Frost build-up on evaporator coils
- Lack of airflow, dirty filters, dirty coils.
Low suction in the condenser
- Low refrigerant charge or leaks.
- Blocked expansion valve (moisture, dirt, etc).
- Reduction of flow in evaporator.
Leak detection
- Ultraviolet dye.
- Soap bubbles.
- Electronic detectors.
- First check all fittings and coils. If leak cannot be found, system must be reclaimed and pressure tested.
Signs of leaking Freon
- Warm air supply and low airflow.
- Increase in electricity bills.
- Bubbling or gurgling noises.
- Refrigerant poisoning.
Low suction pressure
- Insufficient heat getting to the evaporator caused by low airflow (dirty filter, slipping belt, restricted ductwork). Check for proper superheat.
- Defective, plugged, or undersized metering device. superheat doesn’t change, and the subcooling increases. Check sight glass. Obstructions in filter/dryer.
- Low refrigerant. Superheat is high and the subcooling is low.
- Check superheat and subcooling to make the correct diagnosis.
- Superheat indicates how much refrigerant is in the evaporator (high superheat indicates not enough, low superheat indicates too much).
- Subcooling gives an indication of how much refrigerant is in the condenser.
How to Measure Superheat
- Take pipe temperature at the suction line using a contact thermocouple (don’t use IR).
- Convert suction pressure to temperature.
- Subtract the two numbers.
How to Measure Supercooling
- Attach a thermometer to the liquid line near the condenser.
- Take the head pressure and convert it to temperature.
- Subtract the two numbers.
Surging in Chiller Compressors
- Surging is caused by increased condenser pressure, problem with cooling tower or water in between (blockage).
- Occurs when pressure in the condenser is too great and starts to push back into the evaporators.
- Can cause very serious damage.
- Chiller will make very loud “groan” from compressor. Sound will suddenly stop when pressure equalizes. Also causes fluctuation in compressor motor current.
- Change in flow rate, drop below minimum.
- Pump strainer blockage.
- Cooling tower unable to reject enough heat: Motor, drive belt, water distribution (leaves, flow blockage), etc.
- Fouling in condenser.
