Mode Selection Jumpers; Compressor Winding Sensor Operating Range - Lennox HP21 Unit Information

IMPORTANT
If the control locks out, it can be reset by breaking
thermostat demand for about five seconds then re-
making thermostat demand. Also, anytime thermo-
stat demand is removed or power is interrupted, the
control resets to zero faults.
A fault occurs when:
1− Compressor operation is monitored by high and low pres-
sure switches. These controls are wired in series. If either
one trips, compressor operation is interrupted and one
fault is counted. The control locks out compressor opera-
tion for a minimum of five minutes when a safety device
terminates operation. High pressure switch must be reset
manually but low pressure switch resets automatically.
It is likely that the control could count three unit faults
from the low pressure switch during a single thermo-
stat demand since this switch resets automatically.
However, the cycle counter can only count unit faults
from the high pressure switch if the reset button is
pushed without interrupting thermostat demand.
2− On all units using the TSC two-speed control, terminals
S1 and S2 on the control are connected to temperature
sensors (thermistors) which monitor the temperature of
the compressor motor windings. The two-speed control
measures the resistance through the sensors. The sen-
sors increase their resistance as temperature increases
(for example, too much superheat). When the resistance
through the sensors increases above a preset limit, the
control stops compressor operation for a minimum of
five minutes. As the compressor windings cool, the re-
sistance through the sensors drops below the reset
limit, the control resets automatically and one fault is
counted.
Check sensors by measuring resistance (ohms) through
the sensors with the wires disconnected from the control
(unit not running). The sensor wires are not polarity sensi-
tive. Table 6 shows winding temperature sensor
resistance values which will cause the TSC to lock out.
When unit is operating normally, resistance through the
sensors should be below the trip value shown in table 6.
TABLE 6
Compressor Winding
Temperature Sensor
TSC−6 Copeland Compressor
IMPORTANT − Normal resistance values of these com-
pressors are above 200 ohms but can read 90 ohms during
certain ambient temperatures. Ohm value below 200 ohms
will cause the two−speed control to cycle the compressor
"off" and will not allow the compressor to cycle back "on"
until the ohm values are above 200 ohms.
To prevent this issue, the field can install a 150 ohm − 1/4
Normal Trip Ohms Reset Ohms
Ohms Temp Rise Temp Fall
90 − 7800 25K − 35K 8.4K − 10K
watt resistor in series with one of the sensor connections on
the two−speed control. (The resistor can be found at elec-
tronic stores such as Radio Shack). Table 7 shows the
resistor in series with the control and compressor.
The control can be checked by comparing the resist-
ance measured through the sensors to the voltage
measured across the sensor terminals with the unit
running. Table 7shows voltage measured across two-
speed control terminals S1 and S2 with the
compressor running.
COMPRESSOR WINDING SENSOR
Resistance Through
Compressor Winding
Temperature Sensor
K-ohms (ohms x 1000)
.090 − .200
1.0
5.5
6.9
8.4
10.0
16.0
20.0
24.0
25.0
30.0
35.0
-
DC volts
Measured with unit running.
S1
S2
Compressor

MODE SELECTION JUMPERS

The control has six mode selection jumpers for selection of
operating modes and problem code recall or test. Choose
one of the first four modes for operation.
Normal: Normal operation (default mode). Unit
runs on high or low speed as the indoor
thermostat load demands.
Latch 1: After high speed demand is met, the unit
remains in high speed until the low speed
demand is satisfied.
Page 13
TABLE 7
OPERATING RANGE
Voltage Across TSC-6
compressor sensor terminals
with Unit Running DC Volts
0
Short in Sensor
1.70 − 1.82
6.07 − 6.48
6.86 − 7.33
7.55 − 8.07
Reset
8.16 − 8.72
Range
9.69 − 10.36
10.34 − 11.05
10.82 − 11.57
10.93 − 11.68
Trip
11.35 − 12.14
Range
11.68 − 12.48
+
Resistor
S1
S2