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Heating and cooling second floor with mini-splits wall units versus mini split ducted

sbrady46 | Posted in General Questions on

I am updating the heating and cooling system in my home. My second floor consists of 3 bedrooms with a bathroom. I am struggling deciding between a ducted mini-split system versus mini split with wall units for each bedroom.

My concern with the ducted system is the noise generated from the air forced from the registers. I am accustomed to a central air system that generated a fair amount of noise on start-up as well as when running. The new system would have variable speeds and likely not create the same amount of noise. But considering this will provide heat and cooling, I am concerned about the noise at the registers. An additional benefit of the ducted system would allow for a supply register in the bathroom.

I am also considering the possibility of placing wall units in each of the bedrooms, the down-side of this option is running the piping on exterior walls as well as not providing any direct heat or cooling to the bathroom.

The install costs are roughly equivalent.

Is one proposal far superior to the other based on efficiency?

Any input would be most appreciated.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    S. Brady,
    It's hard to evaluate which option will be more noisy. Either option will probably be less noisy than a conventional forced-air system, but there are lots of variables.

    The ducted system will provide a better match between the appliance rating and the load (assuming that the system is well designed). A separate head in each bedroom is almost always overkill.

  2. Expert Member
    Dana Dorsett | | #2

    The air volumes of right-sized ducted mini-splits running at low speed (where it will spend MOST of it's time) is quite low, and the noise typically much quieter than your refrigerator. And it will run continuously in sub-whisper quiet mode except when there is effectively no cooling/heating load when it begins to cycle on/off.

    Contrast this to a typical ducted air that doesn't modulate, is 2x oversized for the actual peak loads (with 2-3x the needed air volumes for the peak), and MANY times oversized for the average load (with many times the need air volumes).

    The head in every room usually results in oversizing even at the minimum blower speed, which results in substantially more on/off cycling, more noise. (though still quieter than most ducted central air.) The modulation range is not infinite, and when cycling on/off during low load periods the minimum output muli-split compressors is usually around the maximum output of a half-ton mini-split head, so the individual head will often be forced to run at it's maximum blower speed when cycling if only one head is calling for cooling/heating.

    Calculate the individual room loads and the combined load, and look a the modulation ranges of both options. Ducted usually wins the modulation game.

  3. sbrady46 | | #3

    Thank you for the input. Based on the input, I am leaning toward the ducted mini-split..

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