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1- Transformer (T20) is a 600V to 120/240V stepdown trans-
former mounted in the blower compartment.
2-T20has twoin line fuses (F20),oneoneachlegofthetrans-
former. Both are rated at 15 amps.
3-The strip heater (HR6) is located as close as possible to the
gas valve. It is wired in series with T20. The strip heater is
rated at 500 Watts
4- A thermostat mounting box is installed on the vesti-
bule of the heating compartment. Included in the box
are the following thermostat switches:
a - Thermostat switch (S59) is an auto-reset SPST .
switch which acts as a low limit and opens on a tem-
perature drop. The switch is wired to open 24v pow-
er to the burner control. When the temperature drops
below-35° C (-30° F)the switch opens and the gas heat
section is de-energized. The switch automatically re-
sets when the heating compartment temperature
reaches -12° C (10° F).
b - Thermostat switch (S60) is an auto-reset SPST
switch and is the controller of HR6. When the tem-
perature rises above -7° C (20° F) the switch opens
and the electric heater is de-energized. The switch
automatically resets when the heating compartment
temperature reaches -23.3° C (-10° F).
c -Thermostat switch (S61) is an auto-reset SPST
switch which acts as a high limit and closes on a
temperaturedrop. S61remains closed during low
ambient conditions and opens when tempera-
tures rise. When temperature drops below -6.7° C
(20° F) theswitch closes.The switch automatical-
lyopens when heating compartment temperature
reaches 24° C (76° F).
I-Control Systems
Three different types of control systems may be used with
the LGA / LCA series units. All thermostat wiring is con-
nected to terminal block TB1 located in the blower
compartment of the unit. Each thermostat has additional
control options available. See thermostat installation in-
structions 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 inboth 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 corneroftheblowerdeckin
the blower compartment. Wiring for the blower provingswitch
is shown on the temperature control section (C2) wiring dia-
gram 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) Theswitch ismounted on the topfilter
channel corner. Wiring for the dirty filter switch is shown on
the temperature control section (C2) wiring diagram in back of
this manual.
M-Indoor Air Quality (CO
2
) Sensor A63
The indoor air quality sensor monitors CO
2
levels and re-
ports thelevelstothe main controlmoduleA55.The board
adjusts the economizer dampers according to the CO
2
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 fortheindoorair qualityswitchisshown onthetem-
peraturecontrol section (C2) wiring diagraminback ofthis
manual.
N-LP / Propane Kit
Anaturalto LP/ propane gas changeoverkitis requiredfor
gas conversion on LGA036/072 series units. The kit includes
a gas valve and burner orifices.
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