Honeywell 7800 Series Manual page 6

CR7890B 7800 SERIES INTEGRATED BURNER CONTROL
Sight Pipe Ventilation
It may be necessary to ventilate the sight pipe to cool the
CR7890 or to clear a viewing path through UV radiation
attenuating material.
For a negative pressure combustion chamber, drilling a few
holes in the section of the sight pipe outside of the combustion
chamber allows air at atmospheric pressure to flow through
the sight pipe and into the chamber. A perforated pipe nipple
between the sight pipe and the CR7890 can also be used.
For a positive pressure combustion chamber, connect a
supply of pressurized air from the burner blower to flow
through the sight pipe and into the chamber. The air pressure
must be greater than the chamber pressure.
Swivel Mount
To facilitate proper flame sighting, use 118367A Swivel Mount
(ordered separately). The swivel mount requires a reducer of
the proper size to mount it onto the sight pipe. It also requires
a 3/4-inch close nipple for mounting to a CR7890 with a
one-inch connector. (For 118367A Swivel Mount mounting
details, refer to 60-0361.)
Antivibration Mount
The CR7890 withstands normal burner vibration. If the
vibration is excessive, 123539 Antivibration Mount is
available. (For mounting details, see form 60-0361.) If you use
this mount, install it before positioning and sighting the
CR7890.
Mount the CR7890 (Fig. 4)
Mount the CR7890 onto the sight pipe, reducer, or other fitting
(see Fig. 4).
The CR7890 incorporates an oscillating shutter mechanism
and, therefore, require special consideration for mounting
positions other than vertically sighting downward or upward,
as illustrated in Fig. 4. The CR7890 has notch and arrow
indicators (see Fig. 4) on the faceplate to facilitate mounting in
positions other than those shown in Fig. 4. The notch and
arrow must be vertically aligned with the notch in the UP
position and the arrow pointing downward (see Fig. 4). The
CR7890 must be mounted with the conduit opening located
approximately 45 degrees below the horizontal (see Fig. 4).
65-0259—1
CR7890 CAN BE MOUNTED
HORIZONTALLY, VERTICALLY, OR
AT ANY ANGLE IN BETWEEN
VERTICAL
PLANE
HORIZONTZAL
PLANE
NOTCH AND ARROW
MUST ALWAYS BE
ALIGNED IN A
VERTICAL PLANE
CR7890
MUST NOT
BE ROTATED
AROUND
ITS AXIS
Fig. 4. CR7890 mounting positions.
IMPORTANT
The notch and arrow on the faceplate of the CR7890
must be aligned in a vertical plane with the notch up
and the arrow pointing downward.
To mount a CR7890B (Fig.5):
1. The mounting flange is in two pieces. Loosen (but do
not remove) the three screws holding the flange
together.
2. Slightly rotate the device clockwise so the slots in the
back section of the mounting flange clear the screws in
the front section; then separate the two sections.
3. Screw the front section of the mounting flange onto the
sight pipe, reducer, or other fitting.
4. Fit the slots in the back section of the mounting flange
(with the device) over the three screws in the front
section, and rotate the device counterclockwise so the
screws hold the flange together.
5. Tighten the screws securely.
6
90
90
NOTCH IN FACEPLATE
MUST BE UP
HORIZONTZAL
PLANE
45
ADE IN U.S.A.
MOUNT WITH
ARROW DOWN
ARROW ON FACEPLATE
MUST BE POINTING
DOWNWARD
M6816GR