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FLASH RATE INDICATIONS:

1 — Flash/Second

= Normal operation.

2 — Flashes/Second

= Fault A (Low DT) i.e.: Inoperative compressor, loss of charge, open ambient sensor, shorted coil sensor.

3 — Flashes/Second

= Fault B (20 defrosts terminated on time)

Fault C (High DT) i.e.: SOV stuck in heating, shorted ambient sensor, open coil sensor, closed TXV,OD motor
failure, OD fan on in defrost, undercharged unit.

4 — Flashes/Second

= Fault A & C or A & B

For additional information consult Pub. No. 34-1001 Heat Pump Defrost Controls.

Demand Defrost System

PROCEDURE FOR TESTING SENSORS

Measure the temperature the subject sensor is exposed to.  If the sensor is mounted on a
tube, place the lead on an Annie A-8 (or equiv.) temperature tester on the same tube near
the sensor and insulate the bulb.

Unplug the sensor and measure the resistance with a good quality ohmmeter (Simpson
260 or equiv.).  Read the value as quickly as possible to prevent the meter current from
changing the resistance reading.

Using the chart on the right, locate (as close as possible) the actual sensor temperature.
The measured resistance should be relatively close to the resistance value shown in the
chart.

Example:

Sensor temp.

= 19°F.

Measured Resistance

= 46K ohms

This sensor is good since the measured value is relatively close to the
chart value.

TEMP °F

RESISTANCE

86

 7.85K

81

 8.85K

75

10.24K

70

11.59K

65

13.14K

59

15.32K

55

16.93K

50

19.41K

45

22.20K

41

24.76K

36

28.45K

32

31.84K

25

37.50K

19

46.44K

14

53.94K

10

57.64K

5

67.06K

0

78.05K

DEFROST CONTROL

The demand defrost control measures heat pump outdoor ambient
temperature with a sensor located outside the outdoor coil.  A
second sensor located on the outdoor coil is used to measure the
coil temperature.  The difference between the ambient and the
colder coil temperature is the difference or delta-T measurement.
This delta-T measurement is representative of the operating state
and relative capacity of the heat pump system.  By measuring the
change in delta-T, we can determine the need for defrost.  The coil
sensor also serves to sense outdoor coil temperature for termina-
tion of the defrost cycle.

FAULT DETECTION

A fault condition is indicated by the flashing light on the defrost
control inside the heat pump control box.

In normal operation, the defrost control light will flash once each
second. If the light is flashing more than once per second or not-at-
all, refer to the service manual for that unit.

PIN   IDENTIFICATION (See Figure)

1. TEST_COMMON (Shorting any of  the other pins to this pin

causes  the function of the other pin to be executed. Leaving this
pin open results in the normal mode of operation.)

2.  TST   =   Test  (Shorting TEST_COMMON  to this pin speeds up

all defrost board timings.)

3.  FRC_DFT  =  Forced Defrost  (Short TEST_COMMON to this pin

for two (2) seconds to initiate a forced defrost. Remove the short
after defrost initiates.)

▲ 

WARNING:

PIN IDENTIFICATION

FRC_DFT

TEST_COMMON

TST

DEFROST CONTROL CHECKOUT

Normal operation requires:

a.  LED on board flashing 1 time/second.

b.  24V AC between R & B

c.  24V AC between Y & B with unit operating

d. Defrost initiation when FRC_DFT pin is shorted to

TEST_COMMON pin.

If a defrost control problem is suspected, proceed to DEMAND
DEFROST CONTROL CHECKOUT in this Service Facts.

                                                Do NOT connect 24 VAC to T1
(ODS-A) terminal. ODS-A thermistor WILL BE BLOWN.

Summary of Contents for WCH024C1

Page 1: ... conducting electri cal current are grounded If grounding wires screws straps clips nuts or washers used to complete a path to ground are removed for service they must be returned to their original position and properly fastened ALL phases of this installation must comply with NATIONAL STATE and LOCAL CODES These instructions do not purport to cover all variations in systems nor to provide for eve...

Page 2: ...ade to deflect the warm discharge air from under the overhang See Figures 1 2 and 5 The unit must also be situated to permit easy and unrestricted access for service Install internal accessories to the unit at the shop if practical Position the unit so roof run off water does not pour directly onto the unit CAUTION MUST ALWAYS BE TAKEN TO AVOID PER SONAL INJURIES AND OR DAMAGE TO THE EQUIPMENT In ...

Page 3: ...1 INSTALLATION SERVICE CLEARANCE BACK 48 0 LEFT SIDE 24 0 RIGHT SIDE 36 0 TOP 36 0 MODEL APPROX CORNER WTS LBS TOTAL WEIGHT LBS COIL DIMENSION in W1 W2 W3 W4 A B WCH024C 79 73 63 68 282 14 16 WCH030C 80 71 62 70 284 14 16 WCH036C 83 75 66 73 297 14 16 WCH042C 84 79 72 77 312 20 16 ...

Page 4: ...d Clearances WCH048 060F Outline 1 INSTALLATION SERVICE CLEARANCE BACK 48 0 LEFT SIDE 24 0 RIGHT SIDE 36 0 TOP 36 0 MODEL APPROX CORNER WTS LBS TOTAL WEIGHT LBS W1 W2 W3 W4 WCH048F 128 128 97 97 447 WCH060F 115 115 114 114 457 ...

Page 5: ...d The pad must not contact the structure Be sure the outdoor portion of the supply and return air ducts are as short as possible The installation should proceed as follows The unit must be isolated with mounting pads The mounting pads must provide a minimum of 1 4 clearance beneath the unit to permit air circulation and prevent corrosion of the base See Figure 3 Attach the supply and return air du...

Page 6: ...RNING TO PREVENT INJURY OR DEATH DUE TO ELECTRICAL SHOCK OR CONTACT WITH MOVING PARTS LOCK UNIT DISCONNECT SWITCH IN OPEN POSITION BEFORE SERVICING UNIT Do not short thermostat wires since this will damage the control transformer Recommended wire sizes and lengths for installing the unit thermostat are provided in Table 1 Thermostat Wire Size and Maximum Length The total resistance of these low vo...

Page 7: ...perature The outdoor fan motor compressor and evaporatorfan motor will oper ate automatically Start Up Operating Pressures After the unit has operated in the cooling mode for a short time install pressure gauges on the gauge ports of the discharge and suction line valves Check the suction and discharge pressures and compare them to the normal operating pressures provided in the unit s SERVICE FACT...

Page 8: ... fan relay F which starts the indoor fan motor SUPPLEMENTARY HEAT The supplementary electric heat is brought on when the indoor temperature drops 1 1 2 degrees below the thermostat setting TSH 2 contacts close providing power to the W termi nal on the indoor thermostat and to the supplementary heater control circuit NOTE The fan relay F must have been ener gized An outdoor thermostat may have been...

Page 9: ...y dry before re installing them in the unit Replace permanent filters annually if washing fails to clean them or if they show signs of deterioration Use the same type and size as was originally installed Outdoor Coil Unfiltered air circulated through the unit s outdoor coil can cause the coil s surface to become clogged with dust dirt etc To clean the coil stroke the coil surface with a soft brist...

Page 10: ...door ambient temperature with a sensor located outside the outdoor coil A second sensor located on the outdoor coil is used to measure the coil temperature The difference between the ambient and the colder coil temperature is the difference or delta T measurement This delta T measurement is representative of the operating state and relative capacity of the heat pump system By measuring the change ...

Page 11: ...nsor 2 Does OD fan cycle off in defrost N Replace defrost control 3 Windy weather preventing normal termination 7 Defrost initiates on approximately 15 25 minute intervals Be sure OD coil is clean N Complete Check 2 1 Coil sensor open or reading a very high resistance Y Replace coil sensor 2 Ambient sensor reading less than normal N Complete Check 3 Y Replace ambient sensor 3 OD fan off in defrost...

Page 12: ...ally this limited warranty will not apply unless the packaged unit is 1 installed by a licensed or qualified HVAC technician 2 applied and installed in accordance with the manufacturer s recommendations and its Installer s guide and 3 in compliance with all industry standards national state and local codes This limited warranty does not cover failure of your packaged unit if it is damaged while in...

Page 13: ...antor shall not be obligated to pay for the cost of lost refrigerant No liability shall attach to Warrantor until products have been paid for and then liability shall be limited solely to the purchase price of the equipment under warranty shown to be defective This limited warranty does not apply if the packaged unit was purchased direct i e from internet websites or auctions on an uninstalled ba ...

Page 14: ...record the following information to ensure your product registration process is quick and easy Packaged Unit Serial Number_____________________________________________________ Packaged Unit Model Number_____________________________________________________ Date of Installation______________________________________________________________ Dealer_______________________________________________________...

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