shall be selected such as not to
cause a negative pressure to develop in the boiler house and to maintain the difference between inlet and
extract flow rates shown above.
The calculated extract flow rate is the actual inlet flow rate minus the appropriate figure in the table above.
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.
D 1.4. Boiler House Temperatures
The air supplied for boiler house ventilation shall be such that the maximum temperatures within the boiler house
shall be as follows:
At floor level (or 100mm above floor level) = 25°C.
At mid
-
level (1.5m above floor level) = 32°C.
At ceiling level (or 100mm below ceiling level) = 40°C.
D 1.5. General Requirements
The air supply should be free from contamination such as building dust and insulation fibres from lagging. To
avoid unnecessary cleaning and servicing of the boiler modules, the boilers should not be fired whilst building
work is being undertaken.
High and low level ventilation grilles shall be positioned as high and as low as practicably possible. Low level
grilles should be located within 1 metre of the floor for Natural Gas and within 250mm of the floor for LPG. High
level grilles should be positioned within 15% of the boiler room height from the ceiling. High and low level grilles
shall communicate with the same room or space where compartment ventilation is used. Where grilles
communicate directly with outside air, they shall be positioned on the same wall.
Flow rate per kW
total rated heat input (net)
Boilers
Without
Draught
Diverters
Inlet air
(Combustion
ventilation)
Difference
between inlet and
extract air (Inlet
minus extract
ventilation)
m³/h
m³/h
2.6
1.35 +/
-
0.18
