Carrier 30XW150-400 specifications Refrigerant Circuit, Maintenance, Troubleshooting

Refrigerant Circuit

LEAK TESTING — Units are shipped with complete operat- ing charge of refrigerant R-134a or nitrogen (see Physical Data tables supplied in the 30XW installation instructions) and should be under sufficient pressure to conduct a leak test. If there is no pressure in the system, introduce enough nitrogen to search for the leak. Repair the leak using good refrigeration practices. After leaks are repaired, system must be evacuated and dehydrated.

REFRIGERANT CHARGE — Refer to Physical Data tables supplied in the 30XW installation instructions. Immediately ahead of filter drier in each circuit is a factory-installed liquid line service valve. Each valve has a 1/4-in. access connection for charging liquid refrigerant.

Charging with Unit Off and Evacuated — Close liquid line service valve before charging. Weigh in charge shown on unit nameplate. Open liquid line service valve; start unit and allow it to run several minutes fully loaded. Check for a clear sight glass. Be sure clear condition is liquid and not vapor.

Charging with Unit Running — If charge is to be added while unit is operating, loop water temperatures should be near the ARI rating point (54/44 F evaporator; 85/95 F condenser). At these conditions and with the circuit at full load, charge to a clear sightglass and a liquid line temperature of 90 to 93 F (32.2 to 33.9 C).

Add 5 lb (2.3 kg) of liquid charge into the fitting located on the tube entering the bottom of the cooler. This fitting is located between the electronic expansion valve (EXV) and the cooler.

Allow the system to stabilize and then recheck the liquid temperature. If needed, add additional liquid charge, 5 lb (2.3 kg) at a time, allowing the system to stabilize between each charge addition. Slowly add charge as the sight glass begins to clear to avoid overcharging.

IMPORTANT: When adjusting refrigerant charge, circu- late fluid through cooler and condenser continuously to prevent freezing and possible damage to both. Do not overcharge, and never charge liquid into the low-pressure side of system.

Safety Devices — The 30XW chillers contain many safety devices and protection logic built into the electronic control. Following is a description of the major safeties.

COMPRESSOR PROTECTION

Motor Overload — The compressor protection modules (CPM) protect each compressor against overcurrent. Do not bypass the current transducers or make any changes to the factory-installed and configured headers. The configuration of these headers defines the Must Trip Amps (MTA) at which the CPM will turn the compressors off. Determine the cause for trouble and correct the problem before resetting the CPM. See Appendix D for MTA settings and configuration headers.

Each CPM board also reads the status of each compressor’s high-pressure switch. All compressors have factory-installed high-pressure switches. See Table 47.

Table 47 — High-Pressure Switch Settings

30XW UNIT	SWITCH SETTING
	psig	kPa
STD	217.6 +7.25, –14.5	1500 +50, –100
HIGH COND	304.5 +7.25, –14.5	2099 +50, –100

If the switch opens during operation, the compressor will be shut down. The CPM will reset automatically when the switch closes, however, a manual reset of the control is required to restart the compressor.

COOLER PROTECTION

Low Water Temperature — Microprocessor is programmed to shut the chiller down if the leaving fluid temperature drops below 34 F (1.1 C) for water or more than 8° F (4.4° C) below set point for Fluid Type = brine. When the fluid temperature rises 6° F (3.3° C) above the leaving fluid set point, the safety resets and the chiller restarts. Reset is automatic as long as this is the first occurrence of the day.

IMPORTANT: If unit is installed in an area where ambient temperatures fall below 32 F (0° C), a suit- able corrosion-inhibited antifreeze solution must be used in the chilled water and condenser water circuit.

Relief Devices — Fusible plugs are located in each cir- cuit between the condenser and the liquid line shutoff valve. PRESSURE RELIEF VALVES — Valves are installed in each circuit and are located on all coolers and condensers. These valves are designed to relieve if an abnormal pressure condition arises. Relief valves on all coolers relieve at 220 psi (1517 kPa). These valves should not be capped. If a valve relieves, it should be replaced. If the valve is not replaced, it may relieve at a lower pressure, or leak due to trapped dirt from the system which may prevent resealing. Valves on standard condensers relieve at 220 psi (1517 kPa). Valves on high condensing and heat reclaim units relieve at 300 psi (2068 kPa).

Pressure relief valves located on shells have 3/4-in. NPT connections for relief. Some local building codes require that relieved gases be exhausted to a specific location. This connec- tion allows conformance to this requirement. Refer to Installa- tion Instructions for details.

MAINTENANCE

Recommended Maintenance Schedule — The fol- lowing are only recommended guidelines. Jobsite conditions may dictate that maintenance schedule is performed more often than recommended.

Every month:

• Check moisture indicating sight glass for possible refriger- ant loss and presence of moisture.

Every 3 months:

•Check refrigerant charge.

•Check all refrigerant joints and valves for refrigerant leaks; repair as necessary.

•Check chilled water and condenser flow switch operation.

•Check oil filter pressure drop.

Every 12 months:

•Check all electrical connections; tighten as necessary.

•Inspect all contactors and relays; replace as necessary.

•Check accuracy of thermistors; replace if greater than ±2° F (1.2° C) variance from calibrated thermometer.

•Check accuracy of transducers; replace if greater than ±5 psi (34.47 kPa) variance.

•Check to be sure that the proper concentration of antifreeze is present in the chilled water and condenser loops, if applicable.

•Verify that the chilled water loop is properly treated.

•Check refrigerant filter driers for excessive pressure drop; replace as necessary.

•Check chilled water and condenser strainers, clean as necessary.

•Perform Service Test to confirm operation of all components.

•Check for excessive cooler approach (Leaving Chilled Water Temperature – Saturated Suction Temperature) which may indicate fouling. Clean cooler vessel if necessary.

•Obtain oil analysis; change as necessary.

TROUBLESHOOTING

See Table 48 for an abbreviated list of symptoms, possible causes and possible remedies.

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