Lennox LGM Series Manual

S e r v i c e L i t e r a t u r e
The LGM156H, 180, 210, 240 and 300 units are config-
ure to order units (CTO) with a wide selection of factory
installed options.
The LGM156 \ 300 is available in 169,000 to 480.000
Btuh. See SPECIFICATIONS-GAS HEAT for more detail
per model.
Gas heat sections are designed with aluminized steel tube
heat exchangers with stainless steel as an option.
Cooling capacities range from 13 to 25 tons (45.7 to 88
kW).
LGM156 and 180 utilize three compressors and four con-
denser fans, while LGM210, 240 and 300 utilize four com-
pressors and six condenser fans.
Multi-Stage Air Volume MSAV® blower option is available.
The VFD-driven blower will operate at lower speeds when
demand is low and increase to higher speeds when de-
mand is high.
Variable speed VAV system is available as an option which
enables supply duct static measurement to control blow-
er CFM and discharge air temperature to control cooling
stages.
All LGM units are designed to accept any of several differ-
ent energy management thermostat control systems with
minimum field wiring. Factory- or field-provided control op-
tions connect to the unit through Smartwire connectors.
When "plugged in" the controls become an integral part of
the unit wiring.
The CORE Control System is designed to accelerate
equipment install and service. Standard with all Model L™
rooftop units, control system integrates key technologies
that lower installation costs, drive system efficiency, and
protect your investments.
The CORE Unit Controller is a microprocessor-based con-
troller that provides flexible control of all unit functions.
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.
UNIT INFORMATION UNIT INFORMATION
100024
Revised 08/2021
LGM156U through 300U
Page 1
WARNING
Improper installation, adjustment, alteration, 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.
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.

Table of Contents

Options / Accessories . . . . . . . . . . . . . . . . . . .Page 2
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . .Page 6
Gas Heat Specifications / High Altitude
Blower Data . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 10
Electrical Data . . . . . . . . . . . . . . . . . . . . . . . . . Page 13
Unit Parts Arrangement . . . . . . . . . . . . . . . . . . Page 16
I-Unit Components . . . . . . . . . . . . . . . . . . . . . . Page 16
II-Placement and Installation . . . . . . . . . . . . . . .Page 33
III-Charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 33
IV-Start Up - Operation . . . . . . . . . . . . . . . . . . . Page 35
V-System Service Checks . . . . . . . . . . . . . . . . .Page 37
VI-Maintenance . . . . . . . . . . . . . . . . . . . . . . . . .Page 39
VII-Accessories . . . . . . . . . . . . . . . . . . . . . . . . .Page 40
VIII-Hot Gas Re-Heat . . . . . . . . . . . . . . . . . . . . Page 44
IX-Staged Blower . . . . . . . . . . . . . . . . . . . . . . . Page 48
X - VAV System . . . . . . . . . . . . . . . . . . . . . . . . .Page 50
XI-Wiring and Operation Sequence
LGM SERIES
13 to 25 ton
45.7 to 88 kW
. . . . Page 9
. . . . . . . .Page 52