Heat Pump Service

1
Heat Pump Service
2
HEAT PUMPS

• TOTAL ELECTRIC UNIT CAPABLE OF PROVIDING HEATING
  AND COOLING
• MOVES HEAT WITH REFRIGERATION SYSTEM.
• CURRENT TECHNOLOGY ALLOWS US TO ABSORB ENERGY
  FROM THE OUTDOOR AIR EFFICIENTLY, DOWN TO 20º.

3
During the winter months the heat pump
absorbs heat from the outdoor air.

• Then releases the heat (energy) into the indoor
  air.
• There is energy (heat) present to minus 460º.
• Just as it is more efficient to move an object
  than it is to build or make one. It is more
  energy efficient to move heat, than generate it
  (depending on thermal/economic balance points).

4
Heat pumps are sized for the cooling demand of
the application.

• The heat pump will be the sole source of cooling
  for the application. It may be the only source of
  heat, depending on heating requirements.
• Most areas of the country will also require an
  additional source of heat. This may be as little
  as a 5KW heat strip, or as much as a 80,000 BTU
  furnace.
• Well look at this in more detail later.

5
HEAT PUMPS

• COOLING SEASON
• HEAT PUMP PERFORMS THE SAME AS ANY AIR
  CONDITIONING SYSTEM BY PICKING UP HEAT FROM THE
  SPACE TO BE CONDITIONED AND REJECTING IT OUTDOORS

6
HEAT PUMPS

• HEATING SEASON
• UNIT ABSORBS HEAT FROM THE OUTDOOR AIR AND MOVES
  IT TO THE CONDITIONED SPACE
• REVERSE-CYCLE AIR CONDITIONERS

7
HEAT PUMPS

• CLASSIFIED BY THE SOURCE OF HEAT DURING THE
  HEATING CYCLE AND THE MEDIUM TO WHICH THE HEAT IS
  TRANSFERRED
• AIR-TO- AIR
• WATER-TO-AIR

8
INSIDE THE HEAT PUMP

• COMPRESSOR CAPABLE OF OPERATING AT LOW OUTDOOR
  TEMPERATURES
• INDOOR / OUTDOOR COIL DESIGN
• METERING DEVICE FOR INDOOR / OUTDOOR COIL
• REVERSING VALUE ( 4-WAY VALUE )
• ACCUMULATOR
• CRANKCASE HEATER
• AUXILIARY HEAT
• EMERGENCY HEAT
• DEFROST CYCLE

9
HEAT PUMP

• ACCUMULATOR
• CLIMATUFF - PART OF COMPRESSOR SHELL
• LOCATED IN SUCTION LINE BETWEEN THE COMPRESSOR
  AND REVERSING VALUE
• WHY HAVE ONE?
• MOST IMPORTANT
• HEATING CYCLE - COLD TEMPERATURES, OUT DOOR COIL
  MAY NOT BE ABLE TO EVAPORATE ALL THE REFRIGERANT
• END OF DEFROST CYCLE
• LIQUID CARRYOVER WILL BE CAUGHT BY THE
  ACCUMULATOR TO PREVENT COMPRESSOR DAMAGE

10
WHAT MAKES A HEAT PUMP UNIQUE

• SPECIAL COMPRESSOR
• MUCH HIGHER COMPRESSION RATIO
• MOST SEVERE APPLICATION
• HEAT PUMP COILS
• ALTERNATELY FUNCTION AS EVAPORATOR AND CONDENSER
• MUST TOLERATE CHARGE IMBALANCE
• OUT DOOR COIL MUST BE DESIGNIED FOR EASY DEFROST

11
HEAT PUMP

• CRANKCASE HEATER
• LOCATED ON COMPRESSOR, OLDER SYSTEMS USED
  COMPRESSOR WINDINGS.
• RAISES TEMPERATURE OF OIL SO THAT THE ABSORPTION
  OF REFRIGERANT INTO THE COMPRESSOR IS KEPT TO A
  MINIMUM

12
COOLING CONDITION
INDOOR COIL
SAT. SUCT. T. 41F ENT. AIR T. 76F
4-WAY VALUE
SUCT. P. 70 PSIG SUCT. T. 52F SUPERHEAT 11F
METERING DEVICE SUBCOOLING 10F
DISCHARGE PRESSURE 260 PSIG
OUTDOOR COIL
SAT. COND. T. 120F ENT. AIR T. 90F
COMPRESSOR
13
HEATING CONDITIONS
INDOOR COIL
SAT. COND. T. 95F ENT. AIR T. 70F
4-WAY VALUE
METERING DEVICE SUBCOOLING 10F
METERING DEVICE SUBCOOLING 10F
SUCT. P. 43 PSIG SUCT. T. 35F SUPERHEAT 10F
DISCHARGE PRESSURE 182 PSIG
OUTDOOR COIL
SAT. SUCT. T. 20F ENT. AIR T. 45F
COMPRESSOR
14
HEAT PUMP

• TOTAL HEAT REJECTED EQUALS
• HEAT ABSORBED
  HEAT OF COMPRESSOR

15
HEAT PUMP

• THE REVERSING VALUE
  CONTROLS THE
• DIRECTION
• THE REFRIGERANT FLOWS

16
COOLING CONDITION
INDOOR COIL
SAT. SUCT. T. 41F ENT. AIR T. 76F
4-WAY VALUE
SUCT. P. 70 PSIG SUCT. T. 52F SUPERHEAT 11F
METERING DEVICE SUBCOOLING 10F
DISCHARGE PRESSURE 260 PSIG
OUTDOOR COIL
SAT. COND. T. 120F ENT. AIR T. 90F
COMPRESSOR
17
HEATING CONDITIONS
INDOOR COIL
SAT. COND. T. 95F ENT. AIR T. 70F
4-WAY VALUE
METERING DEVICE SUBCOOLING 10F
METERING DEVICE SUBCOOLING 10F
SUCT. P. 43 PSIG SUCT. T. 35F SUPERHEAT 10F
DISCHARGE PRESSURE 182 PSIG
OUTDOOR COIL
SAT. SUCT. T. 20F ENT. AIR T. 45F
COMPRESSOR
18
Heat pump Thermostats

• Thermostats with adjustable heat anticipation
  need to have it adjusted for proper operation!

19
F
HEAT
COOL
OFF
O
HA
CA
BAYSTAT239 OR 240 HEAT PUMP THERMOSTAT
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
T
TSH
W
BL
U
RD
B
R
20
Fault Indication Light
F
HEAT
COOL
OFF
O
HA
CA
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
T
TSH
W
BL
U
RD
B
R
21
(No Transcript)
22
Fault Indication Light
F
HEAT
COOL
OFF
SOV Energized In Cooling
O
HA
CA
Brings On Compressor In Both Heating And Cooling
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
T
TSH
W
BL
U
RD
B
R
23
Fault Indication Light
F
HEAT
COOL
OFF
SOV Energized In Cooling
O
HA
CA
Brings On Compressor In Both Heating And Cooling
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
Energizes Auxiliary Heat When Unit Is In Defrost
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
T
TSH
W
BL
U
RD
B
R
24
Fault Indication Light
F
HEAT
COOL
OFF
SOV Energized In Cooling
O
HA
CA
Brings On Compressor In Both Heating And Cooling
NORM
Y
C1
TS
RHS-1
COOL
H1
Energizes Auxiliary Heat When Unit Is In Defrost
X2
HEAT
AUTO
FAN
G
SM-2
Brings On Indoor Fan
ON
RHS-2
NORM
T
TSH
W
BL
U
RD
B
R
25
Fault Indication Light
F
HEAT
COOL
OFF
SOV Energized In Cooling
O
HA
CA
Brings On Compressor In Both Heating And Cooling
NORM
Y
C1
TS
RHS-1
COOL
H1
Energizes Auxiliary Heat When Unit Is In Defrost
X2
HEAT
AUTO
FAN
G
SM-2
Brings On Indoor Fan
ON
RHS-2
NORM
Part of Heat Anticipation Circuit (Used with
Trane Electro-Mechanical Tstats
T
TSH
W
BL
U
RD
B
R
26
Fault Indication Light
F
HEAT
COOL
OFF
SOV Engerized In Cooling
O
HA
CA
Brings On Compressor In Both Heating And Cooling
NORM
Y
C1
TS
RHS-1
COOL
H1
Energizes Auxiliary Heat When Unit Is In Defrost
X2
HEAT
AUTO
FAN
G
SM-2
Brings On Indoor Fan
ON
RHS-2
NORM
Part of Heat Anticipation Circuit (Used with
Trane Electro-Mechanical Tstats
T
TSH
This Is The Second Stage-Brings On The Electric
Heat
W
BL
U
RD
B
R
27
Fault Indication Light
F
HEAT
COOL
OFF
SOV Engerized In Cooling
O
HA
CA
Brings On Compressor In Both Heating And Cooling
NORM
Y
C1
TS
RHS-1
COOL
H1
Energizes Auxiliary Heat When Unit Is In Defrost
X2
HEAT
AUTO
FAN
G
SM-2
Brings On Indoor Fan
ON
RHS-2
NORM
Part of Heat Anticipation Circuit (Used with
Trane Electro-Mechanical Tstats
T
TSH
This Is The Second Stage-Brings On The Electric
Heat
W
BL
U
Functions As An Internal Connection For The Blue
Light
RD
B
R
28
Fault Indication Light
F
HEAT
COOL
OFF
SOV Engerized In Cooling
O
HA
CA
Brings On Compressor In Both Heating And Cooling
NORM
Y
C1
TS
RHS-1
COOL
H1
Energizes Auxiliary Heat When Unit Is In Defrost
X2
HEAT
AUTO
FAN
G
SM-2
Brings On Indoor Fan
ON
RHS-2
NORM
Part of Heat Anticipation Circuit (Used with
Trane Electro-Mechanical Tstats
T
TSH
This Is The Second Stage-Brings On The Electric
Heat
W
BL
U
Functions As An Internal Connection For The Blue
Light
RD
B
This Is The Common Side Of The Transformer
R
29
Fault Indication Light
F
HEAT
COOL
OFF
SOV Engerized In Cooling
O
HA
CA
Brings On Compressor In Both Heating And Cooling
NORM
Y
C1
TS
RHS-1
COOL
H1
Energizes Auxiliary Heat When Unit Is In Defrost
X2
HEAT
AUTO
FAN
G
SM-2
Brings On Indoor Fan
ON
RHS-2
NORM
Part of Heat Anticipation Circuit (Used with
Trane Electro-Mechanical Tstats
T
TSH
This Is The Second Stage-Brings On The Electric
Heat
W
BL
U
Functions As An Internal Connection For The Blue
Light
RD
B
This Is The Common Side Of The Transformer
This Is The Other Side Of 24 Volts From The
Transformer
R
30
F
HEAT
COOL
OFF
O
HA
CA
BAYSTAT239 OR 240 HEAT PUMP THERMOSTAT
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
T
TSH
W
BL
U
RD
B
R
31
F
HEAT
COOL
OFF
O
HA
CA
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
T
TSH
W
BL
U
RD
B
R
32
F
HEAT
COOL
OFF
O
HA
CA
NORM
FAN ON - ON
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
T
TSH
W
BL
U
RD
B
R
33
BAYSTAT240A
F
HEAT
COOL
COOLING ON FAN - AUTO
OFF
O
HA
CA
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
ODA
T
TSH
W
BL
U
RD
B
R
COOLING ON FAN - AUTO
34
BAYSTAT240A
F
HEAT
COOL
OFF
O
HA
CA
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
ODA
T
TSH
W
BL
U
RD
B
R
COOLING ON FAN - AUTO
35
F
HEATING - ON - FIRST STAGE FAN - AUTO
HEAT
COOL
OFF
O
HA
CA
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
ODA
15 TO 22 VOLTS (T) FROM ODS-A TO (R)
T
TSH
W
BL
U
RD
B
R
36
BAYSTAT240A
F
HEAT
COOL
OFF
O
HA
CA
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
ODA
T
TSH
W
BL
INDOOR UNIT
U
RD
G
B
B
W1
R
R
37
OUTDOOR UNIT
BAYSTAT240A
Defrost Board
F
HEAT
COOL
OFF
O
HA
CA
NORM
R
Y
C1
TS
Y
RHS-1
R/W
COOL
H1
X2
X2
HEAT
O
AUTO
BL
FAN
G
SM-2
BL
ON
RHS-2
Y
NORM
O
ODA
T
TSH
ODS-A
W
BL
INDOOR UNIT
U
RD
G
B
B
W1
R
R
38
HEATING - ON - 2ND STAGE FAN - AUTO
F
HEAT
COOL
OFF
O
HA
CA
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
ODA
15 TO 22 VOLTS (T) FROM ODS-A TO (R)
T
TSH
W
BL
U
RD
B
R
39
F
HEAT
COOL
OFF
24 VOLT S (O) FROM DEF. BRD
O
HA
CA
NORM
Y
C1
TS
RHS-1
24 VOLT S (X2) FROM DEF. BRD
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
ODA
15 TO 22 VOLTS (T) FROM ODS-A TO (R)
T
TSH
W
BL
U
RD
B
R
40
BAYSTAT240A
HEATING ON EMERG. HTG (OPERATES 1.5 BELOW
SETPOINT) FAN - AUTO
F
HEAT
COOL
OFF
O
HA
CA
NORM
Y
C1
TS
RHS-1
COOL
H1
X2
HEAT
AUTO
FAN
G
SM-2
ON
RHS-2
NORM
ODA
T
TSH
W
BL
INDOOR UNIT
U
RD
G
B
B
W1
R
R
41
WHAT IS COOLING DROOP?

• Cooling droop is caused by the cooling
  anticipator heating up during the off cycle,
  causing the tstat to come on sooner, to help
  overcome the thermal lag of the system.
• This also provides night time cooling that helps
  keep humidity under control

42
DROOP (cont)

• Then there is Heating Droop.
• Heating Droop moves the temperature in the wrong
  direction. To compensate for this, the T
  circuit is added.

43
WHAT DOES THE T CIRCUIT HAVE TO DO WITH
ANYTHING?

• The T circuit is a heat anticipation circuit
  that adds heat to the thermostat to slow down
  thermostat response, and removes heat to speed up
  the response.

44
T Circuit

• As the outdoor temperature drops, the resistance
  in the T, actually a thermistor (ODS-A), goes
  up.
• The higher the resistance, the less voltage is
  supplied to the resistor (ODA) located inside the
  thermostat.
• The less voltage to the ODA, the colder the
  tstat thinks it is.

45
DEFROST THERMISTOR RESISTANCE
10000
9000
8000
7000
6000
5000
RESISTANCE
4000
3000
2000
1000
75
115
35
-40
0
OUTDOOR TEMPERATURE
46
-20F
.0034 A
4000
3000
13.6 V
10.4 V
.047 W
.036 W
47
-20F
.0034 A
4000
3000
ODS-A
13.6 V
10.4 V
.047 W
.036 W
.0048 A
2000
0F
3000
9.6 V
14.4 V
.046 W
.069 W
48
-20F
.0034 A
4000
3000
ODS-A
13.6 V
10.4 V
.047 W
.036 W
.0048 A
2000
0F
3000
ODS-A
9.6 V
14.4 V
.046 W
.069 W
.0063 A
30F
800
3000
5 V
19 V
.031 W
.119 W
49
-20F
.0034 A
4000
3000
ODS-A
13.6 V
10.4 V
.047 W
.036 W
.0048 A
0F
2000
3000
ODS-A
9.6 V
14.4 V
.046 W
.069 W
.0063 A
30F
800
3000
ODS-A
5 V
19 V
.031 W
.119 W
.0073 A
70F
300
3000
2.2 V
21.8 V
.013 W
.159 W
50
DEFROST BOARD DURING DEFROST
K2
OD Motor
230 VOLTS
BR/BL
TSTAT
R
R
Y
Y
K1
F
RD/W
X2
BK
O
O
T
BL
COMPR
Y
SOV
O
AMB.
SENSORS
COL
51
WHY IS THE BLUE LIGHT ON?
52
THE BLUE LIGHT IS AN INDICATION THAT THE
AUXILIARY HEAT IS ON.

• It is on in several instances.
• If the tstat is adjusted above set point.
• If the outdoor temperature is below 40F it will
  cycle off and on to maintain room temperature.
• If it stays on constantly above 30F or cycles on
  when the outdoor temp. is above 50F, the system
  should be checked.

53
WHY IS THE RED LIGHT ON STEADY?
54
The Red Light on steady is an indication the
Emergency Heat Switch is on.

• The switch is used only if the heat pump is
  inoperative, but not due to a power failure.
• Using the heating in this mode will increase your
  power consumption.
• The red light is to remind the customer that the
  temperature is being controlled by resistance
  heat only.

55
THE RED LIGHT ON, BUT IT IS FLASHING

• The Emergency Heat switch is in the Normal
  position.

56
RED LIGHT FLASHING

• If the red light is flashing, this is an
  indication that the defrost board has detected a
  defrost fault.
• Reset by moving the Emergency Heat Switch to the
  on position for 30 seconds.
• If the flashing returns, service on the heat pump
  may be required.

57
HEAT PUMP

• REVERSING VALUE
• ILLUSTRATION

58
SUCTION LINE
INDOOR COIL
OUT DOOR COIL
.
.
.
TP-4
TP-2
TP-3
.
TP-1
COMPRESSOR DISCHARGE
59
TO ACCUMULATOR
TO INDOOR COIL
FROM OUTSIDE COIL
.
.
.
TP-4
TP-2
TP-3
.
FROM COMPRESSOR DISCHARGE LINE
5F MAX TEMP. DIFFERENCE
TP-1
HEATING MODE
60
TO ACCUMULATOR
FROM INDOOR COIL
TO OUTDOOR COIL
.
.
.
.
.
.
.
TP-4
TP-3
TP-2
.
.
.
TP-1
FROM COMPRESSOR DISCHARGE LINE
5F MAX TEMP. DIFFERENCE
COOLING MODE
61
HEAT PUMP

• METERING DEVICES
• HEATING CYCLE, REFRIGERANT IS METERED TO THE
  OUTDOOR COIL
• COOLING CYCLE, REFRIGERANT IS METERED TO THE
  INDOOR COIL

62
HEAT PUMP

• METERING DEVICES
• REFRIGERANT METERED TO COIL WHICH ABSORBS HEAT
• HEATING CYCLE REFRIGERANT METERED TO OUTDOOR COIL
• COOLING CYCLE REFRIGERANT METERED TO INDOOR COIL

63
METERING DEVICES

• CAPTUBE
• FIXED ORFICE
• TXV

64
METERING DEVICES
FLOW BYPASSES METERING DEVICE
CHECK VALUE OPEN
METERING DEVICE
FLOW IS METERED
CHECK VALVE SHUT
METERING DEVICE
65
The role of the defrost control

• To extract heat from the outdoor air, the heat
  pump must lower its outdoor coil temperature
  below that of the outdoor ambient.
• Depending on the humidity and temperature, frost
  may form on the outdoor coil.
• This frost will insulate the coil from the
  outdoor air, reducing its ability to absorb the
  heat from the outdoor air.

66
HEAT PUMP DEFROST CONTROLS

• - CONTROLS THE DEFROST CYCLE IN A HEAT PUMP
  DURING HEATING OPERATION.
• - THE DEFROST CONTROL CONTROLS THE FOLLOWING
  FUNCTIONS
• 1 - SWITCH OVER VALVE OR REVERSING VALVE
• 2 - OUTDOOR FAN MOTOR
• 3 - ELECTRIC OR GAS AUX. HEAT
• 4 - INDICATES A FAULT HAS OCCURRED (OPTIONAL)
• - CONTROL THAT ESTABLISHES THE NEED FOR A DEFROST
• - BOTH TIMED AND DEMAND CONTROLS ARE USED TODAY
• - ELECTRO MECHANICAL TIMERS AND PRESSURE SWITCHES
  USED IN THE PAST

67
Heat pump defrost controls

• Several types of defrost controls have been used
  through the years.
• We will discuss their function and diagnostics of
  each type.
• The newer solid state and Demand Defrost controls
  will be the main focus of our time today.

68
As the frost accumulates on the outdoor coil, the
systems capacity is reduced.

• To remove the frost/ice from the outdoor coil,
  the system will shift itself into a variation
  the cooling mode.
• During a defrost cycle the outdoor fan will
  stop, leaving the heat in the coil to remove the
  frost.
• The type of defrost control system will dictate
  how much frost/ice is allowed to accumulate
  prior to initiating a defrost.

69
DEFROST CYCLE

• SYSTEM IN COOLING MODE- -ENERGIZE
  REVERSING VALVE
• DIRECTS HOT GAS TO OUTDOOR COIL TO MELT THE FROST

70
DEFROST CONTROLS

• THE MUCH OLDER EQUIPMENT UTILIZED
  ELECTRO-MECHANICAL TIME CLOCKS.
• ELECTRONIC TIMER - TIME TEMPERATURE DEFROST
• SOLID STATE - DEMAND DEFROST

71
DEFROST CYCLE

• TEMPERING INDOOR AIR
• ELECTRIC HEAT IS TURNED ON TO TEMPER THE AIR
  DURING DEFROST CYCLE.

72
DEFROST CYCLE

• OUTDOOR FAN OFF
• ENHANCES DEFROST

73
Electro-Mechanical systems

• All electro-mechanical systems are a
  time/temperature based control.
• A predetermined amount of time must pass before a
  defrost cycle can be initiated.
• As mentioned earlier, the outdoor conditions have
  major impact on the amount of defrost needed.
• These systems are temperature activated as well.

74
Large amounts of frost may accumulate before the
Time has elapsed.

• This results in lower seasonal efficiency.
• The reduced capacity will result with a greater
  dependence on a secondary heat source.

75
ELECTRONIC TIME-TEMPERATURE DEFROST CONTROL

• 50 - 70 - 90 MINUTE COMPRESSOR RUN TIME SELECTION
• 10 MINUTE TIME OVERRIDE IN DEFROST CYCLE
• TWO TEST PINS - ADVANCES ELECTRONIC TIMER AND
  PUTS SYSTEM INTO DEFROST CYCLE FOR TESTING
• ON BOARD DEFROST RELAYS FOR OUTDOOR FAN, SOV
  VALVE AND AUXILIARY HEAT
• DEFROST TERMINATED ON TIME OR TEMPERATURE
• COMPRESSOR RUN TIME IS KEPT ONLY WHEN COIL
  THERMOSTAT IS CLOSED

76
The defrost thermostat is set to close at 25º.

• When the DT is closed, supplying 24 VAC to the D
  terminal, jumpering the test pins will speed up
  the internal clock.
• If you are testing the system, and have a jumper
  from R to D, remove the jumper as soon as the
  system shifts into defrost. To prevent excessive
  refrigerant pressures.

77
These controls will default to the 90 minute
setting if the selector jumper is not connected.
Which is how the equipment is shipped.

• I recommend one of the shorter time settings, 50
  or 70 minutes.
• The water run off from a unit in defrost is pure
  water, and has never been reported to caused roof
  damage to date!
• Trying to catch the water could damage the
  outdoor coil (if the collected water froze and
  backed up under the coil).

78
TST EDR R R B B
X2 Y O O D
T
79
TST EDR R R B B
X2 Y O O D
T
80
TST EDR R R B B
X2 Y O O D
T
81
TST EDR R R B B
X2 Y O O D
T
82
TST EDR R R B B
X2 Y O O D
T
83
TST EDR R R B B
X2 Y O O D
T
84
TST EDR R R B B
X2 Y O O D
T
85
There are several versions of these DFC boards.
Many feature the exact same functions, with the
only difference being the terminal for the
defrost thermostat being labeled D or DT.
TST EDR R R B B
X2 Y O O D
T
86
There are several versions of these DFC boards.
Many feature the exact same functions, with the
only difference being the terminal for the
defrost thermostat being labeled D or DT.
TST EDR R R B B
X2 Y O O D
T
87
There are several versions of these DFC boards.
Many feature the exact same functions, with the
only difference being the terminal for the
defrost thermostat being labeled D or DT.
TST EDR R R B B
X2 Y O O D
T
88
There are several versions of these DFC boards.
Many feature the exact same functions, with the
only difference being the terminal for the
defrost thermostat being labeled D or DT.
TST EDR R R B B
X2 Y O O D
T
89
There are several versions of these DFC boards.
Many feature the exact same functions, with the
only difference being the terminal for the
defrost thermostat being labeled D or DT.
TST EDR R R B B
X2 Y O O D
T
90
DFC CNT1152ORCNT1642
K2
1
K1
M1
ODFAN
M2
90 70 50 TST EDR R R B
B X2 Y O O D T

24V AC24V COMMON
INDOOR THERMOSTAT

MS SC
CNT1152 may be replaced by CNT 1642
1
DT
91
DFCCNT1642
K2
K1
M1
ODFAN
M2
90 70 50 TST EDR R
R B B X2 Y O
O DT T

X2

INDOOR THERMOSTAT
YOT
SC
EDR

DT
EDR
24V AC 24V COMMON
ECONOMIZER(OPTIONAL)
EDC OR LPCO
MS
F
INDOORTHERMOSTAT
G
COMMON FORELECTRIC HEATER
TR TR1
92
TIMER DEFROST CONTROL
93
DEMAND DEFROST CONTROLS
94
DEMAND DEFROST

• FEATURES
• ADAPTABILITY
• LEARNING PROCESS
• DEFROST ON DEMAND
• DIAGNOSTICS
• TIME OVERRIDE
• SOFT SWITCHOVER

95
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96
DEMAND DEFROST CONTROLS
97
HEAT PUMP DEMAND DEFROST CONTROLS

• - TRANE DEMAND DEFROST CONTROLS OPERATE IN AN
  ADAPTIVE PROCESS TO OPTIMIZE THE HEAT PUMP
  PERFORMANCE.
• - THE DEMAND DEFROST CONTROL WILL ADAPT TO THE
  HEAT PUMP IT IS INSTALLED ON AND LEARN ITS
  OPTIMUM DEFROST CONDITIONS AND STORE THEM IN
  MEMORY.
• - THE DEMAND DEFROST CONTROL WILL ADJUST THE TIME
  BETWEEN DEFROST CYCLES TO MATCH THE WEATHER
  CONDITIONS.

98
HEAT PUMP DEMAND DEFROST CONTROLS

• - THE DEMAND DEFROST CONTROL WAS DEVELOPED BY
  TRANE IN 1984 AND IS PATENTED.
• - HEAT PUMP SYSTEMS WITH DEMAND DEFROST CONTROLS
  BENEFIT FROM A 6 HEATING SEASONAL PERFORMANCE
  FACTOR (HSPF) ADVANTAGE.
• - THERMISTOR SENSORS SENSE THE OUTDOOR AMBIENT
  TEMPERATURE AND OUTDOOR COIL TEMPERATURE.
• - THE DIFFERENCE BETWEEN THE OUTDOOR TEMPERATURE
  AND THE OUTDOOR COIL TEMPERATURE IS CALLED THE
  DELTA TEMPERATURE OR JUST DELTA-T.

99
The Defrost Cycle is Initiated

• As ice builds on the coil, the delta-t of the
  system increases until it reaches the initiate
  value, and the control starts the defrost
  process.
• The initiate value is not constant, but instead,
  is a value that the defrost control has learned
  will provide a fast, thorough defrost at a given
  outdoor temperature.
• Low initiate values waste energy by defrosting
  too often, while high initiate values fail to
  defrost the coils thoroughly.
• The control is continually varying the initiate
  value slightly to learn the best value.
• It measures the success of each initiate value by
  measuring the delta-t of the system during the
  next heating cycle.

100
DEFROST IS TERMINATED

• Once the temperature of the outdoor coil reaches
  the termination value, the defrost control turns
  on the outdoor fan. After waiting the
  soft-switch over time, it changes the switch over
  valve to the heating mode.
• This soft-switch over delay time, 12 seconds,
  gives the outdoor coil time to cool, reducing the
  refrigerant pressure and reducing the surge that
  occurs when the switch over valve is switched.
• If the compressor or Y cycles off during
  defrost, the switchover valve remains energized
  but the X2 output will be OFF. If Y cycles
  off during the soft-switchover time, the
  switchover valve is switched OFF immediately.

101
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102
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103
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104
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105
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106