Tsc-6 Two-Speed Control; Tsc−6 Control - Lennox HP21 Unit Information

TSC-6 Two-Speed Control

HP21 -4 and -5 and late model HP21 units (single and
three phase) are equipped with a TSC-6 two-speed con-
trol. The TSC-6 (A14) two-speed control contains relays
which energize compressor operation in response to
thermostat demand. High speed operation can be ener-
gized and de-energized without passing through low
speed. The control also contains safety timed-off delays
and compressor over-temperature sensing which pro-
tect the compressor. The control has an external
temperature probe to lock out low speed during low tem-
peratures, plus a potentiometer used for setting the low
speed lock out temperature. The adjustment range is
38° F (3.3° C) to 55° F (12.7° C) ±2° F (1.1° C). This lock
out will occur in both heating and cooling modes.
A timed-off delay in the control prevents short cycling by
locking out compressor operation for five minutes after
the end of a thermostat demand or after a power failure.
The control also counts unit fault conditions." When the
compressor stops due to a safety limit trip, or if the com-
pressor winding temperature becomes too hot, the
control's internal cycle counter accumulates one fault. If
three unit faults are counted during the same thermostat
demand, the control locks out" and stops all unit opera-
tion. The control can be reset by breaking and remaking
thermostat demand. Unit faults are erased when power
is interrupted. When thermostat demand changes
stages, compressor operation stops for approximately
one minute to allow refrigerant pressure to equalize in
the system.
A manual override button aids servicing and trouble-
shooting, on the control. The manual override button,
when pressed and released, bypasses the five-minute
delay so low speed or high speed operation can be im-
mediately energized. However, the control provides a
one-minute delay between speed changes, which can-
not be bypassed.
Do not use the override button immediately after power-
up. If the button is pushed during the ten-second
power-up delay, it has no effect. The control completes
the five-minute delay.
The control continually self-tests its internal circuits and uses
the diagnostic lights to indicate control failure.
TSC-6 SHOWN
Normal Operation Sequence
1− After self-test, the control begins a five-minute delay dur-
ing 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.
2− After receiving a thermostat demand, the TSC de-
lays three seconds before responding.
3− Low speed demand (JP44-9) energizes low speed
operation OR high speed demand (JP44-8) ener-
gizes high speed operation.
4− 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 sec-
onds before responding. Then, all unit operation
stops for 60+5 seconds (control de-energizes
JP44-8 and JP44-9). This allows refrigerant pres-
sure to equalize in the system. At the end of the 60+5
second delay, the control responds to whatever
thermostat demand is present. If no thermostat de-
mand is present, the control resets (see unit fault
conditions section) and returns to step 2 above.
5− When thermostat demand is satisfied, all unit opera-
tion stops after a three-second delay (control
de-energizes JP44-8 and JP44-9), the control re-
sets (see unit fault conditions section) and returns to
step two.
6− General Operation
On power-up, the control begins a ten-second initial
delay.
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