System Sensor Pipe Installation - Manual (Page 14)

User Guide: Aspirating Smoke Detector Pipe Installation
14
Object Protection
Cabinet Sampling
Equipment cabinet sampling may be accomplished in two
ways: pipe networks and sampling ports can be installed di-
rectly inside the equipment cabinet, or directly over the
equipment cabinets being monitored if the cabinets have
ventilation grills.
In-Cabinet Sampling
For in-cabinet sampling, capillary tubes can be used to enter
the equipment cabinet. The capillary tube is connected to the
pipe network via a tee connection with an adapter. The
maximum length of these capillary tubes is 26 ft. (8 m).
PipeIQ can help create an appropriate design.
An alternate to capillary tubes is a rigid drop tube. In this
application, the pipe network is run over a row of cabinets and
drop tubes are run down to each cabinet. This tube or pipe
should be less than or equal to the network pipe diameter and
is connected to the top of the cabinet and to the pipe network
via a tee connection. The pipe could also come up from under
a floor void in to a cabinet.
Cabinets with extractor fans may cause sampling problems
when the sample port is on the top of the cabinet. The
extractor fan creates a low pressure area within the cabinet that
can stop air from being drawn into the detector system at the
sampling port. This type of installation must be checked care-
fully for proper sampling operation. This can be accomplished
using canned smoke at the sample port location.
Above-Cabinet Sampling
In above-cabinet sampling, the pipe network should be installed
directly over the cabinets that will be protected. Sampling ports
are placed over the cabinet ventilation grills. Ports should be
oriented so that they face into the air stream coming from the
cabinet. If there is more than one exhaust from a cabinet, a
sampling port should be installed over each opening.
NOTE: With either application, it is best to locate the sampling
port in the path of the air flow near the top of the cabinet.
Figure 18: In-cabinet sampling.
Figure 19: Above-cabinet sampling.
Top View of Cabinet