Control Systems; Smoke Detectors; Blower Proving Switch; Dirty Filter Switch - Lennox LGA Series Unit Information

b − Thermostat switch (S60) is an auto-reset SPST
N.C. switch which opens on a temperature rise.
The switch is wired in series with HR6 and T20.
When the temperature rises above 20°F (-6.7°C)
the switch opens and the electric heater is de-ener-
gized. The switch automatically resets when the
heating compartment temperature reaches -10°F
(−23.3°C).
c −Thermostat switch (S61) is an auto-reset SPST
N.O. switch which closes on a temperature drop.
The switch is wired in series with HR6 and T20.
When temperature drops below 20°F (-6.7°C)
the switch closes and electric heater is ener-
gized. The switch automatically opens when
heating compartment temperature reaches 50°F
(10°C).
I−Control Systems
Three different types of control systems may be used with
the LGA/LGC/LCA/LCC series units. All thermostat wiring
is connected to terminal block TB1 located in the control
box of the unit. Each thermostat has additional control op-
tions available. See thermostat installation instructions for
more detail.
1− Electro-mechanical thermostat (13F06)
The electro-mechanical thermostat is a two stage heat /
two stage cool thermostat with dual temperature levers.
A non-switching or manual system switch subbase
may be used.
2− Electronic thermostat (see price book)
Any two stage heat / two stage cool electronic ther-
mostat may be used.
3− Honeywell T7300 thermostat (81G59)
The Honeywell T7300 thermostat is a programmable, in-
ternal or optional remote temperature sensing thermo-
stat. The T7300 provides occupied and unoccupied
changeover control.
J−Smoke Detectors A17 and A64
Photoelectric smoke detectors are a factory installed op-
tion. The smoke detectors can be installed in the supply air
section (A64), return air section (A17), or in both the supply
and return air section. Wiring for the smoke detectors are
shown on the temperature control section (C2) wiring dia-
gram in back of this manual.
K−Blower Proving Switch S52
The blower proving switch monitors blower operation and
locks out the unit in case of blower failure. The switch is
N.O. and closes at .14" W.C. (34.9 Pa) The switch is
mounted on the upper left hand corner of the blower deck.
Wiring for the blower proving switch is shown on the tempera-
ture control section (C2) wiring diagram in back of this manual.
L−Dirty Filter Switch S27
The dirty filter switch senses static pressure increase indi-
cating a dirty filter condition. The switch is N.O. and closes
at 1" W.C. (248.6 Pa) The switch is mounted on the top filter
channel corner. Wiring for the dirty filter switch is shown on
the temperature control section (C2) wiring diagram in back of
this manual. Actuation of this switch does not affect unit opera-
tion.
M−Indoor Air Quality (CO
The indoor air quality sensor monitors CO
ports the levels to the main control module A55. The board
adjusts the economizer dampers according to the CO
levels. The sensor is mounted next to the indoor thermo-
stat or in the return air duct. Refer to the indoor air quality
sensor installation instructions for proper adjustment.
Wiring for the indoor air quality switch is shown on the tem-
perature control section (C2) wiring diagram in back of this
manual.
N−LP / Propane Kit
Two natural to LP / propane gas changeover kits are re-
quired for gas conversion on LGA/LGC units (one for each gas
heat section). The kit includes manifold adjustment spring,
manifold cap, eleven burner orifices, and three stickers. For
more detail refer to the natural to LP gas changover kit installa-
tion instructions.
O−Supply Air VFD
Units may contain a supply air blower equipped with a vari-
able frequency drive A96 (VFD) which varies supply air
CFM. As duct static increases, the supply air volume will
decrease. As duct static decreases, the supply air volume
will increase.
The IMC uses input from a pressure transducer (A30) to
maintain a 1.0" w.c. (default) static pressure. Refer to the
IMC manual ECTO 0.04 and 0.05 to adjust the static pres-
sure setpoint.
The pressure transducer is shipped in a box in the blower
compartment. Install the transducer according to manufac-
turer's instructions.
Note −Make sure the transducer is installed in the main duct
at least 2/3 of the distance away from the unit.
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