Connect Control Wiring; Sequence Of Operation - Carrier 38CKC Installation And Start-Up Instructions Manual

CONNECT GROUND AND POWER WIRES
Connect ground wire to ground connection in control box for
safety. Connect power wiring to contactor as shown in Fig. 7.
DISCONNECT
PER N.E.C. AND/OR
LOCAL CODES
FIELD POWER
WIRING
3 PHASE ONLY
FIELD GROUND
WIRING
Fig. 7—Line Power Connections

CONNECT CONTROL WIRING

Route 24-v control wires through control wiring grommet and
connect leads to control wiring. (See Fig. 8.)
Use No. 18 AWG color-coded, insulated (35°C minimum) wire. If
thermostat is located more than 100 ft from unit, as measured
along the control voltage wires, use No. 16 AWG color-coded wire
to avoid excessive voltage drop.
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All wiring must be NEC Class 1 and must be separated from
incoming power leads.
Use furnace transformer, fan coil transformer, or accessory trans-
former for control power, 24-v/40-va minimum.
NOTE: Use of available 24-v accessories may exceed the mini-
mum 40-va power requirement. Determine total transformer load-
ing and increase the transformer capacity or split the load with an
accessory transformer as required.
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IMPORTANT: Check factory wiring and field wire connections
to ensure terminations are secured properly. Check wire routing to
ensure wires are not in contact with tubing, sheet metal, etc.
Step 8—Compressor Crankcase Heater
When equipped with a crankcase heater, furnish power to heater a
minimum of 24 hr before starting unit. To furnish power to heater
only, set thermostat to OFF and close electrical disconnect to
outdoor unit.
A crankcase heater is required if refrigerant tubing is longer than
50 ft. Refer to Residential Split System Long-Line Application
Guideline.
Step 9—Install Electrical Accessories
Refer to the individual instructions packaged with kits or acces-
sories when installing.
Step 10—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.
CONTACTOR
BLUE
GROUND
LUG
A94025
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• 3-phase scroll compressors are rotation sensitive.
• Excessive noise or equalized pressures indicates reverse
rotation.
• This will cause compressor damage or failure.
• Disconnect power to unit and interchange 2 field wiring
leads on unit contactor.
To prevent personal injury wear safety glasses, protective
clothing, and gloves when handling refrigerant and observe
the following:
• Back seating service valves are not equipped with Schrader
valves. Fully back seat (counter clockwise) valve stem before
removing gage port cap.
• Front seating service valves are equipped with Schrader
valves.
Do not vent refrigerant to 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 tube 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. Replace caps finger-tight and tighten with
wrench an 1/12 turn for back seating valves (male square
stem).
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 COOL and fan control to ON or AUTO
mode, as desired. Operate unit for 15 minutes. Check system
refrigerant charge.

SEQUENCE OF OPERATION

Turn on power to indoor and outdoor units. Transformer is
energized.
On a call for cooling, thermostat makes circuits R-Y and R-G.
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.
When thermostat is satisfied, its contacts open, de-energizing
contactor and blower relay. Compressor and motors stop.
If indoor unit is equipped with a time-delay relay circuit, the
indoor blower runs an additional 90 sec to increase system
efficiency.
Step 11—Check Charge
UNIT CHARGE
Factory charge is shown on unit rating plate. Adjust charge by
following procedure shown on charging tables located on unit.
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NOTE: If superheat or 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
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