Hobby_Man22
Well-known member
You can turn the ac off all day and have it be 85 in the house and have it knocked down to 75 in a couple hours lol
The upside to an oversized ac
- Thread starter Hobby_Man22
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with high humidity
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Hobby_Man22
Well-known member
It should knock the humidity down just fine in 2hrs. it stays around 45-55 at all times where I live it's typically 80 plus percent humidity outside.
fitter30
Well-known member
Yes it will cool the air but any temperature rise in the mass will take longer to cool back down. Last house 1850 sq ft 2 story had 5.5 tons of cooling with with a 2 ton for the second floor and no heat. 3 bed two bath. 3.5 ton for the first floor and second floor. House was built with one system and after a few years installed the 2 ton for second floor. Worked great day ran 3.5 night 2 ton cooling 2nd air would fall to main floor. The big upside could entertain have 15 - 20 people turn both systems on and a ceiling fan top of the stairs push cool air down kept everyone comfortable.
Humidity is the problem. If you live in a humid area that's the comfort item that has to be addressed.
most feel comfortable at higher temps with low humidity ... also -- depending on what is in the space and how much water the items will hold ....... can take a lot to remove the humidity.
those who live in low humidity areas don't suffer the same. solar gain can be a problem in many building types -- that has to be addressed with capacity or a better way is spray foam
most feel comfortable at higher temps with low humidity ... also -- depending on what is in the space and how much water the items will hold ....... can take a lot to remove the humidity.
those who live in low humidity areas don't suffer the same. solar gain can be a problem in many building types -- that has to be addressed with capacity or a better way is spray foam
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Hobby_Man22
Well-known member
It stays around 50 percent humidity once it gets to its set temp. You can even shut it off for a few days and the most it will get to is like 62
bwringer
Well-known member
We have a heat pump, so sized correctly for Indiana in the winter, and with a decently insulated house, it's rather overpowered when in A/C mode.
It's a newer smarter system, so as I understand things it throttles back to keep air moving more often, manage humidity in Indiana's swampy climate, and keep things more even. If it could only run at full blast, it would be short cycling or we'd have temperature and humidity swings.
It's a newer smarter system, so as I understand things it throttles back to keep air moving more often, manage humidity in Indiana's swampy climate, and keep things more even. If it could only run at full blast, it would be short cycling or we'd have temperature and humidity swings.
mike93lx
ALLIANCE MEMBER
Hey, let the guy enjoy his improperly designed system. Short cycling is a problem for tomorrow hobby man, not today hobby manThen what ???? …….it hits the new target temperature ……….then the system goes in to short cycle and all the known problems of an oversized system come back
TRITOON
Well-known member
Ditto. People dont take lifestyle into account. If you live alone, or if you and your partner work outside of the house the majority of the day then oversizing is great. For years my wife and i would be gone most days from 5-6 am - 6-7pm at night, on the weekends we were active and out and about. We didnt even have a programmable thermostat during the early years, but we could basically keep it off during the day.
I could spend summers beign comfortable overnight and on weekends and barely break $100 a month in electric.
Even now, 2 years ago when we replaced our lake house A/C we deliberatly oversized it. Its a heat pump and it helps cool it down/ heat it up on the weekends and its not the most well insulated house. During the winter we keep it on 45 degrees, and its off during the summer when we arent there.
Old Man Roger
Well-known member
This is going to sound like a stupid question, maybe it is a stupid question, but I’ll ask anyway..lol
It’s a three parter. Could you compensate for an oversize system by having a multi speed blower motor? Meaning you would leave the motor on high speed, if let’s say, the AC has been off all day and you want to cool the house quickly, then switch to a lower speed once the desired temp is reached?
My second thought was a type of zone system. Would it keep the system running longer if it cooled one section of the house at a time? Maybe include the attic? Or even vent some of the air out of the house? Probably not very efficient, I know, but the person having an over sized system probably isn’t to worried about efficiency.
I’m asking for the sake of lowering humidity with an over sized system.
It’s a three parter. Could you compensate for an oversize system by having a multi speed blower motor? Meaning you would leave the motor on high speed, if let’s say, the AC has been off all day and you want to cool the house quickly, then switch to a lower speed once the desired temp is reached?
My second thought was a type of zone system. Would it keep the system running longer if it cooled one section of the house at a time? Maybe include the attic? Or even vent some of the air out of the house? Probably not very efficient, I know, but the person having an over sized system probably isn’t to worried about efficiency.
I’m asking for the sake of lowering humidity with an over sized system.
mike93lx
ALLIANCE MEMBER
Running a fan won't lower humidity. If the temp setpoint is hit, the dehumidification stops, regardless of the level.
You could have a separate dehumidifier, I guess, but that's even more equipment to buy and run
You could have a separate dehumidifier, I guess, but that's even more equipment to buy and run
Old Man Roger
Well-known member
I meant to run the blower motor on a slower speed to keep the ac running longer? I don’t even know if it would cause the ac to run longer?
OP
Hobby_Man22
Well-known member
They have two stage systems where the compressor changes size
mike93lx
ALLIANCE MEMBER
You would have to have a variable speed compressor. Lower air flow with the compressor running full bore won't help
nbpt100
Well-known member
I took an HVAC class many years ago. Lots of it I am sure I forgot. A few things I recall about sizing.
If you over size the system, it may start and stop more frequently and/or you have higher temperature swings. Hence more wear and tare on the system.
Consider the worst case Sun load. Think how that may change on your property overtime by trimming trees or if you have plans to removing trees.
Slightly oversized often works out but not hugely oversized.
If you over size the system, it may start and stop more frequently and/or you have higher temperature swings. Hence more wear and tare on the system.
Consider the worst case Sun load. Think how that may change on your property overtime by trimming trees or if you have plans to removing trees.
Slightly oversized often works out but not hugely oversized.
Old Man Roger
Well-known member
Ahh, like a dual turbo car. You only ever really spool up the big turbo when needed.
mike93lx
ALLIANCE MEMBER
Sort of. Most twin turbo cars have two of the same size. Sequential systems have two of differing sizes to cover different parts of the band.
A dual stage system might be like a sequential, but variable speed is more like a dimmer switch
Shiftless
Well-known member
We all know how the 1981 Cadillac 8-6-4 engine ended up right?
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Hobby_Man22
Well-known member
Sequential has a small turno to get things moving then a big turbo to take over.
Old Man Roger
Well-known member
It should be a law in Florida that all roofs be white, and anyone caught cutting down a shade tree should be shot lol
The house I live in now had a huge shade tree, it shaded half of the house all summer long. The previous owner cut it down because she was worried about hurricanes. The tree was probably 100 years old.
nbpt100
Well-known member
It can be a tough call if the tree is threatening the house. Insurance companies can sometimes request it. White roofs are a great idea in places like FL. I am not sure why more people do not do it on their own when it comes time to re-roofing.It should be a law in Florida that all roofs be white, and anyone caught cutting down a shade tree should be shot lol
The house I live in now had a huge shade tree, it shaded half of the house all summer long. The previous owner cut it down because she was worried about hurricanes. The tree was probably 100 years old.
mike93lx
ALLIANCE MEMBER
Appearance is my first guess. I bet they don't stay a pretty white very long and with how many transplants are in FL, you are dealing with people used to a certain look
Old Man Roger
Well-known member
It’s 11:21 AM and the ceiling in my attic is 120° right now. It’s only going to get hotter.
chrispyny
Well-known member
Not really sure how you figure a 10 degree decrease over 2 hours is ‘oversized’. I would expect those results from a properly sized, well working a/c system. What am i missing here?
mike93lx
ALLIANCE MEMBER
Really? My systems feel decently sized (they maintain temp on the hottest day) and they won't do 10 degrees in 2 hrs throughout the whole space. Why would a properly designed system need to do that?
OP
Hobby_Man22
Well-known member
It only does it at night time when the sun has gone down and it's only 85. It will take most of the day to do it if you attempt the same thing at 2pm when it's 100 outside. Besides I think everyone's ac is oversized in tx otherwise they would all be bitching it doesn't keep up when it's 100 out
chrispyny
Well-known member
I suppose my situation is a bit different. Not sure where you hail from. I have ductless minisplits which are mildly oversized in upstate NY. . I wouldn’t, but If i were to ever let the house get to 90+(which it could easily, we are forcasted for 99°f thursday) my splits can easily have the house down to 72 in 30-45 min. they recover and dump heat FAST. My home is always dry and i prefer mildly oversized to undersized any day with splits and dc driven inverter motors/compressors.
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Hobby_Man22
Well-known member
Not sure why everyone loves the ac running 24/7 must be the same people who complain about a $500 electric bill.
mike93lx
ALLIANCE MEMBER
It only runs all day on the hottest day.
And a smaller system costs less per hr to run than a big system.
I don't ever want my house anywhere hear 85 degrees. Constant is way more comfortable and keeping humidity more consistent is better for for the house and everything in it
engineer2
Well-known member
It would take longer to cool off 60-odd tons of building materials. Aren't the walls still radiating heat for a while?
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Hobby_Man22
Well-known member
The house runs a bunch at night and the shop hardly runs once it hits the target temp of you leave it on at night. I think it's because the attic of the house retains the 150 degree heat from the daytime. You'll have mold if you insulate the roof in my area so only can floor joists can have insulation.
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Hobby_Man22
Well-known member
walls are insulated
mike93lx
ALLIANCE MEMBER
Insulation isn't perfect, plus you have everything inside of it that was heated up, like drywall, framing, furniture and fixtures
engineer2
Well-known member
True but the drywall and the contents of the home will still be warm.
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Hobby_Man22
Well-known member
So what's the point?
mike93lx
ALLIANCE MEMBER
There is none. Keep on doing what you are doing.
reader2580
Well-known member
I turn on my A/C around late May and don't turn it off until around mid September other than when I am gone overnight or more. 78 degrees during the weekdays, 75 degrees in the evening and weekend days, and 74 degrees at night. I work from home three of every four weeks now so I set it to 75 degrees during the day when I am home working.
My electric bill has never been more than about $110 during the hottest month of the summer.
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Hobby_Man22
Well-known member
How hot does it get in Minnesota?
mike93lx
ALLIANCE MEMBER
I am basically the same in VA, but electric bills run in the mid 200's during the summer. 75 on the second floor all day since I WFH and my office is in a bedroom. downstairs is 78 at night, 75 during the day. Even when we are away, 78ish is as high as I let it go