5
®
INSTALLATION
The best scanner sighting results are obtained when the scanner is aimed so that its line of sight inter-
sects the burner center line at a slight angle, as shown in Figure 3. The area of maximum ultraviolet
radiation is near the base of the flame envelope. When only one scanner is used per burner, the inter-
section should be made so the line of sight or viewing angle can also see the pilot flame. Consider-
ation must be given to burner secondary air rotation (some burners have clockwise air rotation and
others counter-clockwise). Figure 3 illustrates how scanner location is influenced by the pilot posi-
tions and secondary air circulation. Physical obstructions such as air register blades should not fall in
the line of sight of the scanner.
FIGURE 3.
1.
AN ACCEPTABLE SCANNER LOCATION MUST ENSURE THE FOLLOWING:
— Reliable pilot flame detection.
— Reliable main flame detection.
— Rejection of pilot flame too short or in the wrong position to ignite the main flame reliably,
thus prohibiting main fuel admission.
NOTE: Reliable signals must be obtained at all air flows and furnace loads (ranges of fuel firing).
FIGURE 4.
2.
If combustion air enters the furnace with a rotational movement of sufficient velocity to deflect
pilot flame in direction of rotation, position the scanner 0 to 30 degrees downstream of the pilot
burner and close to the periphery of the throat where the ultraviolet radiation is at a maximum.
(See Figures 3 and 4).
3.
Having determined an appropriate location for the sight tube, cut a clearance hole for a 2 inch
pipe through the burner plate. If register vanes interfere with the desired line of sight, the inter-
fering vane(s) should be trimmed to assure an unobstructed viewing path at all firing levels, see
Figure 4.
PRIMARY
COMBUSTION
AIR REGISTER
BLADES
SCANNER
LINE OF
SIGHT
BURNER
THROAT
FLAME
ENVELOPE
SINGLE BURNER SCANNER SIGHTING
BURNER
CENTER LINE
BASE
ZONE
IGNITOR
SCANNER
MAIN
BURNER
CCW ROTATION
IGNITOR
SCANNER
MAIN
CW ROTATION
BURNER
SCANNER LOCATION VS. SECONDARY AIR ROTATION
