VESDA VFT Product Guide
VESDA by Xtralis
46 www.xtralis.com
B.1.2 Microbore Air Sampling Methods
Generally, microbore systems are used to sample air some distance away from the detector, often in
enclosed areas like cabinets, or in applications that require concealed sampling points or addressability. The
guidelines for microbore sampling are:
l Use 50 m (164 ft) length microbore tubes for all installations. Excess tubing must be coiled close to the
sampling point end.
l The positioning of the sampling hole for in-cabinet sampling is dependant on air flow conditions. In
most instances the sampling hole is positioned close to the top of the interior of the cabinet.
B.1.3 Plan and Map a Microbore Network
Regulatory Requirements
Local codes and standards determine the maximum spacing between microbore and sampling holes. These
values may change depending on the environment being protected. Local codes and standards for aspirating
smoke detectors will have precedence over any parameters suggested by Xtralis. Some of the key
requirements are listed below.
l Maximum permissible transport time
l Maximum area for a fire zone
l Area of coverage per sample hole (point detector)
l Maximum spacing between sampling points
l Maximum area for aspirating systems
l Air changes per hour
Fire Zones and VESDA Addresses
Fire zones are created to meet regulatory requirements, whereas, VESDA Addresses (also known as VESDA
Zones) are areas that can be monitored by one VESDA detector. VESDA addresses are created for the
system to operate within defined parameters for optimum smoke detection.
Site conditions have an impact in defining VESDA Addresses. Some key guidelines need to be observed
when creating an Address.
l One detector can monitor only one VESDA Address
l The VESDA Addresses must comply with the local codes and standards
l The environmental conditions within each VESDA address should be the same. For example, the level
of pollution and ambient air pressure within each VESDA Address should not change.
l The appropriate VESDA detector parameters are met.
Planning the Network
In planning a pipe network, you must:
l Have an understanding of the area to be protected
l Understand the environmental conditions of the protected area
l Identify any forced air ventilation and air flows (fans, air conditioners etc.)
l Take into account any customer specifications
l Determine if the design needs to address:
l Ceiling and under floor voids
l Consideration for high ceilings and stratification effect
l Any requirement for focused detection
The microbore network is mapped onto the construction drawings. The objective of mapping the network is to
determine the placement of sampling holes and to optimize the location of the VFT detector.
B.1.4 Design Performance
Microbore system performance is mainly dependant upon transport time and hole sensitivity.
Alarm thresholds can be configured for the detector via Xtralis VSC software or through the display panel, but
transport time is influenced by the number of microbore tubes used by the detector.
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