153
NOTE: Disassembly of the top cover may be required under
special service circumstances. It is very important that the ori-
entation and position of the top cover be marked on the unit
prior to disassembly. This will allow proper replacement of the
top cover onto the unit and prevent rainwater from leaking into
the unit.
COMPRESSORS — Each compressor is readily accessible
from sides of unit.
LIQUID SERVICE VALVES, SUCTION SERVICE
VALVES, AND SIGHT GLASSES — Access to these com-
ponents is from the sides of the unit.
SUPPLY-FAN MOTORS, PULLEYS, AND BELTS — Ac-
cess to these components is through the 2 doors labeled FAN
SECTION on each side of the unit.
POWER EXHAUST MOTORS, PULLEYS, AND BELTS —
Access to these components is through the door at the return
end of the unit.
RETURN AIR FILTERS — Access to these filters is through
the door marked FILTER SECTION.
UNIT CONTROL BOX — Access to this component is
through the door marked ELECTRICAL SECTION on the
condenser end of the unit.
UNIT POWER BOX — Access to the power components is
through the door marked ELECTRICAL SECTION in the con-
denser section of the unit.
GAS HEAT SECTION (48N Only) — Access to the gas heat
section is through the door labeled HEAT SECTION on the
right side of the unit (when facing return air end). Figures 44
and 45 show typical modulating gas heat section. For modulat-
ing heat units, Fig. 46 replaces section 1 in Fig. 45.
MAIN BURNERS (48N Only) — At the beginning of each
heating season, inspect for deterioration due to corrosion or
other causes. The main burner assembly is shown in Fig. 43-49
for 2-stage heat. For modulating gas heat, see Fig. 48 and 49.
Refer to Main Burners Removal and Replacement section on
page 171 for burner removal sequence. Observe the main burn-
er flames and adjust if necessary. See Gas System Adjustment
sections on page 171.
FLUE GAS PASSAGEWAYS (48N Only) — The flue col-
lector box and heat exchanger cells may be inspected by
removing heat exchanger access panel, flue box cover, and
main burner assembly (Fig. 45 and 46). If cleaning is
required, remove heat exchanger baffles and clean tubes
with a wire brush.
PRESSURE SWITCH (48N Modulating Gas Only) — In-
spect the riveted surface of the pressure fitting (see Fig. 44) by
removing the flue box cover. Clean as necessary to ensure the
proper function of the combustion air proving switch. When
assemble back the flue box, ensure that both ends of pressure
switch tubing are tight pressed into fitting and pressure switch,
respectively.
COMBUSTION-AIR BLOWERS (48N Only) — Clean peri-
odically to assure proper airflow and heating efficiency.
Inspect blower wheel every fall and periodically during heat-
ing season. For the first heating season, inspect blower wheel
bi-monthly to determine proper cleaning frequency.
To inspect blower wheel, remove heat exchanger access
panel. Shine a flashlight into opening to inspect wheel. If clean-
ing is required, remove motor and wheel assembly by remov-
ing screws holding motor mounting plate to top of combustion
fan housing. The motor and wheel assembly will slide up and
out of the fan housing. Remove the blower wheel from the mo-
tor shaft and clean with a detergent or solvent. Replace motor
and wheel assembly. See Fig. 50.
ECONOMIZER DAMPER MOTOR(S) — On units so
equipped, the economizer motor(s) is located in the mixing
box section. Access to it is through the door labeled FILTER
SECTION.
CONDENSER FANS AND FAN MOTORS — Remove the
wire fan guard on top of the unit to gain access to the condenser
fans and motors.
IMPORTANT: After servicing is completed, make sure
door is closed and relatched properly, and that the
latches are tight. Failure to do this can result in water
leakage into the indoor-air section of the unit.
DETAIL A
FLUE
BOX
COVER
PRESSURE
FITTING
Fig. 44 — Gas Section Detail, Modulating Gas Heat
a48-8593
GAS
VALVE
INDUCER
MOTOR
FLUE
OUTLET
NOTE: UNITS CONTAIN 2 TO 5 SECTIONS
Fig. 45 — Standard Gas Heat
a48-8704
NOTE: 120 to 150 ton units shown. 75 to 105 ton units have a
maximum of 4 sections numbered 4, 1, 2, 3 from top to bottom.
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