Carrier 24SCA4, 24SCA5 Comfort Series Air Conditioner Installation Instructions

Safety Considerations

IMPORTANT: This appliance shall only be installed by EPA qualified personnel having appropriate certification. This appliance is not intended for use by persons (including children) with reduced physical, sensory or mental capabilities or lack of experience and knowledge, unless they have been given supervision or instruction concerning use of the appliance by a person responsible for their safety.

Improper installation, adjustment, alteration, service, maintenance, or use can cause explosion, fire, electrical shock, or other conditions which may cause death, personal injury, or property damage. Consult a qualified installer, service agency, or your distributor or branch for information or assistance. The qualified installer or agency must use factory-authorized kits or accessories when modifying this product. Refer to the individual instructions packaged with the kits or accessories when installing.

Follow all safety codes. Wear safety glasses, protective clothing, and work gloves. Use quenching cloth for brazing operations. Have fire extinguisher available. Read these instructions thoroughly and follow all warnings or cautions included in literature and attached to the unit. Consult local building codes and current editions of the National Electrical Code (NEC) NFPA 70. In Canada, refer to current editions of the Canadian electrical code CSA 22.1.

Recognize safety information. This is the safety-alert symbol ⚠️. When you see this symbol on the unit and in instructions or manuals, be alert to the potential for personal injury. Understand these signal words; DANGER, WARNING, and CAUTION. These words are used with the safety-alert symbol. DANGER identifies the most serious hazards which will result in severe personal injury or death. WARNING signifies hazards which could result in personal injury or death. CAUTION is used to identify unsafe practices which would result in minor personal injury or product and property damage. NOTE is used to highlight suggestions which will result in enhanced installation, reliability, or operation.

General

ℹ️ NOTE: In some cases noise in the living area has been traced to gas pulsations from improper installation of equipment.

1. This unit is intended to be installed in a location that is 10,000 feet (3000 meters) above sea level or lower.
2. Locate unit away from windows, patios, decks, etc. where unit operation sound may disturb customer.
3. Ensure that vapor and liquid tube diameters are appropriate for unit capacity.
4. Run refrigerant tubes with no bends with centerline bend radius less than 2.5 times the external pipe diameter.
5. Leave some slack between structure and unit to absorb vibration.
6. When passing refrigerant tubes through the wall, seal opening with RTV or other pliable silicon-based caulk. (See Fig. 1.)
7. Avoid direct tubing contact with water pipes, duct work, floor joists, wall studs, floors, and walls.
8. Do not suspend refrigerant tubing from joists and studs with a rigid wire or strap which comes in direct contact with tubing (see Fig. 1).
9. Ensure that tubing insulation is pliable and completely surrounds vapor tube.
10. When necessary, use hanger straps which are 1 in. (25 mm) wide and conform to shape of tubing insulation. (See Fig. 1.)
11. Isolate hanger straps from insulation by using metal sleeves bent to conform to shape of insulation.
12. Provision shall be made for expansion and contraction of long runs of piping.
13. Piping and fittings shall be protected as far as possible against adverse environmental effects. For example, the accumulation of dirt and debris.
14. Piping should be installed to reduce the likelihood of hydraulic shock damaging the system.
15. Certified piping and components must be used in order to protect against corrosion.
16. Flexible pipe elements shall be protected against mechanical damage, excessive stress by torsion, or other forces. They should be checked for mechanical damage annually.
17. Piping material, routing, and installation shall be include protection from physical damage in operation and service, and be in compliance with the national and local codes and standards of the installation site.
18. When setting up refrigerant piping, precautions shall be taken to avoid excessive vibration or pulsation.

Installation

IMPORTANT: Effective January 1, 2015, all split system and packaged air conditioners must be installed pursuant to applicable regional efficiency standards issued by the Department of Energy.

Check Equipment and Job Site

Unpack Unit

Move to final location. Remove carton taking care not to damage unit.

Inspect Equipment

File claim with shipping company prior to installation if shipment is damaged or incomplete. Locate unit rating plate on unit corner panel. It contains information needed to properly install unit. Check rating plate to be sure unit matches job specifications.

Install on a Solid, Level Mounting Pad

If conditions or local codes require the unit be attached to pad, tie down bolts should be used and fastened through knockouts provided in unit base pan. Refer to unit mounting pattern in Fig. 2 to determine base pan size and knockout hole location.

For hurricane tie downs, contact local distributor for details and PE (Professional Engineer) certification, if required.

Make Piping Connections

Fig. 1 - Piping Installation Diagram: Illustrates refrigerant tubing passing through a wall, with details on insulation, caulking, and hanger straps. Shows indoor and outdoor wall separation, joist, suction tube, and liquid tube.

On rooftop applications, mount on level platform or frame. Place unit above a load-bearing wall and isolate unit and tubing set from structure. Arrange supporting members to adequately support unit and minimize transmission of vibration to building. Consult local codes governing rooftop applications.

Roof mounted units exposed to winds may require wind baffles. Consult the Application Guideline and Service Manual - Residential Split System Air Conditioners and Heat Pumps for wind baffle construction.

ℹ️ NOTE: Unit must be level to within ±2° (±3/8 in./ft.±9.5 mm/m) per compressor manufacturer specifications.

Clearance Requirements

When installing, allow sufficient space for airflow clearance, wiring, refrigerant piping, and service. Allow 24 in. (610 mm) clearance to service end of unit and 48 in. (1219 mm) (above unit. For proper airflow, a 6-in. (152 mm) clearance on 1 side of unit and 12-in. (305 mm) on all remaining sides must be maintained. Maintain a distance of 24 in. (610 mm) between units or 18 in. (457 mm) if no overhang within 12 ft. (3.67 m) Position so water, snow, or ice from roof or eaves cannot fall directly on unit.

ℹ️ NOTE: 18" (457 mm) clearance option described above is approved for outdoor units with wire grille coil guard only. Units with louver panels require 24" (610 mm) between units.

On rooftop applications, locate unit at least 6 in. (152 mm) above roof surface.

Operating Ambient

The minimum outdoor operating ambient in cooling mode without accessory is 55°F (13°C).

Fig. 2 - Tiedown Knockout Locations: A table showing unit base pan dimensions and corresponding tiedown knockout locations (A, B, C) in inches (mm).

Hazards and Tubing

Outdoor units may be connected to indoor section using accessory tubing package or field-supplied refrigerant grade tubing of correct size and condition. Rated tubing diameters shown in Table 1 are recommended up to 80 ft. (24 m). See Product Data for acceptable alternate vapor diameters and associated capacity losses. For tubing requirements beyond 80 ft. (24 m), substantial capacity and performance losses can occur. Following the recommendations in the Residential Piping and Long Line Guideline will reduce these losses. Refer to Table 1 for field tubing diameters. Refer to Table 6 for accessory requirements.

There are no buried-line applications greater than 36-in. (914 mm) allowed.

If refrigerant tubes or indoor coil are exposed to atmosphere, they must be evacuated to 500 microns to eliminate contamination and moisture in the system.

Outdoor Unit Connected to Factory Approved Indoor Unit

For proper unit operation, check refrigerant charge using charging information located on control box cover and/or in the Check Charge section of this instruction.

When outdoor unit is connect to factory-approved indoor unit, outdoor unit contains approximate system refrigerant charge for operation with factory approved AHRI rated indoor unit when connected by 15 ft. (4.6 m) of field-supplied or factory-accessory tubing, and factory supplied filter drier. Check refrigerant charge for maximum efficiency.

Unit is factory charged for 15ft (4.57 m) of lineset (except for 24SCA4 18 and 24 sizes. Add 18 oz for the 18 size and 6 oz for the 24 size for 15 ft lineset). For all sizes, adjust charge by adding or removing 0.6 oz/ft of 3/8 liquid line above or below 15 ft. (4.6 m) respectively.

Refrigerant Tubing Connection Outdoor

IMPORTANT: Maximum liquid-line size is 3/8-in. OD for all residential applications including long line. Refer to Residential Piping and Long Line Guideline for further information.

IMPORTANT: Always install the factory-supplied liquid-line filter drier. If replacing the filter drier, refer to Product Replacement Parts List. for appropriate part number. Obtain replacement filter driers from your distributor or branch.

Connect vapor and liquid tubes to fittings on vapor and liquid service valves (see Table 1.) Use refrigerant grade tubing

Sweat Connection

Use refrigeration grade tubing. Service valves are closed from factory and ready for brazing. Clean line set tube ends with emery cloth or steel brush. Remove any grit or debris. Insert line set tube ends into service valve tube stubs. Apply heat absorbing paste or heat sink product between service valve and joint. Wrap service valves with a heat sinking material such as a wet cloth. Braze joints using a Sil-Fos or Phos-copper alloy. Consult local code requirements.

Refrigerant tubing and indoor coil are now ready for leak testing. This check should include all field and factory joints.

ℹ️ NOTE: Some outdoor units contain a mechanical fitting at the liquid distributor. This connection is not field serviceable and should not be disturbed.

Table 1 - Refrigerant Connections and Recommended Liquid and Vapor Tube Diameters (In.)

Indoor Coil and Evacuation

Install Liquid-Line Filter Drier Indoor

Refer to Fig. 3 and install filter drier as follows:

1. Braze 5-in. liquid tube to the indoor coil.
2. Wrap filter drier with damp cloth.
3. Braze filter drier to above 5-in. (127 mm) liquid tube. Flow arrow must point towards indoor coil.
4. Connect and braze liquid refrigerant tube to the filter drier.

Fig. 3 - Liquid Line Filter Drier Diagram: Shows the installation of a liquid line filter drier, including brazing points and flow direction.

Evacuate Refrigerant Tubing and Indoor Coil

Refrigerant tubes and indoor coil should be evacuated using the recommended deep vacuum method of 500 microns. The alternate triple evacuation method may be used (see triple evacuation procedure in service manual). Always break a vacuum with dry nitrogen.

Deep Vacuum Method

The deep vacuum method requires a vacuum pump capable of pulling a vacuum of 500 microns and a vacuum gage capable of accurately measuring this vacuum depth. The deep vacuum method is the most positive way of assuring a system is free of air and liquid water. A tight dry system will hold a vacuum of 1000 microns after approximately 7 minutes. See Fig. 4

Fig. 4 - Deep Vacuum Graph: A graph illustrating vacuum depth (microns) over time (minutes) for a deep vacuum system, showing "LEAK IN SYSTEM", "VACUUM TIGHT", and "DRY SYSTEM" levels.

Mandatory Requirements

Pressure Proof Check

1. Preform a pressure check of the unit with a nitrogen charge of about 200psi.
2. The Nitrogen holding charge must NOT decrease in pressure for 1 hour, as indicated by the test gauge. The measuring test gauge resolution not exceeding 5% of the holding charge.

Leak Check

This leak check requires a vacuum pump capable of pulling a vacuum of at least 500 microns and a vacuum gage capable of accurately measuring this vacuum depth.

Final Tubing Check

IMPORTANT: Check to be certain factory tubing on both indoor and outdoor unit has not shifted during shipment. Ensure tubes are not rubbing against each other or any sheet metal or wires. Pay close attention to feeder tubes, making sure wire ties on feeder tubes are secure and tight.

Unit Configuration and Charging

Installing with Indoor Piston

Outdoor Unit Connected to Factory Approved Indoor Unit

Check piston size shipped with indoor unit to see if it matches required indoor piston size. If it does not match, replace indoor piston with correct piston size.

The piston included with the FMA, FMC and FMU fan coils are unique to those products and CANNOT be replaced with the piston shipped with outdoor unit. Refer to the AHRI Directory to check if a certain combination can use a piston or requires an accessory TXV.

When changing indoor piston, use a back-up wrench. Hand tighten hex nut, then tighten with wrench 1/2 turn. Do not exceed 30 ft-lbs. The indoor piston contains a Teflon ring (or seal) which is used to seat against the inside of distributor body, and must be installed properly to ensure proper seating. See Fig. 5

Fig. 5 - Indoor (Cooling) Piston Diagram: Shows the components of an indoor cooling piston, including hex nut, Teflon seal, rings, distributor, piston, and retainer.

Units with Cooling Mode TXV

Units installed with cooling mode TXV require charging by the subcooling method.

1. Operate unit a minimum of 15 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 2 - Rating Plate (required) Subcooling Temperature. 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 (±1.7°C).

Units with Indoor Piston

Units installed with indoor pistons require charging by the superheat method.

The following procedure is valid when indoor airflow is within ±21 percent of its rated CFM.

1. Operate unit a minimum of 15 minutes before checking charge.
2. Measure suction pressure by attaching an accurate gage to suction valve service port.
3. Measure suction temperature by attaching an accurate thermistor type or electronic thermometer to suction line at service valve.
4. Measure outdoor air dry-bulb temperature with thermometer.
5. Measure indoor air (entering indoor coil) wet-bulb temperature with a sling psychrometer.
6. Refer to Table 3 - Superheat Charging - AC Only. Find outdoor temperature and evaporator entering air wet-bulb temperature. At this intersection, note superheat. Where a dash (--) appears on the table, do not attempt to charge system under these conditions or refrigerant slugging may occur. Charge must be weighted in, adding or removing 0.6 oz/ft of 3/8 liquid line above or below 15 feet (4.6m) respectively.
7. Refer to Table 4 - Required Suction-Line Temperature. Find superheat temperature (from #6 above) and suction pressure. At this intersection, note suction line temperature.
8. If unit has a higher suction line temperature than charted temperature, add refrigerant until charted temperature is reached.
9. If unit has a lower suction line temperature than charted temperature, reclaim refrigerant until charted temperature is reached.
10. When adding refrigerant, charge in liquid form into suction service port using a flow-restricting device.
11. If outdoor air temperature or pressure at suction valve changes, charge to new suction line temperature indicated on chart.
12. Optimum performance will be achieved when the operating charge produces 10°F suction superheat at suction service valve with 95°F (35°C) outdoor ambient and 80°F (27°C) dry bulb (67°F / 19°C) wet bulb) indoor temperature (DOE "A" test conditions) at rated airflow.

Table 2 - Rating Plate (required) Subcooling Temperatures

Table 3 - Superheat Charging - AC Only

Notes:
- Optimum performance point, 95°F (35°C) outdoor ambient and (80°F / 27°C dry bulb), (67°F / 19°C wet bulb) indoor conditions. (DOE A Test Conditions)
- Where a dash (--) appears do not attempt to charge system under these conditions or refrigerant slugging may occur. Charge must be weighed in.
- Superheat °F is at low-side service port, Allow a tolerance of ±3°F (±1.7°C)
- Indoor dry bulb between 70°F and 80°F (21°C and 27°C)

Table 4 - Required Suction-Line Temperature

Electrical Connections

Make Electrical Connections

Be sure field wiring complies with local and national fire, safety, and electrical codes, and voltage to system is within limits shown on unit rating plate. Contact local power company for correction of improper voltage. See unit rating plate for recommended circuit protection device.

ℹ️ NOTE: Operation of unit on improper line voltage constitutes abuse and could affect unit reliability. See unit rating plate. Do not install unit in system where voltage may fluctuate above or below permissible limits.

ℹ️ NOTE: Use copper wire only between disconnect switch and unit.

ℹ️ NOTE: Install branch circuit disconnect of adequate size per NEC to handle unit starting current. Locate disconnect within sight and readily accessible from unit, per Section 440-14 of NEC. Refer to Product Data for breaker sizing.

Route Ground and Power Wires

Remove access panel to gain access to unit wiring. Extend wires from disconnect through power wiring hole provided and into unit control box.

Connect Ground and Power Wires

This appliance incorporates an earth connection for safety purposes only. Connect ground wire to ground connection in control box for safety. Connect power wiring to contactor as shown in Fig. 6.

Fig. 6 - Line Connections Diagram: Shows wiring from a disconnect to the unit's contactor, including field power wiring, field ground wiring, and phase connections.

Connect Control Wiring

Route 24-v control wires through control wiring grommet and connect leads to control wiring. Refer to thermostat Installation Instructions for wiring specific unit combinations (see Fig. 7 ).

Use No. 18 AWG color-coded, insulated (35°C minimum) wire. If thermostat is located more than 100 ft. (30 m) from unit, as measured along the control voltage wires, use No. 16 AWG color-coded wire to avoid excessive voltage drop.

All wiring must be NEC Class 2 and must be separated from incoming power leads.

Use furnace transformer, fan coil transformer, or accessory transformer for control power, 24v/40va minimum.

ℹ️ NOTE: Use of available 24v accessories may exceed the minimum 40va power requirement. Determine total transformer loading and increase the transformer capacity or split the load with an accessory transformer as required.

Fig. 7 - Generic Wiring Diagrams: Illustrates typical wiring connections between an A/C thermostat, furnace/fan coil, and the air conditioner for various configurations.

Start-Up and Monitoring

Final Wiring Check

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.

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 80 ft. (24 m) or when outdoor unit is 35 ft. (6 m) below indoor unit. Refer to the Residential Piping and Long Line Guideline and Service Manual.

Install Electrical Accessories

Refer to the individual instructions packaged with kits or accessories when installing.

Start-Up

Follow these steps to properly start up system:

1. After system is evacuated, fully 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. Replace caps finger-tight and tighten with wrench an additional 1/12 turn.
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.

3-Phase Monitor

In 3-phase units a small circuit board is factory installed to monitor line voltage. A small led will flash if a phase problem exists. See code descriptions on monitor. If LED is flashing, disconnect power to unit and interchange 2 field-wiring leads on unit contactor.

Fig. 8 - 3-Phase Monitor Control Diagram: Shows the 3-phase monitor control board with LED indicator and status table.

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 should stop. If indoor unit is equipped with a time-delay relay circuit, the indoor blower will run up to 90 seconds to increase system efficiency.

Charge Check and Accessories

Check Charge

Factory charge amount and desired subcooling are shown on unit rating plate. Charging method is shown on information plate inside unit. For TXV, use subcooling method. For piston, use superheat method. To properly check or adjust charge, conditions must be favorable for subcooling charging. Favorable conditions exist when the outdoor temperature is between 70°F and 100°F (21°C and 38°C), and the indoor temperature is between 70°F and 80°F (21°C and 27°C). Follow the procedure below:

Unit is factory charged for 15ft (4.57 m) of lineset (except for 24SCA4 18 and 24 sizes. Add 18 oz for the 18 size and 6 oz for the 24 size for 15 ft lineset). For all sizes, adjust charge by adding or removing 0.6 oz/ft of 3/8 liquid line above or below 15 ft. (4.6 m) respectively.

Allow system to operate at least 15 minutes. If conditions are favorable, check system charge by super heat method for fixed metering device and subcooling method for TXV. If any adjustment is necessary, adjust charge slowly and allow system to operate for 15 minutes to stabilize before declaring a properly charged system.

If the indoor temperature is above 80°F (27°C), and the outdoor temperature is in the favorable range, adjust system charge by weight based on line length and allow the indoor temperature to drop to 80°F (27°C) before attempting to check system charge by subcooling method as described above.

If the indoor temperature is below 70°F (21°C), or the outdoor temperature is not in the favorable range, adjust charge for line set length above or below 15 ft. (4.6 m) only. Charge level should then be appropriate for the system to achieve rated capacity. The charge level could then be checked at another time when the both indoor and outdoor temperatures are in a more favorable range.

ℹ️ NOTE: If line length is beyond 80 ft (24 m) or greater than 35 ft (11 m) vertical separation, See Residential Piping and Long Line Guideline for special charging requirements.

Table 6 - Accessory Usage

* For tubing set lengths between 80 and 200 ft. (24 and 61 m) horizontal or 35 ft. (10.7 m) vertical differential (total equivalent length), refer to the Residential Split-System Long Line Application Guideline.
‡ In units equipped with ECM OD motor, motor and fan needs to be replaced per unit accessory guide to work properly. Unit will not meet AHRI rated efficiency once motor and fan are replaced to use this accessory.
† Required if Low Pressure Switch is factory or field installed.

Final Checks and Maintenance

Final Checks

IMPORTANT: Before leaving job, be sure to do the following:

1. Ensure that all wiring is routed away from tubing and sheet metal edges to prevent rub-through or wire pinching.
2. Ensure that all wiring and tubing is secure in unit before adding panels and covers. Securely fasten all panels and covers.
3. Tighten service valve stem caps to 1/12-turn past finger tight.
4. Leave Owner's Manual with owner. Explain system operation and periodic maintenance requirements outlined in manual.
5. Fill out Dealer Installation Checklist and place in customer file.

Repairing Refrigerant Circuit

When breaking into the refrigerant circuit to make repairs, or for any other purpose, the following procedures shall be used.

1. Safely remove the refrigerant using a recovery pump certified for flammable refrigerants.
2. Purge the refrigerant circuit with nitrogen gas.
3. Evacuate the refrigerant circuit to 1500 microns.
4. Break vacuum with a nitrogen purge of the refrigerant circuit ensuring that the outlet of the vacuum pump is not near a potential ignition source.
5. Open the circuit by cutting or brazing.

CARE AND MAINTENANCE

For continuing high performance and to minimize possible equipment failure, periodic maintenance must be performed on this equipment. Frequency of maintenance may vary depending upon geographic areas, such as coastal applications. See Owner's Manual for information.

Training

My Learning Center is your central location for professional residential HVAC training resources that help strengthen careers and businesses. We believe in providing high quality learning experiences both online and in the classroom. Access My Learning Center with your HVACpartners credentials at www.mlctraining.com. Please contact us a mylearning@carrier.com with questions.

©2022 Carrier. All rights reserved. Edition Date: 10/22 Catalog No: 24SCA4-24SCA5-2SI Replaces:24SCA4-1SI