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Discussion Starter · #1 ·
I moved into this townhome back in March 2020, it's a two level townhome that's roughly 1,450 sqft, built in 2015, located in North West Indiana, and I have neighbors homes connected on both ends. I have a 2 ton AC unit and an evaporator coil designed for 1.5 to 2 tons. I change the air filter regularly and keep the outdoor unit clean.

In winter, I have no issues with heat, like furnace not keeping up with heat or heat running too much, and etc. So I assume ductwork and blower are fine.

Now, when it comes to cooling, I'm not sure what exactly is normal/sufficient. From what I've read, a properly sized unit should be able to easily cool your home down by about 15-20F from what the outside temp is (so if it's like 90F, you should have no problem reaching 70F), and it should be able to keep it there. So, after reading stuff like that, I became concerned.

Once it's sunny and gets up to around 80-85F, today it was upto 85F, the AC just never seems to turn off. Just several hours of running non-stop to hit and stay at the thermostat setpoint of 70-71F.

On June 5th the high was 90F, the AC ran for a total of 14 hours that day. The 6th, high of 86F, AC ran 13 hours. The 7th, high 77F, AC 8.5 hours. 8th, 84F, 12.75 hours. And today on the 9th, 85F, 13.1 hours so far.

So I just want to know, is this what I should expect/normal? Or I need to try checking something or doing something?
 

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If your system is properly sized then you can expect it to run non stop all day while it cools your house to the designed indoor temp.

Compressors love to run. They hate to start. There is nothing wrong with a compressor running all day long. They are happy to do that.

If your indoor temp can’t stay within a reasonable setpoint (what it was designed to achieve) then you may have a problem.

Humid days will make it harder to achieve your indoor temperature setpoint.
 

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70F is absolutely freezing for a cooling setpoint!
75 is a more normal design indoor temp units are sized to maintain.
It's not a good idea to keep it very cold in very humid conditions unless you want mold growth in exterior walls walls.

There's no rule of thumb that's valid with respect to temperature difference between outside and inside, what's normal it depends on the way it was sized.
 

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Discussion Starter · #4 ·
70F is absolutely freezing for a cooling setpoint!
75 is a more normal design indoor temp units are sized to maintain.
It's not a good idea to keep it very cold in very humid conditions unless you want mold growth in exterior walls walls.

There's no rule of thumb that's valid with respect to temperature difference between outside and inside, what's normal it depends on the way it was sized.
I do use a dehumidifier unit, I keep the indoor humidity at around 45%-52%.

It's funny to see that reply about 70F being freezing, because as I read through stuff about AC issues and etc, I kept seeing recommended temperatures to set your thermostat to for summer time, it was in various articles, comments, and etc. I just kept thinking to myself that they were just some ridiculous super conservative numbers for people who want to know what the most energy efficient settings would be, but it appears people really do use those numbers or close to. The reason I thought of the recommendations as ridiculous was because of my warmer than most body (most likely due to the muscle mass accumulated through couple decades of weightlifting). I'm the kind of person that is perfectly comfortable wearing a t-shirt when it's 50F outside, one time when I was doing some good lengthed, intense manual labor outside in winter, I stripped down to a t-shirt in -10F weather cause I couldn't stand how hot I got, I was hot enough to be comfortable in the t-shirt until we finished the job, if I wear a long sleeve shirt or jacket inside a store I'll start getting uncomfortable, and I'll be sweating after a few minutes of walking around. Some of the recommendations I saw were 78F when home, I go into a light instant sweat when I go outside in 78F weather. I could say more, but I think I've made the point, lol.

You know, now that I think about all this, and my preferred setpoint temperature, a couple days ago I went to the alpine home air website, which sells AC units and the like, and they have a sizing estimator for heating and cooling equipment, you go through the little form using various information about your home, and then they give you the recommended size AC unit for your home. The recommendation for my place was a 2 ton unit, BUT, there was a field in the form that I initially didn't notice the first time through, there was a field titled "Desired Indoor Cooling Temperature" and by default it puts it at 75F. So, I decided to just change that variable to 70F, and it ended up recommending the 2.5 ton unit, I changed it to 71F, same thing, 72F, same thing, but once I got to 73F, it went back to recommending the 2 ton unit.

So, when you said, "75 is a more normal design indoor temp units are sized to maintain" that seems to match/explain that default number in the alpine sizing estimator. All this may help explain my years of frustration, frustration I experienced at my previous single family home, and now this townhome. I remembered that despite the reasonable good sounding advice from some HVAC folks about the previous homes cooling situation, I just couldn't shake off the thinking that I had an AC unit that was just one size too small. And now, considering this variable that I never thought about and never brought up before about how cool I desire the indoor temperature to be, I may have actually been right about it. The AC unit size that is recommended and perfect for the average person, and their home, are not necessarily right for the small minority of different folks like myself.
 

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Your ducts probably aren't large enough for a bigger unit.
You can't just upsize and keep everything the same.
Live with what you have, perhaps ceiling fans would help.
 

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If your AC is running 13 hours a day, you are using 54% of your equipment's capacity.

I agree with user -- 70F is pretty cool. But only thing that matters is what is comfortable to you, not to to me. Just glad I am not paying your power bill.
 

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Discussion Starter · #7 ·
Your ducts probably aren't large enough for a bigger unit.
You can't just upsize and keep everything the same.
Live with what you have, perhaps ceiling fans would help.
Understood, thanks.

If your AC is running 13 hours a day, you are using 54% of your equipment's capacity.

I agree with user -- 70F is pretty cool. But only thing that matters is what is comfortable to you, not to to me. Just glad I am not paying your power bill.
Well, I just noticed something with the wiring on the furnaces electronic board; I have a few wires for blower speeds, Low (Red), Medium Low (Orange), Medium (Blue), and Hi (Black). Looks like for Cooling, it's set to Medium Low. I understand if you set the blower speed too high, the home doesn't dehumidify as well, but not too concerned about that as my dehumidifier unit seems to work pretty well. Should I change it to HI? Or perhaps Medium speed? I would assume this would make some kind of difference.
 

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Without knowing the air handler/furnace specs (blower capacity, etc) and having measurements taken, it's a guess.
 

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Should I change it to HI? Or perhaps Medium speed? I would assume this would make some kind of difference.
You need a certain amount of airflow to avoid having the evaporator ice up. I think rule of thumb is 400 cfm per ton, but there are other variables too.
If your AC furnace coil is not freezing up (you would know it if it is), its unlikely to be too far off.
Slower speed = quieter operation. I prefer my HVAC quiet.
 

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In FL and in NY we set the AC at 72 day and 68 night. I don’t believe in 75 to 80 being the best they can do. I am hot at 75 degrees. A couple of days ago it was 92 degrees at my NY house and it was 72 inside. Even my 1800 square foot shop stays at 70. When I buy a system I describe what I want and have not been disappointed. A properly designed, installed and maintained system should do what is needed to maintain 72 degrees.
‘Here is what I would do: Check airflow (registers open, filter good, blower moving air), see if the outdoor unit is plugged up (we have shedding poplars right now so I hose mine off every day), then call for help.
 

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In FL and in NY we set the AC at 72 day and 68 night. I don’t believe in 75 to 80 being the best they can do. I am hot at 75 degrees. A couple of days ago it was 92 degrees at my NY house and it was 72 inside. Even my 1800 square foot shop stays at 70. When I buy a system I describe what I want and have not been disappointed. A properly designed, installed and maintained system should do what is needed to maintain 72 degrees.
‘Here is what I would do: Check airflow (registers open, filter good, blower moving air), see if the outdoor unit is plugged up (we have shedding poplars right now so I hose mine off every day), then call for help.
A system should not be expected to exceed once it’s met the design conditions. If it was designed for a 75 deg indoor temp then that may be it’s limit when the outdoor temp or humidity gets high. That would be a design issue, not a mechanical issue.

If the system was designed to achieve 68 on the design conditions then it will be able to achieve that.

Airflow can possibly be increased to encourage more sensible work, but be aware this can cause motors to over amp, water to fly off the coil, and noisy ductwork, if it’s operating outside of its normal operating conditions.

What is the temperature differential through the air handler?

What is the return air humidity and temperature, and outdoor temperature at the time the above mesure ment was taken?
 

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I wouldnt worry about it running for hours .A system that cycles on and off too much is too big and will wear out faster.
 

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Medium low is correct if your ducts were sized correctly for the 800 cfm it needs.
I wouldn't mess with it.

Increasing speed may net you a little bit more actual cooling capacity, but there's no point if it doesn't pull out as much humidity.
 

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On the bright side, a small unit running more means better dehumidification thus more comfort at a higher temperature. No idea about what your service needs may be.
 

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Discussion Starter · #18 ·
Medium low is correct if your ducts were sized correctly for the 800 cfm it needs.
I wouldn't mess with it.

Increasing speed may net you a little bit more actual cooling capacity, but there's no point if it doesn't pull out as much humidity.
I ended up changing the speed to high, it made a noticeable difference between medium low in its ability to get the temp to drop a little faster, it ran close to an hour less in total time yesterday, and yesterday was about the same temp as the previous day before I decided to change it.

The humidity levels in my home don't really appear to be too much of an issue, the highest I've ever seen it on my thermostat would be about 54-55% and that was back before I changed the blower speed and before I started using the dehumidifier unit.

So, so far this seems to be working out better this way. I'll have a better idea of how well over the next few days. I've noticed some saying something about not liking the noise of the air from a higher speed blower, I really didn't notice much of an audible difference, I don't know if that's because we have flexible ducts (not sure if that makes any difference) or just cause I always have sleept with the ceiling fan at high speed and an air purifier at medium speed in room. I find the air circulation sound of the HVAC system rather soothing, lol
 

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You said reach 70. So are you allowing the homes temp to rise to 76 or higher. And then turning on the A/C?
 
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