4
Trimming the Inlet Sampling Tube (See Figure 4)
a. Measure the outside width of the duct.
b. Add 2.25 inches to obtain proper length of tube.
Example:
Outside width of duct
2 ft 6in
Add 2.25 inches + 2.25 in
Length of sampling tube
2 ft 8.25 in
The length (2 ft 8.25 in) determines (Table 1 above) the model
number of the appropriate sampling tube (STA-3).
c. Measure the sampling tube, starting from the end with the four mounting holes.
d. Trim tube to the correct length, remove all burrs, and insert a rubber stopper (Figure 3,
Item 9) in the tube.
b.
Affix the adhesive backed template (5) to the side of the ductwork.
c.
Drill the four 0.110 diameter holes with a No. 35 drill bit and cut or punch out two 7/8-inch
diameter holes as indicated on the template.
d.
Attach the appropriate model housing to the air duct using two No. 10 1½
inch screws (6) and
also using two No. 10 1-inch screws (7) with lockwashers (8).
e.
Cut a 12 inch by 12 inch access hole in the duct adjacent to the housing to permit checking
and cleaning of the sampling tubes. The access hole must be covered and sealed when not
in use.
Sampling Tube Selection
To insure accurate air sampling, inlet sampling tubes are available in four lengths. To select the
appropriate length, determine the outside width of the duct. Select the sampling tube nearest
to, but greater than, the duct width (Table 1). The outlet sampling tube for all ducts is a fixed
length of 4
inches (10.1 cm). Trim the inlet sampling tube at the job site as described below.
TABLE 1 - Sampling Tube Selection Chart
Outside Duct Width
Sampling Tube Model No. Standard Tube Length
1 ft 9 ¾ in or less
STA-2
2 ft
1 ft 9 ¾ in - 3 ft 3 ¾ in
STA-3
3 ft 6 in
3 ft 3 ¾ in - 6 ft 3 ¾ in or less
STA-6
6 ft 6 in
6 ft 3 ¾ in - 9 ft 9 ¾ in or less
STA-10
10 ft
Greater than 9 ft 9 ¾ in
Consult factory
Note:
Each model is manufactured with a different number and size of hole. Therefore, only
the specific tube must be used for the specified duct width.
Figure 4
Sampling Tube Orientation
