Appendix D Ventilation - Hamworthy F40V Installation, Commissioning And Operating Instructions

APPENDIX D - VENTILATION
D1.1 Air Supply
Detailed recommendations for air supply are given in BS 6644 and BS5440 Pt 2. 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.
Note: For Open flue applications, combustion air for the boiler is drawn through the rear of the boiler casing. The
air inlet must be kept open and free from blockage at all times.
D1.2 Air Supply by Natural Ventilation - Open Flue applications
The boiler room must have, or be provided with, permanent air vents directly to the outside air, at high 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 vicinity of the boiler.
Boiler house ventilation
Low level (inlet) - 4cm² per kW of total rated input (Net)
High level (output) - 2cm² per kW of total rated input (Net)
Compartment ventilation
Where the boiler is to be installed in a cupboard or compartment, permanent high and low level ventilation is
required which must communicate direct to outside, for cooling purposes.
Low level (inlet) - 10cm² per kW of total rated input (Net)
High level (output) - 5cm² per kW of total rated input (Net)
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.
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.
The calculated extract flow rate is the actual inlet flow rate minus the appropriate figure in the table above.
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. 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.
HAMWORTHY HEATING LTD
Volume
Figure D1 Mechanical Ventilation Flow Rates
50
FLEET V series
Flow rate per kW
total rated heat input (Net)
Inlet air
Difference between
(Combustion
Inlet & Extract air *
ventilation)
m³/h.
2.6
m³/h.
1.35
500001213/G