Types of Systems And Waters Supplies Explained
Direct Mains Fed Systems
These are systems where the mains pressure and flow delivery is adequate to feed the sprinkler operating requirements directly. The use of a priority demand valve may be used on such systems; this is to ensure that in the event of operating the sprinkler system, the branch of the pipe work feeding the domestic demand will be automatically shut down
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Water supply Connections.
Experience has shown that the required pressure/flows may not be met even when a town’s main supply is considered adequate and the commonly used pipe sizes selected for the connection of 32mm (domestic) and 63mm (residential) in MDPE pipe are used.
It is essential that the friction and static pressure losses in a connection pipe to a system should be hydraulically assessed at the maximum anticipated flow rate,including any domestic demand if appropriate, and taken into account within the design requirements of the system. This is of particular importance when the distance from the town’s main is unusually long.
Category 1 sprinkler system
Individual dwelling for occupation as a single family unit used or constructed or adapted to be used wholly or principally for human habitation, such as individual dwelling houses, individual flats, maisonettes
Our designers will carry technical drawings and flow calculations; the system will require at least 1/2 bar of pressure at each sprinkler head.
The building height also adds to the pressure required, each storey being circa 3 metres adds 0.3 bars.Pipe work friction then adds losses, which must be compensated for. So for a three storey building you could expect 0.5bars (sprinkler) + 0.3 x 3 =0.9 bars (height) circa 1.0 bar (frictional loss created by the pipe system itself-varies with pipe size and system complexity) = 2.4 bars, similar to the pressure in your car tyres.
This pressure is a constant running pressure at the sprinkler control valve @ the desired flow rate i.e 84 L per minute for a period of 10 minutes
Design Criteria
1 x sprinkler head operating @60 Liters per minute = 60 Liters per minute (Max room size 4.5m x 4m)
2 x sprinkler heads operating @49 Liters per minute = 98 Liters per minute (max room size 40m2)
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Installation standard: |
BS9251 |
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Hazard classification: |
CATEGORY 1 |
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Density of Discharge: |
60L / 84L Per Min Plus frictional losses |
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Area of Operation: |
40m2 |
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Protection: |
Life Safety |
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Design basis: |
Pre-calculated |
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Occupancy: |
Domestic (CATEGORY 1) |
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Maximum area coverage per sprinkler head: |
20m2 |
Category 2, 3 & 4 sprinkler systems
Occupancy for multiple occupation not exceeding 20 m in height, with a maximum individual room size of 180 m2, such as apartments, residential homes, houses of multiple occupancy (HMOs), blocks of flats, boarding houses, aged persons homes, nursing homes, residential rehabilitation accommodation and dormitories
Our designers will carry technical drawings and flow calculations; the system will require at least 1/2 bar of pressure at each sprinkler head.
The building height also adds to the pressure required, each storey being circa 3 metres adds 0.3 bars.
Pipe work friction then adds losses, which must be compensated for. So for a three storey building you could expect 0.5bars (sprinkler) + 0.3 x 3 =0.9 bars (height) circa 1.0 bar (frictional loss created by the pipe system itself-varies with pipe size and system complexity) = 2.4 bars, similar to the pressure in your car tyres.
This pressure is a constant running pressure at the sprinkler control valve @ the desired flow rate i.e 240 L per minute for a period of 30/60 minutes.
NOTE 1 where multiple occupation buildings exceed 18 m in height, special circumstances need to be considered and the authority having jurisdiction should be consulted. This matter is receiving the attention of the relevant BSI committee with a view to issuing an amendment.
NOTE 2 this occupancy classification is not suitable for secure accommodation, asylum centers and large, open, communal dormitories or equivalent hazards.
Design Criteria
2 – 4 sprinkler head operating @49 Liters per minute
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Installation standard: |
BS9251 |
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Hazard classification: |
CATEGORY 2, 3 & 4 |
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Density of Discharge: |
100 L – 240L Per Min Plus frictional losses |
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Area of Operation: |
40 – 80m2 |
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Protection: |
Life Safety |
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Design basis: |
Pre-calculated |
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Occupancy: |
Residential homes / HMO / Schools / Block of flats |
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Maximum area coverage per sprinkler head: |
20m2 |
Stored water and boosted Systems
This type of system relies upon a stored volume of water to meet the demands of the sprinkler system.
Category 1 systems = 600 1000 Liters
Category 2 systems = 3000/4500 Liters
Category 3 systems = 6000/12000 Liters
Category 4 systems = TBC
All storage tanks must have appropriate back flow prevention arrangements at the inlet & an A/B air gap. The dedicated feed pipe from the tank will usually feed a booster pump of an appropriate rating to meet the demand of the sprinkler system.
