AirConditioning & Household Air questions
 

Our AC is having trouble keeping up with this extreme heat. I only set it to 78 to 79 in the daytime and we set it to 74/75 at night. Usually it cools down to 75 by bedtime but lately the AC barely cools the house to 75 by 3 or 4 in the morning. In the daytime the house heats up to 82 by 2:00 in the afternoon and the AC cannot get it back down till late in the night.

(Side Note: I HATE hot weather and turning the AC off is just not an option. I get physically sick from the heat.)

Lately I have tried experimenting with closing doors to bedrooms during the day to hold the cooler air in those rooms. Since our "main room" is all open - kitchen / dining / living area / small office area / then those are where the outside door opens/closes during the day. Everyone is very careful to keep the outside door closed and yes, we do close curtains.

My sister claims that closing doors to rooms will make it harder for the AC to work since the air flow is changed? But - the cool air does stay in those rooms and we open those doors at about 7 at night. We have not noticed it helps the main rooms though and are still experimenting.

Any ideas to help the AC work better or any ideas to help keep the house cooler?

Thank you.

Ahh, where to start:
Your AC unit may be dirty - does it have a filter? - have you cleaned off the fins (like the back of the refridge)?
If it's an older unit the some of the gas may have leaked out and you may have to have the unit re-charged.
Maybe you have an unknown air leak around one of the doors or windows in the house or maybe an entrance to the attic is open?
Or etc etc etc.........

My AC is not keeping up either and we had it checked in the winter because of heat problems. A new part was replaced and freon put in. I went through the house this weekend and put sheets and/or dark curtains on all the windows. This has helped tremendously. We have so many windows in this house which is fantastic for light...but oh that sun is a killer right now. We hit 107 yesterday and it is really unbearable right now. I shut the doors to the rooms not being used and shut the bathroom door in my master bedroom and put the dark sheets over the windows and now it is very cool in there as are the other rooms.

As with most things the answer is; it depends. I'm assuming you have central air so shutting some rooms may cause problems and you prevent the air in the room you want to get cool to be pulled into the air return.

You need to check the filters as mentioned but you should also check the duct work. Cat, rats, mice, possums and other critters like to stay cool and warm as much as we do therefore they will rip open the ducts to let the cool/warm air out for themselves. And for some reason they seem to like having more than one place to stay comfortable. A couple of ripped open ducts will allow for lots of loss.


If you are truly desperate I can give you some hints. You can rig "walls" in your open spaces. Drive some large nails where the walls and ceiling meet. The holes or repair will be less noticeable when you remove the nails. Run a rope from one side of the room to the other and hang sheets or blankets. They don't need to go all the way to the ceiling but they need to reach the floor. Heat raises and cold sinks, you want to keep the cold in the room.

Put some water in a sprayer, spritz your windows and apply aluminum foil to them. YOU STAND A GOOD CHANCE OF DAMAGING THE WINDOW GLASS DOING THIS. But it will reflect darn near 100% of the sun's heat. If you are worried about the windows you can cut a piece of cardboard to fit in the window then cover the cardboard with AL foil.

Is the unit exposed to the sun alot? My mothers was and I was able to reduce the load on it by mounting a sheet metal canopy a couple feet over the unit to shade it while not interfering with the air flow from the exhaust fan.

Shrek has a great point, same thing happened to us. Also, we have drop blinds (home depot carries them) on the outside. If you don't let the sun hit your windows it will really reduce your temperature inside.

What kind of R rating does your insulation have? Is the home well insulated or minimally insulated? Perhaps time to add some.

I could be wrong about this....and it wouldn't surprise me if I were....but I thought I once heard that the typical AC unit cannot cool anymore than 20º less than the outdoor temp.

A/C units aren't sized for "extreme" temps. They would be oversized.

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On the side of the home where the afternoon heat from the sun hits put those roll up bamboo type shades on the OUTSIDE of the windows. The solar gain from the windows is a major cause of the problem you are experiencing.

I may get some disagreement on this but if the heat really bothers you that much, after doing all the clean filter and fins, checking freon, checking for ripped ducts, lower your thermostat to 72 and leave it. If your unit is running constantly it will not make much difference in your costs. This will allow it to "catch up" over night and start off cooler in the morning, even if it takes until 6 am, you will have a better start at the day. Also if there are any unused rooms you can shut down completely that will help too. I used to put a heavy book, or tape a piece of cardboard over registers, then close the door and place a rolled towel at the bottom. The rooms would get up into the lower 80's, but reduced the amount of air my unit had to cool. If you have a return in the closed of room, you would need to seal it too. If you still can't stand it, you could put a window unit in one room to help out for a couple hundred bucks...

Mathew is correct. If your units are running full time , leave them run 24/7. I cool my house with three 5000 btu window units and have ran them 24/ 7 the last 2 months and this last month had more 90 degree plus days than the previous month but both months electric bills were within $2 of each other. This month with the 100 degree days my kilowatt use is tracking within the same use as last month.

Of course some nights it gets a little cool and I need to put a blanket on the bed but its worth the 10 degrees of extra cool after the sun rises.

It has been the fad, or gospel, depending on how you look at it, to place just barely adequate A/C...something that will run all the time in really hot weather, on the assumption it actually is more efficient to do so.

Me, I want to hang beef, if I want to hang beef. I want a unit to cycle.

The last unit I put in the house (1950 sq ft) was 3.5 tons. I will not go that low again.

I did put mine down to 74 from 76. It did make a difference. It does run all the time. My bill the month before was 187 this month was 246. That was a big difference to me. But I have to have the air as I had a heat stroke several years ago and the heat really bothers me now.

Cleaning air conditioner? I can clean the front filters; but how do you clean the back part? (I am not able to take the ac out of the window and it sits on a wooden platform "outside" the window. (Don't want to hijack; so can someone pm me about this please?)

I just adapt to the temp. The only time I use ac is when I am sleeping. Since I spend so little time indoors keeping it cold would be a waste. It is possible for most people to adapt to the temp if they start out the year not using ac. It isn't as hard as it seems, a little sweat is good for you.

My cabin took 2 days to reach comfort zone after turning on a/c a few years back. We called an insulation company-there was NO insulation in the attic. We paid $300 for insulation, the electric went down $150 month and it took 2 HOURS to reach comfort zone.
Also check weather stri[pping around doors as cool can leak out that way. If you see daylight wnen door is closed re-strip.

Not if you are easily heatsick. Heat triggers my asthma, and it almost killed me in 2007. Some people A/c is a matter of life and death.

glad i live in Michigan...i don't use a home air conditioner, just car

A location in your profile would be helpful!

This is true though, I used to work at a summer camp with no AC at all in the humid foothills of NC, got to where I never really felt hotter or cooler with minor temp swings (90-100), I would just feel more fatigued one day, then someone would tell me it was a record setting day! While the heat was not as hard on me when I was working without AC, it was certainly not comfortable.

An A/C unit normally can't cool circulating air any more than 20 degrees F, and can usually cool in the range of 12 to 20 degrees. Typical modern units are designed to cool about 15 degrees. In other words, the return air coming into the unit can't be cooled more than 20 degrees as it passes across the A-coil. Therefore, you won't see the cooled register air any cooler than 20 degrees below the return air.

But A/C units can keep a home a lot cooler than just 20 degrees below outside temperature. In fact, we've had consistent high temps of 110 around here lately, while I've kept my home in the mid-70s.

I've heard what you've said a number of time before. I suspect that someone misunderstood, then passed it on to others.

That's the first thing I would check.

Having installed a new A/C unit myself this spring, I've learned the magic of properly charging a home A/C unit. Having an A/C unit serviced by a professional can be expensive (~$200 around here, plus refrigerant), so if there is genuine interest in HT members learning how to do it themselves I can create a howto post.

If I do a DIY A/C service howto we might consider placing it in a sticky, or perhaps cross-posting it in the "frugal" sticky thread in Coutryside Families.

I live in the middle of Ms.
Last week it was 101 degrees with 95% humidity. I worked outside all day.

Thats hot enough to bake boxer biscuits if you dry powder your drawers :eek:

That was the hottest day last week. The rest were in the high 90's

One other desperation tip. You can hang a tarp on the side of the house. If possible mount it so the top is 6" or so away from the house and anchor the bottom at least that far from the house, 2-4 FEET at the bottom is better.

Also attic ventilation.

My husband used to work on furnaces/central air. He said one of the worst things you can do is close rooms off. It's hard on the unit.

I'd just as soon have the windows open but when it gets really hot and humid I turn on the AC. This year I used weed barrier on the inside of my windows along with the mini blinds, I cannot believe the difference that makes for helping to keep the sun out.

As noted earlier... be sure A/C BTU rating matches house size, check A/C unit for proper function, make sure unit is operating in the shade, be sure house is properly insulated (less heat getting in is less heat to deal with) and if the temp is still too much run it at night if outside temp requires it.

One last thought...dehumidifier. Humidity will affect PERCEIVED temp.

It can be, but it depends. It depends on the unit and where it draws air in vs where the ducts are.

If your AC units intake is in a hallway and you shut all doors to the hallway then yes it could be bad for it. As long as there is ample air flow it's not an issue.

Another thing on an older central unit is to open it up and clean off the evaporator coil in the house. Many filters over the years can let enough dirt/hair/pet hair/etc. especially if not well maintained to get by to block up the coil after years.

Thanks to this thread I just realized why my ac unit isn't cooling and has been blowing the breaker! Um, some nameless idiot forgot to remove the cover. DUH!

A properly sized air conditioner will just barely keep up in extremely hot temperatures. This may seem crazy, but I assure you it is not (if you are located in even mildly humid areas).

When I was working in movie theatres, we had humongous air conditioners on the roof, and they were redundant, just in case one failed. Those units were designed to handle a load of 500 or 1000 or more people on a hot day. When electricity costs were noticed as a major issue, instructions went out to turn OFF the air conditioners after the start of the last show, and not turn them back on until fifteen minutes before customers started arriving the following day.

Over the night, the auditoriums would heat up, there was some air exchange, and what with mopping floors and outside humidity, they felt damp during the day. The air conditioners could EASILY drop the temperatures down in fifteen minutes, but the comfort level was horrid. It felt cold and clammy, like a dripping cave.

Almost half the work an air conditioner does is dehumidifying the air. Getting water to condense takes a lot of energy, much more than dropping the air temps a few degrees. During the hot humid summer, an AC is designed to run much of the time so that it can constantly be pulling that water out of the air.

Why does the air coming off the cooling coil only get about 20 degrees cooler than the return air? The amount of drop usually means the coil itself is a little less than 55 degrees. Coil temps are not even across the width of a coil and there can be cool and hot spots, especially as the system ages. If the average coil temp gets much lower, ice can start forming. One even a small amount of ice starts blocking airflow, the entire coil can start to freeze up.

Shading the outside coil - does it help? It helps reduce the head pressure on the compressor, but not too much more than that. The cooling that occurs is because of a restriction or valve just before the cooling coil. The refrigerant is liquid right up to that restriction, and once it passes through it converts into a gas. The change of state from liquid to gas is what creates the cooling. Shading the coil doesn't make the liquid any more liquid. The liquid might get a couple of degrees cooler, but compared to the energy required to change liquid to gas it is only a small percentage of that energy.

Closing off rooms. Whatever. The load on the fan in the air conditioner will increase if the air is restricted, whether it be from dirty filters, improper ducting, or closed doors. If the air coming out of the vent is still in the 20 degree below the return air temperature range and there is good flow, don't worry about it.

If you need to help your AC, the biggest thing you can do it to limit the effect of the sun. Plant trees. Use insulation. Shield windows with outside awnings. Spray the sunny side of the house with water a couple of times during the hottest part of the day and then once about a couple hours before sundown. If your roof is poorly insulated, spray the roof as an emergency measure.

Otherwise, minimize use of energy in the house. Cook outside. Cut off lights. Turn fans OFF in unused areas. Have quick showers and use the exhaust fan to vent the moisture. Then use the night to build your cool bank. Let the house get down to 70 overnight, and give the walls and furniture a chance to really release their heat from the previous day. It will take longer for it to heat back up.

Even if you have central air, consider using a window unit in a problem area. Modern window units are VERY efficient. If all else fails, make a cool room by using a window unit in a small room and retreat to it mid-day. Have foods ready to eat and eat in there.

Just so no one is misled here, when air ducts are restricted the load on the fan goes down, not up. That's because when the fan doesn't move as much air it's partially free-wheeling. You observe that when you put your hand over a vacuum cleaner hose and hear the motor race. Likewise, you can put a piece of cardboard against the suction side of a box fan and the motor will race.

Great catch on that. It is a lot more complicated than should be discussed here, non-linear, and even pros get confused. (I once had a similar discussion on cavitation in swimming pool pumps and the effect on power usage. A totally blocked pool pump uses less power than a partially blocked or free flowing one. It just doesn't get any real work done.) The bottom line is that some loading is perfectly acceptable, but an excess can cause problems (frozen coil, insufficient motor cooling, etc.).

After reading this thread earlier today, I broke out my old drapes (heavyweight, tightly-woven fabric, heavyweight liners...you know, the kind that you have to install center supports or the rods will break!) and changed my window coverings on the front of my house.

I went into my office (on the front of the house) and played around on the 'puter for a while. Within an hour or so in the hottest part of the day, I could tell a HUGE difference in the temp in my office...I wasn't sweating! Woo hoo!

Doesn't matter to ME that they're country blue and mauve florals from the 80s! :D

Thank you everyone! What great ideas - I will get to work today. We do have some old window bamboo blinds and I can hook those outside the house and ...curtains. And I can block off the air in one room to force that air to others.

Thank you - I really appreciate the tips and information.

We are doing the same thing here. It is chilly in the morning but it keeps it decent in the afternoon when the temps really skyrocket.

we live in southwest ms, recently had some minor a/c work done on our central a/c unit: my theory of thinking was everytime i heard the unit kick on I saw $$$$, dh thinks is by setting thermstat higher it make a/c work harder to cool, so we ask the a/c man, he agreed with dh, by kicking it way up high during the day (thermostat 80 or so when we are not home, everything in the house gets warmer, furniture, walls ect... so the a/c has to work harder to cool the air plus walls and funiture. so we now keep the house set at 76 degreess at all times and it doesnt kick on quite so often, and electric bill was about the same or a little less.

Hello again everyone -
To answer some of the questions: Our Unit is only 6 years old, it is cleaned and serviced regularly, and we do keep the inside filters clean.

From all the suggestions and information, I think our problem was that the Unit IS in the hot sunny side of the house so we plan to put a screen behind it this weekend when husband is home. Also, I have been setting the thermostat WAY up in the day time, sometimes as high as 84. I was mistaken and thinking that "helped" the unit by giving it a "rest" - but now I have learned that is not OK.

I was also turning the thermostat way back down in early evening, which of course then meant the unit was half killing itself trying to undo all the damage (heat and humidity) I had done during the day.

The hottest rooms in the house have a good overhand where we have now hung shades on the outside and this weekend we will shade the Unit. Also, I am leaving the thermostat up and just making everyone CLOSE THAT DOOR to the kitchen porch.......which I am sure will help too.

Thank you everyone - this was a big help and since the bad heat will return tomorrow, I think we will be cooler. Thank you very much.