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XPG20 SERIES

Defrost Control Board Diagnostic LEDs

The state (Off, On, Flashing) of two LEDs on the DCB (DS1 [Red] and DS2 [Green]) indicate diagnostics conditions that are
described in Table 11.

Table 11. Defrost Control Board Diagnostic LEDs

DS2
Green

DS1
Red

Condition/Code

Possible Cause(s)

Solution

OFF

OFF

Power problem

No power (24V) to board terminals R
and C or board failure.

1

Check control transformer power (24V).

2

If power is available to board and LED(s) do not
light, replace board.

Simultaneous

SLOW Flash

Normal operation

Unit operating normally or in standby
mode.

None required.

Alternating SLOW

Flash

5−minute anti−short cycle
delay

Initial power up, safety trip, end of
room thermostat demand.

None required (Jumper TEST pins to override)

Simultaneous

FAST Flash

Ambient Sensor Problem

Sensor being detected open or shorted or out of temperature range. Board will revert to time/
temperature defrost operation. (System will still heat or cool).

Alternating 

FAST Flash

Coil Sensor Problem

Sensor being detected open or shorted or out of temperature range. Board will not perform
demand or time/temperature defrost operation. (System will still heat or cool).

ON

ON

Circuit Board Failure

Indicates that board has internal component failure. Cycle 24 volt power to board. If code does
not clear, replace board.

FAULT and LOCKOUT CODES 

(Each fault adds 1 strike to that code’s counter; 5 strikes per code = LOCKOUT)

OFF

SLOW

Flash

Low Pressure Fault

1

Restricted air flow over indoor or out-
door coil.

2

Improper refrigerant charge in sys-
tem.

3

Improper metering device installed or
incorrect operation of metering de-
vice.

4

Incorrect or improper sensor location
or connection to system.

1

Remove any blockages or restrictions from coils
and/or fans. Check indoor and outdoor fan motor for
proper current draws.

2

Check system charge using approach and subcool-
ing temperatures.

3

Check system operating pressures and compare to
unit charging charts.

4

Make sure all pressure switches and sensors have
secure connections to system to prevent refrigerant
leaks or errors in pressure and temperature mea-
surements.

OFF

ON

Low Pressure Discharge Sen-
sor Lockout

SLOW

Flash

OFF

High Pressure Fault

ON

OFF

High Pressure

 

Discharge

Sensor Lockout

SLOW

Flash

ON

Discharge Line Temperature
Fault

This code detects shorted sensor or high discharge temperatures. If the discharge line
temperature exceeds a temperature of 300ºF (148ºC) during compressor operation, the board
will de−energize the compressor contactor output (and the defrost output if active). The
compressor will remain off until the discharge temperature has dropped below 225ºF (107ºC).

FAST
Flash

ON

Discharge Line
Temperature 

Discharge

Sensor Lockout

OFF

Fast

Flash

Discharge Sensor Fault

The board detects open sensor or out of temperature sensor range. This fault is detected by
allowing the unit to run for 90 seconds before checking sensor resistance. If the sensor resist-
ance is not within range after 90 seconds, the board will count one fault. After 5 faults, the board
will lockout.

Fast

Flash

OFF

Discharge Sensor Lockout

Summary of Contents for XPG20

Page 1: ...Lennox Engineering Handbook Coils previously charged with HCFC 22 must be flushed INSTALLATION INSTRUCTIONS Dave Lennox Signature Collection XPG20 SunSourcet Comfort System SOLAR ASSIST HEAT PUMPS 50...

Page 2: ...H VOLTAGE 37 940 SOLAR MODULE WIRING ELECTRICAL INLET CONTROL WIRING LOW VOLTAGE Field Supplied Components The followings items are field supplied not included Parts Lennox Catalog Numbers Solar Modul...

Page 3: ...PANEL TERMINAL BLOCK BI FLOW FILTER DRIER FAN MOTOR SOLAR ASSIST DC MOTOR COUPLER HIGH PRESSURE SWITCH LOW PRESSURE SWITCH COMPRESSOR TERMINAL PLUG FAN MOTOR MOUNT Control Panel Parts Arrangement GROU...

Page 4: ...use check thermal expansion valve CTXV refrigerant metering device Operating Gauge Set This instruction is intended as a general guide and do not supersede local codes in any way Consult authorities...

Page 5: ...line service valves are used for removing refrigerant flushing leak testing evacuating checking charge and charging Each valve is equipped with a service port which has a factory installed valve stem...

Page 6: ...lve S Compressor has internal vacuum protection that is designed to unload the scrolls compressor stops pumping when the pressure ratio meets a certain value or when the suction pressure is as high as...

Page 7: ...perty not from the installation property Install the unit as far as possible from the property line S When possible do not install the unit directly outside a window Glass has a very high level of sou...

Page 8: ...ay cause panels to be blown around and battered WARNING Unit must be grounded in accordance with national and local codes Electric Shock Hazard Can cause injury or death Line voltage is present at all...

Page 9: ...when unit is raised above the factory height Elevated units could become unstable in gusty wind conditions Stabilizers may be used on factory height units when mounted on unstable an uneven surface ON...

Page 10: ...d to the size of cooling unit Existing line set of proper size may be reused If system was previously HCFC 22 then lines must be flushed see Flushing the System on page If a Lennox RFC1 liquid line is...

Page 11: ...s dry nitrogen to pressurize a refrigeration or air conditioning system use a regulator that can control the pressure down to 1 or 2 psig 6 9 to 13 8 kPa CAUTION Brazing alloys and flux contain materi...

Page 12: ...tem port connection on the liquid line service valve and out of the valve stem port connection on the suction service valve NOTE The fixed orifice or CTXV metering device at the indoor unit will allow...

Page 13: ...ING INDOOR UNIT GAUGE MANIFOLD INVERTED HCFC 22 CYLINDER CONTAINS CLEAN HCFC 22 TO BE USED FOR FLUSHING LIQUID LINE SERVICE VALVE INLET DISCHARGE TANK RETURN CLOSED OPENED RECOVERY CYLINDER RECOVERY M...

Page 14: ...provided Teflon rings around the stubbed end of the CTXV and lightly lubricate the connector threads and expose surface of the Teflon ring with refrigerant oil 3 Attach the stubbed end of the CTXV to...

Page 15: ...sal of appliance Approved methods of recovery recycling or reclaiming must be followed WARNING Improper installation adjustment alteration service or maintenance can cause personal injury loss of life...

Page 16: ...A into the line set and indoor unit Weigh in a trace amount of HFC 410A A trace amount is a maximum of two ounces 57 g refrigerant or three pounds 31 kPa pressure Close the valve on the HFC 410A cylin...

Page 17: ...off the vacuum pump and closing the manifold gauge valves 6 When the absolute pressure requirement above has been met disconnect the manifold hose from the vacuum pump and connect it to an upright cy...

Page 18: ...th Unit must be grounded in accordance with national and local codes Line voltage is present at all components when unit is not in operation on units with single pole contactors Disconnect all remote...

Page 19: ...uits A Run 24VAC control wires through hole with grommet B Make 24VAC thermostat wire connections NOTE Do not bundle any excess 24VAC control wires inside control box 4 ROUTE THERMOSTAT WIRES A B DEFR...

Page 20: ...the DC motor applies a torque on the fan shaft and reduces the load of the AC motor The AC motor inverter control senses this reduction in load and realize that the AC motor does not have to work as...

Page 21: ...s Solar module should be mounted according to manufacturer s recommendations Stainless Steel hardware nuts and bolts is recommended for longevity Two solar module mounting kits are available See Field...

Page 22: ...W00 CAT 48W03 CONDUIT FIELD PROVIDED WATERTIGHT FLEXIBLE CONDUIT FIELD PROVIDED CONDUIT ELBOWS FIELD PROVIDED TERMINAL FOR EARTH GROUND XPG20 CONTROL BOX PIPING MODULE GROUND LUG CONTACTOR WATERTIGHT...

Page 23: ...the power produced by the solar module The K227 Defrost relay switches the solar assist motor off when the heat pump is in defrost mode The relay has a 240VAC coil that is wired in parallel with the K...

Page 24: ...gure 17 7 Set the thermostat for a cooling demand Turn on power to the indoor indoor unit and close the outdoor unit disconnect switch to start the unit 8 Recheck voltage while the unit is running Pow...

Page 25: ...BULB DRY BULB WET BULB B TDrop 19 A Dry bulb Wet bulb F A 72 B 64 C 53 air flow air flow All temperatures are expressed in F 1 Determine the desired DT Measure entering air temperature using dry bulb...

Page 26: ...ing amperage being drawn by the heat unit s Then apply the measurements taken in following formula to determine CFM CFM Amps x Volts x 3 41 1 08 x Temperature rise F CHARGING METHOD Use either WEIGH I...

Page 27: ...ith Table 4 being sure to note any additional charge for line set and or match up 10 If subcooling value is greater than shown in Table 4 for the applicable unit remove refrigerant if less than shown...

Page 28: ...0 4 4 329 89 50 10 344 109 1 Most popular match up pressures Indoor match up indoor air quality and indoor load cause pres sures to vary 2 Temperature of the air entering the outdoor coil 3 Liquid 10...

Page 29: ...tdoor unit control circuit is isolated from power and field provided relays bypass the outdoor thermostats An amber indicating light simultaneously comes on to remind the homeowner that the unit is op...

Page 30: ...d with 19 28VAC Table 8 LSOM System LED Troubleshooting Codes Status LED Condition Status LED Description Status LED Troubleshooting Information Red LED ON Thermostat demand signal Y1 is present but c...

Page 31: ...s open and requires manual reset 5 Open circuit in compressor supply wiring or connections 6 Unusually long compressor protector reset time due to extreme ambient tempera ture 7 Compressor windings ar...

Page 32: ...ond stage operationof the unit O 24VAC thermostat input for reversing valve operation Y1 24VAC thermostat input for first stage compressor operation P3 55 50 45 40 Five position square pin header If t...

Page 33: ...close NOTE Individual HI PS and LO PS trips are totaled by the DCB S Up to four pressure switch trips are allowed in a single thermostat demand without locking out the DCB If the thermostat demand is...

Page 34: ...r to the Demand Defrost Control Y1 Active Place a jumper on TEST pins for longer than one second but less than two seconds Clears any short cycle lockout and five strike fault lockout function if appl...

Page 35: ...ure 14 illustrates the correct Y2 field wiring configuration NOTE The LSOM has a five second delay between Y2 being powered and the solenoid energizing If first stage compressor output is active in he...

Page 36: ...ature conditions S Coil S Discharge Line S Ambient Air As the detected temperature changes the resistance across the sensor changes Figure 25 shows how the resistance varies as the temperature changes...

Page 37: ...IL SENSOR 12 TUBES UP FROM BOTTOM 11 1 2 OUTSIDE ROW DISCHARGE LINE SENSOR DETAIL A DETAIL B Place ambient sensor and wire from DCB inside of plastic sleeve and route through gap between corner post a...

Page 38: ...ll display the appropriate fault code Heating and cooling operation will be allowed in this fault condition 3 Discharge Line Sensor RT28 This sensor see mounting location in Figure 24 Detail C which c...

Page 39: ...ult 1 Restricted air flow over indoor or out door coil 2 Improper refrigerant charge in sys tem 3 Improper metering device installed or incorrect operation of metering de vice 4 Incorrect or improper...

Page 40: ...als should ever be used on the coated front glass No alkali based chemicals should be used including ammonia based solutions Always wear rubber gloves for electrical insulation when maintaining washin...

Page 41: ...may vary somewhat from the description below its operation will be similar 1 Temperature Setting Levers Most heat pump thermostats have two temperature selector levers one for heating and one for coo...

Page 42: ...ssor Discharge Line Higher Higher Indoor Return Air Same Same Indoor Coil Discharge Air Lower Higher Pressures Suction Vapor Lower Down Liquid Higher Higher NOTE Heat pump may have a low ambient contr...

Page 43: ...apor Pressure Liquid Pressure Supply Air Temperature Ambient Temperature Return Air Temperature HEATING MODE Vapor Pressure Liquid Pressure Supply Air Temperature Ambient Temperature Return Air Temper...

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