Cooling System Service Checks; Maintenance; Filters; Lubrication - Lennox LGA Series Unit Information

2− Remove lead from sensing electrode and install a
0−50DC microamp meter in series between the sens-
ing electrode and the sensing lead.
3− Reconnect power and adjust thermostat for
heating demand.
4− When flame is established compare reading to table
21. Do not bend electrodes.
5− Disconnect power to unit before disconnecting meter.
Make sure sensor wire is securely reconnected
before reconnecting power to unit.
TABLE 21
Manufacturer Nominal Signal
RAM
JOHNSON
FENWAL
NOTE−If the meter scale reads 0, the leads are re-
versed. Disconnect power and reconnect leads for
proper polarity.
10−Combustion Air Inducer
The combustion air inducer is factory set and is not field adjust-
able. However, operation should be monitored to ensure prop-
er operation. The combustion air inducer is used to draw fresh
air into the combustion chamber while simultaneously ex-
pelling exhaust gases. The inducer operates through-
out the heating cycle.
On a heating demand, the ignition control is energized by the
main control module A55. The ignition control then allows 30 to
40 seconds for the combustion air inducer to vent exhaust
gases from the burners. When the combustion air induc-
er is purging the exhaust gases, the combustion air prove
switch is closing proving that the combustion air inducer is op-
erating before allowing the ignition control to energize. When
the combustion air prove switch is closed and the delay is over,
the ignition control activates the first stage operator of the gas
valve (low fire), the spark and the flame sensing elec-
trode. Sparking stops immediately after flame is
sensed.
B−Cooling System Service Checks
All units are factory charged and require no further adjustment;
however, charge should be checked periodically using the nor-
mal operating pressure method.
1−Gauge Manifold Attachment
Attach high pressure line to discharge line schrader port and
the low pressure line to the suction line schrader port.
NOTE−When unit is properly charged discharge line pres-
sures should approximate those in tables 6 through 19.
Drop Out
1.7−3.6 0.5
0.5−1.0 .09
1.7−3.6 0.7
V−MAINTENANCE
Electrical shock hazard. Turn off power to unit
before performing any maintenance, cleaning or
service operation on the unit.
A−Filters
All units are equipped with twelve 20" x 20" x 2" (508mm x
508mm x 51mm) pleated throw−away type filters. Filters
may be accessed through the economizer / filter access
door (left of the blower door). All filters are removed by
pulling on the pull tab, located on the bottom of each row
of filters. Filters should be checked monthly (or more fre-
quently in severe use) and cleaned or replaced regular-
ly. Take note of the AIR FLOW DIRECTION" marking on
the filter frame when re−installing.
NOTE−Filters must be U.L.C. certified or equivalent for
use in Canada.
Be careful when servicing unit to avoid accidental
contact with sharp metallic edges which may
cause personal injury.
B−Lubrication
All motors and blower wheels used are prelubricated; no
further lubrication is required.
C−Supply Air Blower Wheel
Annually inspect supply air blower wheel for accumulated
dirt or dust. Turn off power before attempting to remove
access panel or to clean blower wheel. If balancing clips
are removed, make sure they are reinstalled in the same
location when cleaning is completed.
NOTE−Do not lose balancing clips.
D−Evaporator Coil
Inspect and clean coil at beginning of each season. Clean
using mild detergent or commercial coil cleanser. Check
condensate drain pan and line, if necessary. Flush coil and
condensate drain with water taking care not to get insula-
tion, filters and return air ducts wet. Check connecting
lines and coil for evidence of oil and refrigerant leaks.
E−Condenser Coil
Clean condenser coil annually with detergent or com-
mercial coil cleaner and inspect monthly during the cool-
ing season. Check connecting lines and coil for evidence
of oil and refrigerant leaks.
NOTE−If owner complains of insufficient cooling, the
unit should be gauged and refrigerant charge checked.
Refer to Gauge Manifold Attachment and Charging
sections in this manual.
Page 59
CAUTION
CAUTION