Hamworthy Purewell VariHeat he Installation, Commisioning And Maintenance Instructions page 51

APPENDIX D - VENTILATION
D1.1 Air Supply
Detailed recommendations for air supply are given in BS 6644 and BS 5440 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.
Combustion air for the boiler is drawn through the rear of the boiler casing. The area must be kept open and free
from blockage at all times.
D1.2.1 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 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.
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)
If the boilers are to operate during the summer months for 75% of the time a further 1 cm
2
a further 2 cm should be added per kW to both high & low openings.
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 maintains the difference between inlet and extract flow rates shown in
figure D1.
3) Mechanical extract ventilation with natural inlet ventilation MUST NOT be used.
4) Additional rates may be required for summer operation.
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.
HAMWORTHY HEATING LTD
46
PUREWELL VariHeat he
2
or for 100% of the time
500001155/F