Maintenance - Lennox F8AUH series Service Manual

C−External Static Pressure
1 − Tap locations shown in figure 19.
2 − Punch a 1/4" diameter hole
in supply and return air ple-
nums. Insert manometer
hose flush with inside edge
of hole or insulation. Seal
around the hose with per-
magum. Connect the zero
end of the manometer to the
discharge (supply) side of the system. On ducted sys-
tems, connect the other end of manometer to the re-
turn duct as above. For systems with non−ducted re-
turns, leave the other end of the manometer open to
the atmosphere.
3 − With only the blower motor running and the evaporator
coil dry, observe the manometer reading. Adjust blow-
er motor speed to deliver the air desired according to
the job requirements.
4 − External static pressure drop must not be more than
0.5" W.C.
5 − Seal around the hole when the check is complete.
D−Blower Speed Taps
Blower speed tap changes are made on the control board.
See figure 6. Unused taps must be secured on two dummy
terminals labeled "PARK on the control board. The heat-
ing tap is connected to the "HEAT−H " terminal and the
cooling tap is connected to the "COOL−H" terminal. The
continuous blower tap is the same as the heating tap.
To change existing heat tap, turn off power then switch out
speed tap on "HEAT−H" with tap connected to "PARK" .
See table 8 for blower motor tap colors for each speed.
TABLE 8
VI−MAINTENANCE
At the beginning of each heating season, the system
should be checked as follows:
A−Filters
Return air filter is not supplied with unit. See Optional Ac-
cessaries section in this manual for filter and rack size. A
filter must be used in order to ensure long life and proper
STATIC PRESSURE
TEST
MANOMETER
F8AUH UNIT
FIGURE 19
Page 17
operation. The filter is located in the return air duct or return
air register. Filters must be cleaned or replaced when dirty
to assure proper unit operation.
B− Heat Exchanger and Burners
Due to crimps designed in the heat exchanger, cleaning is
not recommended. Removal is for inspection only.
NOTE−Use papers or protective covering in front of fur-
nace while cleaning furnace.
To clean burners:
1 − Remove screws holding upper burner mounting rail.
Remove rail.
2 − Slide burners off each orifice pull burners from heat ex-
changer.
3 − Clean holes in burner head (retention ring) with a wire
brush. See figure 20.
FIGURE 20
4 − With a shop vacuum or rags, clean out soot and scale
deposits from burners.
5 − Remove screws securing flue box to vestibule panel.
Remove flue box from unit. Leave combustion air
blower attached to flue box.
6 − With a shop vacuum or rags, clean out soot and scale
deposits from heat exchanger tubes and flue box. If tur-
bulators are removed make sure they are re-installed
before reassembling units.
7 − Inspect heat exchanger for corrosion damage, holes or
cracks.
8 − Replace burners making sure to fully engage on orifice.
Resecure burner mounting rail and flue box. Inspect flue
box gasket. Replace gasket if necessary.
9 − Slide heat exchanger into cabinet and re-secure heat
exchanger screws.
10 − Reinstall filler piece making sure that there is a good
seal between the cabinet sides, blower and deck and
filler piece.
11 − Re-secure flue pipe, gas piping and access panels.
12 − Carefully check all piping connections (factory and
field) for gas leaks. Use a leak detecting solution or oth-
er preferred means.
13 − Turn on gas and electrical supply.