System Sensor DH500 specifications B. Installation for Ducts More Than 8 Feet Wide

Figure 4. Tube mounting configurations with varying air flow direction and orientation of detector housing. Vertical as well as horizontal mounting is acceptable.

DOTS INDICATE POSITION OF

SAMPLING TUBE HOLES

AIR FLOW	AIR FLOW
	DIRECTION
DIRECTION

DETECTOR HOUSING

INLET

TUBE

DETECTOR

HOUSING

A.		B.
EXHAUST	EXHAUST	INLET
TUBE	TUBE	TUBE

HORIZONTAL MOUNTING OF HOUSING

EXHAUST
TUBE	DETECTOR
	HOUSING

	EXHAUST
AIR FLOW	TUBE		AIR FLOW
DIRECTION			DIRECTION
	INLET	INLET
DETECTOR	TUBE	TUBE	D.	H0109-00
HOUSING	C.

VERTICAL MOUNTING OF HOUSING

WARNING

In no case should more than 2 air inlet holes be cut off the tube. There must be a minimum of 10 holes in the tube exposed to the air stream.

B. Installation for Ducts More Than 8 Feet Wide

NOTE: To install inlet tubes in ducts more than 8 feet wide, work must be performed inside the air duct. Sampling of air in ducts wider than 8 feet is accom- plished by using the ST-10 inlet sampling tube.

Install the inlet tube as follows:

1.Drill a 3/4-inch hole in the duct directly opposite the hole already drilled for the inlet tube.

2.Slide the inlet tube with the flange into the right housing bushing. Position the tube so that the arrows point into the air flow. Secure the tube flange to the housing bush- ing with the two #6 self-tapping screws.

3.From inside the duct, couple the other section of the inlet tube to the section already installed using the 1/2- inch conduit fitting supplied. Make sure the holes on both of the air inlet tubes are lined up facing the air flow.

4.Trim the end of the tube protruding through the duct so that 1 to 2 inches of the tube extends outside the duct. Plug this end with the tube end cap and tape closed any holes in the protruding section of the tube. Be sure to seal the duct when the tube protrudes.

5.Any tube (over 3 feet long) that doesn’t protrude through the duct (on the side opposite the housing) must be sup- ported by other means.

NOTE: An alternate method to using the ST-10 is to use two ST-5 inlet tubes. Remove the flange from one of the tubes and install as described above. After the installation, use electrician’s tape to close off some of the sampling holes so that there are a total of 12 holes spaced as evenly as possible across the width of the duct.

NOTE: Air currents inside the duct may cause excessive vibration. This vibration can slowly open the seal around the tube and permit air to escape. To prevent this from occurring, a 3-inch floor flange, available at most plumbing supply houses, may be used. This flange/connector mounting technique makes the initial installation easier because a 1- inch to 1-1/4-inch hole may be drilled where the flange/connector will be used. It is easier to push the inlet tube through the larger hole.

Modification of Inlet Sampling Tubes

There may be applications where duct widths are not what is specified for the installation. In such cases, it is permis- sible to modify an inlet sampling tube that is longer than necessary to span the duct width.

Use a 0.193-inch diameter (#11) drill and add the appro- priate number of holes so that the total number of holes exposed to the air flow in the duct is 10 to 12. Space the additional holes as evenly as possible over the length of the tube.

D500-08-00 4 I56-512-07R