035-19699-001-B-0804
Unitary Products Group 5
CLEANING BURNERS
Remove them from the furnace as explained in
BURNER INSTRUCTIONS section in the Unit Installa-
tion Instructions. Clean burners with wire brush and
vacuum as needed.
CLEANING FLUE PASSAGES AND
HEATING ELEMENTS
With proper combustion adjustment, the heating ele-
ment of a gas fired furnace will seldom need cleaning.
If the element should become sooted, it can be cleaned
as follows:
1. Remove the burner assembly as outlined in
“BURNER INSTRUCTIONS” of the unit installation
instructions.
2. Remove the unit roof from over the gas heat section.
3. Remove the top plate and the top draft blower
wheel from the upper draft blower housing.
4. Remove the screws holding the top of the flue col-
lector box. Carefully remove the top of the flue col-
lector box without ripping the adjacent insulation.
Then remove the center divider plate separating
the upper and lower flue boxes.
5. On the inside of the flue collector box, remove the
flue baffles from the tube interiors. Note the last
bend of the baffle fits tightly against the tube forc-
ing the end of the baffle to lock into the tube collar.
This collar is formed when the tube is expanded
into the end sheet. To remove, move the end of the
baffle toward the center of the tube releasing the
end of the baffle from the tube collar, then pull
straight out of the tube. Refer to Figure 4.
6. Using a wire brush on a flexible wand, brush out
the inside of each heat exchanger from the burner
inlet and flue outlet ends.
7. Brush out the inside of the flue collector box and
the flue baffles.
8. Run the wire brush down the vent hoods from the
flue collector end.
9. If soot build-up is particularly bad, remove the vent
motor and clean the wheel and housings. Run the
wire brush down the flue extensions at the outlet of
the vent housings.
10. After brushing is complete, blow all brushed areas
with air or nitrogen. Vacuum as needed.
11. Replace parts in the order they were removed in
Steps 1 thru 5.
12. When replacing the center and top of the flue col-
lector box, be careful not to tear the adjoining insu-
lation.
13. Ensure that all seams on the vent side of the com-
bustion system are air tight. Apply a high tempera-
ture (+500°F) sealing compound where needed.
AIR FILTERS
All units contain 2" filters. Filters can be installed in the
building at a suitable return air location if an econo-
mizer or outside air accessory is not used. Filters must
always be used. They should be inspected once a
month and thoroughly cleaned or replaced if it appears
they are beginning to accumulate excessive dirt. Filter
sizes and quantities are shown in the following table.
To install the filters, remove the filter access panel
located to the left of the condensate drain connection
as shown in Figure 5.
NOTE: Filters must be installed with “Air Flow” arrows
pointing inward -- toward the indoor coil. In the
event the spacers in the filter section are
removed, they must be reinstalled in their origi-
nal position.
FIGURE 4 - TYPICAL FLUE BAFFLE INSTALLATION
THROWAWAY
FILTER
SIZES
(Inches)
QUANTITY PER UNIT (Nom, Tons)
15 TON
STD
& HIGH
EFF.
15, 20, 25
TON REHEAT
20 TON
STD & HIGH
EFF.
25 TON
STD
EFF.
15 - 25
TON
ULTRA
HIGH
EFF.
12 x 24 - - 12 12
16x 20 - 4 - -
16 x 25 - 4 - -
18 x 24 5 - - -
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