providing electrical potential to second heater sequencer (if used). If outdoor temperature falls below setting of outdoor thermostat
When thermostat is satisfied, its contacts open,
→Quiet Shift
Quiet Shift is a
When Quiet Shift switch is placed in ON position, and a defrost is initiated, the following sequence of operation will occur. Revers- ing valve will energize, compressor will turn off for 30 sec, then turn back on to complete defrost. At the start of heating cycle after conclusion of defrost mode, reversing valve will
→Defrost
The defrost control is a time/temperature control which includes a
To initiate a forced defrost, two options are available depending on the status of the defrost thermostat.
If defrost thermostat is closed, speedup pins (J1) must be shorted by placing a flat head screwdriver in between for 5 sec and releasing, to observe a complete defrost cycle. When the Quiet Shift switch is selected, compressor will be turned off for two 30 sec intervals during this complete defrost cycle as explained previously. When Quiet Shift switch is in factory default OFF position, a normal and complete defrost cycle will be observed.
If defrost thermostat is in open position, and speedup pins are shorted (with a flat head screwdriver) for 5 sec and released, a short defrost cycle will be observed (actual length is dependent upon the selected Quiet Shift position). When Quiet Shift switch is in ON position, the length of defrost is 1 minute (30 sec compressor off period followed by 30 sec of defrost with com- pressor operation). On return to heating operation, compressor will again turn off for an additional 30 sec and the fan for 40 sec. When the Quiet Shift is in OFF position, only a brief 30 sec cycle will be observed.
If it is desirable to observe a complete defrost in warmer weather, the thermostat must be closed as follows:
1.Turn off power to outdoor unit.
2.Disconnect outdoor fan motor lead from OF2 on control board (See Fig. 15.) Tape to prevent grounding.
3.Restart unit in heating mode, allowing frost to accumulate on outdoor coil.
4.After a few minutes in heating mode, liquid line temperature should drop below closing point of defrost thermostat (ap- proximately 30°F).
NOTE: Unit will remain in defrost until defrost thermostat reopens at approximately 80°F coil temperature at liquid line or remainder of defrost cycle time.
5.Turn off power to outdoor and reconnect fan motor lead to OF2 on control board after above forced defrost cycle.
Step 13—Check Charge
Factory charge is shown on unit rating plate. To check charge in cooling mode, refer to Cooling Mode Procedure. To check charge in heating mode, refer to For Heating Only Procedure.
COOLING ONLY PROCEDURE
NOTE: If subcooling charging conditions are not favorable, charge must be weighed in accordance with unit rating plate ± 0.6 oz/ft of
EXAMPLE:
To calculate additional charge required for a
25 ft - 15 ft = 10 ft X 0.6 oz/ft = 6 oz of additional charge
Units installed with cooling mode TXV require charging with the subcooling method.
1.Operate unit a minimum of 10 minutes before checking charge.
2.Measure liquid service valve pressure by attaching an accurate gage to service port.
3.Measure liquid line temperature by attaching an accurate thermistor type or electronic thermometer to liquid line near outdoor coil.
4.Refer to unit rating plate for required subcooling temperature.
5.Refer to Table 3. Find the point where required subcooling temperature intersects measured liquid service valve pressure.
6.To obtain required subcooling temperature at a specific liquid line pressure, add refrigerant if liquid line temperature is
higher than indicated or reclaim refrigerant if temperature is lower. Allow a tolerance of ± 3°F.
| T2 C |
| C |
| O |
O | DFT |
R | T1 |
W |
|
2
Y |
|
|
|
|
|
|
C | Y |
|
|
|
|
|
SPEEDUP | P1 |
|
|
|
|
|
J1 | P3 | 90 INTERVALTIMER | 60 30 | 30 60 | 120 | |
| DFT |
| OFF | QUIET SHIFT | ON | |
| Speedup |
|
|
| Quiet | |
| Pins |
|
|
| Shift | |
OF2 | OF1 |
Defrost interval
DIP switches
HEATING ONLY PROCEDURE
1.Defrost unit before checking charge. Outdoor coil must be free of frost and/or ice.
1.Accumulator may momentarily hold refrigerant after defrost cycle, therefore, allow 15 min. of normal operation following defrost cycle before checking charge.
2.This outdoor unit is equipped with a thermal expansion device, therefore the subcooling chart (See Table 4) may be used for checking purposes only.
Fig. 14−Defrost Control
A99442
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