Lennox LGM Series Unit Information

S e r v i c e L i t e r a t u r e
Ultra High Efficiency LGM036U through 074U with R-454B
LGM036U, 048U, 060U, and 074U are ultra high efficien-
cy gas packaged units equipped with variable speed di-
rect drive blowers, an inverter-driven variable speed com-
pressor, and a variable speed outdoor fan.
LGM036 units are available in 65,000 to 108,000 Btuh
(19 to 31 kW) heating inputs. LGM048, 060 and 074 units
are available in 65,000 to 150,000 Btuh (19 to 43.9 kW)
heating inputs. Gas heat sections are designed with alu-
minized (stainless optional) steel tube heat exchangers.
Cooling capacities range from 3 to 6 tons (7 to 21kW).
Information contained in this manual is intended for use
by qualified service technicians only. All specifications are
subject to change. Procedures outlined in this manual are
presented as a recommendation only and do not super-
sede or replace local or state codes.
If the unit must be lifted for service, rig unit by attaching
four cables to the holes located in the unit base rail (two
holes at each corner). Refer to the installation instructions
for the proper rigging technique.
False ceilings or drop ceiling may be used as a return air
plenum only if the unit being installed has a Refrigerant
Detection System installed.
All maintenance staff and others working in the local area
shall be instructed on the nature of work being carried out
with work in confined spaces being avoided.
Ensure that the area is in the open or that it is adequately
ventilated before breaking into the system or conducting
any hot work. A degree of ventilation shall continue during
the period that the work is carried out. The ventilation
should safely disperse any released refrigerant and pref-
erably expel it externally into the atmosphere.
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal
injury. Take care while handling this equipment and
wear gloves and protective clothing.
WARNING
Improper installation,
service or maintenance can cause property damage,
personal injury or loss of life. Installation and service
must be performed by a licensed professional
HVAC installer or equivalent, service agency, or the
gas supplier.
UNIT INFORMATION UNIT INFORMATION
adjustment, alteration,
100126
01/2025
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
Electrostatic
electronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
Options . . . . . . . . . . . . . . . . . . . . . . . . Page 4
Specifications . . . . . . . . . . . . . . . . . . . . Page 7
High Altitude . . . . . . . . . . . . . . . . . . . . . Page 8
Blower Data . . . . . . . . . . . . . . . . . . . . . Page 9
Electrical Data . . . . . . . . . . . . . . . . . . . Page 13
I-Unit Components . . . . . . . . . . . . . . . . Page 17
- RDS Sensors . . . . . . . . . . . . . . . . . Page 23
II-Placement and Installation . . . . . . . . . . Page 36
III-Start Up Operation . . . . . . . . . . . . . . . Page 36
IV-Charging . . . . . . . . . . . . . . . . . . . . Page 37
V-System Service Checks . . . . . . . . . . . . Page 46
VI-Maintenance . . . . . . . . . . . . . . . . . . Page 48
VII-Accessories . . . . . . . . . . . . . . . . . . Page 51
VIII-Decommissioning . . . . . . . . . . . . . . Page 60
IX-Diagrams . . . . . . . . . . . . . . . . . . . . Page 61
Page 1
LGM SERIES
3 to 6 ton
CAUTION
discharge

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can affect