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making an A/C unit more efficient

B

bobdole369

Diamond Member
Our summer cooling bill approaches $500 in July-Sept. Its about par for south FL and the size of the house (3br townhouse, 2 stories). Nothing wrong with the unit, but it is in full sun most of the day.

Any thoughts for reducing the cooling bill? (even in winter now its over $150 to keep the house cold during the snowbird season).

Also in the dead heat of summer it can barely keep the temp under 79 (it would be 95-100 out). I've read that this is probably the best it can do, but I know ATOT has some tricks up it's sleeves right?!
 
Making sure the unit is in peak operating condition is how you would make it the most efficient.

Does it run all the time? Sounds like you might need a bigger unit.
 
Also, if the condenser's dirty, cleaning that off would probably improve efficiency. I don't know if it's so much a problem with outdoor condensers, but for window units they seem to get clogged up really bad with dust. Same for the condenser on your refrigerator, they get pretty nasty as well.
 
Make sure there are no mice inside.

Clean the filter and try to vacuum any dust on the inside that you can get at. Keep it at a constant setting? My parents claim (from the central air people) that keeping it cooled is easier, because after the home is cooled down, it's fairly easy to keep it at that temperature. Thus, if that's true, make sure you have decent insulation and put curtains/shades on sun-facing windows to help cool the house during the day.

But overall, if it's having a hard time cooling the area, you probably need a bigger air conditioner for the room.
 
Keep the filter clean/change it regularly, clean the condensor unit on a regular basis, (I hose mine out at least twice per year) and it MIGHT be worth paying to have the coils inside the unit cleaned by a professional. (the way my unit is built, they have to be cut out to clean...that means evacuating the system, removing them, cleaning them, having them welded back into place, then pulling a vacuum on the system and recharging it...BIG bux)
 
Originally posted by: Brainonska511
Make sure there are no mice inside.

Clean the filter and try to vacuum any dust on the inside that you can get at. Keep it at a constant setting? My parents claim (from the central air people) that keeping it cooled is easier, because after the home is cooled down, it's fairly easy to keep it at that temperature. Thus, if that's true, make sure you have decent insulation and put curtains/shades on sun-facing windows to help cool the house during the day.

But overall, if it's having a hard time cooling the area, you probably need a bigger air conditioner for the room.
Click to expand...

Without going through the check list such as Tinting the windows, planting shading shrubbery, checking the wall insulation, etc. the single most effective thing you can do is to get rid of your outdated technology and step up to a slightly larger, more efficient unit.

Also, on your old unit, make sure the fins are cleaned and straight on the heat exchanger. You want to get that foaming cleaner that HVAC guys use. It's nasty shit, so be careful with it. Also, old ducting is probably sealed with duct tape, and that stuff fails over time, so you may be wasting AC in non livable space. New insulated ducting is far more effecient as well.
Also, if the hot air return is not located properly, the system will never cool as well as it could.

 
Originally posted by: bobdole369
Our summer cooling bill approaches $500 in July-Sept. Its about par for south FL and the size of the house (3br townhouse, 2 stories). Nothing wrong with the unit, but it is in full sun most of the day.

Any thoughts for reducing the cooling bill? (even in winter now its over $150 to keep the house cold during the snowbird season).

Also in the dead heat of summer it can barely keep the temp under 79 (it would be 95-100 out). I've read that this is probably the best it can do, but I know ATOT has some tricks up it's sleeves right?!
Click to expand...

Replace the AC air filter, keep the coils clean, move the unit to the shaded side of the house, install shades on the out side of all the sunside windows, an attic fan will help a lot by pulling hot air out of the house.
 
Clean out the Filters regularly, make sure that it is powerful enough for the room that it is cooling, and make sure the windows are well sealed. Also close the window drapes during the late morning through mid-afternoon hours to minimize radiative heat input into the room.
 
You could always plant a south-facing tree on your property.

As long as it's large enough to provide adequate shade for teh house, then you'll save tons.
 
Originally posted by: bobdole369
Our summer cooling bill approaches $500 in July-Sept. Its about par for south FL and the size of the house (3br townhouse, 2 stories). Nothing wrong with the unit, but it is in full sun most of the day.

Any thoughts for reducing the cooling bill? (even in winter now its over $150 to keep the house cold during the snowbird season).

Also in the dead heat of summer it can barely keep the temp under 79 (it would be 95-100 out). I've read that this is probably the best it can do, but I know ATOT has some tricks up it's sleeves right?!
Click to expand...

On a serious note, that is NOT on par for South FL!!! The most I paid in the summer for keeping a 1100 sq ft apt. cold (I mean icy, 75 F) in Tampa was $100. When the A/C broke, and was running non-stop and completely iced over for nearly two weeks, our bill went up to $130. This was in July.

I just paid $70 for last month. WTF man, get a new unit.
 

1. Turn it off.
2. Set temperature at 77-79F
3. Regularly clean condenser/evaporator, and replace/clean filter.
4. Annual maintainance/refrigerant level check.
5. Replace system with higher efficency modle (18-19 SEER)
6. Install higher efficency windows, and add insulation to house.
7. Install geothermal heat pump.
8. Buy a new smaller house with better insulation and less windows/doors.
9. Move to a more milder climate.
10. Move into a cave.
 
To clear one thing up - it's $500 for the month of July, $485 for August, $503 for September. Neighbors bill is the same for the same house. Thats why I didn't question in. We also have 9 PC's, a fridge, a dryer, electric stove, iguanas, fish, 4 TV's (roomie has an HD CRT that weighs like 300 lbs - I bet that thing alone uses a kilowatt).

Once it hits may or so it just stays on continuously until mid-october.

TO clear another thing up - its central air and all spaces are cooled. The hot air return is a huge louvered hole in the living room. No returned air from the upstairs, it all gets sucked in through this one vent in the LR - vents are in 3 BR's and bathrooms upstairs, one in the kitchen and LR downstairs. This is 1980's sprawl-building ghetto townhouses that were built when SFL was experiencing tremendous growth - so no real thought was given to how the AC unit actually works, or its efficiency. Without tearing up walls I see no easy way to resolve the return air problem. It's just stuck that way.

On hot days I go out several times in the afternoon - run the hose until the water gets cool and spray off the condensor for about 3 minutes. It noticeably cools the air coming through the condensor unit and the air inside gets noticeably cooler for a bit.


No mice, but boy do we get a lot of lizards in there. Believe it or not, despite the oppressive supervillianish heat ray laser sun that we get in the summer, those little lizards are always looking for heat, and since theres nearly always some water via the hose, thats where they hang out.
I used to work at a place that did heat pumps for your pool so I kinda get the HVAC cycle. One thing that we ARE missing that I think would make a difference is to shade the condensor. It's untouchable in the summer. I could easily cook an egg on that thing.


So I AM regularly cleaning the coils, all the fins are straight, the pressure is right with no leaks, the filter is regularly changed out, I even recently cleaned the evap coils inside the air handler with a degreaser/bleach mix to retard any nasty growths. Got a good deal of slime outta there. I also flushed the drain and made sure the automatic drain overflow turn off mechanism was working and not being activated.

OK so in short the basics are covered. I don't see any suggestions that make me go "OOOOOH I didn't think about that".

I don't own the house, my roommates family does. I live with a girl and her brother and my fiancee any myself - its owned by their dad who is loath to upgrade something that is "working". I don't blame him, he makes no money on us. The unit is likely undersized. If it were mine I'd have already gone 2 steps up on the condensor unit and compressor.

I was considering building a timed water spray mechanism, seeing as how hitting it with the hose cools it down a bit. (sorta like the intercooler water spray deals you see on turbo cars). Anyone ever do something like that?
 
My a/c bill last summer was horrible. At the end of the summer I noticed the fan on my outside unit was failing and hard to turn. I suspect that the increased load from the fan bearings failing might be the cause.

I was in the same position you're in - cleaned everything, checked everything, there was no reason for the insane bills. I hope it was the fan..
 
You are probably pulling more KWh from 9 PCs than your AC unit.

Oh yeah, I know that. ANd the heat output from those is also tremendous, which the AC unit must cool as well. The issue is that in the dead heat of summer, the unit just can't keep up.
 
Originally posted by: iamwiz82
You are probably pulling more KWh from 9 PCs than your AC unit.
Click to expand...

I'd estimate that the 9 PCs are drawing about 1.35kWh/day if they're on 24/7.

Originally posted by: bobdole369
You are probably pulling more KWh from 9 PCs than your AC unit.

Oh yeah, I know that. ANd the heat output from those is also tremendous, which the AC unit must cool as well. The issue is that in the dead heat of summer, the unit just can't keep up.
Click to expand...

Yeah, it sounds like you need a bigger unit. Does it run all the time when its on?
 

Yeah, it sounds like you need a bigger unit. Does it run all the time when its on?


Continously from May - Mid-October. It cycles as expected this time of year.
 
Originally posted by: AlienCraft
Originally posted by: Brainonska511
Make sure there are no mice inside.

Clean the filter and try to vacuum any dust on the inside that you can get at. Keep it at a constant setting? My parents claim (from the central air people) that keeping it cooled is easier, because after the home is cooled down, it's fairly easy to keep it at that temperature. Thus, if that's true, make sure you have decent insulation and put curtains/shades on sun-facing windows to help cool the house during the day.

But overall, if it's having a hard time cooling the area, you probably need a bigger air conditioner for the room.
Click to expand...

Without going through the check list such as Tinting the windows, planting shading shrubbery, checking the wall insulation, etc. the single most effective thing you can do is to get rid of your outdated technology and step up to a slightly larger, more efficient unit.

Also, on your old unit, make sure the fins are cleaned and straight on the heat exchanger. You want to get that foaming cleaner that HVAC guys use. It's nasty shit, so be careful with it. Also, old ducting is probably sealed with duct tape, and that stuff fails over time, so you may be wasting AC in non livable space. New insulated ducting is far more effecient as well.
Also, if the hot air return is not located properly, the system will never cool as well as it could.
Click to expand...

Yeah, it sounds more like his system is designed improperly and has undersized equipment than anything else.
 
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