Air conditioning systems with expansion valve Troubleshooting Procedures parti2

Air conditioning systems with expansion valve
Troubleshooting Procedures
parti2



expansion valve Air conditioning


Correct evaluation of the pressure manometer display is particularly important. Here are some examples:
 expansion valve
The expansion valve’s place in the system is at the evaporator inlet. Like any other valve, its job is to control flow; in this case, the amount of refrigerant entering the evaporator. Since system operating conditions vary (sometimes high cooling demand, sometimes low cooling demand) it is necessary to be able to adjust the amount of refrigerant entering the evaporator. For any given operating condition, if we were to allow too much refrigerant to enter the evaporator, it would get too cold, and the moisture collected on it could freeze. This would not allow the hot interior air to pass through its fins, and the refrigerant flowing inside the evaporator would not be able to absorb the heat from the air. This would eventually bring cooling to a halt. If we were to allow too little refrigerant to enter the evaporator, there may not be enough to properly absorb the interior heat, which would also result in inadequate, or no cooling. This process of varying refrigerant flow based on system cooling demand is referred to as “metering” the refrigerant into the evaporator.
Air conditioning systems with expansion valve:
6-
Low pressure:
normal, but inconsistent

High pressure:
normal, but inconsistent

Outflow temperature at the centre vent:
higher

Possible causes:
humidity in the system, defective
expansion valve

7-
Low pressure:
 fluctuating

High pressure:
fluctuating

Outflow temperature at the centre vent: 
fluctuating

Possible causes: 
expansion valve or compressor
defective

8-  
 Low pressure:
 normal to low

 High pressure:
 normal to low

Outflow temperature at the centre vent: 
higher

Possible causes:  
evaporator contaminated, lack of
refrigerant

9-  
 Low pressure:
 high

 High pressure:
 low
Outflow temperature at the centre vent:
higher, almost ambient
temperature
Possible causes:
expansion valve stuck in opened
position, compressor defective
10-  
 Low pressure:
 low

 High pressure:
 low

 Outflow temperature at the centre vent:
 higher, up to ambient
temperature

Possible causes
 lack of refrigerant
11- 

 Low pressure:
 low pressure and high pressure are
the same

 High pressure:
 low pressure and high pressure are
the same
 
 Outflow temperature at the centre vent:
 ambient temperature

Possible causes
lack of refrigerant, compressor
defective, fault in the electrical
system

         abo bahaa eddine 
 

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