ANSWER: 1. Installation methods: base fixed 2. Hole fixed+base fixed 3. Hole Fixed

 

Q2. How many refrigerants are suitable for compressors?

ANSWER: General classification of refrigerants: inorganic compounds, organic compounds, mixtures (azeotropic and non-azeotropic)  

Inorganic Compound Refrigerants: add Integer Part of the Relative Molecular Weight of Inorganic Compounds to R700 

NH3 (ammonia)       H2O (water) CO2 (carbon dioxide)

Molecular weight  17 18 44 

No. R717 R718 R744

Organic compound refrigerants:

R134a (tetrafluoroethane) chemical formula is CH2FCF3.

Mixed refrigerants (azeotropic and non-azeotropic):            

The number of azeotropic refrigerant mixtures is R5, starting from R500, such as R501, R502, etc. 

The number of non-azeotropic refrigerants is R4, such as R404a, R407C, R410, etc. 

R404A is a non-azeotropic refrigerant composed of HFC125, HFC-134a and HFC-143. 

R407c is a ternary non-azeotropic refrigerant composed of R32, R125 and R134a in proportion of 23:25:52.

 

Q3. What does PWM control mean? 

ANSWER: CAN control: The compressor uses CAN bus protocol to communicate with the air-conditioning system controller, sending information like compressor start-stop, rotation speed, fault information, status information etc. Compressor start-stop, operation and information feedback can be controlled by this way. 

PWM control: The compressor receives PWM duty cycle signal sent by the air conditioning system controller to adjust the speed, thus realizing the frequency conversion and speed regulation function. 

Fixed-speed control: The compressor runs at a fixed speed (e.g. 3000rpm, 4000rpm etc.) and controls the start and stop of the compressor with high-voltage ON/OFF or low-voltage ON/OFF.

 

Q4.Failure analysis and maintenance method of freezing system.

ANSWER:1. Frozen plug of expansion valve hole

Failure analysis:

Improper drying of main components in the refrigeration system;

The entire system is not completely evacuated;

The moisture content of the refrigerant exceeds the standard.

Judgment method: intermittent cooling, normal cooling starts, frost on the entire surface of the expansion valve after a period of maintenance, the evaporation temperature reaches below 0 degrees, moisture accumulates at the expansion valve hole, and the valve hole is gradually blocked. Then frost appears on the evaporator, and the sound of airflow cannot be heard, and the suction pressure is in a vacuum state. Heating the expansion valve with hot water is because the ice at the valve hole melts and can be cooled normally.

Discharge method: A filter equipped with a moisture absorbent (silica gel, anhydrous calcium chloride) is inserted in the refrigeration system to filter out the water in the system, and then the filter is removed.

 

2. Dirty plug at the filter of the expansion valve

Failure analysis: When there are more coarse powdery dirt in the system, the entire filter will be blocked, and the refrigerant cannot pass through, resulting in no refrigeration.

Judgment method: knock on the expansion valve, sometimes it can be cooled by some refrigerant.

 

3. The filter is clogged

Failure analysis: The desiccant is used for a long time to form a paste to seal the filter or the dirt is gradually accumulated in the filter and causes blockage.

Judgment method: After tapping the filter, there will be ventilation. Touching the filter by hand is cooler than usual. The filter can be removed for cleaning and drying, and the desiccant can be replaced and installed into the system.

 

4. Refrigerant leakage in the temperature sensing package of the expansion valve

Failure analysis: After the temperature sensor in the expansion valve's temperature sensor leaks, the two forces under the diaphragm push the diaphragm upward, the valve hole is closed, and the refrigerant cannot pass through the system, resulting in no refrigeration, and the expansion valve does not frost at this time , The low pressure is vacuum, and no airflow sound can be heard in the evaporator.

Judgment method:

Unscrew the inlet of the expansion valve to see if there is refrigerant ejection, and it will be quickly closed.

Open the expansion valve to see if there is refrigerant ejection. If not, it means that it is blocked.

Discharge method: Shut down the shut-off valve, remove the expansion valve to see if the filter is clogged, if not, you can blow the inlet of the expansion valve with a nozzle to see if there is ventilation. It can also be inspected visually or disassembled and replaced when damaged.

 

5. The system is filled with too much refrigerant

Failure analysis: Too much refrigerant causes the discharge pressure to rise significantly, exceeding the normal value.

Discharge method: shut down and discharge excess refrigerant out of the system through the high-pressure exhaust hole.

 

6. Residual air in the system

Failure analysis: There is air circulation in the system, and the exhaust pressure will be too high, the exhaust temperature will be high, the exhaust pipe will be hot, and the cooling effect will be poor. The compressor will run soon and the exhaust pressure will exceed the normal value, forcing the pressure relay to act.

Discharge method: stop, release air at the exhaust valve hole.

 

7. Shutdown caused by low suction pressure

Failure analysis: When the suction pressure in the system is lower than the setting value of the pressure relay, the electric shock action cuts off the power supply.

Discharge method: refrigerant leakage. The system is blocked.

 

8. The compressor suddenly stops during operation

Failure analysis: cold storage with air-cooled condenser

The fan is not on

Damaged fan motor

Fan reverse

High ambient temperature (up to 40 degrees or more)

The condenser fins are blocked by oil and dust and the air is not circulating.

Shutdown caused by high exhaust pressure. (Poor cooling effect of condenser)

 

9. Motor overload

Failure analysis:

When using, put too much and excessive food in the storehouse;

The power supply is abnormal.

Discharge method: reduce heat load, pay attention to the change of power supply voltage.

 

10. Malfunctions in electrical appliances cause downtime.

Failure analysis: The thermostat fails to adjust or the temperature sensor is installed improperly.

Discharge method: remove the thermostat to repair the electric shock, adjust, adjust the position of the temperature sensor.

 

11. Sudden shutdown caused by other reasons.

Failure analysis: In the process of use and maintenance, it is often necessary to open and close the exhaust ‘inhalation, liquid reservoir and other shut-off valves, sometimes due to inadvertently opening the shut-off valve, causing the exhaust pressure to rise suddenly.

Discharge method: stop immediately to prevent danger.