Reasonable A/C thermostat setting in summer (Houston, San Antonio: leasing, new house)

[houstmom]

My family and I are moving from Houston to San Antonio in a week. We are leasing a home in SA that is about 11 years old, 2 story house (2500 sqr ft). I have no idea how energy efficient it is etc.

I went to the house last weekend to make sure everything is working. The house has to A/C units. I was able to cool the 2nd floor to my liking. However, I set the 1st floor A/C until to 74F and the actual temp. never got below 78F. I had the landlord bring A/C repair out to look at it.

The A/C people were saying that the units are old and probably need to be replaced. They also said that these units come from the factory guaranteed only to 78F. I have never heard of such a thing!

I am currently living in a 3000sq ft house that can easily cool to 74F but it is only 1.5 yrs old and has a lot of energy saving features.

With an 11 yr old house with old units, should I not expect to cool the house down to 74-75F in the summer?

[Sunderpig2]

I guess you're getting the "actual temperature never got below 78F" from the thermostat itself? The thermostat may not be reading the correct value. You might need an additional temperature monitor to get a second "opinion". But regardless, I'm guessing the temperature wasn't to your liking, like it was for the 2nd floor.

It could be the A/C unit(s) and/or the thermostat. The thermostat would be a much easier and cheaper way to attempt to fix the problem. That's absolutely ridiculous about units being "guaranteed to only 78F". Whoever said that is full of cr*p, and you should be especially suspicious of them.

An 11 year old house shouldn't be an issue either. I live in a 33 year old house, and it can cool to 74 degrees (verified independently). The A/C may run quite a bit, and the inefficiencies are noticeable, but it's not something extremely difficult to achieve. One note though: the square footage might not be equivalent (single story, 3-BD). It seems like a two-story house, and anything in the 3000 sq. ft. range, should have two units. Someone else might know better, and add their comments.

[a_guerrajr]

A lot of factors

are the outside units provided any shade? always exposed to the sun?
is the a/c zoned properly, maybe a fault in the duct work for the 1st floor
constant cooking, heat source?

weird thing is if you can get the 2nd floor to cool, some of the cool air should come down to your first floor and help cool it. unless the thermostat is just not accurate.

[HoustonRonnie]

Go with what makes you (the woman) comfortable.

And this is not a joke. My g/f controls the thermostats in our house. If I kept it where I feel comfortable, she'd be freezing and I'd be sleeping on the couch.

Just sayin'...


Ronnie

[davidtk]

An eleven year old house should have pretty decent insulation, so I think something else is the issue. 11 years sounds too soon to replace the A/C units. The issue may be a number of things:

1. Low freon / freon leak. I assume the A/C technician checked this, but I always wonder how honest they are. It's easy for them to say "replace" and you really have no idea what the truth is. The coils may also need to be cleaned. It makes the unit more efficient.

2. Poor installation. No way to fix this easily, and it isn't your house anyways.

3. Undersized A/C.

4. Replacement. The unit may genuinely need to be replaced.

Setting aside what the thermometer says, because it may be inaccurate, is the first floor not comfortable? If so, your landlord needs to address this, whether it's getting a second opinion or replacing the units. While you may have to live with the problem, it isn't your problem to fix.

[CptnRn]

Originally Posted by davidtk

An eleven year old house should have pretty decent insulation, so I think something else is the issue. 11 years sounds too soon to replace the A/C units. The issue may be a number of things:

1. Low freon / freon leak. I assume the A/C technician checked this, but I always wonder how honest they are. It's easy for them to say "replace" and you really have no idea what the truth is. The coils may also need to be cleaned. It makes the unit more efficient.

2. Poor installation. No way to fix this easily, and it isn't your house anyways.

3. Undersized A/C.

4. Replacement. The unit may genuinely need to be replaced.

Setting aside what the thermometer says, because it may be inaccurate, is the first floor not comfortable? If so, your landlord needs to address this, whether it's getting a second opinion or replacing the units. While you may have to live with the problem, it isn't your problem to fix.

I wanted to highlight that comment about cleaning the coils, these are the cooling coils inside the house, usually inside of the air handler assembly. In 11 years they can accumulate a lot of dust and hair fibers which makes them less effective.

There is no question in my mind (architect) that a first story HVAC unit in good condition in an 11 year old house should be able to cool the space below 74 degrees.

The average life expectancy for an HVAC system is 15 years, so they are not old yet. Duct leaks can also be a problem in older systems, but shouldn't be in an 11 year old house.

[mtgmike]

I have an eleven year old 2900 sq ft house with two units. We dont use the upstairs hardly at all, keep it at 78-82, and just kick it down if we go up for something. Downstairs its 72 at night, easily gets there.

You wouldnt believe how well blackout curtains work. The AC doesnt have to work nearly as hard.

[jasonamd]

Originally Posted by houstmom

They also said that these units come from the factory guaranteed only to 78F. I have never heard of such a thing!

That's not an entirely untrue statement. The factory doesn't guarantee any certain temperature but the installers usually do. A properly calculated, designed and installed A/C system should be able to maintain 78 degrees at the outdoor design temperature. I'm not sure of the exact outdoor design temp for Houston but it should be in the upper 90's. Just for an example, let's say the design temp is 98. All the calculations for the system are done assuming it is 98 degrees outside. If done properly, the system should be able to maintain 78 inside by running continously when it is 98 outside. If it is less than 98, your system will cycle on and off and you'll be able to get a cooler temp indoors. If it is hotter than 98, your system will run continously and you probably won't be able to maintain 78 indoors.

I purchased a new house last year and the warranty on the heating/cooling system states they only consider it a problem when the A/C won't maintain 78 or the furnace won't maintain 68...as that is what the system is designed to do. Have a friend who purchased from a different builder and their warranty states the same thing.

Almost all A/C systems are oversized (and thus less efficient) because people tend to think something is wrong if they can't get their house down to 65 when it is 110 outside.

So it really depends on how well the calculations were done and what size system was installed as to if there is a problem or not. But only being guaranteed to 78 isn't all that uncommon.

[Volt61]

Originally Posted by HoustonRonnie

My g/f controls the thermostats in our house. If I kept it where I feel comfortable, she'd be freezing and I'd be sleeping on the couch.

But somehow, if a man demands such a thing from a woman, it is seen as unreasonable and women become uppity.

A woman needs it just like a man, so I suggest you develop a pair and stop putting your head willingly on the emasculation block.

[HoustonRonnie]

Originally Posted by Volt61

But somehow, if a man demands such a thing from a woman, it is seen as unreasonable and women become uppity.

A woman needs it just like a man, so I suggest you develop a pair and stop putting your head willingly on the emasculation block.

I'd suggest you learn to pick your battles. This one isn't one of them. "Grow a pair.." Pffftt....

Just sayin'...

Ronnie