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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.

Ask a HVAC Technician

gotoman for ac
gotoman for ac, HVAC Technician
Category: General
Satisfied Customers: 4766
Experience:  51 years of experience install design and repair of all makes and models of AC
19613070
Type Your HVAC Question Here...
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7 HVAC Technicians are Online Now

How JustAnswer Works:

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  • 100% Satisfaction Guarantee
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HVAC Technicians are online & ready to help you now

gotoman for ac
HVAC Technician
Satisfied Customers: 4657
51 years of experience install design and repair of all makes and models of AC
Phil
Mechanical Engineer
Satisfied Customers: 3888
Retired HVAC/ Electrical & Boiler contractor. Industrial
Rick Mather
HVAC Technician
Satisfied Customers: 3132
35 years experience, HVAC

Recent Evaporator Questions

  • MY NEW HVAC COMPANY TELLS ME THAT THE "HIGH LIMIT SWITCH IS FAULTY". THEY PRICE

    MY NEW HVAC COMPANY TELLS ME THAT THE "HIGH LIMIT SWITCH IS FAULTY". THEY PRICE THE PART AT $395 PLUS INSTALLATION. I AM NOT AN HVAC GUY, BUT HAVE WORKED ON CARS, MOTORCYCLES, AIRPLANES, REPLACED SOME AC PARTS ON MY HOUSE, AND A PROFESSIONAL PILOT. SEEMS TO ME I SHOULD BE ABLE TO DO THIS SAFELY WITH THE PROPER GUIDANCE.
  • Hi Tim,Scott here. I looked at a Armstrong 90% furnace the

    Hi Tim,Scott here. I looked at a Armstrong 90% furnace the other day. The burner rollout switch had been jumped. When I fire it up the burner cover gets extremely hot!. The furnace has a 90 elbow on top to pull combustion air. It is barely pulling any air through the 90 but seems to be exhausting outside ok. The 90 is clear and the burner compartment is clear. What would be my next check?
  • 1. An induced-draft air-cooled condenser A. uses magnetic

    1. An induced-draft air-cooled condenser
    A. uses magnetic induction to create air movement instead
    of a fan.
    B. relies on natural convection and doesn’t use a fan.
    C. uses a fan to blow air across the condenser coil.
    D. uses a fan to suck air across the condenser coil.
    2. What happens to the pressure at locations moving vertically
    up or down a PH diagram’s constant-enthalpy line?
    A. The pressure isn’t related to vertical movement along a
    constant-enthalpy line.
    B. The pressure decreases as you move down.
    C. The pressure remains the same.
    D. The pressure decreases as you move up.
    3. When the refrigerant passes through the metering device, some of it starts to flash
    from a liquid to a gas because
    A. the pressure has increased above the saturation point.
    B. of the turbulators located near the end of the metering device.
    C. the pressure has dropped to the saturation point.
    D. a large amount of heat is added to the refrigerant in the metering device.
    4. In an evaporative-cooling air-conditioning system, cooling occurs by evaporating
    A. the heat out of the air.
    B. water, which reduces the temperature of the air.
    C. HFC refrigerants into the air, which reduces air temperature.
    D. refrigerant inside the component called an evaporator.
    5. Which of the following condenser types requires the most maintenance?
    A. Air-cooled condensers
    B. Water-cooled condensers
    C. Condensers don’t require maintenance.
    D. The maintenance requirements for air-cooled condensers and water-cooled
    condensers are comparable.
    6. The fins on finned tube coils increase heat transfer by
    A. directing the air smoothly across the coil.
    B. increasing the surface area exposed to the air.
    C. increasing the laminar air flow through the coil.
    D. increasing the laminar refrigerant flow through the coil.
    7. An air-conditioning system’s evaporative condenser
    A. is really just another name for evaporator.
    B. works by evaporating refrigerant to cool the condenser coil.
    C. cools air through the evaporation of refrigerant inside the condenser.
    D. works by evaporating water to cool the condenser coil.
    8. In the compression refrigeration cycle, the refrigerant is saturated
    A. in the evaporator and condenser.
    B. only in the compressor.
    C. in the compressor and condenser.
    D. only in the metering device.
    9. Which of the two refrigerant lines connected to the compressor has a larger diameter?
    A. The low-pressure discharge line
    B. The high-pressure discharge line
    C. The high-pressure suction line
    D. The low-pressure suction line
    10. The pressure difference in a compression refrigeration system is maintained by which
    components?
    A. The metering device and evaporator
    B. The compressor and the condenser
    C. The compressor and the metering device
    D. The condenser and evaporator
    11. How is entropy defined in refrigeration?
    A. Entropy is the ratio of the refrigerant’s heat content to its absolute temperature.
    B. Entropy is the total amount of heat in the refrigerant.
    C. Entropy is the ratio of absolute pressure to absolute temperature.
    D. Entropy is the amount of heat remaining after subtracting the heat of compression
    from the enthalpy.
    12. Three different design screw compressors found in refrigeration systems are
    A. open screw, semi-hermetic screw, and welded hermetic screw.
    B. single screw with gate rotors, dual screw, and triple screw.
    C. micro screw for small appliances, standard screw for two- to five-ton applications,
    and the mega screw for industrial applications.
    D. single screw, compound screw, and the compound-complex screw.
    13. An oil slinger is found in a reciprocating compressor employing what type of lubrication
    system?
    A. Pressure lubrication
    B. Both splash and pressure lubrication
    C. Splash lubrication
    D. Oil slingers are only found in scroll compressors
    14. Compared to the condenser coils in older systems, the condenser coils in new highefficiency
    systems
    A. are made of larger-bore tubing to improve refrigerant flow.
    B. have fewer fins per inch to allow for better air flow.
    C. are physically smaller because of their improved efficiency.
    D. are physically larger than older low-efficiency coils.
    15. A dark or discolored compressor valve plate in a refrigeration system indicates
    A. normal wear.
    B. operation at lower-than-normal superheat.
    C. the compressor has been operating at excessively high temperatures.
    D. the valve plate is manufactured of inferior materials.
    16. Gas trapped in a reciprocating-piston compressor’s clearance space expands at the
    beginning of the suction stroke. What effect does this have on the system?
    A. It reduces compressor capacity.
    B. It makes the refrigerant colder because it’s expanded more than once.
    C. It increases efficiency by converting pressure into mechanical energy, helping to
    push the piston down.
    D. It has no measurable effect on system performance.
    17. When antifreeze is added to water, the water’s specific heat
    A. increases, dec
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