4 Reasons to Choose a Modulating AC or Heat Pump

Temperature and Humidity

Originally published on August 19, 2014

Do you have hot and/or cold spots in your home?

Finding a way to evenly manage temperature and humidity control are two main advantages of a modulating system. While a fixed speed system can only run at full speed, a modulating system can have two or more speeds. In terms of temperature control, this means a modulating system will provide consistent air conditioning that is commensurate with the need in the home, as opposed to a fixed speed’s just turning on or off. Rooms that receive the least airflow often have these hot or cold spots which the modulating systems help even out.

Are you too warm or cold while sleeping?

Another instance of consistent airflow impacting quality of life is during the night when comfort can directly relate to the ability to sleep. A fixed speed system can cause a homeowner to be both too hot and too cold, depending on whether the system is cycling on or off.  Conversely, a modulating system can provide a longer-lasting and less intense airflow, which keeps rooms at a more precise temperature and allows the homeowner to have better comfort control while they sleep, with fewer cycles than a fixed speed unit.

Have you ever gotten a “clammy” or a “sticky” sensation from the air at home?

In terms of comfort, humidity increases how warm an environment feels and may lead to the sensation of clamminess. Since modulating HVAC systems run more consistently, more air is cycled through the system, which removes moisture, and lower indoor humidity is achieved. Lower humidity allows the homeowner to raise the thermostat temperature, thereby saving energy.

Have you ever experienced issues with mold growth in the home?

In addition to how the air feels, high relative humidity can lead to mold growth. The Centers for Disease Control and Prevention (CDC) recommends to, “Keep humidity levels as low as you can—no higher than 50 percent — all day long.” A fixed speed system allows relative humidity to go as high as 60 percent while modulating systems do not break 50 percent. Mold is harmful to the physical features of the home, in addition to human health; a modulating HVAC system prevents harmful mold growth by removing moisture from the air.

In the end, it comes down to what will best fit your home, preferred lifestyle, and budget. Keep in mind while modulating systems may have a higher upfront cost, there are energy savings and rebates to consider. Learn more about heat pump rebates and tax credits here.

Read Next: Advantages of Modulation: Modulating vs. Single and Two-Stage Furnaces


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35 thoughts on “4 Reasons to Choose a Modulating AC or Heat Pump

  1. Dear Sir, greetings from India. We are operating a food supplement manufacturing unit and the requirement for temperature is below 25 degree C and humidity below 30%. The floor area is 30 sq, mtr, and height is 3.8 meters.The plant is having an old AHU which was found not meeting the requirements. After complete servicing a drier of 2T capacity. It reduced the humidity from around 50% to about 27%. But temperature hovered around 33 degrees. Subsequently, 2 cooling elements were added in AHU. Though temperature came down to 27 degrees the humidity jumped to around 40. I request to know how both the parameters can be achieved without abandoning present installations, if possible. Thanks, Ashok K Srivastava

  2. I’ve been told by the pros that fans wear out more from on and off cycling (auto) than being on all the time

  3. Very informative .
    I stumbled on here looking for answers out of frustration with the ppl who installed and serviced our system .
    It’s only about 3 yrs,old and we started having issues .
    Condensation to say the least.
    Feels humid inside.
    I’m in Southeast La.
    They never even mentioned a modulating system to us..

    So I’m simply trying to figure out what to do in expensively or what to suggest to them to check to get it fixed under warranty.
    They have changed the evaporator coil that had a leak ,expansion valve that was sticking ,,and water is coming into the pan .
    Still feels humid .
    The Windows are constantly wet .
    Thank fully I think only on the outside .
    Just frustrating they have not been able to get the system running efficiently.

    • Hi Mary,

      Here are a few suggestions. First, check to see if the system is still under warranty – at 3 years it might have some time left on that for at least parts if not labor. If it is under warranty and still having problems you might try calling the manufacturer – you can usually get the contact info off their web site by typing in the unit name and/or model number which should be on either the outdoor or indoor unit.

      You might also have a contractor (maybe a new one) come out to check the refrigerant charge and pressures. Sometimes the symptoms you are experiencing can be caused by too much or too little refrigerant in the system. In the mean time, you can try leaving the system fan on to run constantly during the more humid times and at night. You can do this by switching the thermostat’s fan switch to “on” instead of “auto”. “Auto” means it only runs when the system runs. “On” means it runs all the time even when the system is not cooling. This might move some air around to help increase run time and reduce humidity. This will increase wear on your fan but it could help until you get the other problems fixed.

      Using ceiling and other fans to keep the air moving might help as well. One other thought, have you changed the indoor air filter recently? Those need to be changed at the beginning of every cooling and heating season. Clogged and dirty filters could affect performance especially in humid situations. I hope these suggestions help.

  4. It has started turning a little colder in the mornings so my daughter flipped on the heat. She turned the heat button too far which put it on auxiliary heat until she realized what she did and switched it off. Now our regular heat won’t come on. Is there something that needs reset on the unit or what?

    • Hi, Lea. It is difficult to tell much from the details you have provided without any actual checking and inspection the unit. May we suggest that you try to contact a qualified technician to check and troubleshoot your unit. Here’s the link for a contractor locator tool which may help you find a technician.

  5. Regis, I am not all that familiar with solar and wind power options. From what I have read I would suggest looking closely at the utility rebates in your area for these technologies to see if there are any rebates to help you justify your investment. Since you are on the beach, you will obviously have to be concerned with salt spray corrosion, etc., so consulting with an engineer or contractor who specializes in beach front installations would probably be a good first step. I will forward this to a few friends who are more into solar so maybe they will post some links for you. We might have to add content in this area soon. Thanks for your post.

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