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Ducted mini-split vent diffuser recommendations

FluxCapacitor | Posted in General Questions on

So my HVAC installer put typical ceiling diffusers on my multi split ducts (see picture).  This type throws the air along the ceiling, which is great in AC mode but not so great for heating mode.  Do any of you guys have suggestions for diffuser that would work well for heating and cooling and would easily replace the current 8”x8” diffusers?




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  1. MattJF | | #1

    What symptoms specifically do you experience that you attribute to the registers? The register you show is generally not a bad style if located appropriately.

    Ideally the register has enough throw to move the air along the ceiling until it can hit a wall and travel down it. This requires sizing the register for the cfm and location along with the register style. This is a good overview:

    I am far from an air distribution expert, but any advice really would require a floor plan showing register locations and cfm specs. Register size is important in getting distribution perfect, so you would need to be willing to change the sizes.

  2. FluxCapacitor | | #2

    Oh OK. I thought this type might be bad because the warm air would stay up high. I didn’t consider that the air might flow down adjacent walls and mix that way.

    Here is a the best picture I could get of ceiling. It’s about 6 feet to side wall and 11 feet to opposing wall.

    The air handler is a Mitsubishi SVZ which regulates between low-med-high fan speeds.

  3. FluxCapacitor | | #3

    Great link. I’m going to study it some.

  4. Jon_R | | #4

    I suggest an experiment - on a moderately cold day, let it modulate the fan as needed (presumably it won't use high) and measure ceiling and floor temperatures. Then force it to run on high for a few hours (better mixing) and measure again.

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