• M-Series and P-Series Catalog (see dimensions on pages 57-58)

Thanks - yes I've seen this. However, the dimension show 14 3/16" which is why I don't understand the dealers saying it requires more than that for install. Especially considering it seems these were created for 16" ON CENTER joists.

It wouldn't make any sense given that the space between the 2x6 joists would be 16 - 1 - 1 + 1/4 + 1/4 = 14-1/2", just the right width for the unit.

Yes I know that's why I'm confused by what the dealers are telling me.

Page EN-4 of the installation manual reads, "Make an opening in the ceiling 15-1/8 × 45-11/16 in. in size." I assumed that the opening was slightly wider than the unit to allow the flange at the bottom of the unit to press up against the joists and prevent the unit from just floating around inside the ceiling. However, further down on the page it says, "When the distance between joints is 15-1/8 in....or less, please refer to the notice affixed to the packing material". I wonder what that notice says!

thanks for your help and eagle eyes. I just don't understand why they would market to standard 16" on center joists which clearly do not have 15.125" between them?

I wouldn't give up. I'd want to "refer to the notice affixed to the packing material".

yah - I'm gonna keep hunting this down. Maybe someone else will show up here who also might have experience with it.

Over 10 yrs ago we installed 2 Fujitsu compact ceiling cassettes. They did have to cut the ceiling joists and sister them for repair. I hired a structural engineering firm for $350 to inspect and approve the work. They wrote a letter for the city inspector. All has been fine.

@mmmm12COzone5: "Over 10 yrs ago we installed 2 Fujitsu mini ceiling cassettes."

Today's Fujitsu Airstage Compact Cassettesare wider so they won't fit between joists. Fujitsu doesn't appear to offer indoor units that fit between joists.

Yeah, and they apparently didn't back then also. Somehow we also thought, like you, that they would. We thought the part that went through the ceiling would fit in between the joist since it made no sense that they wouldn't design it that way. We also thought it would just be the faceplate that extended beyond. :-)

To answer your other questions. Maintenance is minimal. We have both wall units (3) and ceiling cassettes (2) along with 2 outdoor units. You just have to pop out the washable filter a few times a year and rinse it in the sink. We also have air cleaners so usually only do this twice a year. The outdoor units collect cotton from trees and such so we rinse those with a hose a couple of times a year as needed. If there is alot of wildfire smoke and ash we will rinse more often.

Are mini-splits worth it? To me they are fabulous. They also provide a back up heat system which we used when our boiler was being replaced one winter.

The advantage in cooling is that you feel it immediately because the cold air falls around you from the ceiling. The disadvantage is that sometimes you get too cold from cold air falling around you from the ceiling.

We love the zoning capability. One ceiling cassette can fully cool the main open concept of our house except on the hottest days. We have a wall cassette in the family room that directly cools the family room and attached kitchen. We rarely run that one as my husband and dogs get too cold. But on 100+ degree days it can be useful. Especially if cooking in the kitchen is heating it up.

We also put a ceiling cassette in the master bedroom and it tends to over shoot the set temp. So what happens is we end up precooling the bedroom and turning it off at night.

We have another wall unit in the master bath that gets used alot. We also have a wall unit in an upstairs bedroom,used as an office, that is seldom used just because the room is seldom used.

Both ceiling cassettes overshoot their set temps and make the room too cold. The wall units generally maintain the temp exactly as you have it set.

There is a setting on the ceiling cassettes that you can adjust to compensate for this but if the power goes out you have to reprogram everything so we don't bother.

We do set the temp. sensor as the wall controller instead of at the unit. In our scenario the unit is on the second floor over a catwalk and the temp controller is on the main floor under the catwalk.

We have infloor radiant hydronic heat so there is no duct work and this was the only option for air conditioning.

Our ceiling cassettes are 18BTU for our open concept house and 12 BTU for the master bedroom. The master bedroom which has north and east exposure should probably have been 9 BTU.

The kitchen/family room is 18 BTU. It has a wall of south facing windows.

The master bath (south facing windows) and upstairs bedroom (south facing windows) are both 9 BTU.

We keep the house set at 76 and usually just run three units. The open concept ceiling cassette is the first one we turn on. The master bedroom we turn on during the day depending on how hot it is but mostly around 2 p.m or even as late as 6 p.m. The master bath we run through the day and it has double doors open to the master bedroom so it sort of cools both of them. The family room is only turned on when it is really hot out. The door to the master bath opens near the family room and sometimes my husband complains that there is too much cold air coming out of it when we run the master bedroom ceiling cassette and will close the door.

The whole house is too cold at 74F. I am surprised we find 76F so comfortable. I think it is because the cold air falls around you so you constantly feel the cooling. I like sleeveless shirts in the summer but inside will often put on a long sleeve shirt because of the cooling.

Mitsubishi makes ceiling cassette models that fit between the joists and models that don't.

"The whole house is too cold at 74F. I am surprised we find 76F so comfortable."

What's surprising -- or maybe not -- is that a room temperature can be much higher if you have a ceiling fan. My room temperature is now 84 but I'm comfortable with a ceiling fan overhead running at low speed. With AC, I find 78 is best.

"The whole house is too cold at 74F. I am surprised we find 76F so comfortable."

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What's surprising -- or maybe not -- is that a room temperature can be much higher if you have a ceiling fan. My room temperature is now 84 but I'm comfortable with a ceiling fan overhead running at low speed. With AC, I find 78 is best.

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Even More surprising maybe a bit alarming:

I don't like constant wind from a ceiling fan blowing on me or blowing stuff (rustlng papers or whatever else happens to be in the room) around to mimic the effect of a wind tunnel. I like to sleep at 72F at night, wake to an in home office that has in the realm of 47% RH sometimes lower nearly always lower than 50%RH.

click to enlarge: Home Office Zone Temp and Humidity.

Once I wake, 76F is fine in the office / 74F in the evening slowly drifting to that sweet 72F over night.

The thermostat makers realized that a single temperature would not appease everyone. If you can get the house (residents thereof) to agree on one temp maybe you too can live in peace.

Maintenance Note: Seldom used equipment WILL NOT need as much maintenance. In terms of dust, dirt and grime -- no two homes are alike. Your mileage and how you use or don't use the equipment will vary. Tales from the AC crypt vault of a nearly always hot climate and nearly always dead equipment that wasn't really maintained as it should have been.

What do you mean? where you live it's just as hot as it is everwhere else: Check back in October / November sometimes in January & February to realize what I am talking about. LOL.

Ah HVAC: No one likes what I like? We're not getting nothing over you and your opinion.

I service the Katy, Texas area.

ASHRAE performed a pretty comprehensive study on comfort as a function of temperature, humidity ratio, air speed, level of clothing, metabolic rate, and thermal radiation on occupants. The results are incorporated in ASHRAE standard 55-2023 (Thermal Environmental Conditions for Human Occupancy.) HVAC designers should have a good working knowledge of the standard. I suspect most residential HVAC designers are completely unaware of it.

i just had 2 MLZKP12 12,000 btu cassette minisplits put in in december and the crackle and pop so much i cannot sleep! I'm not getting help except for guys coming out and tinkering and not getting anywhere - i feel they're trying to run my warranty out. it takes very little time to google and see mitsubishi cassette min splits are Noisy!!! sound like someones closing a door so scary in middle of the night - ridiculous product and class action lawsuit is coming their way!

i just had 2 MLZKP12 12,000 btu cassette minisplits put in in december and the crackle and pop so much i cannot sleep!

Yeah, unfortunately that is a well documented problem that happens with these kinds of products that place the Evaporator section with blower (often called the "head" of the unit) right in the room you are trying to sleep in. From all mini split manufacturers far and wide, they claim these noises as "normal"

AI OverviewThe crackling/popping in your Mitsubishi MLZ cassette mini-splits is likely caused by thermal expansion/contraction of the plastic casing or internal components as temperatures fluctuate, which is common during winter heating cycles. While often considered "normal" by manufacturers, it is clearly excessive in your case, possibly due to improper installation tension or mounting.

-------- So the blame game begins... the manufacturer considers this normal, but also then blames the installer as improper installation. Not likely for operator to win that battle. The problem has been well documented / affect more than just one brand, model, etc. -----------

This is one such reason to not use mini splits in areas of the house in which sleeping is the main activity.

From what I can tell from what others have suggested as the best way to fix it is to put in ducted central air. (Perform a search on the subject you'll likely see the same things)

We have a Fujitsu ceiling cassette in our bedroom and they do not make any popping or snapping noise. We usually use it for only AC but have also used it for heat in a pinch when we are having our boiler worked on during the winter but have never had anything like that. Yours is a much different design since ours is square so maybe there is a design problem or as stated by another poster it is installed too tight somewhere. Sorry to hear about the problem but thanks for alerting people.

I think they are a more elegant engineering solution for providing HVAC to multiple areas of a home and allowing individual temperature control of indoor units than ducted systems.

Because I am a service provider and not a builder, I know they are a recipe for maintenance headaches, when they start breaking you'll have multiple areas of a home doing the tag team comfort tango on your wallet.

The more equipment, the more maintenance, the more maintenance the more problems come, the more problems come the more they need to be fixed, the more they need to be fixed the flatter your wallet.

Now if you live in some mild climate nirvana maybe you have a different experience because the unit(s) don't run as much and aren't tested harshly due to mild climate nirvana.

Elegant Engineering? Plastic! LOL. I have a differing view. That is supported far and wide by complaints of clicking and popping.

Well you should provide a solution? I have, not one that will be necessarily more liked but a solution I know will work. (You want it to work don't you?)

When my car needs to be repaired, I don't dispose of it and buy a different one. I get it repaired. The problem may require some combination of human expertise and technology to diagnose and even more than one attempt, but it shouldn't require a complete replacement of an expensive asset. The same is true for the OP's mini split heat pump. This thread exists because the OP's HVAC technician is short on expertise. I think he/she is in good company.

When my car needs to be repaired, I don't dispose of it and buy a different one.

Cars are covered by insurance, the choice is not always yours to make. Insurance companies total cars to the junk yard every day Charles.

If your car has a rattle? imagine the fiasco of that.

Short on expertise, short on common sense too. ~Well common sense isn't so common.

You're in good company... yeah there is no shortage of people who lack common sense in Today's world.