What can cause a restriction in a HVAC system?
Liquid line restrictions can be caused by a restricted filter-drier, a restricted thermostatic expansion valve screen, a kinked liquid line, a bent lower condenser coil, or an oil-logged capillary tube. An evaporator that is starved of refrigerant will house a starved compressor and condenser as well.
How do I know if my orifice tube is clogged?
Symptoms of a Bad or Failing Expansion Valve (Orifice Tube)
- AC system performing worse than usual and blowing warm air.
- Frost on AC evaporator or coming from the vents.
- AC compressor constantly running.
What happens when an orifice tube is clogged?
A clogged orifice tube is typically caused by compressor failure. When this happens, little pieces of metal and aluminum shrapnel will be found in the tube’s screen filter. If the filter’s filled with white or brownish debris, the desiccant bag in the accumulator has broken, sending desiccant throughout the system.
What is a common symptom of a severely restricted filter drier?
A starved evaporator from the liquid line (filter drier) restriction will cause high superheats. High compression ratios from the low evaporator pressure will cause high heat of compression, thus high discharge temperatures. This is assuming there’s still some mass flow rate of refrigerant through the system.
What causes refrigerant restriction?
This is caused from a lack of internal volume in the condenser to hold the added refrigerant. Even the receiver may overfill if too much refrigerant is added.
What happens when an evaporator becomes blocked?
As a cooling coil (or evaporator coil) in an air conditioner becomes blocked with dust and debris the air flow across the coil is reduced. This reduced air flow (in cubic feet per minute or CFM) across the coil means that the cooling capability of the whole air conditioning system is reduced.
How do you know if you have a bad expansion valve?
If you have a bad expansion valve, the expansion tube will start to frost over. When the valve leaks, it causes the refrigerant to overflow and mix with the compressor oil.
How can you tell when a filter drier is stopped up?
If the filter drier is partially clogged, there may be a few degree temp drop across it. However, if the filter drier is completely clogged, there will be a large temperature drop across it and likely frost due to the low temp of the refrigerant exiting the clogged filter drier.
How are liquid line restrictions diagnosed?
Symptoms of a liquid line restriction include:
- Low evaporator (suction) pressure;
- High superheats;
- Higher-than-normal discharge temperatures;
- Low amp draw;
- Short-cycle on low-pressure control (LPC);
- Somewhat high discharge temperature;
- Low condensing (head) pressure;
- Low condenser split;