→• 3–phase scroll compressors are rotation sensitive.
•A flashing LED on phase monitor indicates reverse rotation. (See Fig. 18 and Table 3.)
•This will not allow contactor to be energized.
•Disconnect power to unit and interchange 2 field wiring leads on unit contactor.
SEQUENCE OF OPERATION
NOTE: Defrost control board is equipped with a 5-minute lock- out timer which may be initiated upon an interruption of power.
With power supplied to indoor and outdoor units, transformer is energized.
→Cooling
On a call for cooling, thermostat makes circuits R-O, R-Y, and R-G. Circuit R-O energizes reversing valve, switching it to cooling position. On three phase models with scroll compressors, the units are equipped with a phase monitor to detect if the incoming power is correctly phased for compressor operation. (See Fig. 18 and Table 3.) If the phasing is correct, circuit R-Y energizes contactor, starting outdoor fan motor and compressor circuit. R-G energizes indoor unit blower relay, starting indoor blower motor on high speed.
NOTE: If the phasing is incorrect, the contactor will not be energized. To correct the phasing interchange any two of the three power connections on the field side.
When thermostat is satisfied, contacts open, de-energizing the contactor and blower relay. Compressor and motors should stop.
NOTE: If indoor unit is equipped with a time-delay relay circuit, the blower runs an additional 90 sec to increase system efficiency.
→Heating
On a call for heating, thermostat makes circuits R-Y and R-G. If phasing is correct, circuit R-Y energizes contactor, starting out- door fan motor and compressor. Circuit R-G energizes indoor blower relay, starting blower motor on high speed.
Should temperature continue to fall, R-W2 is made through sec-stage room thermostat bulb. Circuit R-W2 energizes a se- quencer, bringing on first bank of supplemental electric heat and providing electrical potential to sec heater sequencer (if used). If outdoor temperature falls below setting of outdoor thermostat (field-installed option), contacts close to complete circuit and bring on sec bank of supplemental electric heat.
When thermostat is satisfied, its contactors open, de-energizing contactor and sequencer. All heaters and motors should stop.
→TABLE 3—PHASE MONITOR LED INDICATORS
LED | STATUS |
OFF | No call for compressor operation |
FLASHING | Reversed phase |
ON | Normal |
| |
Quiet Shift
Quiet Shift is a field-selectable defrost mode, which will eliminate occasional noise that could be heard at the start of the defrost cycle and restarting of heating cycle. It is selected by placing DIP switch 3 (on defrost board) in ON position.
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 de-energize, the compressor will turn off for another 30 sec, and the fan will turn off for 40 sec, before starting in the heating mode.
Defrost
The defrost control is a time/temperature control which includes a field-selectable time period (DIP switch 1 and 2 on the board) between defrost cycles of 30, 60, 90, or 120 minutes (factory set at 90 minutes).
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. 19.) 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.
PressureGuard™ Switch
This outdoor unit is equipped with a heating vapor pressure limiting device, PressureGuard™ , which cycles the outdoor fan at high ambient heating conditions. The exact ambient at which outdoor fan cycles depends on indoor and outdoor unit sizing. The effect of outdoor fan cycling on HSPF (Heating Seasonal Perfor- mance Factor) is insignificant, due to its occurrence at outdoor ambients where building load is very low.
Puron® is a high-pressure refrigerant. The purpose of this switch is to provide maximum flexibility and minimum cost for the installer/owner by not requiring special thicker wall vapor tubing and indoor coils, thus allowing limited retrofit. The use of this switch also allows the maximum number of indoor coil choices at minimum cost for the installer/owner, since it can use standard refrigeration tubing.
NOTE: Due to presence of a PressureGuard switch in outdoor unit fan circuit and the possibility of fan cycling, this unit may go into brief defrost at high ambient heating conditions.
