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Page 8

Demand Defrost Operation

The demand defrost control board initiates a defrost cycle
based on either frost detection or time.

Frost Detection

 − If the compressor runs longer than 34

minutes and the actual difference between the clear coil
and frosted coil temperatures exceeds the maximum differ-
ence allowed by the control, a defrost cycle will be initiated.

IMPORTANT − The demand defrost control board will allow
a greater accumulation of frost and will initiate fewer defrost
cycles than a time/temperature defrost system.

Time

 − If 6 hours of heating mode compressor run time has

elapsed since the last defrost cycle while the coil tempera-
ture remains below 35°F (2°C), the demand defrost control
will initiate a defrost cycle.

Actuation

 − When the reversing valve is de−energized, the

Y1 circuit is energized, and the coil temperature is below
35°F (2°C), the board logs the compressor run time. If the
board is not calibrated, a defrost cycle will be initiated after
34 minutes of heating mode compressor run time. The con-
trol will attempt to self−calibrate after this (and all other) de-
frost cycle(s). Calibration success depends on stable sys-

tem temperatures during the 20−minute calibration period.
If the board fails to calibrate, another defrost cycle will be
initiated after 90 minutes of heating mode compressor run
time. Once the defrost board is calibrated, it will use de-
mand defrost logic to initiate a defrost cycle. A demand de-
frost system initiates defrost when the difference between
the clear coil and frosted coil temperatures exceeds the
maximum difference allowed by the control OR after 6
hours of heating mode compressor run time has been
logged since the last defrost cycle.

Termination

 − The defrost cycle ends when the coil temper-

ature exceeds the termination temperature or after 14 min-
utes of defrost operation. If the defrost is terminated by the
14−minute timer, another defrost cycle will be initiated after
34 minutes of run time.

Test Mode

 − When Y1 is energized and 24V power is being

applied to the board, a test cycle can be initiated by placing
the termination temperature jumper across the Test" pins
for 2 to 5 seconds. If the jumper remains across the Test"
pins longer than 5 seconds, the control will ignore the test
pins and revert to normal operation. The jumper will initiate
one cycle per test.

HPXA12 DEFROST CONTROL BOARD

Figure 6

24V TERMINAL STRIP

CONNECTIONS

DIAGNOSTIC LEDs

PRESSURE SWITCH

CIRCUIT CONNECTIONS

DEFROST INTERVAL

TIMING PINS

NOTE − COMPONENT LOCATIONS WILL VARY WITH BOARD MANUFACTURER

PRESSURE SWITCH

CIRCUIT CONNECTIONS

Y2

Y2

Y1

Содержание HPXA12 SERIES

Страница 1: ...quipment rated for R410A WARNING Warranty will be voided if covered equipment is re moved from original installation site Warranty will not cover damage or defect resulting from Flood wind lightning o...

Страница 2: ...80 181 82 OPTIONAL ACCESSORIES MUST BE ORDERED EXTRA Compressor Monitor Canada Only 45F08 45F08 45F08 45F08 Hail Guards 17L73 17L73 17L73 17L73 Mild Ambient Kit LB 101122 32M08 32M08 32M08 32M08 Monit...

Страница 3: ...B2 L 69J07 Mounting Base Net Weight 6 lbs 3 kg 15 lbs 7 kg 15 lbs 7 kg Refrigerant Li S t 30 ft 9 m length L15 65 30 L15 65 30 Field Fabricate g Line Set 40 ft 12 m length L15 65 40 L15 65 40 Field Fa...

Страница 4: ...62 Power Factor 98 98 99 99 99 99 Outdoor Coil F M t Full load amps 1 55 1 9 9 1 9 9 Fan Motor Locked Rotor Amps 2 3 1 4 1 2 1 4 1 2 1 OPTIONAL ACCESSORIES MUST BE ORDERED EXTRA Compressor Low Ambient...

Страница 5: ...early compressor failure IMPORTANT This unit must be matched with an indoor coil as specified in Lennox Engineering Handbook II UNIT COMPONENTS Unit components are illustrated in figure 1 COMPRESSOR C...

Страница 6: ...nal Y2 for 2nd stage thermostat input 46M8201 56M8501 DELAY pins 56M8501 The demand defrost board uses basic differential temper ature means to detect degradation of system performance due to ice buil...

Страница 7: ...e Y1 Out line is engaged a 5 minute short cycle will occur after the switch closes Operational Description The demand defrost board has three basic operational modes Normal Defrost and Calibration Nor...

Страница 8: ...period If the board fails to calibrate another defrost cycle will be initiated after 90 minutes of heating mode compressor run time Once the defrost board is calibrated it will use de mand defrost log...

Страница 9: ...e board and all sensors FLASH FLASH Normal operation Unit operating normally or in standby mode None required ON OFF Strike Out pressure lockout Short test pins or reset 24V power to board to override...

Страница 10: ...the two scrolls figure 10 1 The centrifugal action of the orbiting scroll seals off the flanks of the scrolls figure 10 2 As the orbiting motion contin ues the gas is forced toward the center of the s...

Страница 11: ...uire a run capacitor In all units the condenser fan is controlled by the compressor contactor ELECTRICAL DATA tables in this manual show specifi cations for condenser fans used in HPXA12s Access to th...

Страница 12: ...ch settings for R410A refrigerant will be significantly higher than units with R22 An auto reset single pole single throw high pressure switch is located in the liquid line This switch shuts off the c...

Страница 13: ...ON OF REFRIGERANT FLOW SERVICE PORT SUCTION EXPANSION CHECK VALVE INDOOR UNIT OUTDOOR UNIT LIQUID LINE SERVICE PORT GAUGE MANIFOLD INTERNAL COMPRESSOR LIMIT DISTRIBUTOR INDOOR COIL COIL SENSOR FIGURE...

Страница 14: ...em out counterclockwise as far as it will go NOTE Use a 3 16 hex head extension for 3 8 line sizes or a 5 16 extension for large line sizes 3 Replace the stem cap Tighten finger tight then tighten an...

Страница 15: ...e high pres sure hose is connected to the liquid line port however connecting it to the vapor port better protects the man ifold gauge set from high pressure damage 6 Adjust the nitrogen pressure to 1...

Страница 16: ...injury or death Units are factory charged with the amount of R410A refrig erant indicated on the unit rating plate This charge is based on a matching indoor coil and outdoor coil with 15 ft 4 5m line...

Страница 17: ...for checking charge Block equal sections of air intake panels mov ing obstructions sideways as shown until liquid pres sure is in the 300 350 psig 2068 2413 kPa range BLOCKING OUTDOOR COIL CARDBOARD O...

Страница 18: ...344 127 380 128 335 100 TABLE 8 R410A Temperature Pressure Chart Temperature F Pressure Psig Temperature F Pressure Psig Temperature F Pressure Psig Temperature F Pressure Psig 32 100 8 63 178 5 94 29...

Страница 19: ...eplaced to eliminate moisture from POE oil VI MAINTENANCE In order to maintain the warranty on this equipment the HPXA12 system must be serviced annually and a record of service maintained The followi...

Страница 20: ...Page 20 VII WIRING DIAGRAM AND SEQUENCE OF OPERATION 5 6 7 8 9 10 11 12 13 15 1 2 3 4 14 1 4 HPXA12 1 5 THROUGH 5 TON UNIT WIRING Single Phase 230V...

Страница 21: ...Page 21 5 6 7 8 9 10 11 12 13 15 2 3 14 1 4 HPXA12 3 THROUGH 5 TON UNIT WIRING Three Phase 230V 7...

Страница 22: ...Page 22 5 6 7 8 9 10 11 12 13 15 2 3 14 1 4 HPXA12 3 THROUGH 5 TON UNIT WIRING Three Phase 460V 7...

Страница 23: ...K1 5 minute anti cylce time must be satisfied first 11 K1 1 N O closes energizing compressor and out door fan motor 460V units only K1 1 closes energizing compressor B1 and outdoor relay K10 energizin...

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