Carrier 24SCA5 Comfort Series Air Conditioner Installation Instructions

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 the pad, tie-down bolts should be used and fastened through knockouts provided in the unit base pan. Refer to the unit mounting pattern in Figure 2 to determine base pan size and knockout hole location.

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

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

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. (609.6 mm) clearance to the service end of the unit and 48 in. (1219.2 mm) above the unit. For proper airflow, a 6-in. (152.4 mm) clearance on 1 side of the unit and 12-in. (304.8 mm) on all remaining sides must be maintained. Maintain a distance of 24 in. (609.6 mm) between units or 18 in. (457.2 mm) if no overhang within 12 ft. (3.66 m). Position so water, snow, or ice from the roof or eaves cannot fall directly on the unit.

NOTE: The 18" (457.2 mm) clearance option described above is approved for outdoor units with wire grille coil guards only. Units with louver panels require 24" (609.6 mm) between units.

On rooftop applications, locate the unit at least 6 in. (152.4 mm) above the roof surface.

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

Make Piping Connections

⚠️ WARNING PERSONAL INJURY AND ENVIRONMENTAL HAZARD
Failure to follow this warning could result in personal injury or death. Relieve pressure and recover all refrigerant before system repair or final unit disposal. Use all service ports and open all flow-control devices, including solenoid valves. Federal regulations require that you do not vent refrigerant to the atmosphere. Recover during system repair or final unit disposal.

❗ CAUTION UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or improper operation.
If ANY refrigerant tubing is buried, provide a 6-in (152.4 mm) vertical rise at the service valve. Refrigerant tubing lengths up to 36-in (914.4 mm) may be buried without further special consideration. Do not bury lines more than 36-in. (914.4 mm).

Outdoor Unit Connected to Factory Approved Indoor Unit

The outdoor unit contains the approximate system refrigerant charge for operation with a factory-approved AHRI-rated indoor unit when connected by 15 ft. (4.57 m) of field-supplied or factory-accessory tubing, and the factory-supplied filter drier. Check refrigerant charge for maximum efficiency.

Refrigerant Tubing Connection Outdoor

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

Sweat Connection

❗ CAUTION UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or improper operation. Service valves must be wrapped in a heat-sinking material such as a wet cloth while brazing.

Use refrigeration-grade tubing. Service valves are closed from the 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 the service valve and the 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 the indoor coil are now ready for leak testing. This check should include all field and factory joints.

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

⚠️ WARNING FIRE HAZARD
Failure to follow this warning could result in personal injury, death, and/or property damage. Refrigerant and oil mixture could ignite and burn as it escapes and contacts the brazing torch. Make sure the refrigerant charge is properly removed from both the high and low sides of the system before brazing any component or lines.

❗ CAUTION BURN HAZARD
Failure to follow this caution may result in personal injury. Components will be HOT after brazing. Wear appropriate personal protective equipment and allow to cool before handling parts and equipment.

Install Liquid-Line Filter Drier Indoor

❗ CAUTION UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or improper operation.

1. Installation of filter drier in the liquid line is required.
2. Filter drier must be wrapped in a heat-sinking material such as a wet cloth while brazing.

Deep Vacuum Method

The deep vacuum method requires a vacuum pump capable of pulling a vacuum of 500 microns and a vacuum gauge 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 Figure 4.

Figure 4 - Deep Vacuum Graph: This graph illustrates the deep vacuum method for system evacuation. It plots vacuum (in microns) against time (in minutes), showing expected vacuum levels for a tight system versus a system that is too wet or leaking.

Pressure Proof Check

1. Perform a pressure check of the unit with a nitrogen charge of about 200 psi.
2. The nitrogen holding charge must NOT decrease in pressure for 1 hour, as indicated by the test gauge. The measuring test gauge resolution should not exceed 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 gauge capable of accurately measuring this vacuum depth.

⚠️ WARNING FIRE HAZARD
Failure to follow this warning could result in personal injury, death, and/or property damage. DO NOT USE FLAMES OR IGNITION SOURCES TO LEAK CHECK.

1. Vacuum unit to 500 microns.
2. When isolating the unit from the pump, the pressure shall not rise above 1500 microns in 10 minutes.

Final Tubing Check

IMPORTANT: Check to be certain factory tubing on both the 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.

Installing with Indoor Piston

Outdoor Unit Connected to Factory Approved Indoor Unit
Check piston size shipped with the indoor unit to see if it matches the required indoor piston size. If it does not match, replace the indoor piston with the 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 the outdoor unit. Refer to the AHRI Directory to check if a certain combination can use a piston or requires an accessory TXV.

When changing the indoor piston, use a back-up wrench. Hand-tighten the hex nut, then tighten with a 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 the distributor body, and must be installed properly to ensure proper seating. See Figure 5.

Figure 5 - Indoor (Cooling) Piston: This diagram shows the components of an indoor piston assembly, including the brass hex nut, Teflon seal/rings, brass hex body, distributor, piston, and piston 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 gauge to the service port.
3. Measure liquid line temperature by attaching an accurate thermistor type or electronic thermometer to the liquid line near the outdoor coil.
4. Refer to the unit rating plate for the required subcooling temperature.
5. Refer to Table 2 - Rating Plate (required) Subcooling Temperature. Find the point where the required subcooling temperature intersects the measured liquid service valve pressure.
6. To obtain the required subcooling temperature at a specific liquid line pressure, add refrigerant if the liquid line temperature is higher than indicated, or reclaim refrigerant if the 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 gauge to the suction valve service port.
3. Measure suction temperature by attaching an accurate thermistor type or electronic thermometer to the suction line at the service valve.
4. Measure outdoor air dry-bulb temperature with a 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 the outdoor temperature and evaporator entering air wet-bulb temperature. At this intersection, note the superheat. Where a dash (--) appears on the table, do not attempt to charge the system under these conditions, or refrigerant slugging may occur. Charge must be weighed 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 the superheat temperature (from #6 above) and suction pressure. At this intersection, note the suction line temperature.
8. If the unit has a higher suction line temperature than the charted temperature, add refrigerant until the charted temperature is reached.
9. If the unit has a lower suction line temperature than the charted temperature, reclaim refrigerant until the charted temperature is reached.
10. When adding refrigerant, charge in liquid form into the suction service port using a flow-restricting device.
11. If the outdoor air temperature or pressure at the suction valve changes, adjust charge to the new suction line temperature indicated on the chart.
12. Optimum performance will be achieved when the operating charge produces 10°F suction superheat at the 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.

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.

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.

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

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.

⚠️ WARNING ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury or death. The unit cabinet must have an uninterrupted or unbroken ground to minimize personal injury if an electrical fault should occur. The ground may consist of electrical wire or metal conduit when installed in accordance with existing electrical codes.

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 Figure 6.

Figure 6 - Line Connections: This diagram illustrates the basic electrical connections for a single-phase unit. It shows the path from the disconnect switch to the contactor, including field power wiring, field ground wiring, and the ground lug.

Connect Control Wiring

Route 24-v control wires through the control wiring grommet and connect leads to control wiring. Refer to thermostat Installation Instructions for wiring specific unit combinations (see Figure 8).

Use No. 18 AWG color-coded, insulated (35°C minimum) wire. If the thermostat is located more than 100 ft. (30.48 m) from the 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.

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.

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 the heater a minimum of 24 hr before starting the unit. To furnish power to the heater only, set the thermostat to OFF and close the electrical disconnect to the outdoor unit.

A crankcase heater is required if refrigerant tubing is longer than 80 ft. (24.38 m) or when the outdoor unit is 35 ft. (6.10m) below the indoor unit. Refer to the Residential Piping and Longline Guideline and Service Manual.

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 the monitor. If the LED is flashing, disconnect power to the unit and interchange 2 field-wiring leads on the unit contactor.

Figure 7 - 3-Phase Monitor Control (Applies to 3-Phase Units Only): This diagram shows the 3-phase monitor control board with its indicator LEDs (OFF, FLASHING, ON) and terminals (24VAC, COM, L1, L2, L3).

Table 5 - Three-Phase Monitor LED Indicator

❗ CAUTION UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage or improper operation.

• Ensure compressor rotation is correct.
• 3-phase scroll compressors are rotation sensitive.
• A flash LED on the phase monitor indicates reverse rotation. (See Table 5). This will not allow the contractor to be energized.
• Disconnect power to the unit and interchange 2 field-wiring leads on the unit contactor.

Sequence of Operation

Turn on power to indoor and outdoor units. The transformer is energized. On a call for cooling, the thermostat makes circuits R-Y and R-G. Circuit R-Y energizes the contactor, starting the outdoor fan motor and compressor circuit. Circuit R-G energizes the indoor unit blower relay, starting the indoor blower motor on high speed.

When the thermostat is satisfied, its contacts open, de-energizing the contactor and blower relay. The compressor and motors should stop.

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

Check Charge

Factory charge amount and desired subcooling are shown on the unit rating plate. The charging method is shown on the information plate inside the unit. For TXV, use the subcooling method. For piston, use the 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:

The unit is factory charged for 15 ft (4.57 m) of lineset. Adjust charge by adding or removing 0.6 oz/ft of 3/8 liquid line above or below 15 ft. (4.57 m) respectively.

Allow the system to operate at least 15 minutes. If conditions are favorable, check system charge by the superheat method for a fixed metering device and the subcooling method for a TXV. If any adjustment is necessary, adjust charge slowly and allow the 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 the 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. (4.57 m) only. The charge level should then be appropriate for the system to achieve rated capacity. The charge level could then be checked at another time when both indoor and outdoor temperatures are in a more favorable range.

NOTE: If line length is beyond 80 ft (24.38 m) or greater than 35 ft (10.7 m) vertical separation, See Long Line Guideline for special charging requirements.

* For 15 ft. (4.57 m) line set.

Accessory Usage

⚠️ WARNING PERSONAL INJURY AND/OR PROPERTY DAMAGE HAZARD
Failure to follow this warning could result in personal injury and/or property damage. For continued performance, reliability, and safety, the only approved accessories and replacement parts are those specified by the equipment manufacturer. The use of non-manufacturer approved parts and accessories could invalidate the equipment limited warranty and result in fire risk, equipment malfunction, and failure. Please review manufacturer's instructions and replacement part catalogs available from your equipment supplier.

Table 6 - Accessory Usage

* For tubing line sets between 80 and 200 ft. (26.7 and 60.96 m) and/or 35 ft. (10.7 m) vertical differential, refer to Residential Piping and Longline Guideline.
† Additional requirement for Low-Ambient Controller (full modulation feature) MotorMaster® Control.
‡ Required if Low Pressure Switch is factory or field installed.

Figure 8 - Generic Wiring Diagrams: These diagrams show typical wiring configurations for connecting an A/C thermostat to an indoor unit (furnace or fan coil) and the outdoor air conditioner. They cover single-phase and 3-phase systems and include a legend for wiring types (24-V Factory Wiring, 24-V Field Wiring, Field Splice Connection, Contactor).

Final Checks

IMPORTANT: Before leaving the 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 the 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 the owner. Explain system operation and periodic maintenance requirements outlined in the manual.
5. Fill out the Dealer Installation Checklist and place in the 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

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