Sequence Of Operation - Carrier 38EYX Installation And Start-Up Instructions Manual

A crankcase heater is required in long-line applications (tubing
greater than 50 ft (15 m) horizontal and/or elevation greater than
20 ft (6 m) between indoor and outdoor units). Refer to Applica-
tion Guideline and Service Manual for Residential Split-System
Air Conditioners and Heat Pumps Using Puron® Refrigerant.
Step 12—Install Electrical Accessories
Refer to the individual instructions packaged with kits or acces-
sories when installing.
Step 13—Start-Up
To prevent compressor damage or personal injury, observe
the following:
• Do not overcharge system with refrigerant.
• Do not operate unit in a vacuum or at negative pressure.
• Do not disable low-pressure switch
In scroll compressor applications:
• Dome temperatures may be hot
To prevent personal injury wear safety glasses, protective
clothing, and gloves when handling refrigerant.
Regulations require that you do not vent refrigerant into the
atmosphere. Recover during system repair or final unit
disposal.
Follow these steps to properly start up the system.
1. Fully back seat (open) liquid and vapor service valves.
2. Unit is shipped with valve stem(s) front seated (closed) and
caps installed. replace stem caps after system is opened to
refrigerant flow (back seated). Replace caps finger-tight and
tighten with wrench an additional 1/12 turn. Use a backup
wrench on valve body flats to prevent distortion of sheet
metal.
3. Close electrical disconnects to energize system.
4. Set room thermostat at desired temperature. Be sure set point
is below indoor ambient temperature.
5. Set room thermostat to HEAT or COOL and fan control to ON
or AUTO mode, as desired. Operate unit for 15 minutes.
Check system refrigerant charge.
Failure to follow this caution could result in unit damage.
• 3–phase scroll compressors are rotation sensitive.
• A flashing LED on phase monitor indicates reverse rotation.
(See Fig. 11 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. 11 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 connected through
room thermostat. Circuit R-W2 energize the supplemental heat (if
used). If outdoor temperature falls below setting of outdoor
thermostat (field-installed option), contacts close to complete
circuit and bring on additional supplemental heat.
When thermostat is satisfied, its contacts open, de-energizing
contactor and supplemental heat. All heaters and motors should
stop.
TABLE 3—PHASE MONITOR LED INDICATORS
LED
OFF
FLASHING
ON
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
7
STATUS
No call for compressor operation
Reversed phase
Normal