Lennox HP21, HP21−411, HP21−413, HP21−511, HP21−513, HP21−651, HP21−653, HP21−36−230, HP21−36−233, HP21−48−230, HP21−48−233, HP21−60−230, HP21−60−233 Unit Information
Specifications and Main Features
Frequently Asked Questions
User Manual
Corp. 9434−L12
Service Literature
Revised 07−2007
HP21 SERIES UNITS INCLUDING TSC−2, TSC−3 AND TSC-6
The HP21 is a high efficiency residential split-system heat
pump with a two-speed compressor. Early models include
HP21−411, −511 and −651. Late models built after March 1,
2000 include HP21−36, −48 and −60. All models are available in sizes ranging from 3 through 5 tons in either single
or three-phase configuration. Early and late models feature
solid-state two-speed control and new solid-state demand
defrost control. The two-speed control regulates compressor speed in response to thermostat demand during
cooling mode. Compressor speed is regulated by outdoor
air temperature during heating mode. The defrost control
monitors outdoor air temperature and liquid line temperature to determine when defrost is needed. The series uses
conventional heat pump circuitry with expansion valves in
the outdoor and indoor units.
This manual is divided into sections which discuss the components, refrigerant system, charging procedures,
maintenance and operation sequences. All specifications
in this manual are subject to change.
Line voltage is present at all components when unit is not in operation on
units with single pole contactors.
Disconnect all remote electrical power
supplies before opening unit panel.
Unit may have multiple power supplies.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal injury or loss of life. Installation and service must
be performed by a qualified installer or service
agency.
WARNING
Refrigerant can be harmful if it is inhaled. Refrigerant
must be used and recovered responsibly.
Failure to follow this warning may result in personal injury or death.
All major components (indoor blower/coils) must be
matched according to Lennox recommendations for the
compressor to be covered under warranty. Refer to Engineering Handbook for approved system matchups. A
misapplied system will cause erratic operation and can result in early failure of compressor or other components.
II−UNIT COMPONENTS
A−Control Transformer T19
All units are equipped with a line voltage to 24VAC transformer which supplies power to unit controls as shown in
table 1. Refer to unit wiring diagram for detailed information
regarding unit wiring.
B−Contactors K1 and K69
The compressor is energized by a set of contactors located
in the control box. Contactors in HP21 units are energized
as shown in table 2.
CRANKCASE
THERMOSTAT S40
COMPRESSOR B1
AMBIENT AIR PORT
(DEFROST CONTROL
AMBIENT SENSOR)
TABLE 1
HP21 ComponentSource of Power
Two-Speed Control A14
Contactor K1
Contactor K69
High Pressure Limit S4
Crankcase Thermostat S40
Defrost Control CMC1
Defrost Relay K4
Speed Control Thermostat S55
Service Light Thermostat S54
Ambient Thermistor RT3
Potential Relay K31
Crankcase Heater HR1
Compressor Run Capacitor C5
Compressor Start Capacitor C7
Bleed Resistor R21
Fan Capacitor C1
Compressor B1
Outdoor Fan B4
24VAC from
Outdoor Unit
Transformer T19
24VAC from
Indoor Unit
Transformer T1
Line Voltage
Page 3
START CAPACITOR C7
(single-phase only)
OUTDOOR FAN CAPACITOR C1
(three-phase only)
DUAL CAPACITOR C12
(single−phase)
EARLY HP21 -1 / -2 / -3 SINGLE PHASE SERIES UNITS USE FAN
CAPACITOR C1 AND COMPRESSOR CAPACITOR C5 IN PLACE OF
START RELAY K31
(single-phase only)
C12
HP21 CONTROL BOX COMPONENTS
Contactor K1
CONTACTOR K69
DEFROST RELAY
K4
FIGURE 2
CONTACTOR K1
TRANSFORMER
T19
DEFROST CONTROL
CMC1
SPEED CONTROL
THERMOSTAT S55
TWO-SPEED CONTROL
A14
24V TERMINAL
STRIP TB15
Contactor Operation: Single-Phase Units
Contactor K1 energizes low speed compressor operation
in all units (single-phase and three-phase.) In single−phase
units K1 is a two pole contactor with two sets of normally
open contacts and in three−phase units K1 is a five pole
contactor with three sets of normally open contacts and two
sets of normally closed contacts. K1 is also equipped with a
set of single-pole double-throw auxiliary contacts located
on the side of the contactor. The contactor is energized in
response to low speed thermostat demand (from twospeed control jackplug J44/P44 pin 9.)
TABLE 2
Compressor Speed
Low
High
Contactors Energized
Single-PhaseThree-Phase
K1K1
K1 & K69K69
In single-phase units, K1 also de-energizes the crankcase
heater during compressor operation.
Contactor K69
Contactor K69 energizes high speed operation in all units
(single-phase and three-phase.) In single−phase units K69
is a five−pole contactor with three sets of normally open
contacts and two sets of normally closed contacts. In three−
phase units K69 is a three−pole contactor with three sets of
normally open contacts.This contact arrangement provides unique switching characteristics for two-speed
operation. K69 is also equipped with a set of single-pole
double-throw auxiliary contacts located on the side of the
contactor. The contactor is energized in response to high
speed thermostat demand from JP44-8 (two-speed control
jackplug J44/P44 pin 8.)
Low speed demand energizes K1. K1 de-energizes the
crankcase heater and energizes the compressor. High
speed demand energizes both contactors K1 and K69. K69
N.O. contacts close to redirect the circuit to the high speed
start windings and the N.C. contacts open to de-energize
the low speed start windings. K69 N.C. contacts also switch
whenever K69 is energized to ensure that K1 is energized
with K69 during high speed operation (refer to unit wiring
diagram).
Contactor Operation: Three-Phase Units
Low speed demand energizes K1. K1 energizes the compressor and locks out contactor K69. High speed demand
de−energizes K1 and energizes contactor K69. K69 locks
out K1 and energizes the compressor on high speed.
K1 is wired so that when de−energized, the contactor forms
a parallel common connection to the motor windings for
high speed forming a parallel Delta" connection for Copeland compressors. When K1 is energized, the contactor
forms a series Delta connection to the compressor windings. Refer to operation sequence in back of this manual for
more information.
C−Defrost Relay K4
All HP21 units are equipped with a defrost relay located
in the unit control box which controls defrost. The relay is
a 3PDT relay powered 24 VAC from the thermostat. K4 is
enabled during both cooling and heating modes (except
emergency heat). It is only powered when the defrost
control is calling for defrost. When energized, the reversing valve and indoor auxiliary heat are energized.
Simultaneously, the outdoor fan is de-energized. K4
latches in for the duration of the defrost period.
Page 4
D−Hard Start Relay K31 (single-phase only)
All single-phase HP21 units are equipped with a hard start
relay located in the unit control box which controls the operation of the compressor starting circuit. The relay is normally
closed when the compressor (contactor K1) is de-energized.
Capacitor (C7) is connected in series to a set of normally
closed K31 contacts and assists the compressor in starting.
When K1 energizes, the compressor immediately begins startup. K31 remains de-energized during compressor start-up and
the start capacitor (C7) remains in the circuit. As the compressor gains speed K31 is energized by electromotive forces
generated by the compressor. When K31 energizes, its contacts open to take the start capacitor out of the circuit.
E−Terminal Strip TB15
All HP21 units are equipped with a low voltage terminal
strip located in the unit control box for making up thermostat wiring connections (refer to figure 2).
F−Compressor B1
See ELECTRICAL DATA or compressor nameplate for
specifications. Figure 3 shows the compressor terminal
box. All compressors are equipped with internal pressure
relief valves set at 450+50 psig. Compressors in all units
use insertion type crankcase heaters which are regulated
by relays in the HP21.
frost relay is energized. In three-phase units, the outdoor
fan is controlled by contactor K10 and is de-energized
when the defrost relay is energized. See figure 4 if outdoor
fan motor replacment is necessary.
1/4"
Condenser fan
and motor
FAN GUARD
Wiring
Drip loop
FIGURE 4
H−High Pressure Limit S4
All units are equipped with a high pressure limit mounted on
the compressor discharge line. The switch can be manually reset and has a cutout" point of 410+10 psig. The switch
is electrically connected in series with crankcase thermostat S40 in the two-speed control’s safety circuit. When
tripped, the TSC interrupts unit operation. If the high pressure switch trips" three times within the same thermostat
demand, the two-speed control locks out and the contactor
cannot energize.
TYPICAL TWO-SPEED COMPRESSOR
TERMINAL BOX
COPELAND SINGLE-PHASE SHOWN
T3T8 T1T7
T2
SINGLE
PHASE
S1 S2
FIGURE 3
G−Outdoor Fan Motor B4
The specifications table on page 1 of this manual shows the
specifications of outdoor fans used in all HP21 units. In
single-phase units, the outdoor fan is controlled by the
compressor contactor and is de−energized when the de-
Although the high pressure limit must be reset manually, if
the two-speed control is locked out it must be reset before
the unit can operate. To reset the control, break and remake thermostat demand.
I−Crankcase Thermostat S40
Crankcase thermostat S40 is electrically connected in series with high pressure limit S4 in the two-speed control’s
safety circuit. It is used in all units to monitor the temperature of the compressor. The switch is a N.C. SPST
belly-band" thermostat strapped to the compressor.
The switch is factory preset to trip at 190°F+5°F on a temperature rise. When tripped, the TSC interrupts unit
operation. The crankcase thermostat automatically resets
when the compressor crankcase drops below 110°F+7°F. If
the crankcase thermostat trips" three times within the
same thermostat demand, the two-speed control locks out
and the contactor cannot energize. If the two-speed control
is locked out it must be reset before the unit can operate. To
reset the control, break and remake thermostat demand.
Page 5
J−Service Light Thermostat S54
All units are equipped with a service light thermostat mounted
on the compressor discharge line. The switch is electrically
connected to the service light in the indoor thermostat. When
compressor discharge line temperature reaches 130+5°F,
the switch opens. If discharge line temperature drops below
110+5°F during unit operation (indicating a problem in the
system), the switch closes. If thermostat demand is present
when S54 closes, the service light is powered to indicate service is needed.
K−Start Capacitor C7
All single-phase HP21 units are equipped with a start capacitor connected in parallel with the run capacitor. The
capacitor is switched off by the potential relay when the
compressor nears full speed. The start capacitor is rated
145−175mfd. @ 330VAC in all single-phase units.
Three-phase HP21 units do not use start capacitors.
L−Bleed Resistor R21
All single-phase HP21 units are equipped with a bleed resistor connected in parallel with start capacitor C7. The
resistor is used to slowly discharge the capacitor when not
in use. R21 is a 15,000 ohm 2 watt resistor.
M−Run Capacitor C5
All single-phase early model HP21 -1 / -2 / -3 units use a
compressor run capacitor to maximize motor efficiency.
The run capacitor is located in the unit control box and is
electrically connected as shown in the unit wiring diagram.
Run capacitors are wired in parallel with the start capacitor.
See side of capacitor for ratings.
O−Dual Capacitor C12
HP21-4 / -5 and late model single-phase units use a single
dual capacitor to maximize motor efficiency in both the fan
motor and the compressor, which use PSC motors. A dual
capacitor has two independent capacitors inside one can.
Each side of the capacitor has different ratings . See side of
capacitor for ratings. The dual capacitor is wired in parallel
with the start capacitor and is electrically connected as shown
in the unit wiring diagram.
P− Two-Speed Controls
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can affect electronic
components. Take precautions during unit
installation and service to protect the unit’s
electronic controls. Precautions will help to
avoid control exposure to electrostatic discharge by putting the unit, the control and the
technician at the same electrostatic potential.
Neutralize electrostatic charge by touching
hand and all tools on an unpainted unit surface
before performing any service procedure.
TSC−2 Two-Speed Control
The TSC two-speed control (figure 5) is a Lennox built control designed for use with two-speed condensing units and
heat pumps. The control provides automatic switching
from low speed to high speed operation and back. The
TSC−2 is designed for use with Bristol and Copeland compressors. All HP21 series units use Copeland
compressors. All early model HP21−1 units use the TSC−2
controls.
N−Fan Capacitor C1
All early model HP21 -1 / -2 / -3 single phase and all HP21
three−phase series units (regardless of dash number) use
single-phase PSC outdoor fan motors which require an external run capacitor. The fan capacitor is located inside the
unit control box. See side of fan capacitor for ratings.
The TSC two-speed control contains relays which energize
compressor operation in response to thermostat demand.
High speed operation can be energized and de−energized
without passing through low speed. The control also contains safety timed−off delays and compressor
over−temperature sensing which help protect the compressor.
Page 6
JP44−124VAC POWER (INPUT)
JP44−224VAC NEUTRAL (GROUND)
JP44−3NOT USED
JP44−42nd STAGE THERMOSTAT DEMAND
JP44−5THERMOSTAT COMMON (C)
JP44−61st STAGE THERMOSTAT DEMAND
JP44−724VAC FROM SAFETY SWITCHES
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).
Normal Operation Sequence
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
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 system. 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 returns 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 returns to step two.
Page 7
Two-Speed Control Fault Conditions
If the control is in low speed operation, high speed operation, OFF" mode or speed change delay, the control
counts" or accumulates faults on an internal cycle counter.
Only faults which occur during compressor operation and
which cause the compressor to shut off are counted. After a
fault is counted, the control stops unit operation, resets and
begins a five minute time delay (step 2, operation sequence). If the control senses a fault at the end of five
minutes, the unit will not restart. If the control counts three
faults during the same thermostat demand, the control
locks out unit operation.
NOTE−If the control locks out, it can be reset by breaking thermostat demand for about five seconds then
remaking thermostat demand. Also, anytime thermostat demand is removed or power is interrupted, the
control resets to zero faults.
It is likely that the control could count three unit faults
from the crankcase temperature switch during a single
thermostat 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 sensors 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.
As the compressor windings cool, the resistance
through the sensors drops below the reset limit, the
control resets automatically and one fault is counted.
A fault occurs when
1− Compressor operation is monitored by high pressure
switch and crankcase temperature thermostat. These
controls are wired in series. If either one trips, compressor operation is interrupted and one fault is
counted. High pressure switch must be reset manually
but crankcase temperature switch resets automatically.
IMPORTANT-If the cycle counter counts three faults
during the same thermostat demand, the control locks
out. The outdoor unit remains inoperable until thermostat demand is broken. This indicates further
troubleshooting is needed. Though the control can be
reset by breaking thermostat demand, the unit may remain inoperable. The high pressure or high
temperature conditions may still exist and must be located and corrected before the unit can be placed back
in service.
NOTE-Intermittent continuity (bad connection or failing
components) can cause false lockout or lit LED. Check
all electrical connections thoroughly.
The sensors can be checked by measuring resistance
(ohms) through the sensors with the wires disconnected from the control (unit not running). The sensor
wires are not polarity sensitive. Table 3 shows winding
temperature sensor resistance values which will cause
the TSC to lock out. When the unit is operating normally, the resistance through the sensors should be below
the trip value shown in table 3.
The control can be checked by comparing the resistance measured through the sensors to the voltage
measured across the sensor terminals with the unit
running. Table 4 shows voltage measured across twospeed control terminals S1 and S2 with the
compressor running.
Page 8
Compressor Winding
Temperature Sensor
TSC−2 Bristol or Copeland
Compressor
Two-Speed Control Manual Override
TABLE 3
Trip Ohms
Temp. Rise
25K to 35K8.4K to 10K
Reset Ohms
Temp. Fall
tion). If compressor starts, the control is good and should
not be replaced. Proceed through the troubleshooting flowchart in the Unit Information Manual to locate the source of
the lockout. If the compressor does not start, a problem
probably exists elsewhere in the unit. Check the unit voltage and proceed through the unit troubleshooting
flowchart in the Unit Information Manual.
The manual override button is designed to be an aid in servicing and troubleshooting the control or the unit. When the
button is pushed and then released, the control bypasses
the five minute override delay.
TABLE 4
COMPRESSOR WINDING SENSOR
OPERATING RANGE
Resistance Through
Compressor Winding
Temperature Sensor
K-ohms (ohms x 1000)
0
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.
Voltage Across TSC Ter-
minals S1 and S2 with
Unit Running
DC Volts +.15
.02
.92
3.4
3.9
4.3
4.7
5.6
6.0
---
6.3
6.8
7.0
Reset
Range
Trip
Range
LED ON"
MEANS TSC FAULT" CONDITION
If the unit will not run and the LED is lit, the TSC may be in
Safety Dormant Lockout (a lockout caused by self-test failure or high voltage spike).
To determine if the control is in Safety Dormant Lockout,
briefly turn off power at the disconnect. When power is restored, check the LED. If the LED is lit, the control is
damaged and must be replaced. If the LED is not lit, the
control is probably good and should not be replaced until
eliminated by all other checks. Confirm this by activating
the compressor (press and release the override button with
thermostat demand present). If the compressor starts, the
control was in safety dormant lockout (due to high voltage
spike or self-test failure) and the control should not be replaced. If the compressor does not start, the control is
probably good and the problem is located elsewhere in the
unit. Proceed through the troubleshooting flowchart to locate the problem. Start by checking all manually reset
controls (high pressure switch etc...)
Service Instructions:
Do not use the override button for eleven seconds after
power-up. If the button is pushed during the ten second
power-up delay, the button has no effect. The control completes the five minute delay.
LED OFF"
MAY MEAN UNIT FAULT" CONDITION
If the unit will not run and the LED is not lit, a unit lockout
condition is indicated. Breaking and remaking thermostat
demand will reset the control. Activate the compressor by
pressing and releasing the override button (see illustra-
1− If light comes on and stays lit, turn off power at dis-
connect for at least 3 seconds.
NOTE−Breaking thermostat demand will not reset the
control if the control is in a Safety Dormant Lockout.
2− If LED is on when power is restored, replace TSC.
3− If light goes out see troubleshooting flowchart in
Unit Information Manual.
Page 9
TSC-3 Two-Speed Control
All early model HP21 -2 series units (single and three
phase) are equipped with a TSC-3 two-speed control. The
speed-control thermostat (formerly key number S55) has
been removed from the unit and incorporated into the circuitry of the TSC-3 control (see figure 6). The function and
operating sequence are otherwise identical to the TSC-2
plus the separate thermostat used in previous HP21 units.
The purpose of the speed control thermostat is to force the
compressor to operate on high speed when outdoor temperature is low. It initiates a speed change delay and
automatically energizes high speed when temperature
drops below the setpoint. The setpoint is factory preset and
can be field adjusted.
TSC-3 TWO-SPEED CONTROL
(with built in speed control thermostat)
TSC
TWO-SPEED CONTROL
When temperature rises above the setpoint, the control
initiates a speed change delay and automatically energizes low speed.
The setpoint can be changed by adjusting the potentiometer shown in figure 6. The potentiometer is factory
set as shown in table 5.
TABLE 5
Speed Control Thermostat
Adjustable Range
Cut-In
(Close on Temperature Drop)
Cut-Out
(Open on Temperature Rise)
Min.
37+2°F42+2°F 55+2°F
47+2°F52+2°F 65+2°F
46+2°F
56+2°F
Mid.
Factory
Setting
Max
.
To adjust the speed control thermostat, insert a small
slot screwdriver into the potentiometer as shown in figures 6 and 7. To lower the setpoint, turn the
potentiometer counter-clockwise. To raise the setpoint,
turn the potentiometer clockwise. Do not force the potentiometer to turn past its stops; the potentiometer will
be damaged.
SENSOR
TEMPERATURE
ADJUSTMENT
(potentiometer)
FIGURE 6
J44
SCREWDRIVER
TSC-3 TWO-SPEED CONTROL
WINDING TEMPERATURE
SENSOR TERMINALS
OVERRIDE
BUTTON
(5 minute delay)
TEMPERATURE
SENSOR
TEMPERATURE ADJUSTMENT
(shown in factory position)
FIGURE 7
The unit wiring diagrams have been revised to reflect the
changes for the HP21-2 (TSC-3), and are shown in section
VII−Wiring Diagrams and Operation Sequence.
Page 10
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 control. The TSC-6 (A14) two-speed control contains relays
which energize compressor operation in response to
thermostat demand. High speed operation can be energized and de-energized without passing through low
speed. The control also contains safety timed-off delays
and compressor over-temperature sensing which protect the compressor. The control has an external
temperature probe to lock out low speed during low temperatures, 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.
TSC-6 SHOWN
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 compressor 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 operation. 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 troubleshooting, 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 immediately energized. However, the control provides a
one-minute delay between speed changes, which cannot be bypassed.
Do not use the override button immediately after powerup. 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.
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 fiveminute 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) energizes 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 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 system. 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 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 resets (see unit fault conditions section) and returns to
step two.
6− General Operation
On power-up, the control begins a ten-second initial
delay.
Page 11
MANUAL
OVERRIDE
BUTTON
COMPRESSOR
SENSOR
CONNECTORS
HEARTBEAT
LED
MODE
SELECTION
JUMPERS
TSC-6 (A14) TWO-SPEED CONTROL COMPONENTS
OPTION 1 ENABLE
JUMPER
OPTION 2 ENABLE
JUMPER
DIAGNOSTIC LEDs
D8, D4, D2, D1
Y1 LED
LOW SPEED lock out
TEMP. ADJUSTMENT
OUTDOOR
TEMP. SENSOR
CONNECTOR
OPTION 1
CONNECTOR
JP44-124VAC POWER (INPUT)
JP44-224VAC COMMON
JP44-324VAC (SPARE, NOT USED)
JP44-42nd STAGE THERMOSTAT DEMAND
JP44-5THERMOSTAT COMMON (C)
JP44-61st STAGE THERMOSTAT DEMAND
JP44-724VAC FROM SAFETY SWITCHES
If the control is in low speed operation, high speed operation,
OFF" mode or speed change delay, the control counts" or accumulates faults on an internal cycle counter. Only faults which
occur during compressor operation and which cause the compressor to shut off are counted. After a fault is counted, the
control stops unit operation, resets and begins a five-minute
time delay (step 2, operation sequence). If the control senses a
fault at the end of five minutes, the unit will not restart. If the
control counts three faults during the same thermostat demand, the control locks out unit operation.
FIGURE 9
IMPORTANT
If the cycle counter counts three faults during the
same thermostat demand, the control locks out. The
outdoor unit remains inoperable until thermostat demand is broken. This indicates further troubleshooting is needed. Though the control can be reset by
breaking thermostat demand, the unit may remain inoperable. The high pressure or low pressure conditions may still exist and must be located and corrected before the unit can be placed back in service.
See diagnostic codes to determine problem.
Page 12
IMPORTANT
If the control locks out, it can be reset by breaking
thermostat demand for about five seconds then remaking thermostat demand. Also, anytime thermostat 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 operation 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 thermostat 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 sensors 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 resistance 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 sensitive. 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.
IMPORTANT − Normal resistance values of these compressors 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
Ohms
Trip Ohms
Temp R i s e
Reset Ohms
Temp F a l l
watt resistor in series with one of the sensor connections on
the two−speed control. (The resistor can be found at electronic 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 resistance measured through the sensors to the voltage
measured across the sensor terminals with the unit
running. Table 7shows voltage measured across twospeed control terminals S1 and S2 with the
compressor running.
TABLE 7
COMPRESSOR WINDING SENSOR
OPERATING RANGE
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.
Resistor
S1
S2
Compressor
+-
Voltage Across TSC-6
compressor sensor terminals
with Unit Running DC Volts
0
1.70 − 1.82
6.07 − 6.48
6.86 − 7.33
7.55 − 8.07
8.16 − 8.72
9.69 − 10.36
10.34 − 11.05
10.82 − 11.57
10.93 − 11.68
11.35 − 12.14
11.68 − 12.48
S1
S2
Short in Sensor
Reset
Range
Trip
Range
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
Latch 2:After the unit operates in low speed for 15
minutes consecutively, it switches to high
speed until low speed demand is satisfied.
Latch 3:After the unit operates in low speed for 30
minutes consecutively, it switches to high
speed until low speed demand is satisfied.
Recall:Used in conjunction with the bypass
button to recall the stored problem codes.
Test:Used in conjunction with the control
button to start test mode.
Latch 2 or 3 modes are recommended in high humidity areas.
If the jumper falls off or is removed, the control will continue to
operate in the previously set mode until the control is reset due
to loss of power, then the control will default to the Normal
mode.
TEST MODE
The control has a test mode. To initiate this mode, move the
jumper to the test position and push the control button. The
unit will operate in low speed for 10 seconds, turn off for ten
seconds, then operate in high speed for 10 seconds. The control will only go into the test mode if there is no thermostat
demand and 5 minutes has elapsed since the unit ran. The indoor blower does not run during this mode. The test mode
cannot run more than once every 5 minutes.
LED LIGHTS
Y1 and Y2 lights are connected directly to the inputs from the
thermostat. They indicate low and high speed demand, respectively.
The HI and LO lights are connected directly across the contactor coils. They indicate if the high and low speed contactors are
energized.
The HEARTBEAT light is connected to the microcontroller unit
(MCU). It indicates when the control’s MCU is operating correctly, and also when the control is in delay mode. It blinks at a
rate of four times a second when the MCU is operating properly and at a rate of once every two seconds when in the delay
mode (such as the 1 or 5 minute delay). If the LED is continuously on or off (assuming the power is on), the MCU is not
operating properly and the control needs to be replaced.
The D1, D2, D4, and D8 (see figure 8) diagnostic lights display
diagnostic codes to aid in unit troubleshooting. Refer to Diagnostic Code Table (table 8).
Diagnostic Code Display
A problem code is normally displayed only for the duration of
the error. There is one exception. During a lock out, the code
for the problem causing the lock out flashes once a second
even if the problem condition no longer exists. If other problems occur during a lock out condition, the codes for those
problems will be saved in memory, but not displayed. The
stored problem codes are displayed by recalling them from
memory. The diagnostic codes can be re-displayed by setting
the jumper to the recall position. The stored codes are dis-
played by pushing the push button. As previously mentioned,
the push button is used to bypass the five-minute delay and to
initiate the test mode. In addition, the button is used to step
back through the stored diagnostic codes and erase the diagnostic code memory. Diagnostic codes are recalled in the
reverse order of actual occurrence. Each subsequent button
push will display additional codes until the last one, which will
stay on with additional button pushes. Hold the button down
until the lights go off (approximately five seconds) to erase the
memory. The control has a nonvolatile memory that stores the
63 most recent diagnostic codes. These codes are stored in
memory, even in the event of a power loss.
Not all codes cause lock outs or indicate problems. The purpose of the diagnostic lights is to let the installer or service
technician know what is going on with the entire system, not
just the two−speed control. Some codes do indicate malfunctions or problems with either the control or the HP21, while
others inform the technician of the unit’s status. All codes, except for three, are stored in memory and may be recalled.
Code 1 − Power Loss for Two Electrical Cycles
This code indicates that the unit’s power skipped two electrical cycles (33−40 milliseconds). It may suggest that
power to the unit is dirty" or is of low quality. Code 1 is
stored.
Code 2 − Input Indication
This code indicates that a change has been made and
that the control acknowledges the change. It does not indicate a problem condition. It indicates activity such as
jumper setting changes, delay overrides, or addition of
an optional safety device to Option 1 or 2. Code 2 is not
stored.
Code 3 − Unsteady Thermostat Input
Code 3 indicates intermittent inputs from the room thermostat. Most likely, there is a loose connection at the
thermostat when this condition appears. Code 3 is
stored.
Code 4 − Pressure Switch Opens < Two Minutes
If the low or high pressure switch opens after the compressor
has run for less than two minutes, Code 4 will be displayed.
This may indicate blockage or fan failure. Code 4 is stored. If
the unit still operates after code is displayed, the low pressure
switch stops operation (low pressure is auto−reset). Check for
low system charge.
Code 5 − Pressure Switch Opens > Two Minutes
If the low or high pressure switch opens after the compressor has run for more than two minutes, Code 5 is
displayed. This may indicate an improper charge or coil
obstruction. Code 5 is stored. If the unit still operates after code is displayed, the low pressure switch stops
operation (low pressure is auto−reset). Check for low system charge.
Code 6 − Hot Compressor < Five Minutes
Code 6 indicates the compressor temperature exceeded its limit after running less than five minutes. Code 6
is stored.
Page 14
TSC-6 DIAGNOSTICS CODES
CODE
TABLE 8
CODE
NUMBER
1Power loss for two
2Input IndicationOFF OFFONOFF
3Unsteady InputOFFOFFONON
4Pressure Switch Open
5Pressure Switch Open
6Hot Compressor < 5
7Hot Compressor > 5 min.
8Option 1 < 5 minutesONOFFOFFOFF
9Option 1 > 5 minutesONOFFOFFON
10Option 2 OpenONOFFONOFF
11Compressor Temp.
12Outdoor temperature
13Not UsedONONOFF
14Test Mode ONONONOFF
15No Jumper in place
CONDITION
cycles
<2 minutes
> 2 minutes
min. (or open sensor)
(or open sensor)
Sensor Problem
Sensor
Indication
DISPLAY LIGHTS
8421
OFFOFFOFFON
OFFONOFFOFF
OFFONOFFON
OFFONONOFF
OFFONONON
ONOFFONON
ONONOFFOFF
ON
ONON
ON
ON
Code 7 − Hot Compressor > Five Minutes
Code 7 indicates the compressor temperature exceeded
its limit after running more than five minutes. Code 7 is
stored.
Code 8 − Option 1 < Five Minutes
Code 8 occurs if the Option 1 safety device switch opens after the compressor runs less than five minutes. Code 8 is
stored.
Code 9 − Option 1 > Five Minutes
Code 9 occurs if the Option 1 safety device switch opens after
the compressor runs more than five minutes. Code 9 is
stored.
Code 10 − Option 2
Code 10 is displayed if the Option 2 safety device switch
opens. Code 10 is stored.
Code 11 − Compressor Temperature Sensor Shorted
This code indicates that the compressor temperature sensor
wires have shorted together. Code 11 is stored.
Code 12 − Outdoor Temperature Sensor
This code indicates a problem with the operation of the outdoor temperature sensor. Code 12 is stored.
Code 13 − Not Used
This code may be used in future models of the two−speed control, but at this time has no function and, therefore, is not
stored.
Code 14 − Test Mode
Code 14 does not indicate a problem. The control is in TEST
mode when this code is displayed. See Mode Jumper Selections section.
Code 15 − No Jumper in Place
Code 15 is displayed when the mode jumper is not in place.
Make sure jumper is placed securely across the selected set of
pins for the appropriate mode of operation.
SERVICE RELAY
The control has a built-in service relay. This relay controls the
thermostat service light or communicates with an alarm device. The relay signals the alarm device in such a manner that
the alarm device can distinguish between a lock out and a nonlock out condition. The relay contacts are normally open when
no problems or lock out conditions occur. A non-lock out condition is reported by closing the contacts for the duration of the
next no-demand period. If the control goes into a lock out state,
the relay will close and remain closed until the next loss of demand. If the service light on the room thermostat is connected
to the service relay, the light will turn on if the control is in a lock
out. It will not turn on if the control is detecting non-lock out
problems. In order for the service relay to indicate only a lock
out condition, one side of the relay must be wired to the alarm
and the other side to Y2. During a simultaneous Y1, Y2 demand with a non-lock out condition, the alarm will energize for
a very short duration (.2 seconds). If both an alarm device and
thermostat service lights are used, an additional external relay
may be required depending on thermostat used.
OPTIONAL INPUTS
The control has two optional inputs for additional protection devices. If options 1 or 2 are going to be used, move the three pin
mini-jumper to the YES side. OPT 1 input will lock out the compressor on the third count. OPT 2 input will not lock out the
compressor at any time, but will display and store the problem
code (see Diagnostic code Table). These inputs are designed
for normally closed switches connected to 24VAC.
CAUTION
Do not remove the jumpers unless additional
protection controls are going to be installed. If OPT
1 jumper is not connected to the NO pin, the control
will lock out the compressor. If OPT 2 is not connected to the NO pin, the display only shows the
problem code.
The unit wiring diagrams have been revised to reflect the
changes for the HP21-4/-5 (TSC-6), and are shown in section
VII−Wiring Diagrams and Operation Sequence.
Page 15
Q−Speed Control Thermostat S55
(Early Model HP21 −1 series units only)
The indoor thermostat regulates compressor speed when
the unit is operating in cooling mode. When the unit is oper-
ating in heating mode, speed control thermostat S55
regulates compressor speed.
ADJUSTING SPEED CONTROL THERMOSTAT
Adjustment screw can be
accessed by inserting screwdriver through slot in underside
of control box.
1st stage heating demand from the indoor thermostat ener-
gizes the compressor (Y1 demand). Speed control
thermostat S55 controls compressor speed. Additional
heating demand from the indoor thermostat (W1 demand)
energizes the indoor auxiliary heat.
Speed control thermostat S55 (figure 10) is a SPST thermostat located in the unit control box. The control uses a
cap-tube sensor to monitor the temperature inside the control box. The cap-tube sensor is coiled adjacent to the
control.
SPEED CONTROL THERMOSTAT S55
Temperature Sensor
(Cap-Tube)
FIGURE 10
S55 continually monitors the temperature inside the control
box. When control box temperature drops below the control setpoint, the control closes. When the control closes,
the contacts shunt across Y1 and Y2 inside the unit. When
heating demand is present and S55 is closed, the two-
speed control electrically sees a high speed demand. The
compressor operates at high speed until control box warms
and S55 opens.
TABLE 9
Speed Control Thermostat
Adjustable Range
Cut-In
(Close on Temperature Drop)
Cut-Out
(Open on Temperature Rise)
Min
37+2°F40+2°F55+2°F
47+2°F50+2°F65+2°F
Factory
Setting
.
Max
.
S55 has field adjustable setpoints. Temperature differential
(difference between cut-in and cut-out) is fixed and cannot
be adjusted. Table 9 shows S55 control setpoints.The control is factory set to close at 40+2°F on a temperature drop
and reset at 50+2°F on a temperature rise.
Turn screw clockwise to increase
switchover temperature.
FIGURE 11
Regional climatic conditions may require the control to be adjusted to a different setting. The adjustment screw is located
on the bottom of the control. A hole cut into the bottom shelf of
the control box provides access to the speed control from the
compressor compartment (see figure 11). Figure 12 shows
the adjustment range of the control. Turn adjustment screw
clockwise to raise the switchover temperature and counterclockwise to lower the switchover temperature.
SPEED CONTROL THERMOSTAT
43
*HP21 FACTORY
SETTINGS
49
*40
37
ADJUSTMENT
SCREW
55
FIGURE 12
R−Reversing Valve and Solenoid L1
A refrigerant reversing valve with electromechanical solenoid is used to reverse refrigerant flow during unit
operation. The reversing valve is energized during cooling
demand and during defrost.
S−Ambient Compensation Thermistor RT3
HP21 units are equipped with an ambient compensation
thermistor (RT3) attached to the outdoor fan motor bracket.
The thermistor is connected in series with the heat anticipation resistor inside the indoor thermostat. The thermistor
helps to prevent abnormal droop caused by the anticipation
resistors. RT3 is a NTC thermistor (negative temperature
coefficient; increase in temperature equals decrease in resistance). As outdoor temperature increases, the
resistance through RT3 drops. As the resistance across
RT3 drops, the current through the heat anticipation resistor increases. Therefore, heat anticipation increases as
outdoor temperature decreases. RT3 resistance values
are shown in table 10.
Page 16
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