Daikin Quaternity

Discussion in 'HVAC Heating & Cooling' started by charles2, Jul 9, 2021.

  1. charles2

    charles2 Member

    Apr 7, 2008
    Last edited: Jul 21, 2021 at 7:40 PM
  2. charles2

    charles2 Member

    Apr 7, 2008
    I did not know that sort of construction was permissible.

    Surely 100% must be the theoretical limit to motor efficiency?

    So theoretically 100 SEER is possible? Why aren't the Japanese low 50s SEER air conditioners available in the US?

    I'm aware of that one. Have you seen/heard anything about its reliability?

    How do you define reasonable in this context?
  3. charles2

    charles2 Member

    Apr 7, 2008
    How should hallways and stairwells be treated?

    When it asks where the ducts are located, do I answer where they are now, or where we want them to be?

    Is a wall between a house and unconditioned garage considered an exterior wall?

    In the Windows section, is the tool asking for area?

    Should french doors be regarded as doors or windows?
    Last edited: Jul 22, 2021 at 6:46 PM
  4. wwhitney

    wwhitney Well-Known Member

    Mar 17, 2019
    Berkeley, CA
    If they have no exterior surfaces, then their load is zero. If you condition the adjacent spaces, they should end up at the average temperature of those spaces (for the appropriate sense of the word average).

    Otherwise, assign them a load as usual, but then if they end up having very small loads so that you don't directly condition them, then I think a standard procedure is to divide up the load among the adjacent directly conditioned spaces. Perhaps in accordance to their joint surface area with those spaces.

    Cheers, Wayne
    charles2 likes this.
  5. Dana

    Dana In the trades

    Jan 14, 2009
    As long as the transitions are tapered the effective "equivalent length" of a short section of smaller duct doesn't have a lot of impact, especially when the overall lengths is short, and all ells & tees & take-offs are radiused rather than sharp-throated. (Sharp turns create a lot of turbulence resulting in a higher static pressure drop.) There can be noise issues due to the higher velocity, but that's about the only drawback. When possible I usually target ~300-350 fpm duct velocity at the cassette's max blower speed for ducts fully inside of conditioned space then taper down to achieve a higher exit velocity at the registers for better mixing with the room air (YMMV), which means at the blower's lowest cfm the exit velocity can be too low to get adequate mixing unless it's tapered down.

    If you want to play "junior duct designer" and sketch out a ducted cassette solution yourself you might find this bit o' bloggery from the folks in Decatur useful. The BetterBuiltNW HVAC tool (that uses appropriate Manual-J U-factor defaults for sizing mini-splits) also has a duct design widget.

    Yes- and the load (friction through the coils) has a theroretical limit of zero, so divide by zero= not defined. ( If the surface area of the coil was the size of the Pacific Ocean it wouldn't need a blower, eh? :)) With real world blowers & coils it's always in the realm of practical engineering & cost limitations.

    Maybe- I'd have to do the hard-math on that one. But it doesn't really matter. The practical economic & engineering limits are more important than theoretical limits.

    That's a marketing question for the vendors.

    It's been out there for about 4-5 years now- haven't heard about any problems with it. There is no theoretical reason it would be any worse than other Midea mini-splits.

    Any SHR <0.9 at low to mid-modulation would be good enough a the seasonal averages for most reasonably tight houses that don't have a dozen tropical fish tanks, fung shui water features, or tropical indoor gardens, or otherwise need the full ASHRAE 62.2 ventilation rate 24/365. Using DRY mode isn't a crime, and is generally efficient than bringing down the indoor humidity with a separate dehumidifier converting a the latent load to a sensible load, (with the exception of a whole house dehumidifier that dumps the latent heat of vaporization to an outdoor coil.)

    A Fujitsu DRY mode may not always keep up the latent load when there is low or no sensible load, so some other dehumidifier may be necessary during high outdoor dew point weeks. It looks like this week qualifies as high enough humidity to matter in Atlanta, with the dew points hovering around 70F (the top green line in the graph).

    But without high ventilation rates or lots of indoor humidity sources (cooking tubs of gumbo in a pot without lids? Are 5 people taking 30 minute showers?) it may not need to run in DRY mode all the time to get there, since the forecasted daily high temps and sunshine levels will be generating a significant sensible load causing the equipment to run a higher modulation level (=colder coils, better SHR) than when the sensible load is small.

    When you have completed the Manual-J load calculations the answer would be pretty obvious. Unless the hallway/stairwell has a large skylight the cooling and heating loads are de minimis. If using a central common return with jump-duct returns to the common area from doored-off rooms the return air is good enough for conditioning ultra-low load spaces. Typically the loads of hallways and stairwells are "within the noise" error of the rest of the calculation, and don't affect system sizing.

    Run it both ways, compare the results.

    You may have to run a fudge-factor here, but yes. If the garage doors are normally left open it's absolutely an exterior wall. If the garage door is normally closed treat it as a somewhat higher-R wall (and higher still if the true exterior walls of the garage are insulated.) Eg: if it's a 2x4/R13 partition wall and the exterior walls are not insulated, treat it as a 2x6/R20 wall. If the garage walls are insulated (R13 or better) treat it as an 2x6/R20 + R5 c.i. wall. It will be close enough.

    Some tools ask for square feet, others want you to enter the width x height (of the entire area, not just the glass) in inches.

    Windows. Most manufacturers of exterior patio doors etc. publish the U-factors, which can be entered manually with some load tools.
    Last edited: Jul 23, 2021 at 9:04 AM
    charles2 likes this.
  6. charles2

    charles2 Member

    Apr 7, 2008
    I was wondering about that. I was thinking about having the new registers for each bedroom just a foot or so from the tops of their doors, the undercuts of which serve as the return air paths. Would the throws always be sufficient? I'll need at most 16 feet of throw.

    That tool is so marvelously comprehensive! I can see why so many contractors just size everything with rules of thumb.

    Do all whole house dehumidifiers dump heat outside?

    Do you have any idea why portable dehumidifiers are so incredibly unreliable? Why can't they be as reliable as refrigerators?

    I'll say. Today feels like the hottest this year.

    I did and the difference was almost half a ton! I wish I knew what the true R-value of the attic duct insulation is. I'm just having to guess at so much.

    Again, I'm having to guess since I don't know for sure which walls are insulated. Nor do I know whether the garage ceiling is insulated. Years ago I found 64 sf of the attic completely uninsulated, which I corrected.

    I'm not asking about some tools, I'm asking about the BetterBuiltNW HVAC tool.:)

    I doubt I'll be able to identify the make and model, and a substantial part of the 3 french doors is insulated steel.
    Last edited: Jul 26, 2021 at 1:43 PM
  7. fitter30

    fitter30 Well-Known Member

    Feb 2, 2020
    Retired service tech
    Peace valley missouri
    Never seen a whole house dehumidifier dump air to the outside because your dehumidifier isn't made for over cooling the space. The colder the air the harder it is to pull RH from. Latant is easy relative is hard.
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