AC not working 100%. Should I call our HVAC foks?

[Car-Guy]

FWIW, a ~30 deg drop from outside temps is about what I get out of ours. And it's a pretty new high efficiency unit by today's standards. It was 100 (exactly) yesterday and mine was still cycling when set at 72... Not a lot but occasionally.

 

[ksr]

I don’t know how people manage at 76 or 78. I’d be a sweaty mess and no way I could sleep with it that hot. Maybe with an air mattress on the basement floor but definitely not in the bedroom.

We are in that heatwave now so I understand how it feels. We keep the temp around 78 but were finding it hard to sleep, as it is warmer upstairs. A few weeks ago we bought a separate room a/c unit from Costco and set it up in the bedroom. We turn it on about ah hour before going to bed, and let it run for a couple of hours. It works surprisingly well. If one of us wakes up hot in the middle of the night, we just turn it on for a couple more hours.

 

[RetiredAndLovingIt]

When our temperature is around 100 my condo ends up being between 78-80 by 4. I can usually get it down to 75 by 10pm and then gradually it gets cooler. Just impossible to keep up with extreme heat.

Terry, don't you use a swamp cooler any of the time where you are, I'm thinking you're in Nevada? That's my main cooling system here in the Southern California desert and I only have to use my a/c about 30 days at the most per year when it's humid and sometimes that's just late afternoon. It's a dry heat so we don't sweat and they're simply more efficient than a/c and cost pennies to run. Right now we're in this ridiculous heatwave till at least next Wednesday, it's 110 degrees in the shade right now and 77 inside at 3.50pm. I'll shut it off when I go to bed and set a timer for it to turn on about 4.00am and just have the fan suck in all that free cold dry air before sunrise which brings the inside temp down to the high 60's before I even get up.

 

[Mark1]

I suspect your unit is fine. I understand wanting it cool to sleep (I too have my set point at 71/70 during sleep), but 70 during the day seems excessive.

If 72 Deg during the heat of the day is too hot, you might need a bigger unit for the hottest days.

 

[Teacher Terry]

Terry, don't you use a swamp cooler any of the time where you are, I'm thinking you're in Nevada? That's my main cooling system here in the Southern California desert and I only have to use my a/c about 30 days at the most per year when it's humid and sometimes that's just late afternoon. It's a dry heat so we don't sweat and they're simply more efficient than a/c and cost pennies to run. Right now we're in this ridiculous heatwave till at least next Wednesday, it's 110 degrees in the shade right now and 77 inside at 3.50pm. I'll shut it off when I go to bed and set a timer for it to turn on about 4.00am and just have the fan suck in all that free cold dry air before sunrise which brings the inside temp down to the high 60's before I even get up.

When I had my house we had a swamp cooler because it works great in Nevada. However, I own a condo now and both our heat and air conditioning is a central system for the entire building.

 

[Turbo29]

I think you’re expecting too much. If my outside temp was over 100 degrees, I’d feel pretty good getting the inside temp below 80 degrees. I keep mine around 78 until evening (for bed time) when I turn the temp down to 76.

That wouldn't work here. I can easily get to 75° or less when it's 115° out. Usually though I go with 80° or 81° because I don't need it that cold during the day. Night is a different story; I keep it at 75° overnight.

 

[CardsFan]

Higher humidity might feel worse to people, but a home A/C unit lowers the temperature virtually the same at any humidity level.

btw, the humidity part of the heat index has no impact on the operation of a residential A/C system, so instead reference the ambient air temperature shown by a thermometer in the shade

I disagree with this.
The inside humidity, which can increase just by going in and out, and just by normal infiltration, needs to be removed. And that takes energy.

 

[GrayHare]

I disagree with this.
The inside humidity, which can increase just by going in and out, and just by normal infiltration, needs to be removed. And that takes energy.

Higher humidity is simply water molecules where there would have been other air molecules. All air molecules contain heat. The difference in heat contained by different air molecules in a parcel of air in a typical home is so slight, even a pro physics lab would have to work hard to measure it. The cooling accomplished by home A/C will be influenced far more by other factors (outside temp, supply voltage, etc. ) than by a varying mix of typical home air molecules.

 

[Turbo29]

To remove humidity an air conditioner condenses the water in the air; this is why water drains from a/c units and more drains when it is very humid. When the water condenses (phase change from vapor to liquid) heat is released that the a/c unit must remove. Note that when the water is condensed this heat is released without the temperature of the water being lowered. Work that the unit does removing humidity is work that cannot go towards lowering the air temperature.

 

[CardsFan]

To remove humidity an air conditioner condenses the water in the air; this is why water drains from a/c units and more drains when it is very humid. When the water condenses (phase change from vapor to liquid) heat is released that the a/c unit must remove. Note that when the water is condensed this heat is released without the temperature of the water being lowered. Work that the unit does removing humidity is work that cannot go towards lowering the air temperature.

^^^^This

 

[Irishgirlyc58]

I live in the Sacramento valley and the temperature today was approximately 115° depending on who was reporting it. But really after 110° who’s counting.
My AC is set at 75° for the summer. 24/7. It is has been holding that temperature. Running the most today- the hottest day so far of this heatwave.
I personally would have the AC technician back out for a looksie next week. If something is going wrong I’d rather find out and get it fixed before the AC broke completely.

I don’t know anyone who uses swamp coolers anymore. They used to be quite the thing back in the 80’s up here but I have always hated them.
I hate humidity.

 

[latexman]

Specific heat, Btu/lb/F
Air = 0.24
Water vapor = 0.45

Even without change of phase considerations, i.e. condensation, water vapor takes 1.9X the energy as air to change 1 degree F.

 

[jimbee]

To remove humidity an air conditioner condenses the water in the air; this is why water drains from a/c units and more drains when it is very humid. When the water condenses (phase change from vapor to liquid) heat is released that the a/c unit must remove. Note that when the water is condensed this heat is released without the temperature of the water being lowered. Work that the unit does removing humidity is work that cannot go towards lowering the air temperature.

Yep, the A/C can't effectively remove the sensible heat of the air until it removes the latent heat of the water vapor in the air by condensing it.

 

[GrayHare]

Of course latent heat exists, but we're not talking huge volumes of humid air, guys. For the OP's question, there's simply not a significant amount of latent heat in a parcel the OP lets into his house by briefly opening his door. How much warmer will the OP's house be due to conditioning that parcel that came in at 50% relative humidity vs one at 20%? It probably can't be measured on typical home thermometers, or sensed by the OP.

 

[Texas Proud]

Higher humidity might feel worse to people, but a home A/C unit lowers the temperature virtually the same at any humidity level.

The AC unit is also removing the humidity... but since humidity affects how temp is felt, even if the temp is 72 it can feel much warmer and you then turn the temp down to 70... and repeat until you feel OK...

 

[MichaelB]

It is currently 96 degrees with a heat index of 104. I noticed a little while ago that although our thermostat is set on 70, the actual room temp was 72. Uh oh. That's not good. The AC is running and is blowing cold air. I have a vent booster fan in our computer room that has a thermometer that shows the air temp coming from the vent and that's reading 57-58 degrees which is normal.

Does it sound like anything is wrong with the system or is it just so damn hot outside that the system can't quite keep up? The system was just fully serviced a couple of months ago including replacing some aging parts so it should be in tip top condition. I've been watching it for a couple of hours and it's maintaining the 72 degree temp. It just isn't getting down to the set temp.

Thoughts?

If the A/C system was failing the temperature would rise more than 2 degrees on such hot days. Does the inside temp reach 70 when the sun sets?

I wouldn’t call a tech for this, but I would start to set money aside for a new unit.

 

[Aerides]

Of course latent heat exists, but we're not talking huge volumes of humid air, guys. For the OP's question, there's simply not a significant amount of latent heat in a parcel the OP lets into his house by briefly opening his door. How much warmer will the OP's house be due to conditioning that parcel that came in at 50% relative humidity vs one at 20%? It probably can't be measured on typical home thermometers, or sensed by the OP.

Living in S. Fla, I can tell when my AC is having a hiccup by the humidity rise - even by just 5% - before I notice the temperature. My thermostat displays both.

But yes the unit has to work harder and longer to reduce humidity vs. temp alone, and many AC's will have an extra cycle to meet the humidity goal after the temp is reached.

 

[Aerides]

If the A/C system was failing the temperature would rise more than 2 degrees on such hot days. Does the inside temp reach 70 when the sun sets?

I wouldn’t call a tech for this, but I would start to set money aside for a new unit.

I'd get a good thermometer, the kind the techs use, and measure the air coming out of the vents. It should be super cold, I think low 50's? We had a lot of analysis done in our house for a similar problem, and the air coming into the bedroom vents furthest from our unit was only 5 degrees higher than when it left the unit - which is not awesome but given it's travelling across a S.fla attic with an older roof, it was totally reasonable.

We also looked into going with a larger seer unit, after we noticed the same problem as the OP for these most brutal weeks, but those can give you other issues, and a good place won't oversize your house. We called around a few places and were very pleased to find companies aren't always looking to sell you something. "Your unit is the right size and working well, no charge" - !!!

We now have a service contract with a good AC company, so we can call them if needed, and they do basic checks for free. OP might consider that vs. a single paid visit.

 

[Winemaker]

An air conditioner will have a limit to cool inside when the outside is 20 degrees warmer.

 

[wrigley]

I hate it, but have no choice. Even if my AC cooled to that low a temp, the bills would be astronomical. They're pretty high now.

I live in Jacksonville. My A/C is never set above 73. At night, before we go to bed, it gets lowered to 70. My last monthly water and electrical bill combined was $238.50. 1900 sf house. I'll pay pretty much whatever to stay comfortable in my own home.

Mike

 

[target2019]

I'm comfortable at 78 during most summer days. I sometimes adjust that to meet weather conditions. Let's say it's 5 deg. warmer outside, and my AC is not cycling enough to move air. Then I bump the thermostat 1 degree lower, and feel what happens.

In the case of extreme weather like now, I stay with 78. When the sun goes down and outside temp drops, the schedule lowers the thermostat in small increments.

We're all different biologically, sit in different spaces (3000 sq ft with 2 systems), have various HVAC systems with low or high mileage., and live in climate systems others don't understand.

Some are pushing their systems more than I would. But that's fine.

 

[FindingForward]

I live in Jacksonville. My A/C is never set above 73. At night, before we go to bed, it gets lowered to 70. My last monthly water and electrical bill combined was $238.50. 1900 sf house. I'll pay pretty much whatever to stay comfortable in my own home.

Mike

I pay much more than you (electricity, water and garbage service) on a small 1500 sq ft house - with the AC set much warmer AND good insulation. All depends upon your power company and rates. If I were to match your temps, I'd love how it felt, but I'd easily be paying 400/month (possibly more) and the system would likely burn out, right on hottest day of summer. I'm used to the higher temps and just deal with it.

 

[AzDreamer]

Did you check the temperature next to the thermostat or was you thermometer in some other part of the house?

 

[disneysteve]

Update: I don't believe anything is wrong with the AC. I think it was just overwhelmed yesterday. I did raise the setting to 72 as suggested here to reduce the strain on the system. As evening fell and the temp dipped into the lower 90s I was able to lower the setting to 70 again and the system did cool the house to that temp and kept it there all night.

We are taking some steps to reduce the strain today. When I got up, I raised it to 71 and around noon I'll make it 72. We're keeping all of the blinds and curtains closed to reduce radiant heating a bit. It'll make for another uncomfortable day but it's better than burning out the AC unit. I want to be comfortable but not at the expense of having to replace the AC prematurely. So another sweaty day is in store for today and probably tomorrow as well.

Thanks for all of the input.

 

[pacergal]

We have our AC set at 75, ceiling fans and one room fan going, along with all the shades drawn. When the temps get to 90-100, we have a couple of UV sunbrella fabric shades that we put up. They work really well to keep the heat coming into windows and walls. Our long ranch house faces East/West, so a ton of windows for that hot sun to bake. The extra sun shades are amazing.