Automatic sprinklers Domestic systems

Question 1

Describe a domestic sprinkler system

Answer 1

The system is wet providing sprinkler protection in
all parts of a dwelling except small bathrooms
(less than 5m2) and cupboards with a floor area
below 2m2. Roof spaces or basements can also be
omitted if they are not used for storage purposes

Question 2

The system comprises of all or any of the following,

depending on the water supply used:

Answer 2

At least one sprinkler head in each room and
stairway/corridor
A check valve to prevent the system drain
back into the water supply at times of low
pressure
A flow switch to activate an audible alarm
A stop valve to close the system down.
A priority demand valve to isolate the
domestic service in the event of sprinkler
operation.

Question 3

Domestic sprinkler systems can get the water supply from ?

Answer 3

Town main
n Pressure tank or vessel
n Automatic pump drawing from a stored
water supply
n Automatic booster pump drawing water
from a town main or elevated storage tank
n A gravity fed water system.

Question 4

Where stored water is used, the capacity required
should be 110% of the minimum amount necessary
to achieve the following:

Answer 4

(a) in domestic occupancies, the quantity
required to maintain pressure and flow for 10
minutes to whichever is the greater of:
(i) A single operating sprinkler in the
hydraulically most favourable position
(ii) A pair of operating sprinklers in a single
room.
(b) in residential occupancies, the amount necessary
should be calculated on the actual
pressures and flows for 30 minutes to which
ever is the greatest of any combination of up
to the maximum design number of sprinklers
operating in a single room (not more than
four) in the hydraulically most favourable
position.
Fire

Question 5

The system uses either conventional spray or side
wall sprinkler heads or residential and domestic
pattern heads, which give an outward and downward
discharge of water. In both cases, the water
flow rate should not be less than:

Answer 5

(i) For domestic occupancies:
(a) 60 1/min through any single sprinkler;
(b) 42 1/min through each of two sprinklers
operating simultaneously in a single
room.
(ii) For residential occupancies:
(a) 60 1/min through any single sprinkler
(b) 42 1/min for each sprinkler operating
simultaneously up to a maximum of
four sprinklers in a single room.

Question 6

The maximum area covered by each sprinkler

should either be

Answer 6

in accordance with the manufacturer’s
specification or 15m:, whichever is the
lesser
Sprinklers should not be more than 4m apart
or more than 2m from any wall or partition.
The
distance between sprinklers in a room should not
be less than 2m.

Question 7

How should domestic sprinklers be positione

Answer 7

(i) Pendant upright conventional or residential
and domestic sprinklers have their heat sensitive
elements not more than 100mm below
the ceiling (100-150mm in the case of sidewall
sprinklers).
(ii) The whole of the floor and the walls up to
0.7m below the ceiling should be wetted by
an operating sprinkler.
(iii) No sprinkler is within 50mm of a wall or partition.
(iv) Sprinklers may be either strutted or glass
bulb and should be colour coded. The temperature
rating for sprinklers should be:
(a) the closest but at least 30°C greater than
the highest anticipated ambient temperature
of the location;
(b) within the range of 79°C-100°C when
installed under glass roofs.
(v) The potential for a shielded fire should be
taken into account.

Question 8

Describe the alarm of a domestic sprinkler system

Answer 8

The discharge through any one-sprinkler head
should cause the alarm valve to trigger an alarm in
the protected property. The alarm should be audible
throughout the property.
An additional alarm should be positioned outside
of the protected property and give both an audible
and visual signal. The alarm should be clearly
labelled ‘Fire Alarm’.