providing electrical potential to second heater sequencer (if used).
If outdoor temperature falls below setting of outdoor thermostat
(field-installed option), contacts close to complete circuit and bring
on second bank of supplemental electric heat.
When thermostat is satisfied, its contacts open, de-energizing
contactor and sequencer. All heaters and motors should stop.
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. 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 3/8-in. liquid line above or below 15 ft respectively.
EXAMPLE:
To calculate additional charge required for a 25-ft line set:
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.
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.
OF2
CESO130076–00
OF1
ON
Q
UIET
SHIFT
120
30
60
60
30
90
INTER
V
AL
TIMER
OFF
P3
DFT
O R
W
2
Y C
T2 C C O
DFT
T1
Y
P1
J1
SPEEDUP
Speedup
Pins
Defrost interval
DIP switches
Quiet
Shift
A99442
Fig. 14−Defrost Control
11
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