andrews L24/31, Installation Manual, Operation And Service Manual

Page: 18 / 61

INSTALLATION SECTION 3
13
Minimum Heights from Roof to Base of Flue Terminal
For all installations, please refer to the table below for calculating requirements. Detailed
recommendations for the air supply are given in BS 5440 Part 2, BS 6644 Clause 19 and
IGE/UP/10 Pt1.
The following notes are provided for general guidance only.
Ventilation shall prevent the heater environment from exceeding 32ºC (90ºF).
The purpose provided space in which the heater(s) are installed must have permanent air vents
communicating directly with the outside air, at high and low level. Where communication with the
outside air is possible only by means of high level air vents, ducting down to floor level for the lower
vents must be used.
For an exposed building, air vents must be fitted on at least two sides, preferably on all four 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 should be so designed that high velocity air streams do not occur within the space
housing the heater(s).
The grilles should have a total minimum free area for the water heater(s) in addition to any other
requirements as follows:-
Where the heater is to be installed in a room the following permanent
ventilation is required:
5cm 2 per kW in excess of 7kW Net for installations up to 54kW Net.
For installations exceeding 60kW the following permanent ventilation is required:
Low Level (inlet) 540cm 2 plus 5cm 2 per kilowatt in excess of 54kW total Net input.
High Level (outlet) 270cm 2 plus 2.5cm 2 per kilowatt in excess of 54kW total Net input.
Where the heater is to be installed in a compartment, permanent air vents are required in the
compartment at high and low level. These air vents must either communicate with a room or
internal space or be direct to outside air.
The minimum effective areas of the permanent air vents required in the
compartment are as follows;-
AIR SUPPLY
AND
VENTILATION
Not within 1.5m (5ft) of a
vertical surface of a
structure
≠
on the roof
Internal Route
On Ridge
Not on Ridge
Pitched
Flat
Pitch
exceeding
45º
Pitch not
exceeding
45º
At or
above
ridge
level
600 mm
(24 in)
above roof
intersection
600 mm
(2 ft)
above roof
intersection
With
parapet
Not
applicable
Without
parapet
250 mm
(10 in)
above roof
intersection
The base of
the terminal
should be
600 mm
(24 in)
above the
level of the
adjacent
roof edge
The base of the
terminal should
be 600 mm
(24 in) above
the level of
the top of the
structure
1m (3.3 ft)
above roof
intersection
1m (3.3 ft)
above roof
intersection
External
Route
Internal
Route
External
Route
Type of Roof
Within 1.5m (5ft) of a
vertical surface of a
structure
≠
on the roof
Air Vent Areas
Position of Air Vents Air from room or internal space Air direct from outside
High Level 10cm 2 per kW Net 5cm 2 per kW Net
Low Level 20cm 2 per kW Net 10cm 2 per kW Net
Note:- Both air vents must communicate with the same room or internal space or must both be
on the same wall to outside air.