HAMWORTHY HEATING LTD
MILBORNE 500 SERIES
500001130/A
17
Air vents must be positioned a minimum of 300 mm
form air vent terminals, whether for supply or
extract, either above, below or horizontally.
Air vents communing between the appliance
compartment and an internal space or room must be
located no higher than 450mm above floor level.
For further information regarding ventilation for
single Milborne 501 boiler installations please see
BS5440 Part 2.
Modular Milborne installations
Detailed recommendations for air supply are given
in BS6644. The following notes are intended for
guidance only. 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
casing for open flue applications or through the
dedicated air supply duct used in room sealed
applications.
Air Supply by Natural Ventilation
The boiler plant 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:
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.
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 (outlet) - 270cm2 plus 2.25cm2
per kilowatt in excess of 60kW total rated
input (Gross).
Air Supply by Mechanical Ventilation
Air supplied to the boiler by Mechanical
means should be as follows;
Atmospheric
Boilers
Inlet air
(Combustion
ventilation)
Extract Air
(Ventilation)
M3/Sec M3/Sec
Volume 1.10
0.45
Flow rate per 1000 kW total rated
input (Gross)
Mechanical inlet and mechanical extract can be
utilised providing the design extraction rate does not
exceed one third of the design inlet rate.
Mechanical extract ventilation only 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.
