Lennox KGC Series Unit Information page 47

J-Power Exhaust Fan
The power exhaust fan (PEF) requires the use of a gravity
exhaust damper and economizer and is used in downflow
applications only. See FIGURE 38. The PEF provides
exhaust air pressure relief and also runs when return air
dampers are closed and the supply air blower is operating.
See installation instructions for more detail.
POWER EXHAUST FAN AND
BAROMETRIC RELIEF DAMPER INSTALLATION
P18
BAROMETRIC
RELIEF
DAMPERS
FIGURE 38
Power Exhaust Setpoint Adjustment
Locate the A6 enthalpy control in the control area. The
EXH SET potentiometer is factory-set at approximately
50% of the dial range. See FIGURE 39. Power exhaust
fans will be energized 30 seconds after dampers are
50% open. Adjust the EXH SET potentiometer higher
(clockwise toward 10V) to energize fans when dampers
are further open. Adjust the EXH SET potentiometer lower
(counterclockwise toward 2V) to energize fans when
dampers are further closed. (Thirty- second delay allows
dampers to partially open before exhaust fan starts.)
K-Optional Cold Weather Kit (Canada only)
Electric heater is available to automatically control the
minimum temperature in the gas burner compartment.
Heater is ETL/CSA certified to allow cold weather operation
of unit down to -60° F (-50° C ).
The kit includes the following parts:
1 - Transformer (T20) is a 600V to 120/240V step-down
transformer mounted in the blower compartment.
2 - T20 has two in line fuses (F20), one on each leg of
the transformer. 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
vestibule of the heating compartment. Included in
the box are the following thermostat switches:
POWER
EXHAUST FAN ASSEMBLY
(ORDERED SEPARATELY)
A6 ENTHALPY CONTROLLER
2V
EXH
2V
DCV
2V
Free
Cool
B
A
a - Thermostat switch (S59) is an auto-reset SPST N.C.
switch which opens on a temperature drop. The switch
is wired in series with 24V power and the combustion
air blower switch. When the temperature drops below
-30° F (-35° C) the switch opens and the gas heat sec-
tion is de-energized. The switch automatically resets
when the heating compartment temperature reaches
-10° F (-12° C).
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 tem-
perature rises above 20° F (-7° C) the switch opens
and the electric heater is de-energized. The switch au-
tomatically resets when the heating compartment tem-
perature 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 (-7° C) the switch closes and elec-
tric heater is energized. The switch automatically opens
when heating compartment temperature reaches 76° F
(24° C).
L-Control Systems
All thermostat wiring is connected to TB1 located in the
control area. Each thermostat has additional control op-
tions available. See thermostat installation instructions for
more detail.
M-Smoke Detectors A171 and A172
Photoelectric smoke detectors are a field-installed option.
The smoke detectors can be installed in the supply air
section (A172), return air section (A171), or in both the
supply and return air sections.
Page 47
EXH
Set
ADJUST POWER
10V
EXHAUST FAN
SETPOINT
ENERGIZED WHEN
Min
Pos DAMPER POSITION
Open
IS HIGHER THAN
EXHAUST FAN
DCV
SETPOINT
Max
10V
DCV
Set
10V
C
D
FIGURE 39