Maintenance - Lennox LGM Series Unit Information

TABLE 11
Input Rate Seconds Natuarl Seconds LP/Propane
65,000 55
105,000 34
150,000 24
6-Heat Exchanger
To Access or Remove Heat Exchanger From Unit:
1 - Turn off gas and electric power.
2 - Remove access panel(s) and unit center mullion.
3 - Remove gas valve, manifold assembly and burners.
4 - Remove combustion air inducer. Pay careful
attention to the order in which gaskets and orifice
are removed.
5 - Support heat exchanger (to prevent it from falling
when final screws are removed.)
6 - Remove screws supporting heat exchanger.
7 - To install heat exchanger, reverse procedure. Be
sure to secure all wires and check plumbing and
burner plate for airtight seal. Screws must be
torqued to 35 in.-lbs. to ensure proper operation.
7-Flame Sensing
Flame current is an electrical current which passes from
the ignition control through the sensor electrode during unit
operation. The current passes from the sensor through the
flame to the ground electrode (located on the flame elec-
trode) to complete a safety circuit. The electrodes should
be located so the tips are at least 1/2" (12.7 mm) inside
the flame envelope.Do not bend electrodes. To measure
flame current, follow the procedure below:
NOTE-Electrodes are not field adjustable. Any alterations
to the electrode may create a hazardous condition that
can cause property or personal injury.
1 - Disconnect power to unit.
2 - Remove lead from sensing electrode and install
a 0-50DC microamp meter in series between the
sensing electrode and the sensing lead.
3 - Reconnect power and adjust thermostat for heating
demand.
4 - When flame is established, microamp reading
should be 0.5 to 1.0. Do not bend electrodes.
Drop out signal is .09 or less.
5 - Disconnect power to unit before disconnecting
meter. Make sure sensor wire is securely
reconnected before reconnecting power to unit.
NOTE-If the meter scale reads 0, the leads are
reversed. Disconnect power and reconnect leads
for proper polarity.
B-Cooling System Service Checks
LGM units are factory charged and require no further ad-
justment;
138
however, charge should be checked periodically using the
86
approach method. The approach method compares actual
60
liquid temperature with the outdoor ambient temperature.
See section IV- CHARGING.
NOTE-When unit is properly charged discharge line pres-
sures should approximate those in tables 6 through 9.
VI-MAINTENANCE
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and
dangerous operation. Verify proper operation after
servicing.
A-Filters
Units are equipped with temporary filters which must be
replaced prior to building occupation. See figure 26. All
units have 20 X 20 X 2 in. (508 X 508 X 51mm) filters.
Refer to local codes or appropriate jurisdiction for ap-
proved filters.
NOTE-Filters must be U.L.C. certified or equivalent for
use in Canada.
B-Lubrication
All motors are lubricated at the factory. No further lubrica-
tion is required.
Page 36
WARNING
Electric shock hazard. Can cause injury or
death. Before attempting to perform any
service or maintenance, turn the electrical
power to unit OFF at disconnect switch(es).
Unit may have multiple power supplies.
IMPORTANT
REMOVE FILTERS
FIGURE 26
PULL TO
REMOVE
FILTERS