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Evaporator Problems

What is an evaporator?

In domestic HVAC use an evaporator is a set of coiled tubes with fins around it to channel air flow. When the cooling cycle is on, compressed gas enters the evaporator where it expands and becomes cold resulting in the tubes also becoming cold. The air blowing through the fins is chilled and creates the cooling effect. An evaporator is also known as a heat exchanger. Evaporator problem can affect the functioning of an HVAC system. Experts on JustAnswer have answered a wide variety of questions on evaporator problems.

How do I clean the evaporator on my Rheem model RCBA-3765GG17 air conditioner? I have removed the cover but the A coil only partially slides out

What you are referring to is the RCBA multiplex coil with 3 rows of short A coils. In many cases, these are not easy to clean. If there is not too much dirt, turn off the unit and allow the coils to get completely dry. Using a soft / medium hard brush, gently brush the dirt off. Be careful not to bend the delicate fins. If there is excessive or coagulated dirt, you can use a spray on cleaner that should be available from HVAC supply or hardware stores. Spray the cleaner into the evaporator. Some cleaners can be left on the coils and the condensate will wash it off when you run the system. Others need to be rinsed off. Follow the instruction on the spray. If rinsing is needed, place some old towels under the coil and rinse with clean water. If this does not work, the evaporator will need to be removed for cleaning and getting a technician to do is advisable.

I had my evaporator coil replacement done earlier this year when it started leaking. Now the air conditioner is not working again and I am told that the evaporator coil is blocked. What does this mean and why did it happen?

When a coil is replaced the normal practice is to purge the system with nitrogen to flush out any air and contaminants. The evaporator is then pressurized and placed in a vacuum to check for leaks. If leaks are found, they are repaired and the flushing is done again. This ensures that the coil is clean and free from any material that could with use, block the tube. It could be that the system was not completely flushed at the time it replaced.

What is the best way to thaw a frozen indoor air conditioner evaporator?

Turn the cooling off using the thermostat and let the fan run. This will allow warm air to flow over the evaporator and melt the ice. A common reason for an evaporator to become covered with ice is inadequate air flow over it. Please check the air filter and if it is dirty or damaged, clean or replace it.

The evaporator on my Lennox air conditioner has a leak. Can it be repaired or is evaporator replacement required? And if evaporator coil replacement is necessary, can you tell me how much it will cost?

The viability of repairing the leak depends on where on the coil it is. It is a very tricky job. Many technicians do not approve of coil repair as even if the repair is done, there may be problems with the condensation not dripping off properly and falling outside the drain pan. As for the cost, indicative prices are: labor – 3 hours; coil - $500 to $700 (without dealer markup); refrigerant – up to $40 per pound (you may need 10 pounds); miscellaneous items - $100. Add to this freight and the technician’s margin. Please note that these are all very approximate figures which may vary considerably.

The evaporator coils on my air conditioner keep freezing up blocking the air flow. I’ve replaced the air filter and cleaned the coils. The fan seems to be okay. What is causing this and what should I do?

If the filter and evaporator are clean and blower working properly, the most likely cause of the evaporator freezing is a low refrigerant level. This can be a complex job and handling the refrigerant requires certification. It would be best to get a technician to locate and repair the leak and refill the refrigerant.

The efficiency of an evaporator can be affected by dirt, physical damage or impurities in the circulating gas which can cause blockages in the tubes. When dealing with evaporator problems, follow the instructions given in the owner’ manual. Evaporator’s are delicate and easily damaged. If the manual does not cover the problem you are facing, getting expert help is advisable.
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