3_Description

Section 3

DESCRIPTION

3.1General Description

3.1.1Refrigeration Unit − Front Section

The unit is designed so that the majority of the components are accessible from the front (see Figure 3.1). The unit model number, serial number, and parts identification number can be found on the serial plate to the left of the compressor.

3.1.2Fresh Air Makeup Vent

The function of the upper or lower makeup air vent is to provide ventilation for commodities that require fresh air circulation. A manually operated venting system is located in the upper left access panel. The optional eAutoFresh vent system is to moderate the atmospheric level in the container in response to cargo respiration. When transporting frozen cargo loads the vent will be closed. The upper left access panel contains the vent slide and motor assembly. It may be removed to allow entry into the evaporator section where the CO₂ sensor and drive pack are located.

Figure 3.1 Refrigeration Unit - Front Section

1.Access Panel (Evap Fan #1) / TXV / HTT

2.Fork Lift Pockets

3.Control Box

4.Unit Display

5.Control Panel

6.Remote Monitoring Receptacle

7.Start−Stop Switch, ST

8.Interrogator Connector

9.Return Temperature Supply/Recorder Sensor Assembly (RTS/RRS)

10.Compressor

11.Condenser Grille

12.Power Cables and Plug (Location)

13.Autotransformer

14.Upper Fresh Air Makeup Vent

- - - - -

3.1.3Evaporator Section

The evaporator section (Figure 2-2) contains the supply temperature sensor, humidity sensor, thermostatic expansion valve, dual-speed evaporator fans (EM1 and EM2), evaporator coil and heaters, defrost temperature sensor, heat termination thermostat, and heat exchanger.

The evaporator fans circulate air through the container by pulling it from the bottom of the unit, directing it through the evaporator coil where it is heated or cooled, and discharging it at the top.

The evaporator components are accessible by removing the upper rear panel (as shown in Figure 3.2).

Figure 3.2 Evaporator Section - Units with Center Access Panel

1.Evaporator Fan Motor #1

2.Supply Recorder Sensor (SRS) / Supply Temperature Sensor (STS)

3.Humidity Sensor

4.Evaporator Fan Motor #2

5.Evaporator Coil

6.Evaporator Coil Heaters

7.Defrost Temperature Sensor (DTS)

8.Heater Termination Thermostat (HTT)

9.Heat Exchanger

10.Thermostatic Expansion Valve (TXV)

11.TXV Bulb

12.Interrogator Connector (Rear) (ICR)

13.USDA Probe Receptacle PR2

14.USDA Probe Receptacle PR1

15.USDA Probe Receptacle PR3

16.Cargo Probe Receptacle PR4

- - - - -

3.1.4Compressor Section

The reciprocating compressor section includes the compressor (with high pressure switch), power cable storage compartment, and autotransformer.

This section also contains the suction modulating valve, discharge pressure regulating valve, discharge temperature sensor, and discharge/suction pressure transducers.

The return temperature sensor, return recorder sensor, and ambient sensor are located at the right side of the compressor.

Figure 3.3 Compressor Section

1.Quench Valve

2.Suction Modulating Valve

3.Suction Temperature Sensor

4.Quench Valve Temperature Bulb

5.Ambient Sensor

6.Suction Service Valve

7.Suction Pressure Transducer

8.Compressor

9.Compressor Sight Glass View Port

10.Discharge Pressure Transducer

11.Discharge Service Valve

12.High Pressure Switch

13.Return Temperature Sensor (RTS)

14.Return Recorder Sensor (RRS)

15.Power Cables and Plug

16.Autotransformer

- - - - -

3.1.5Air-Cooled Condenser Section

The air-cooled condenser section (Figure 3.4) consists of the condenser fan, condenser coil, receiver with sight glass/moisture indicator, quench valve, liquid line service valve, filter-drier, condenser pressure transducer, and fusible plug.

The condenser fan pulls air from around the coil and discharges it horizontally through the condenser fan grille.

Figure 3.4 Condenser Section

1.Condenser Coil

2.Sight Glass

3.Condenser Pressure Transducer

4.Receiver

5.Sight Glass/Moisture Indicator

6.Filter-Drier

7.Liquid Line Service Valve

8.Quench Valve

9.Fusible Plug

10.Condenser Fan Motor

11.Condenser Fan

12.Condenser Grille

13.Condenser Coil Cover

- - - - -

3.1.6Control Box Section

The control box (Figure 3.5) includes the manual operation switches, circuit breaker (CB-1), compressor, fan and heater contactors, control power transformer, current sensor module, controller module and the communications interface module.

3.1.7Communications Interface Module (option)

The communications interface module is a slave module which allows communication between the refrigeration unit and a ship system master central monitoring station. The module will respond to communication, and return information over the ships main power line. Refer to the master system technical manual for further information.

Figure 3.5 Control Box Section

1.Compressor Contactor − CH

2.Compressor Phase A Contactor − PA

3.Compressor Phase B Contactor − PB

4.Heater Contactor − HR

5.Controller/DataCORDER Module (Controller)

6.Remote Monitoring Receptacle

7.Start−Stop Switch, ST

8.Controller Battery Pack (Standard Location)

9.Control Transformer

10.Evaporator Fan Contactor − E1

11.Evaporator Fan Contactor − S1

12.Evaporator Fan Contactor − S2 or EF

13.Evaporator Fan Contactor − E2 or ES

14.Condenser Fan Contactor − CF

15.Circuit Breaker (CB1) − 460V

16.Current Sensor Module

17.Emergency Bypass Switch (EBS)

- - - - -

3.2Refrigeration System Data

Compressor / Motor Assembly	Number of Cylinders	6
	Model	06DR
	CFM	41
	Weight (Dry)	118kg (260 lb)
	Approved Oil	Castrol Icematic
	Oil Charge degrees	3.6 liters (7.6 U.S. pints)
	Oil Sight Glass	The oil level range, with the compressor off, should be between the bottom and one-eighth level of the sight glass.
Expansion Valve Superheat	Verify at -18C (0°F) container box temperature	4.4 to 6.7°C (8 to 12°F)
Heater Termination Thermostat	Opens	54° (+/− 3) C = 130° (+/− 5) F
Heater Termination Thermostat	Closes	38° (+/− 4) C = 100° (+/− 7) F
High Pressure Switch	Cutout	25 (+/− 1.0) kg/cm2 = 350 (+/− 10) psig
High Pressure Switch	Cut-In	18 (+/− 0.7) kg/cm2 = 250 (+/− 10) psig
EXPLOSION HAZARD: Failure to follow this WARNING can result in death, serious personal injury and / or property damage. Never use air or gas mixtures containing oxygen (O2) for leak testing or operating the product. Charge Only With R−134a: Refrigerant must conform to AHRI Standard 700 specification.
Refrigerant	R−134a	Conforming to AHRI standard 700 specifications.
Refrigerant Charge	Unit Configuration	Charge Requirements − R-134a
Refrigerant Charge	Receiver	3.3 kg (7.3 lbs)
When replacing components (g.) and (h.), refer to installation instructions included with replacement part.
Fusible Plug, Receiver*	Melting point	99°C = (210°F)
Fusible Plug, Receiver*	Torque*	6.2 to 6.9mkg (45 to 50ft-lbs)
Sight Glass / Moisture Indicator	Torque	8.9 to 9.7mkg (65 to 70ft-lbs)
Condenser Pressure Transducer	Condenser Fan Starts	Condenser fan will start if condenser pressure is greater than 14.06kg/cm2 (200psig) OR the condenser fan is OFF for more than 60 seconds.
Condenser Pressure Transducer	Condenser Fan Stops	Condenser fan will stop if condenser pressure is less than 9.14kg/cm2 (130psig) AND the condenser fan remains ON for at least 30 seconds.
Unit Weight	Refer to unit model number plate.

* Rupture Disc, part number 14 -00215 -04 may be installed as an alternate for the receiver mounted fusible plug.

3.3Electrical Data

Circuit Breaker	CB-1	Trips at 29 amps
	CB-2 (50 amps)	Trips at 62.5amps
	CB-2 (70 amp)	Trips at 87.5amps
Compressor Motor	Full Load Amps (FLA)	17.6amps @ 460VAC (with current limiting set at 21 amps)
Condenser Fan Motor	Nominal Supply	380 VAC, Three Phase, 50 Hz	460 VAC, Three Phase, 60 Hz
	Full Load Amps	.71 amps	.72 amps
	Horsepower	0.21 hp	0.36 hp
	Rotations Per Minute	1450 rpm	1750 rpm
	Voltage and Frequency	360 − 460 VAC +/− 2.5 Hz	400 − 500 VAC +/− 2.5 Hz
	Bearing Lubrication	Factory lubricated, additional grease not required.
	Rotation	CCW when viewed from shaft end.
Evaporator Coil Heaters	Number of Heaters	6
	Rating	750 watts +5/−10% each @ 230 VAC
	Resistance (cold)	66.8 to 77.2 ohms @ 20°C (68°F)
	Type	Sheath
Evaporator Fan Motor(s)		380 VAC/50 Hz	460 VAC/60 Hz
	Full Load Amps High Speed	1.6	2.1
	Full Load Amps Low Speed	0.6	0.6
	Nominal Horsepower High Speed	0.58	1.0
	Nominal Horsepower Low Speed	0.07	0.12
	Rotations Per Minute High Speed	2850 rpm	3450 rpm
	Rotations Per Minute Low Speed	1425 rpm	1725 rpm
	Voltage and Frequency	360 − 460 VAC +/− 1.25 Hz	400 − 500 VAC +/− 1.5 Hz
	Voltage & Frequency using power autotransformer	180 − 230 VAC +/− 1.25Hz	200 − 250 VAC +/− 1.5 Hz
	Bearing Lubrication	Factory lubricated, additional grease not required
	Rotation EF #1	CW when viewed from shaft end
	Rotation EF #2	CCW when viewed from shaft end
Fuses	Control Circuit	7.5 amps (F3A, F3B)
	Controller / DataCORDER	5 amps (F1 & F2)
Vent Positioning Sensor	Electrical Output	0.5 VDC to 4.5 VDC over 90 degree range
	Supply Voltage	5 VDC +/− 10%
	Supply Current	5 mA (typical)
Humidity Sensor	Orange wire	Power
	Red wire	Output
	Brown wire	Ground
	Input voltage	5 vdc
	Output voltage	0 to 3.3 vdc
	Output voltage readings verses relative humidity (RH) percentage:
	30%	0.99V
	50%	1.65V
	70%	2.31V
	90%	2.97V
Controller	Setpoint Range	-30 to +30°C ( -22 to +86°F)

3.4Safety and Protective Devices

Unit components are protected from damage by safety and protective devices listed in the following table. These devices monitor the unit operating conditions and open a set of electrical contacts when an unsafe condition occurs.

Table 3–1 Safety and Protective Devices
UNSAFE CONDITION	SAFETY DEVICE	DEVICE SETTING
Excessive current draw	Circuit Breaker (CB-1) − Manual Reset	Trips at 29 amps (460VAC)
	Circuit Breaker (CB-2, 50 amp) − Manual Reset	Trips at 62.5 amps (230VAC)
	Circuit Breaker (CB-2, 70 amp) − Manual Reset	Trips at 87.5 amps (230VAC)
Excessive current draw in control circuit	Fuse (F3A & F3B)	7.5 amp rating
Excessive current draw by controller	Fuse (F1 & F2)	5 amp rating
Excessive condenser fan motor winding temperature	Internal Protector (IP-CM) − Automatic Reset	N/A
Excessive compressor motor winding temperature	Internal Protector (IP-CP) − Automatic Reset	N/A
Excessive evaporator fan motor(s) winding temperature	Internal Protector(s) (IP-EM) − Automatic Reset	N/A
Abnormal pressures / temperatures in the high refrigerant side	Fusible Plug − Receiver	99°C = (210°F)
Abnormally high discharge pressure	High Pressure Switch (HPS) − Automatic Reset	Open at 25kg/cm@ (350psig) Close at 18kg/cm@ (250psig)

3.5Refrigeration Circuit

Starting at the compressor (see Figure 3.6), the suction gas is compressed to a higher pressure and temperature.

The gas flows out the compressor through the discharge service valve. Refrigerant gas then moves into the air-cooled condenser, where air flowing across the coil fins and tubes cools the gas to saturation temperature. By removing latent heat, the gas condenses to a high pressure/high temperature liquid and flows to the receiver, which stores the additional charge necessary for low temperature operation.

The liquid refrigerant continues through the liquid line service valve, the filter-drier (which keeps refrigerant clean and dry), and a heat exchanger (that increases subcooling of the liquid) to the thermostatic expansion valve (TXV).

As the liquid refrigerant passes through the variable orifice of the TXV, the pressure drops to suction pressure. In this process some of the liquid vaporizes to a gas (flash gas), removing heat from the remaining liquid. The liquid exits as a low pressure, low temperature, saturated mix. Heat is then absorbed from the return air by the balance of the liquid, causing it to vaporize in the evaporator coil. The vapor then flows through the suction tube back to the compressor.

The TXV is activated by the bulb strapped to the suction line near the evaporator outlet. The valve maintains a constant superheat at the coil outlet regardless of load conditions.

The TXV is a mechanical device that regulates the flow of liquid to the evaporator coil in order to maintain a relatively constant degree of superheat in the gas leaving the evaporator regardless of suction pressure.

The flow of liquid to the evaporator is regulated by a variable orifice which opens to increase refrigerant flow (decrease superheat), or closes to decrease refrigerant flow (increase superheat). The variable orifice is controlled by the temperature sensing bulb which is strapped to the suction line near the evaporator outlet.

During periods of low load, the suction modulating valve (SMV) decreases flow of refrigerant to the compressor. This action balances the compressor capacity with the load and prevents operation with low coil temperatures. In this mode of operation, the quench valve will open as required to provide sufficient liquid refrigerant flow into the suction line for cooling of the compressor motor. The quench valve senses refrigerant condition entering the compressor and modulates the flow to prevent entrance of liquid into the compressor.

The refrigeration system is also fitted with a condenser pressure transducer, which feeds information to the controller. The controller programming will operate the condenser fan so as to attempt to maintain discharge pressures above 130psig in low ambients. At ambients below 27°C (80°F), the condenser fan will cycle on and off depending on condenser pressure and operating times.

1.The condenser fan will start if the condenser pressure is greater than 200psig OR the condenser fan has been OFF for more than 60 seconds.

2.The condenser fan will stop if the condenser pressure is less than 130psig AND the condenser fan has been running for at least 30 seconds.

At ambients above 27°C (80°F), condenser pressure control is disabled and the condenser fan runs continuously.

Figure 3.6 Refrigeration Circuit Schematic