System Sensor Pipe Installation - Manual (Page 15)

User Guide: Aspirating Smoke Detector Pipe Installation
15
Large Area Protection
Large volume areas and areas with high ceilings require
special design considerations for the pipe network design.
Stratification occurs when smoke is heated by smoldering
or burning materials and becomes less dense than the
surrounding cooler air. The smoke rises until there is no longer
a difference in temperature between the smoke and the sur-
rounding air (see NFPA 72-2013 A.5.7.1.10). Stratification,
therefore, may occur in areas where air temperature may be
elevated at the ceiling level, especially where there is a lack of
ventilation. When stratification is likely to occur, conventional
pipe network sampling may not be effective.
One method to overcome smoke stratification is to create
vertical sampling pipes in addition to the horizontal pipe
network on the ceiling. The vertical sampling pipe should
have sampling ports at various heights to sample within any
stratification layers present in the area, as shown in figure 20.
Frequently Asked Question – Does FAAST eliminate
stratification issues?
No, stratification occurs when smoke cools to a temperature
equal to the surrounding air. To overcome the effects of
stratification, provide sample ports on the pipe as it runs
vertically up the wall. It is recommended to provide sample
ports for stratification when the ceiling height exceeds 30 ft.
or when ceiling elevations transition, creating a jet stream.
Cold Area Protection
The FAAST detector is approved for operating temperatures
ranging from 32°F (0°C) to 100°F (38°C) and sampled air
temperature form -4°F (-28°C) to 140°F (60°C). However,
special considerations should be taken when operating at the
extreme end of these ranges.
The temperature in a cold area is typically at or just above
freezing. In designing a pipe system, the pipes should be kept
out of the immediate airflow from a chiller unit, if used, as its air
is often significantly colder than the room itself. Sample ports
should also be located away from frequently used doors
where possible.
Often, the temperature of the cold room is outside the operating
temperature of FAAST and the device must be mounted outside
of the room with the pipe network being run in to the protected
space. Depending on the temperature of the air being removed
from the room, heating elements may be required, and a
condensation trap installed to catch any condensation or
moisture that may enter the device.
For more information on deploying FAAST in cold storage
applications, see the cold storage white paper at
systemsensor.com/faast.
Air sampling test port
located at the end of
each branch pipe -Typ.
Air sampling ports on
vertical pipe to capture
smoke stratification -Typ.
Air sampling ports on
air sampling network -Typ.
FAAST Detector
Stratification Layer
of Smoke
Figure 20: Large area protection.
Figure 21: Cold area protection.
Exhaust pipe back to
area being monitored
From air sampling network,
run additional horizontal piping
after exiting cold area. Sample
air temperature must be above
-4°F (-20°C) before entering
the detector.
Install drip loop on tee
fitting prior to entering
detector.
Always maintain water
halfway of drip loop.
To nearest drain or
condensate collector.
Piping shall be pitched
accordingly based on
the natural flexibility the
pipe will allow.
Maintain a
minimum of 16 in.
of vertical pipe.
FAAST Detector shall be
mounted 5 ft.- 0 in. AFF.