Here is a list of some common HVAC questions that users of air conditioners or heat pumps asked regarding their equipment. This list is not exhaustive and will be added from time to time. If you have any questions that are not found here, feel free to contact us and we will do our best to answer you.

    HVAC Questions

    Q1: The indoor unit of my ductless split air-conditioner drips water when I operate in cooling mode. What are the possible problems and solutions to them?

    Ans: When the air-conditioner is operating, the moisture from the room is removed through condensation at the cooling coil of the indoor unit. The condensed water then drips onto the drain pan that is located underneath the coil.

    The water is then removed from the drain pan through the drain hose that runs from the indoor unit to the outside of the house by gravity or a condensate pump into the drain. Extra PVC piping may be required to connect the drain hose to the drain.

    Check the followings:

    a) If the unit is drained by gravity, check the drain pan to ensure its elevation is correct. It should be slightly sloped to enable the water to flow down and into the drain hose and discharged to the outside of the building.

    b) If the unit is drained by using a condensate pump, make sure the pump is working. The condensate pump is an additional accessory fitted if the indoor unit is installed deep in the building and the distance to drain the water from the pan is too far. The pump helps to provide the suction needed to remove the water from the drain pan.

    c) The drain hose may be stuck or dirty and this prevent the water from flowing out. You will need to blow or use a vacuum to remove the blockage.

    d) Remove and wash the air filters at the return air of the indoor unit as dirty air filters will restrict the air flow.

    Q2: My air-conditioner is showing error codes E3, E4 etc. Timer light is blinking. What is the problem and solution to this HVAC question?

    Ans: Each manufacturer has its own set of error codes shown for when there is a problem with the air-conditioner unit that needs to be rectified. These error codes have been designed to display a particular problem that the user or technician can use to quickly determine the cause and provide a solution to the problem.

    For example, an error code E1 may indicate that there is insufficient refrigerant gas in the system and hence it needs to be topped up. Error E2 may indicate the room sensor has been disconnected.

    Check the operating manual that comes with your unit if any error occurred. With most HVAC software there is usually a table with a list of error codes and their associated problems/solutions.

    If the error codes are not there, you will need to get back to the dealer or manufacturer and get their technical manuals for that particular model.

    Q3: I am using a R22 refrigerant system. Can I change the refrigerant to R410A?

    Ans: No, each refrigerant has been designed to operate in a particular pressure during operation. These two refrigerants have different properties and are not interchangeable. The compressor and other components may be damaged if you change the refrigerant.

    Q4: Can my inverter air-conditioner be converted to conventional air-conditioner by changing the control board and rewiring the unit?

    Ans: No, you can’t do that as the inverter compressor can only be controlled using the specific control board from the particular manufacturer. Furthermore, all the operating conditions of the system have been designed to operate based on the inverter unit.

    Q5: I have another HVAC question. Should I buy an inverter air-conditioner?

    Ans: DC Inverter air-conditioner is the latest technology in the market and it has been proven to save energy and provides better comfort to the occupants in the room. The compressor speed can be varied from low to high depending on the requirements of the load.

    Though it is more costly compared to the normal air-conditioner, it is highly recommended that you purchase it if you have the budget as you will recover your investment due to the lower electricity bill that you will pay over the years.

    Q6: In my country, the power supply is 220V AC. Can the DC inverter air conditioner still operate when the voltage dips to 150V AC?

    Ans: Regarding your HVAC question, you will have to check the manual of the manufacturer to see the lowest operating voltage that the unit can still operate. Some manufacturers have designed their control board to enable the unit to work at low voltage to cater for this dip. Otherwise, the air-conditioner may not work.

    Q7: In the case of on-off type compressor, does it draw the same amount of current while automatic on from off as it draws at the time of initial starting of the unit?

    Ans: It draws the current known as in-rush current when the compressor turns from OFF status to ON status. It can be a few times more compared to the rated running current. The current is not necessarily the same each time the compressor turns on as it depends on which phase the current is when it switches on.

    Sometimes, you will see your fluorescent light blinks when this happen.It is due to the voltage dip when the compressor turns ON as it draws quite a substantial amount of energy from the power supply.

    Q8: How do I reduce the inrush current of the compressor during starting of an ON/OFF type of compressor? 

    Ans: Use a suitable soft starter that will drastically reduce the startup current of the compressor motor. There are electronic devices inside this device that controls the voltage and the phase angle to the motor.

    The other conventional alternative is to use an auto transformer starter to limit the inrush current when starting the compressor motor. 

    Q9: When I turn on the AC , it ON and OFF instantly and comes back ON again? 

    Ans: 1) One reason could be the OFF timer and ON timer are activated. OFF timer off the AC after a certain duration or time whereas ON timer on the AC after a certain duration or time.

    2) Second reason could be you pressed the remote control ON/OFF button in sucession.

    Q10: My split unit is a panasonic non-inverter air-conditioner and I have to deal with this. There is no output on the printed circuit board for the outdoor fan. Do you have any idea why this is so?

    Ans: Usually for non-inverter air conditioner, the outdoor fan is connected together with the compressor. That means the outdoor fan will only on when the compresor is on.

    Q11: Here are my HVAC questions: (1) In a domestic split-type A/C unit, will the inverter electronic components be vulnerable to heat and humidity attack as it is placed inside the outdoor unit? (2) The volume and weight for the inverter outdoor unit is far less than that of a non-inverter type machine. Why is this so?

    Ans: 1) A good outdoor design of the electronics should have been properly insulated against water and humidity. Some manufacturers will use coating on the printed circuit boards to prevent moisture and water from entering the parts. Always make sure that the components are properly sealed after repair work.

    2) For the same capacity, the inverter compressor is lighter than the non-inverter type as it is more efficient. However, more electronics control are required for the inverter type.

    Q12: I found out that my A/C(Panasonic CS-S13PKH) automatically switches to the timer mode. It shows H11 code, and according to the model’s error code table, there is a communication error in indoor and outdoor unit. I showed it to a technician. He suspected that the transistors  in the outdoor PCB may be damaged but is not sure about it. Could you suggest any ideas to solve the problem?

    Ans: This unit is an inverter unit. Here could be the possible problems based on the limited symptoms that you described.

    1) Communicating cable between indoor and outdoor loose or disconnected.

    2) Integrated circuits(IC), transistors, resistors or other components that are related to the communication between both PCBs are damaged. Could be in indoor PCB, outdoor PCB or both PCBs. You must disconnect the power from the mains before checking the PCBs to prevent electrical shock. Better to ask a qualified technician if you are not sure.

    Check the PCBs for burnt marks at the communication parts(this may be difficult to identify if you are not into electronics design). If all looks fine, you will need to remove the communicating components such as transistors or IC and check whether they are still in good conditions using a multimeter.

    3) The electrical noise from other sources of the PCBs or surrounding circuits may have affected the communication lines between the indoor and outdoor PCBs. Proper shielding or noise filtering may be required and this solution will have to come from the manufacturer. This is just our opinion. Contact the dealer for help.

    Q13: Why did the ice built-up on my coil of my indoor unit in my split air conditioner?

    Ans: There are a few possible reasons for this. Air filter and the evaporator coil could be dirty caused air flow to be restricted. The other reason could be the blower fan is not functioning.

    Low refrigerant charge is another possible reason for this to happen. Low outdoor temperature could also be a factor that caused this to happen. 

    See here for more elaborate reasons why this happen.

    Q14: Why is my indoor unit fan noisy? Mine is a ductless split unit.

    Ans: The indoor unit has a blower(usually cylindrical shape made of plastic) fan that discharges the cool air to the room by drawing and blowing the air through the cooling coil. After some years of operation, the fan assembly may be loosed causing unbalance of the blower operation. This is the cause of the noise during operation.

    To solve the problem, the blower fan assembly needs to be taken up and any imbalance be rectified. The motor shaft that is connected to the blower need to be checked to ensure they are firmly secured.

    Q15: Why is my indoor fan working but the compressor cannot turn on? Mine is a ductless split non-inverter cooling unit.

    Ans: The possible “genuine faults” include faulty printed circuit boards, compressor failure, sensors faulty or wiring issues. If manufacturer has built-in error, check the error code through blinking intervals or display and check the manuals to see type of fault.

    The possible “non-genuine faults” could be that the temperature setting is much higher than the room temperature hence no cooling is necessary. Therefore, the compressor does not need to turn on. If this is the case, set the setting at least 3°C below the room temperature and check whether it turns on.

    For some manufacturers, in DRY mode, the compressor will ON for a certain duration and OFF for another duration. Change the mode to COOLING mode.

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    Alora Bopray

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    Alora Bopray is a digital content producer for the home warranty, HVAC, and plumbing categories at Today's Homeowner. She earned her bachelor's degree in psychology from the University of St. Scholastica and her master's degree from the University of Denver. Before becoming a writer for Today's Homeowner, Alora wrote as a freelance writer for dozens of home improvement clients and informed homeowners about the solar industry as a writer for EcoWatch. When she's not writing, Alora can be found planning her next DIY home improvement project or plotting her next novel.

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    Roxanne Downer


    Roxanne Downer is a commerce editor at Today’s Homeowner, where she tackles everything from foundation repair to solar panel installation. She brings more than 15 years of writing and editing experience to bear in her meticulous approach to ensuring accurate, up-to-date, and engaging content. She’s previously edited for outlets including MSN, Architectural Digest, and Better Homes & Gardens. An alumna of the University of Pennsylvania, Roxanne is now an Oklahoma homeowner, DIY enthusiast, and the proud parent of a playful pug.

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