Chiller LAB REPORT

REL/ 212 LAB REPORT

NAMES OF SQUAD MEMBERS:

Joaquin Velez

Nazim Khan

Robert Santana

Darnell Cadle

NAME AND WRITE A BRIEF DESCRIPTION OF THE EQUIPMENT:

COMPRESSOR INFORMATION:

A. Manufacturer: Durham-BushB. Model number: 30H/LFC. Serial number: 71H0508GD. Type of compressor: Semi-hermeticE. Type of compressor motor: ReciprocatingF. Type of Starting relay: Hard wired relayG. Compressor Voltage: 208/230 voltsH. Single phase of Three-phase: Three phaseI. Full load Amperage: 11.5J. Locked Rotor Amperage: 58.0K. Is the compressor thermal overload connected internally of externally: Externally

DEFINE

A. Full load amperage (FLA): As the torque load on a motor increases, the amperage required to power the motor also increases. When the full-load torque and horsepower is reached, the corresponding amperage is known as the full-load amperage (FLA). This value is determined by laboratory tests; the value is usually rounded up slightly and recorded as the nameplate value. Rounding up allows for manufacturing variations that can occur and some normal voltage variations that might increase the full-load amps of the motor. The nameplate FLA is used to select the correct wire size, motor starter, and overload protection devices necessary to serve and protect the motor.

B. Lock rotor amperage (LRA): When AC motors are started with full voltage applied; they create an inrush current that's usually many times greater than the value of the full-load current. The value of this high current can be important on some installations because it can cause a voltage dip that might affect other equipment.

C. Saturation: Saturation is simply the term used to describe the point where a change of state in a substance is taking place

D. Superheat: Superheat is then any temperature of a gas above the boiling point.E. Sub-cooling: Sub cooling is any temperature of a liquid or solid below its saturation temperature.

CONDENSER

A. Type of condenser: Water cooled(tube in shell)B. Manufacturer: Durham-Bush

C. Type of fan motor: D. Fan motor voltage:

E. Fan motor amperage draw:F. Fan motor rotation:

G. Induced draft of forced draft: Forced

WATER COOLED CONDENSERA. Type of regulation valve: Pressure regulating ValveB. Entering water temperature: a. Before stating system b. At start up: c. After 10

min. d. 30 minC. Leaving water temperature: a. Before starting system: b. At start up: c. After 10 min

d. 30 min.

CONDENSER SATURATION TEMPERATURE

a. Before starting system: b. At start up: c. After 10 min d. 30 min.

EVAPORATOR

A. Type of evaporator: Tube in shellB. Manufacturer: Durham-Bush

C. Type of fan motor: D. Superheat: N/A

E. Sub-cooling: N/A

WATER CHILLER

Entering water temperature: a. Before stating system: b. At start up: c. After 10 min: d. 30 min:

Leaving water temperature: a. Before starting system: b. At start up: c. After 10 min: d. 30 min.:

EVAPORATOR SATURATION TEMPERATURE

a. Before starting system: b. At start up: c. After 10 min: d. 30 min.:

FAN COIL TERMINAL

A. Entering air temperature a. Before starting system: b. At start up: c. After 10 min: d. 30 min:

B. Leaving air temperature: a. Before starting system: b. At start up: c. After 10 min: d. 30 min:

TYPE OF REFRIGERATION SYSTEM: Water Chiller

SYSTEM TEMPERATURE RANGE: 45- 55 DegreesF

TYPE OF DEFROSTING SYSTEM:

TYPE OF REFIGERANT: R-12

METERING DEVICE

A. Type of metering device: B. If (TXV) is it internally of externally equalized? C. Check the superheat setting?

Leaving air temperature: a. Before starting system: b. At start up: c. After 10 min d. 30 min.

CHECK THE CONDENSER SUB-COOLING

a. Before starting system: b. At start up: c. After 10 min d. 30 min.

DOES THE SYSEM HAVE THE FOLLOWING?

A. Liquid receiver? B. Accumulator?

C. Sight glass? YES D. Moisture indicator?

E. Oil sight glass: F. Evaporator pressure regulating valve?

G. Crankcase pressure regulation valve? YES

REFRIGERANT TUBING SIZES:A. Discharge Line : B. Liquid line: C. Suction line: D. Hot gas by-pass:

ELECTRICAL COMPONENTSA. Thermostat (description) : Low voltage

B. Liquid line solenoid valve voltage rating:C. Hot gas solenoid valve voltage:

D. Defrost timer voltage:E. Starting capacitor rating;

F. Run capacitor rating: G. Contactor/motor starter voltage:

DOES THE SYSTEM HAVE A DEFROST TIMER? WHAT TYPE?A. Timed defrost, timed termination:

B. Timed defrost, pressure termination: C. Timed defrost, temperature termination:

CONTROL SETTINGSA. Low pressure control: Cut-in : Cut-out:

B. High pressure control: Cut-in : Cut-out:C. Evaporator pressure regulating (EPR) valve setting:

D. Hold back/crankcase pressure regulating (CPR) valve setting:E. Operating thermostat setting:

F. Freeze protection thermostat setting:

EVAPORATOR TEMPERATURE

Not yet Determined.

a. Before starting system: b. At start up: c. After 10 min: d. 30 min:

CABINET TEMPERATURE:


OPERATING PRESSURES

Discharge Pressure:


B. Suction Pressure:


C. Crankcase Pressure:


SERVICE OPERATION

A. Is there a refrigerant Leak? Indicate where:B. Check the oil level, indicate the oil level: C. Is the system properly changed? NO State the reason for you answer:D. Type of capacity control:

OVERALL CONDITION OF SYSTEM:

MECHANICAL COMPONENTS:

3-PHASE COMPRESSOR: A vapor pump that pumps refrigerant throughout the system at a high pressure and returns the refrigerant vapor at a lower pressure

WATER COOLED CONDENSER: A tube in shell. Water is used to cool the condenser. One method is to cool them from water from the city water supply and then exhaust the water into the sewer. This method is expensive and in some instances is not allowed by law. Reject the heat through a “Tube in Shell” or “tube in tube” heat exchanger and then the water is passed through a cooling-tower before circulating back to the condenser or to a storm drain on small systems that use city water.

CHILLER: A chiller is part of a condenser. Chillers are used to cool water. The cooled (chilled) water is then fed through pipes to evaporator. This cools the area in which the evaporators are located. This type of cooling can be used in large air-conditioning units. It can also can be used for industrial processes where cooling is need for a particular operation. Chillers are the answer for requirements of 200 to 1,600 tons of refrigeration. They are used for process cooling, comfort are conditioning, nuclear power plant cooling.

FILTER_DRIER: Installed on the liquid lime of a refrigeration system. System component which absorbs the moisture present and filters it from particulate matter. Moisture will freeze and cause a restriction of the orifice of the expansion valve, will cause the metal in the system to react with the refrigerant to form acids which will cause compressor burnout and oil sludging.

How it works: The filter Drier contains a molded porous core. The core has a high affinity for moisture and also contains acid neutralizing agent. Provides protection of the expansion valve Liquid line, the filter –drier and is installed ahead of these two devices.

SIGHT GLASS- Is installed in the liquid line of a refrigeration system. Located usually ahead of the expansion valve. Provides a convenient means to view refrigerant flow.

EVAPORATOR: System component which absorbs the heat of the load into the system by evaporation of the refrigerant. A tube in shell evaporator

MOISTURE INDICATOR: A device used for determine moisture in a refrigerant.

THERMAL EXPANTION VALVE (TXV):

A specialized valve used in refrigerant systems to control the super in an evaporator by metering the liquid refrigerant flow to the evaporator. The TXV is so devised that the liquid refrigerant will start evaporating the moment that it enters the evaporator. This is called the “Dry” expansion principle

CRANKCASE PRESSURE REGULATOR (CPR): An automatic valve installed in the suction line usually close to the compressor. It is used to keep a compressor from overloading on a hot pull down by limiting the pressure to the compressor. A crankcase pressure regulator (CPR) is a common accessory added to many low-temperature refrigeration applications, such as walk-in and reach-in freezers. They are designed to prevent the compressor's motor from overloading when its crankcase pressure rises above its designed working pressure. On many low-temperature applications, this can occur during or after a defrost cycle, or after a normal shutdown period. The CPR is an outlet pressure regulator and will not allow the crankcase pressure to rise above a predetermined level.

COOLING TOWER- Cooling Towers are used to conserve or recover water. Most of the cooling that takes place in the tower results from the evaporation of part of the water as it falls through the tower. The lower the wet the wet bulb temperature on the incoming air, the more efficient the air is in decreasing the temperature of the water being fed to the tower.

ELECTRICAL COMPONENTS

FUSE: A safety device used in electrical circuits for the protection of the circuit conductor and electrical components. This particular unit is protected by four fuses.

ELECTRONIC THERMOSTATE: A device which detects temperature changes and initiates the system components involved with the heating or cooling operating of the system.

THERMOSTATE SENSOR: A temperature sensor for monitoring and controlling the temperature in the refrigerated room.

LOW-PRESSURE CUT-OUT: A pressure activated switch which detects the amount of pressure in the low side of the system. A safety device that provides protection to the compressor by shutting down the system on low pressure.

FREEZE PROTECTION THERMOSTAT: If an operating condition is reached in which freeze up of the water is imminent, and then the line thermostat will disconnect the cooling signal to the compressor and prevent the water from freezing.

FLOW SWITCH: A N.O switch which will close only when the water pumps are working and water is flowing throughout the system.

HIGH PRESSURE CUT-OUT: A pressure activated switch which detects the amount of pressure in the high side of the system. A safety device that provides protection to the compressor by shutting down the system on high pressure.

WATER PUMP: There are two water pumps on this unit. Both are supplied and operated by 3-phase 208/230 volt power.

LIQUID-LINE SOLENOID VALVE (LLSV): A normally closed electronically controlled valve installed on the condenser liquid line which will only be opened on a call for cooling by the thermostat. It is used to control the flow of liquid into the evaporator. The LLSV is operated by solenoid which will operate by opening and closing an orifice in a valve body that will permit or prevent the flow of liquid refrigerant through the valve. The orifice is opened or closed through the use of a plunger that is raised or lowered within a sleeve tube by energizing the coil. The LLSV is set so that it that if it fails the pressure in the high side of the system will keep the valve closed thus not permitting the valve to leak refrigerant into the low side of the system.

How it works: The solenoid assembly consists of a coil, plunger, and sleeve assembly. In a normally closed valve, a plunger return spring holds the plunger against the orifice, preventing flow through the valve. When the coil is energized, a magnetic field is produced, raising the plunger and allowing flow through the valve. In a normally open valve, when the coil is energized, the plunger seals off the orifice, stopping flow through the valve.

INTERNAL OVERLOAD: Thermal overload protection prevents compressor overheating by using lock-out thermal relay and compressor motor temperature.

The overload is a safety device that prevents the compressor from starting when:* the refrigerator is unplugged or disconnected then reconnected before refrigerant pressures have a chance to equalize* the compressor body is too hot* when start up of the compressor draws too much current due to:* voltage too low* internal electrical problem* internal mechanical resistance* refrigerator is stored outdoors, compressor too cold

COMPRESSOR CONTACTOR: The contactor's purpose is to send 230/208 Volts to energize the compressor. In this unit the compressor motor is initiated by the low pressure control.

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CRANKCASE HEATER: Heat provided for the compressor crankcase in order to prevent the migration of liquid refrigerant into the compressor during the compressor off cycle.

START RELAY (CURRENT TYPE): This current type starting relay contacts are normally open and is used for a single-phase AC induction motor. This starting relay is an electrically operated switch in which the coil of the relay is connected in series with the run winding of the compressor motor. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts. The coil current can be on or off so relays have two switch positions and they are double throw switches. The function of the start relay is to momentarily energize the start winding in the compressor motor and then cut power to the start winding as soon as the motor has reached about 75% of its full speed.

How it works: It is a current-sensing relay, which utilizes the principal of electromagnetism in a solenoid coil to be actuated by the motor main winding current through the coil, opening and closing the contacts of the relay. The relay utilizes the current of the main-winding current and motor speed to actuate the contacts to energize and de-energize the start winding circuit. As the motor accelerates and the main winding current increases, the relay solenoid picks up and closes the contacts to the start winding circuit. As the motor increases its speed, the main winding current begins to decrease, and at the appropriate motor speed (about 75% of its full speed.) the relay drops out, allowing the contacts to open and disconnect the start winding from the circuit. Gravity acting on the plunger opens the contacts.

MECHANICAL SEQUENCE OF OPERATION

The fans and pumps of the chilled water and cooling tower of a chilled water system are the pieces of equipment that would be energized in a normal operation sequence however, on unit #6 they are manually switched on.

The three phase reciprocating compressor continuously draws large quantities of refrigerant of high pressure superheated vapor R-12. Refrigerant enters the condenser tubes which are surrounded by water, in a sealed shell. In the condenser the refrigerant gives up enough latent heat to the water to condense back into a liquid.

From the condenser the sub-cooled low pressure liquid refrigerant goes through a filter drier before entering the TXV. This compressor suction reduces the pressure within the chiller, allowing the refrigerant vapor to coil vigorously at a fairly low temperature, typically 30 to 35 degrees F (-1 to 2 degrees C). Refrigerant from the TXV enters the evaporator tubes which are in a sealed shell filled with water. The refrigerant in the tubes will absorb the latent heat and will boil into a vapor. Liquid refrigerant obtains the energy needed for the change to vapor by removing heat from the water in the cooler tubes. The cold water can then be used in the refrigeration process.

The refrigerant will then enter superheated to the compressor (typically 10-12 Degrees F). A crankcase pressure regulating valve will maintain the pressure of the refrigerant in order for the compressor not to be overloaded.

Water at 45 degrees F from the evaporator shell will be pumped to a fan coil unit where it absorbs sensible heat from the air handler, and raises it to 55 degrees F before it enters the evaporator shell.

The Compressor will raise the refrigerant temperature above that of the water flowing through the condenser tubes. When the warm(typically 100 to 105 degrees F refrigerant vapor contacts the condenser tubes , the relatively cool condensing water(typically 85 to 95 degrees)removes some of the heat and the vapor condenses to a liquid.

Water from the condenser shell, at 95 degrees Fahrenheit, is pumped to the water tower in order to reject the heat it absorbed in the condenser. The 95 degree F water is then sprayed over fins from the top the cooling tower. By the time the water reaches the bottom of the tower (a reservoir) it loses about 10 degrees of sensible heat before returning to the condenser at 85 degrees F to complete the water tower cycle.

A hot gas bypass line (controlled by a hot gas bypass solenoid valve is connected to the compressor discharge line, In the event of an abnormal pressure drop in the evaporator a ‘pressure” signal. The hoe gas bypass valve will open on a pressure signal when there is a difference of pressure in the dishrag and suction pressure. Hot gas bypass will bypass the condenser, filter –drier and TXV. To enter into the evaporator inlet that will give a load to the evaporator to normalize the suction pressure.

A float valve connected the city water supply will maintain the level of the water in the reservoir at the bottom of the tower in order to “make up” water that is lost through the evaporative process of water.

ELECTRICAL SEQUENCE OF OPERATION

Thermostat calls for cool, assuming there are no safety interlocks open, compressor start relay turns on the compressor, (after a time delay on some units), the start relay for the condensor fan comes on. On some units, the indoor blower fan is switched by the outdoor unit, on others, the furnace starts the blower fan as soon as

there is a call for cooling.

The compressor of this u nit is powered by a three phase voltage source from a main disconnect switch (DS). All of the other components (pumps fan coil fan and crankcase heater- CCH) run on 230v available from a transformer connected to 208v between two hot line. The limits are all connected in series with the overload relay contacts (OR) and the compressor coil across the 230v lines to consist the control circuit.

Aside from the main disconnect fuses; the system circuitry is protected by four other fuses. The crankcase heater which is always energized as long as the DS is closed has two fuses on either side of the 230v series, and the control circuit is wired between two fuses between the on ei

When cooling is no longer needed

Chiller LAB REPORT

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