Normal Operation Sequence - Lennox HP21 Unit Information

JP44−1 24VAC POWER (INPUT)
JP44−2 24VAC NEUTRAL (GROUND)
JP44−3 NOT USED
JP44−4 2nd STAGE THERMOSTAT DEMAND
JP44−5 THERMOSTAT COMMON (C)
JP44−6 1st STAGE THERMOSTAT DEMAND
JP44−7 24VAC FROM SAFETY SWITCHES
TO INTERNAL CONTACTOR COIL (INPUT)
JP44−8 HIGH SPEED (24VAC OUTPUT)
JP44−9 LOW SPEED (24VAC INPUT)
A timed−off delay in the control prevents the compressor
from operating for five minutes after the end of a thermostat
demand or after a power failure to prevent short cycling
(see miscellaneous section.) The control also counts unit
fault conditions." Whenever the compressor stops due to a
safety limit trip or if the compressor winding temperature
becomes too hot, the control's internal cycle counter accu-
mulates one fault. If three unit faults are counted during the
same thermostat demand, the control locks out" and stops
all unit operation. The control can be reset by breaking and
remaking thermostat demand. Also, unit faults are erased
when power is interrupted. When thermostat demand
changes stages, compressor operation stops for approxi-
mately one minute to allow refrigerant pressure to equalize
in the system.
In order to aid servicing and troubleshooting, a manual
override button has been placed on the control. The manu-
al override button, when pressed and released, bypasses
the five minute delay so low speed or high speed operation
can be immediately energized.
A red LED located on the face of the control can be used for
diagnostics. The control continually self-tests its internal
circuits and uses the diagnostic LED to indicate control fail-
ure or Safety Dormant Lockout. A Safety Dormant Lockout
is caused by abnormal line voltage (such as a lightning
strike near the unit).
TSC-2 TWO-SPEED CONTROL
S1 and S2
TO COMPRESSOR WINDING
TEMPERATURE SENSORS
S1 MANUAL OVERRIDE
OF 5 MINUTE DELAY
RED DIAGNOSTIC LED
JP44
3 2 1
6 5 4
9 8 7
FIGURE 5
1− General Operation
On power−up, the control begins a ten second initial
power−up delay.
2− The control then begins a five minute delay during
which the unit is not operational (control and outdoor
unit do not respond to thermostat demand.) Once the
five minute delay is complete, the control waits in
OFF mode for thermostat demand.
3− After receiving a thermostat demand, the TSC delays
three seconds before responding.
4− Low speed demand (JP44−6) energizes low speed op-
eration (JP44−9) OR high speed demand (JP44−4)
energizes high speed operation (JP44−8.)
5− During unit operation, if low speed demand changes to
high speed demand or if high speed demand changes
to low speed, the control delays three seconds before
responding. Then, all unit operation stops for 60+5
seconds (control de−energizes JP44−8 and JP44−9.)
This allows refrigerant pressure to equalize in the sys-
tem. At the end of the 60+5 second delay, the control
responds to whatever thermostat demand is present. If
no thermostat demand is present, the control resets
(see unit fault conditions section) and the control re-
turns to step 2 above.
6− If thermostat demand stops compressor operation, all
unit operation stops after a three second delay (control
de−energizes JP44−8 and JP44−9,) the control resets
(see unit fault conditions section) and the control re-
turns to step two.
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JP44
TOP VIEW

Normal Operation Sequence