VESDA by Xtralis VESDA Pipe Network Installation Guide
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5.2 Return Air Grilles and Air Ducts
5.2.1 Return Air Grilles
Return air grille sampling is used to monitor the grille air drawn to an exhaust ventilation system or to an air
handling unit (AHU). The pipe network design will specify where return air sampling is required.
Figure 5-8: Return air grille sampling
The guidelines that need to be considered in a return air grille sampling installation:
1. Follow the guidelines specified in Section 5.1 on page 17 then use the guidelines below.
2. Fix appropriate pipe mounting clips or pipe clamps with standoff posts over the return air grille.
3. Sampling pipes on return air grilles having high velocity air flows which may require mounting on
standoff posts to keep the sampling pipe 25 mm to 200 mm (1 to 8 inches) away from the grille. Refer
to the pipe network design for requirements.
Figure 5-9: Pipe position on a return air grille
Return air grilles may be removed and replaced for maintenance. To ensure the orientation of
sampling holes are maintained at the correct angle once the air grille is replaced:
l Cut sampling pipe of specified diameter to the length of the air grille.
l Fix appropriate pipe mounting clips or pipe clamps with standoff posts over the return air grille.
4. Connect the sampling pipe using socket unions and do not glue them in place. The socket unions must
be between the end of the air grille and the mounting clips or pipe clamps. Refer to Figure 5-9 for
details.
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