Odd thermostat problem, or I'm finally senile!

[Mr. D]

In a previous post you stated that an independant thermometer didn't indicate a drop in temperature as you noticed the comfort level change. If this is true even when the independant thermometer is located away from the thermostat then the problem is not the thermostat and not the wall load or return grill placement and is very likely that you are feeling the comfort difference in the change of humidity. A Honeywell TH8321U1097 thermostat is capable of controlling the AC to dehumidify and I would set it up with a higher temperature setpoint then you currently use. Then lower the dehumid setpoint until you are comfortable. This is a commercial thermostat and is expensive compared to residential tstats. Alternatively you could try getting a stand alone dehumidifier and I would run a hose to a floor drain somewhere so its not necessary to empty a tank repeatedly. Humidity usually spreads through out a house so the location of the dehumidifier is not critical. Before you spend money though, I would get a cheap humidity / temperature display device and check to see what it reads when you feel comfortable and what it reads when the unit is running continuously and you feel too warm. You will then know if you are on the right track before you spend a significant amount of money.

Sounds like a good way to go! The feeling is much like getting into a car on a very hot and humid day and turning the AC full on! You get a uncomfortable chill until the humidity goes down! What happens then is the chill gets uncomfortable as the AC runs, and runs until my wife puts on a quilt or turns up the temp on the thermostat to shut off the compressor. Then within a short time we get hot and the cycle repeats itself! I think the issue must be related to humidity! We don't open up the windows at any time to allow outside air/humidity in mostly because it is windy here and we both have allergies!

To figure it out I've closed the vents feeding the bedrooms to see if the situation changes when returning air from a smaller square footage! We'll see what happens!

Aren't you guys lucky you didn't install the heating and air and have to listen to all these looney complaints! Actually, the guy who did is history and I knew I'd have to figure it out on my own using some expertise from professionals! The internet is very helpful for that! We'd better protect the internet! It is too valuable to lose to corporate control! It should stay uncontrolled and uncensored, or it will wind up like are news programs that present very little in actual news! (Off topic, I know... but important!)

[crab master]

Closing bedroom vents could cause you more problems and will dehumidify faster, but at the possible and likely expense of freezing up your indoor coil, unless you have a grossly over-designed indoor blower.

Go out and buy a humidity sensor and/or a thermostat with a humidity sensor built in. Just because its 9% rh outside doesn't mean that's what it is inside. You may have something 'wet/moist' inside the house and that is what the AC is trying to pull out. I'd do an attic and basement inspection looking for moisture...

After you've checked your indoor humidity levels then the room you mainly spend time in you might close a few vents in there for a few days and test, you may just be sensitive to the airflow across your skin. The other thing is just because you insulated the wall behind your thermostat and it being an interior wall doesn't mean you don't have hot air leaking out the wall penetration for the t-stat wire. I've seen that as well so I sealed the hole so air couldn't leak back thru. Certain winds or for what ever reason(s), the attic/home pressure changed and the hot attic air pushed down the walls and out any crevices it could find. Do you have an attic fan(s) that quit working? I've seen people try to push air into the attic and not pull it out and that cause issues or they had an attic fan that just quit working and now they are learning how the house operates without.
Another thought, you say the last 2 yrs you've had this issue, have you been retired now for the last 2 years and possibly just spending more time at the house and noticing it more?
You might also post the model of the t-stat you have, maybe there's some settings there that could be adjusted?

At my desert house I keep the cooling setpoint around 78 deg F during the peak of the summer, and now around 76. I flew to my uncle's house near St. Louis and was comfortable at 70 deg F due to all the humidity....

[Mr. D]

Crab Master,

I'm using a Robertshaw Model 9600. Do you have a replacement recommendation?

Thanx for the help!

[MaxBurn]

If you are concerned with the wall contaminating the temp reading of the stat I don't think you need a new stat, just add some insulation behind the stat. Should be a foam wall plate backing available in the hardware store for this purpose.

For humidity any other humidistat in the hardware store should do for this purpose too, again no need to replace what you have.

[crab master]

http://www.robertshawtstats.com/imag...%20Cropped.pdf

Look at pg 5 & 6 and then find out what your temperature differential is set to, after you check your home humidity levels.

[Mr. D]

If you are concerned with the wall contaminating the temp reading of the stat I don't think you need a new stat, just add some insulation behind the stat. Should be a foam wall plate backing available in the hardware store for this purpose.

For humidity any other humidistat in the hardware store should do for this purpose too, again no need to replace what you have.

Thanx, I already did the wall insulation thing.

[Mr. D]

http://www.robertshawtstats.com/imag...%20Cropped.pdf

Look at pg 5 & 6 and then find out what your temperature differential is set to, after you check your home humidity levels.

Thanx for the help1

[Mr. D]

I got feeling hot so I lowered the thermostat manually one degree to 77! The compressor ran for over an hour and the temperature still read the same on two thermometers (77) although my wife and I were freezing! The A/C unit does remove humidity as I get water out of the system outside! We just feel like we are freezing, but the temperature does not drop enough to shut off the compressor!

Is this a case of the unit being too small, or old, for the square footage being cooled! It seems I didn't have this problem when the house was new. It seems to have started after about 10 years of service. As in most areas in the High Desert humidity has gone up!

Still Confused,

[controls21]

Mr. D,
it will sound like a cop out but you might want to have a pro in, just to investigate with expensive tools you don't have to buy yourself. A Laser Heat gun would do wonders because I see you've been checking temp with regular thermometers. You'll be amazed the difference from room to room, and using better equipment versus cheap thermo's.

If I duplicate anything, sorry for that, but from what I read you've got a 10 year old system with a RobertShaw stat. The first thing I would do is confirm the stat is completely accurate. I would expect, even in high heat and humidity, to have the outside compressor running for a while, but then shut off after 30 minutes tops.

What square footage is the unit trying to cool? Have you ever had the R-22 or R-141a changed in the unit? Have you noticed any leaks outside on the slab or area where your condensing unit is located? My two cents, for it to continually run, it's either too small for the space, short on Freon or the compressor is failing. 10 years in would be no surprise if you had bad parts, but units last 20 years routinely. Any of those problems could be checked out by a HVAC contractor for less than 100 bucks. Here in the South, $69-75 would get a system check.

They might find problems and then suggest a total overhaul or new equip, but you could always decline that and at least know what's wrong. Good luck.

[Mr. D]

Thanx a lot for your reply!

Question: Is there any scenario where the temp does not go down for long compressor runs, but it gets cold enough that you are uncomfortable? If the compressor ran on and on, but it was still to warm that would be a more usual complaint and easier to figure out. It feels much like when you get in a single seat cab pickup when it is humid and the A/C makes it uncomfortably cold very quickly before the compressor shuts off. You get very chilly, due to the drop in temp with high hmidity... I think!

The reason I have not had someone come out to look at the unit is that it sounds crazy to tell a tech that "the house is getting too cold, but the temperature stays exactly the same!" I sound like a loon, or at least senile! I'd think someone was out of it if they said that to me! LOL!

[controls21]

Thanx a lot for your reply!

Question: Is there any scenario where the temp does not go down for long compressor runs, but it gets cold enough that you are uncomfortable? If the compressor ran on and on, but it was still to warm that would be a more usual complaint and easier to figure out. It feels much like when you get in a single seat cab pickup when it is humid and the A/C makes it uncomfortably cold very quickly before the compressor shuts off. You get very chilly, due to the drop in temp with high hmidity... I think!

The reason I have not had someone come out to look at the unit is that it sounds crazy to tell a tech that "the house is getting too cold, but the temperature stays exactly the same!" I sound like a loon, or at least senile! I'd think someone was out of it if they said that to me! LOL!

Mr. D,
there are at least 2 scenarios where that would happen. The first would be an incorrect temperature reading on the thermostat, triggering the unit to run until it hit setpoint. Sounds like it rarely reaches its happymedium. An easy way to check that in the absence of tools would be to kick up your desired temp to say 79 until the unit shuts off, and then see how you all feel.

Second scenario for you feeling cold without a temperature drop is explained by the removal of humidity. If the unit is running that long, I expect a ton of moisture to be sucked out of the cooled space. Your condensate evac pipe should be pouring out water by the bucket if the unit is working properly. You'll feel the difference because of the drier air, but it's possible that you have hot and humid air flooding right back into your house somehow. A heat gun would tell you where it's warmest in the house and identify crappy insulation.

I see 3 possibilities- bad temp reading at the thermostat, mechanical issue with your compressor and condenser unit outside, or the space is bleeding air. If the unit were too small for the space, you would've noticed this problem a long time ago in terms of comfort and your energy bills.

[Nuclrchiller]

A third scenario occurs to me, based on the repeated reference to being in a pickup truck. Mr. D, you and your wife wouldn't happen to be sitting in the air stream from a duct, would you? I sometimes get requests and/or complaints from commercial building occupants about this. Some want to feel that cooling or heating on them so they know it's working. Those that do feel it like that complain, and we correct it. Much like coming inside on a very cold day, it's nice to stand in front of the fireplace. But after a while, it's too hot, and you have to move. Same with that initial blast of cold air from the A/C. It feels great, but after a while it's too much. Maybe, if you're not directly in the airstream, you're close enough to feel an effect. Just a thought ...

[Mr. D]

Thank you both so much for the time taken to make these responses! It gives me some good areas to look into to solve my problem.