Check CO
2
, CO & Stack
Temperature
Flue gas samples are to be taken from inside one of the
secondary tubes. If the sample is taken from the flue box
rather than the tube, the sample will be diluted with outside
air and lower readings will result. If flue gas temperature is
to be measured, this must be done in the flue box, not in the
tube . The temperature gradient within the tubes will cause high
readings near the center of the tube and low readings near the
edge. Measure temperatures within the flue box where a good
mix will be present. The flue box includes two 5/16
"
holes for
test purposes . One hole lines up with the end of a secondary
tube for taking flue gas samples. The other hole, through the
side of the flue box, is for thermometer insertion.
If the CO
2
and/or CO readings are not within the range
Troubleshooting Chart, page 26
Sections 4 .1 and 4 .2 .
Figure 15:
Checking Temperature
Typical Readings:
CO
2
9½ to 10½ percent at maximum rate
9 to 10 percent at minimum rate
CO .001 percent (10 PPM) or less
Cleaning Heat Exchangers
Models 032 thru 200 (see
)
1 .
Remove the flue box front wrap (1) and the rear
inspection cover (3) .
2 . Remove and clean the turbulator (2) from each tube and
clean the flue box.
3 . Clean each tube with a 2-1/2
"
round flue brush.
4 . Remove the bushings, and if required, clean the
combustion chamber and header through the rear
inspection door port .
5 . Reinstall the inspection cover (3) . Snug the screws but
do not overtighten and crush the insulation .
6 .
Reinstall a turbulator in each tube approximately flush
with the tube ends, locking them in place with the wedge
clip on each turbulator .
7 .
Reinstall the flue box front wrap (1).
Figure 16: Models 032 through 200 Heat Exchanger
Figure 17:
Models 020 through 025 Heat Exchanger
Co
2
Sample
Measure
Temperature
300º
400º
500º
600º
Temperature Gradient
within Tube
3
2
1
2 1/2 Round Flue Brush With 7 Foot Handle
Co ndensa te Dr ain
3
2 1/2 Round Flue Brush With 4 Foot Handle
2
1
Condensate Drain
Wind Deflector
Service
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IM 684-6 • ROOFTOP SYSTEMS
