Steps to Troubleshooting Refrigerated Truck Unit Issues

As is known to us all, an efficient transport refrigeration system is mainly composed of engine system, refrigeration unit, backup power and electrical control device. If the refrigeration compressor operates normally, but not cooling down, we conclude the reasons and troubleshooting methods as the following:

◆ The Filter is Blocked

The filter inlet has refrigerant, but there is no refrigerant leaking out when the outlet screw is loosened;

◆ The Thermal Expansion Valve (TEV) is Blocked

the manifestations are dirty blockage and ice blockage; Check whether the filter screen of the TEV is dirty. If yes, it should be cleaned and dried with nitrogen; if not, it should be cleaned with nitrogen too. When the temperature sensing bulb leaks, nitrogen cannot pass through the expansion valve, Then the TEV should be replaced in time;

If there is ice blockage during inspection, the entire truck refrigeration system must be dried with nitrogen to eliminate the ice blockage.

◆ TEV Adjustment

The TEV adjustment is too large or too small; 

--Too large, the compressor runs wet, and the suction pressure is low;

--Too small, little frosting occurs;

Check whether there is a leak in the refrigeration system, and adjust the expansion valve to achieve the best cooling effect.

◆ Cooling Fan Issues

Check the evaporator fan motor fuse and load distributor, and replace it in time if damaged. Check whether the voltage of the evaporator fan and the motor is lower than 12V. If so, you should focus on checking the 12V alternator and load distributor; The speed of the evaporator fan motor is not enough, which means that the wind force is weakened and the air volume is small.

◆ Refrigerant Leakage

If there is a refrigerant leak, leak detection should be underwent. The inspection parts include: compressor shaft seal, high-pressure exhaust port, low-pressure air outlet connector, connection of other truck refrigeration parts, and pipeline welding. Refrigerant leakage can generally be checked with halogen lamps, electronic leak detectors and other equipment. But in actual work, most people use soapy water for leak detection. After the leak point is well-treated, it must be pressurized with nitrogen to 1.2MPa and kept for 24 hours. When the gauge pressure does not drop, it can be evacuated and the refrigerant can be injected.

◆ Lack of Refrigerant

Insufficient refrigerant is manifested as slow cooling. If the liquid in the sight glass is in an intermittent flow state, it is mainly because the suction pressure is low; The reason for the low high pressure and low pressure is the lack of refrigerant.

◆ Too Much Refrigerant

The reasons for both high pressure and low pressure are too much air, too much refrigerant, poor cooling effect of the condenser, and too much opening of the expansion valve. First observe whether there is frost on the low-pressure pipe, if there is frost, the opening of the expansion valve is too large. Rinse the condenser with water again. If the effect is obviously improved, the cooling effect of the condenser is poor. If there is no change, there is air in the system. What's left is too much refrigerant. If there are no air bubbles in the glass eyes when turning on and off the air conditioner, it can be determined that there is too much refrigerant. As long as you let out some refrigerant, the fault can be eliminated. During operation, the low pressure is sometimes a vacuum and sometimes normal, which can diagnose moisture in the system. To re-vacuum, it is necessary to replace the liquid storage dryer, and then refill the refrigerant; the low pressure always indicates the cause of the vacuum: the system is blocked, and the refrigerant does not circulate. Most of the expansion valves and liquid storage dryers are blocked, and they can be replaced. The low pressure is high and the high pressure is low, because the compressor itself is not good. Disconnect the low pressure pipe of the compressor and try to plug the high pressure pipe behind the pressure gauge. Start the engine and connect the 12V power supply to the electromagnetic clutch. If the pressure is lower than 15kg/cm2, the compressor is definitely broken. Generally, only the compressor assembly can be replaced.

◆ Dirty Evaporator and Condenser

The surface of the condenser is too dirty, causing blockage of the air passage, which is manifested as high exhaust temperature and poor condensation effect; clean the condenser to improve the condensation effect; the surface of the evaporator is blocked by carton dust or other dirt, and the cold air is blocked; clean the evaporator , remove dirt and reduce cold air resistance;

 Truck reefer system and refrigerated truck bodies play the most essential role in affecting the cooling efficiency of medium to large refrigerated trucks. Therefore, it is very important to strengthen their daily maintenance.

The main function of the refrigerating unit is to freeze and keep cargoes chill at the desired temperature. The cold air is distributed to all corners of the box truck, to ensure the stable and low temperature inside the vehicle and maintain the freshness of the transported products.

1. The truck refrigeration compressor keeps working for a long time. There are too many impurities in the compartment, which will cause the compressor to lock up and destroy the transport refrigeration system. For this reason, except for daily cleaning, the vehicle refrigeration unit generally takes the initiative to carry out a comprehensive maintenance after 2000 kilometers’ travelling.

2. Regularly check whether the refrigeration system is stable, adjust the refrigeration compressor belt and bracket in time, and replace the drier. Always check the circuit facilities inside the box to prevent the power cord from being damaged, exposed, or soaked in water, which will cause the wire to be disconnected.

3. Some hot lighting equipment is easily damaged and should be replaced in time. When the refrigeration unit is used for a short time in winter, or if the refrigeration unit is not used for many consecutive months for other reasons, it should be started and operated once a month, and each operation time is about 10 minutes.

 

The refrigerated body is composed of thermal insulation material polystyrene foam (or polyurethane foam and extruded polystyrene foam), glass fiber reinforced plastic (or aluminum alloy, color steel plate), and steel frame.

 

4. Usually pay attention to safe driving and parking to prevent the body from being squeezed and injured, which will affect the structural stability and thermal insulation effect of the car body. 5. The goods to be shipped should be handled with care to avoid damage to the inner surface caused by sharp goods or packing boxes.

5. Park your refrigerated truck in a shady place when it's hot in summer, and in a carport when it's raining. The surface of the refrigerated compartment body is easily contaminated with dirt, and the dirt and dust should be cleaned in time. If you wanna keep the normal operation of the TRU while the vehicle stops, you can add an electric standby system on it, more environment-friendly and fuel-saving.

6. The maintenance of the inner surface of the refrigerated truck is very important. The stains should be cleaned after each transportation task, especially the eight corners and the rear door. Scrub the seal with warm water to keep the seal elastic.

7. Do a good job in the temperature control to prevent the surface of the truck from freezing. The refrigerated food should be packaged and sealed as much as possible to reduce the evaporation of moisture into the interior of the box and the possibility of freezing inside.

8. If the inner surface of the refrigerated truck is frozen, it should be removed with a deicing shovel in time after unloading. Scrub the inside and outside surfaces of the freezer with a soft cotton cloth dipped in non-corrosive detergent, and then dry with a dry cloth. Do not use organic solvents, hot water, washing powder, etc. to clean. Remember to cut off the power before each cleaning.

9. When loading, the refrigerated truck must be pre-cooled or pre-heated. Because the vehicle is parked in an open-air parking lot, the general cabin temperature is the outside ambient temperature. If the temperature of the delivered goods is not the ambient temperature, and the goods are loaded into the compartment, the ambient temperature will affect the temperature of the delivered goods, resulting in changes in the quality of the delivered goods. Therefore, it is necessary to pre-cool the carriage to the required temperature before loading.

Integrated Electric Standby for Refrigerated Trucks

Introduction of Integrated Electric Standby Refrigeration system

At present, the refrigeration system of most refrigerated vehicles relies on the vehicle engine to drive the transport refrigeration compressor to work, so as to achieve the purpose of refrigeration and food preservation. The compressor can only work when the vehicle is running. Once the engine is turned off, the refrigeration unit stops working. The electric standby system on the refrigerated truck is the second cooling power source activated when the engine of the chassis is not working or malfunctions. It can be used as a back-up refrigeration solution to solve some emergencies, and the refrigerated truck can also be used as a temporary cold storage.

Simply speaking, the vehicle powered refrigeration unit generally relies on the engine to drive the compressor of the refrigeration unit. After the engine is stopped, the refrigeration unit will stop working. If an integrated electric standby is installed, it can be directly powered after the engine is stopped. The truck refrigeration unit can still work afterwards, providing the preset refrigeration and fresh-keeping temperature for the truck compartment, so as to keep our goods fresh. The integrated electric standby system is more suitable for long-distance transportation, generally for refrigerated trucks over 7 meters.

Integrated Electric Standby System Composition

The electric standby system is composed of a motor, an independent compressor, an external power cord, and refrigerant pipeline, etc. It is independent of the original truck refrigeration compressor unit, but shares the same condensing system. Separate compressor for refrigeration, no need to start the vehicle. After the standby unit is installed, when the refrigerated vehicle engine stops working, through the electric standby system of the external power supply, the compressor can also be used when the vehicle is temporarily parked, broken down or repaired. Keeping the temperature in the compartment, and our goods fresh.

Working principle: Use the external power cord to rotate the motor, drive the independent compressor to work, and provide the circulating refrigerant for the refrigeration unit to work, without the chassis engine running.

Installation location: Generally, it is installed next to the beam of the refrigerated truck. It is also installed inside the box of a refrigerated truck, with a small side door open next to it.

Application: There are usually two models that are more suitable to be equipped with electric standby systems. One is a refrigerated truck used to transport temperature-sensitive cargoes to avoid abnormal cooling caused by the sudden condition of the vehicle's engine during transportation; the other is for refrigerated vans, short-distance cargo transportation. If you need to rest during transportation or during unloading, the integrated standby system comes into play. It can make the refrigerated van continue to supply the power required by the refrigerated truck unit through the backup compressor when the engine is stopped. The goods can be kept in a good condition in a constant temperature environment, and it can play a very good role in some goods with higher temperature requirements.