Mini split and humidity

[jjrbus]

Need to see what is happening with my mini's due to high humidity in house, usually over 60%. 1350 Sq ft house in SW FL so always high humidity outside. 3 Daikin 15 series DIY installed, 2 9k and one 12K. All single installs no dual head unit.

As near as I can figure checking run time on compressor would be technically challenging at best. So decided to try measuring condensate. Need to start someplace so did 1 12k unit and 1 9k unit.

Took 3 hours to get the pans full, the one on the left is the 12k unit and it had 44 oz of water and the 9k on the right had 48 oz of water. After test I realized the 9k unit was in dry mode and 12k was in cool mode with fan on automatic. Apples to oranges, I don't know.

Outside humidity today was around 80%, the high temperature was 92. 92 degrees with 80% humidity, great day to do nothing.

Looking at the 9k because it is a simple number to figure 48 oz is 3 pints in 3 hours or 1 pint an hour, 24 pints or 3 gallons a day. IIRC the 9k 15 seer unit is rated at 1 pint an hour, but need to look it up.

Posting this to see if there is any interest, I will experiment more and hopefully get some input.

 

[PsRumors]

You have to much cooling capacity, 2.5 tons for 1300 sq ft

The units are not running a long enough cycle to remove the humidity.

Run the fans at their slowest speed, that should help

 

[jjrbus]

Hmm, central air I replaced was 2 1/2 ton. Whole house calculator said 27,258 btu for my house. The only contractor that did a manual J for house said 2 1/2 ton. Many houses in my development have 3 tons. Estimates all wanted to put in 3 ton.

According to what I read the mini's should be able to modulate down to 7000 btu, if you can believe everything on the net.

But yes it is starting to look and smell like over capacity. Have to wait for the real hot weather to make a judgement.

 

[yeldogt]

You are in Fl -- but I can do my 3k foamed house with 3T in PA when it's 100 out.

What inside temp ?

 

[MattT]

According to what I read the mini's should be able to modulate down to 7000 btu, if you can believe everything on the net.

I doubt your 15 seer units will modulate that low. The ones I've looked up specs for modulate down to about 1/3 of nameplate. Guessing 3K for the 9Ks and 4K for the 12K. Still plenty low enough to remove water from 1,350 square feet.

Based on your sizing, and measured water removal, I'd start looking for the source of the humidity. If your indoor RH and temp stayed flat during that 3 hour test 6 pounds of water came from somewhere. Outside air leaking in is a prime suspect. Or maybe there's something you're doing inside the house to generate a lot of water vapor.

 

[jjrbus]

It is tough being a home owner and trying to figure out what on the net is reliable information.

I usually keep the temp set around 78 or 80. 30 year old concrete block stucco house with all new doors and windows, so should be at least fair to good as far as leakage. Poor insulation 3/4" batt in walls and 6 inch fiberglass in ceilings.

 

[yeldogt]

turn the units down -- you have to hit the dew point and have them running. A mini at 80 is not doing anything.

They are efficient --- put them on 75/ 74 for a while and see what happens.

With AC you need to remove the water -- that's the expensive part. I never go over 76 ..keep the one on the largest part of the house low enought o remove the humidity

 

[jjrbus]

Good idea I will do a test at lower temp and see what happens.

Big issue for me here is if house temp is 75 and it is over 90 out, I do not want to go out the door.

Today's high will be 93 so good day to test

 

[rpcraft]

Who has AC and sets it at 78 or 80???? Turn it down for sure and your probably going to see some better results.

 

[QwikKotaTx]

Who has AC and sets it at 78 or 80???? Turn it down for sure and your probably going to see some better results.

That would still be livable in Houston summers with our humidity. Lord knows I would love my garage to be that temp. I would keep my house warmer than 74 if it weren't for the wife but if you do anything other than watch TV you will be sweating. If I go upstairs that I keep at 76 and help her with laundry I am uncomfortable. Still better than when I mow, don't get me wrong!

Sent from my SM-G900V using Tapatalk

 

[cspcrx]

Who has AC and sets it at 78 or 80???? Turn it down for sure and your probably going to see some better results.

keep ours at 80 all the time here in Phoenix. But we don't have the humidity issues you all do. its 99 here right now and feels like 96. So when my house is set at 80 it feels like 77 inside

 

[jjrbus]

So much for this test, it is 91 out with 69% humidity. It is 75 in the house with 55% RH and I'm ready to put on a jacket and gloves. Walking out the door is like walking into a wall of heat. Too cold for me!

 

[MattT]

It is tough being a home owner and trying to figure out what on the net is reliable information.

Very true. The only way to know for sure is to look up the manufacturers specifications for those particular units.

I usually keep the temp set around 78 or 80. 30 year old concrete block stucco house with all new doors and windows, so should be at least fair to good as far as leakage. Poor insulation 3/4" batt in walls and 6 inch fiberglass in ceilings.

Masonry should be pretty much air tight but can be permeable. Do you know whether there's a vapor barrier in the walls?

The windows and doors should be pretty tight IF they were installed correctly.

One thing you could do is see if your light company offers free, or cheap, energy audits that include a blower door test.

Big issue for me here is if house temp is 75 and it is over 90 out, I do not want to go out the door.

Are you in and out a lot? That's one potential source of the water if you do.

And I hear you on not wanting the temp too low. We compromise on 76* which is a little cooler than I'd prefer. Left to her it'd be set at 70* and she'd still be hot

 

[MattT]

turn the units down -- you have to hit the dew point and have them running. A mini at 80 is not doing anything.

The OPs evaporator coils are definitely hitting the dew point since they're making a reasonable amount of water.

I just stuck a meat thermometer in the vent of one of mine and it's putting out 45* air with a 76* set point. That's cold enough to remove moisture until RH drops into 30s.

http://www.dpcalc.org/

 

[yeldogt]

The OPs evaporator coils are definitely hitting the dew point since they're making a reasonable amount of water.

I just stuck a meat thermometer in the vent of one of mine and it's putting out 45* air with a 76* set point. That's cold enough to remove moisture until RH drops into 30s.

http://www.dpcalc.org/

Not at the set point of 80 -- if he is hitting that temp ... the unit is not running.

When not a set temp -- the unit is cooling.

The OP needs to run his system for a while == when I get to my house in SC .. it tales a day or two to get all the humidity out of the house .... even with the unit running ..... but on 80

 

[jjrbus]

House built in 86 so doubt there is a vapor barrier in walls, ceiling is 6" with paper face. House occupied by 2 adults, wife works so not a lot of opening and closing doors. I installed doors and windows myself, I am **** about such things so they are in right and not leaking.

Which reminds me, the windows I replaced were awning type windows which were no good the day they were put in. Slightly better than having screens only. Wish I would have checked RH before I replaced them! I know the electric bill dropped significantly.

Electric company will do energy survey, but it is a simple one, no infiltration tests.


Something was nagging at me so checked the operators manual, under tips for saving energy Daikin recommends keeping temp between 78-82. Not sure if that means anything or not?

If it is 92 out and 78 in the house, there is water coming out of drains, system must be running.

At night when it is cooler system must not be running. When setting on dry function the system keeps cooling so temp in house can get too low.

 

[PsRumors]

I keep my house at 72 degrees and 46% humidity during the day and drop the temp to 67 at night


Have no idea how yall keep your houses at 75+

 

[jjrbus]

I have been experimenting here. The minis keep putting out water so I do not see not reaching dew point as an issue.

I have 3 minis one 9k in the master bed area, a 12k in the living area and another 9k in a small bedroom, too small for 9k, is the room I use for office and door is left open all the time.

So far what I have found that works is setting the 2 9k on 79 and leaving the 12k on dry mode. This keeps the temp in the living area around 76 and the humidity stays between 50 and 60%. Have not had any very hot days to see what happens yet.

I am guessing because the temp is easy to maintain that I have no large air leaks in house, which would bring in humidity.

 

[PsRumors]

I have been experimenting here. The minis keep putting out water so I do not see not reaching dew point as an issue.

I have 3 minis one 9k in the master bed area, a 12k in the living area and another 9k in a small bedroom, too small for 9k, is the room I use for office and door is left open all the time.

So far what I have found that works is setting the 2 9k on 79 and leaving the 12k on dry mode. This keeps the temp in the living area around 76 and the humidity stays between 50 and 60%. Have not had any very hot days to see what happens yet.

I am guessing because the temp is easy to maintain that I have no large air leaks in house, which would bring in humidity.

Where are you in Florida....that isn't hot?

 

[jjrbus]

SW FL, Ft Myers area. It is hot but not hitting the upper 90's. The highest temp in the next 10 days will be 93. It is not the heat it is the humidity, it is 6:30 am and the temp is 76 with 95% humidity outside.

 

[PsRumors]

low 90s should put enough load on the unit for it to perform. I doubt it will change much with another 10 degrees

 

[SALIV8]

I have been experimenting here. The minis keep putting out water so I do not see not reaching dew point as an issue.

I have 3 minis one 9k in the master bed area, a 12k in the living area and another 9k in a small bedroom, too small for 9k, is the room I use for office and door is left open all the time.

So far what I have found that works is setting the 2 9k on 79 and leaving the 12k on dry mode. This keeps the temp in the living area around 76 and the humidity stays between 50 and 60%. Have not had any very hot days to see what happens yet.

I am guessing because the temp is easy to maintain that I have no large air leaks in house, which would bring in humidity.

Good stuff. Glad to hear it's performing how you want after some experimenting with settings.

 

[jjrbus]

Thanks for the response.

It is not performing the way I would like. Using the 12k on dry mode the house is cooler than I would like. Staying around 76 and I prefer 79-80.

I am afraid running 12k in dry mode it will quickly grow mold, never shutting off and drying out. The minis are not designed to be cleaned, and are a PIA. I had to pull the bower wheel for the first cleaning due to mold. I am watching Craigslist for a dehumidifier to experiment with.

The only conclusion I can come to is I have too much capacity. According to the whole house calculator I need 28,000 btu. I am at 30,000. The only option I see is remove the 12k unit and put in a 9k. which would leave me at 27,000 btu. Seems like a lot of effort to reduce by 3,000. More effort and expense than I a willing to go through.

 

[iced98lx]

Do you still have ductwork for central? If so, consider a larger whole house dehumidifier. It will put some heat in the air which isn't ideal in FL but also won't over cool your home. I have an UltraAire brand unit and they make all different sizes. Hook the intake up to your old air returns and the output to your ducts and use the old central system for just dehumidification. Set the humidistat where you want it, set the coolers where you want them, and let them not run if they don't need to.

I have a smaller unit (70H) but we've been 80-85 degrees and over 80% RH here for several weeks now and even with a full block basement that lets in way too much water it's kept my little 1200sq ft bungalow at 50% RH, though we do cool down to 74 as well with central air. I suspect a larger unit may be able to keep your humidity in check so you can use your AC units as AC's and not dehumidifiers.

 

[jjrbus]

Duct work is still there, part of going to mini's is the ductwork needed redoing, so do not want to use it.

I will experiment with a portable dehumidifier before pulling the trigger on a quality one. I would guess one of the high end ones could be installed without ductwork?

 

[iced98lx]

Duct work is still there, part of going to mini's is the ductwork needed redoing, so do not want to use it.

I will experiment with a portable dehumidifier before pulling the trigger on a quality one. I would guess one of the high end ones could be installed without ductwork?

I know some of the smaller ones have built in humidistats (mine included) and I ran mine not plumbed in within my basement for several months with good results. I will say plumbing it in really helped even out humidity room to room though.

Perhaps the duct work wasn't suitable for replacing the forced air cooling but could be used for dehumidification purposes? not sure obviously, but something to think about.

 

[MattT]

Something was nagging at me so checked the operators manual, under tips for saving energy Daikin recommends keeping temp between 78-82. Not sure if that means anything or not?

Basically means exactly what it says. The higher you set the thermostat the less power you'll use.

I have been experimenting here. The minis keep putting out water so I do not see not reaching dew point as an issue.

Yeah it sounds like your minis are modulating during the day. And probably cycling overnight. Is your indoor humidity higher first thing in the morning?

I am guessing because the temp is easy to maintain that I have no large air leaks in house, which would bring in humidity.

Any outside air leaking in will be close to 100% RH at your indoor temperature. So it's worth trying to hunt for leaks. Maybe take a look at the ceilings.

Duct work is still there, part of going to mini's is the ductwork needed redoing, so do not want to use it.

Have all the old registers and returns been capped off?

 

[jjrbus]

I do not see anything that is an obvious leak, old system is capped off. No idea what to look for in the ceiling?

90 out today with high humidity. Put all 3 minis on dry mode. Temperature stayed around 77 degrees and humidity dropped from 68% to 50% in a few hours.

I seem to have too much cooling capacity, with modulation seems pretty hard to do. The easy way out seems to be to add a dehumidifier. Which goes to #1 on the bucket list. Just a portable one for now to see what happens.

Cooling Capacity (Min – Max) 9k unit BTU/h 4,400-10,200 12k unit 4,400-13,000 This is from the Daikin site for my 15 Seer units. 2 9k units at min 4,400 btu and one 12k unit at 4,400 would total out to 13,200 btu minimum. Difficult to believe that is too much capacity for a poorly insulated 1350 sq ft house in SW Florida.

I would not care about the humidity except for the difficulty of cleaning the mold off the mini blower wheel. Piss poor design!

 

[SALIV8]

I just don't see how any cooling systems design would be to maintain 77* indoor temps if properly sized.

I believe design criteria is much closer to 72* which would also remove so much more humidity.


I think you're asking too much from your system, or any cooling system for that matter, and need to go with a dehumidifier.

 

[PoorOwner]

I have a daikin 9000 btu minimum is 4400 btu or so. It’s 26 SEER I think.
It’s very hard to get condensate out of it because it runs really lazy. Like it is always trying to keep a duty cycle of 50% or so. It would kick on the compressor for 5 minutes and stop for a while even if the set temperate is not reached.

It does use very little energy this way and power consumption is low while compressing as well. It keeps the room cool / heated given enough time but it’s the only one in my house that works this way. I have pioneer gree mitsubishi etc.

There is a powerful mode that I haven’t tried.

 

[fitter30]

Humidity flows high to low just like temp. A blower door test will tell you how tight your house is. Being in Florida you probably have a crawl space. Is it insulated with foam, is there a vapor barrier or all the piping and wiring holes caulk up. Your electric company might offer a energy audit which includes a blower door test.

 

[jjrbus]

Daikin Powerful mode simply runs fan very high speed for about 20 minutes and then kicks down. I assume the outside unit is doing something special also. I think once you set it to powerful you are stuck with it till it shuts down.

No crawlspace, house is on a slab and likely no vapor barrier. Home energy audit here is a simple one.

 

[PoorOwner]

Daikin rant continued...

My outdoor unit is so tightly put together it makes a rattling sound at certain load that goes away when I put my hand on it.

The indoor unit plastic, every other brand have some shiny white ABS plastic, while the daikin seems like is made of recycled milk carton, yellow and cheap looking.

It does have some pretty nice features like electric louvers that moves left and right and a weekly schedule built into the remote.

But I think the 4400 BTU minimum is not going to give a lot of comfort due to frequent cycling.
I also read the service manual it's got some kind of crazy logic if it is set to 73 or so it behaves differently than if it is set to below 73.

 

[jjrbus]

The only complaint I have against Daikin is the piss poor design for cleaning, but I do not see where any of the others are any better! Not one person said "Boy is brand X super easy to clean"

What Daikin does have going for it is thicker copper coils, same as Mitsubishi or Fujitsu.

When researching I found most of the pros working on Mitsubishi, Fujitsu or Daikin. Rarely see them working on any of the other brands. Coincidence or ???

 

[PoorOwner]

most Pros are going to stick with the big 3 brands, they are supposively more reliable, less warranty and callback