Speedup
Pins
Quiet Defrost interval
Shift DIP switches
A99442
Fig. 14_Defrost Control
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• 3_hase 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 _all, 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 tum off for 30 sec, then
turn back on to complete defi'ost. 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.
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