What is the Physics Behind More Efficient Air Conditioners?

Multiple speed fans and compressors add efficiency.....and cost....The real basic improvements have been the new refrigerants which are more efficient and larger coils with slower fans...How did you determine the actual cfm flow? The EER ratings are determined at max load which is generally 95°F, the EER increases below that...

I went by the the furnace manufacturer's estimated air flow number and a simple air velocity reading of air going through the air filter opening which is a fix area then went with +- 10% for a reasonable margin of error on actual volumes of air being moved.

After that it was just a matter of temperature drop and humidity drop across the A coil.

From there I came up with a estimated applied BTU's of heat being moved and factored that against the wattage being used by the system as read from a digital watt meter setup.

Going by the worst reading and estimates at a outdoor temp of 93 F in direct sunlight and a house temp of 85 F I was using ~3800 watts to move ~ 45,500 BTU's giving me the EER of ~12. On the best day with a cooler outside temp and in the shade plus a lower house temp I came up with ~3400 watts moving ~51,500 BTU's.

The compressor is an old Lennox commercial unit rated at 4 ton and the A coil is a brand new 4 ton unit.

Granted it was not a scientifically perfect measurement method but using the upper and lower margins of error I came up with no worse than a 11.5 EER or at best a 15.2 EER when I did my readings.

Overall I would say the system has a fairly honest average EER of about 13 over the range of conditions it's being used in.

Would you please share which new refrigerants are more energy efficient?

I am going to be installing a new split system in my home and so far I have found that an energy efficient R22 unit pulls roughly 58% less current than a 134A and 61% less than a 410A for the same cooling capacity size mostly due to the excessively high head pressure.

I have found some water cooled systems to more energy efficient but the cost of installation is outrageous so I have not pursued that option yet.

Thanks for the information in advance.

The key is SEASONAL EER.

EER is a literal number. SEER is an indication of efficiency in your climate zone.

That's my recollection, but it could be wrong.

SEER vs EER

http://asm-air.com/airconditioning/seer-vs-eer-what-is-seer-what-is-eer/

Probably the best thing is to increase condenser area, resulting in lower discharge pressure. Increasing evaporator area could boost Btu/kWh, but it wouldn't reduce humidity very well, so probably not much room to maneuver there.

eer or seer?

you could have offered more info

if you're super bored you can dive into the tech aspect of newer refrigerants and coil circuiting herehttp://fire.nist.gov/bfrlpubs/build06/PDF/b06043.pdf

if you're using a high seer unit like the ductless wall mounts from one of the Asian manufacturers they also go the extra mile in their compressor design and use plenty of rare earth metals to maximize the fields on their ...and they are expected to be recycled at the end of service life.

if you asked for a quick answer I'd tell you speed of the motors and compressor and the use of variable speed drives to achieve that. but I prefer you get confused looking at entropy and cop charts

Basically from the info given an average EER of ~13 for a mix and match of new and 30+ year old components is not bad which puts it in the same average efficiency as most any modern units that use fixed frequency compressors and fan motors.

The only realistic improvement I can see at this point would be to switch out the R-22 for R-290 which by the numbers would only get me maybe one more EER point on the average.

As for more info what do you need? I was wearing my avengers underwear with black socks at the time.

Men's or Ladies ?

Men's boxers of course!

FWIW the biggest air conditioning efficiency issue I have here is my wife. It's approaching 90 degrees and sunny today and when I came home for lunch all the window shades are open and some of the windows as well and she is complaining that the AC is not working properly because it's nearing 80 degrees and humid in the house.

Seriously ~ 4 tons of central air capacity for a roughly 1150 square feet of house space should be more than enough for my midwest climate.

You've got too much air conditioner for your space....It cools the house down too fast and raises the humidity making it dank in the house....The A/C must be sized to run long enough to drop the humidity as it cools and densifies(new word score) the air...2.5 tons should be plenty...Unless of course you have humidity controlled speed feature on the evaporator section of your unit...this then drops the blower speed to half when humidity is too high....

Normally I would agree but it's an old trailer house which for the most part is like trying to air condition a greenhouse.

The original central air system that was in the house was a 2.5 ton and it wasnt worth crap for keeping the place cool so it got the boot and three tons worth of window AC units took its place and even at that they barely kept up on really warm days.

Surprisingly The 4 ton system is working right in its optimum capacity range cooling the whole house now. Most days it cycles on for about 30 - 45 minutes then goes off for 15 - 20 minutes and its not the least bit damp feeling in here. Cool and dry for once!

Hey, if it ain't broke, don't fix it, I always say...

Yea still looking forward to when the new house is done and this much AC capacity can cool ~3000 square feet of space!

These old trailer houses are like trying heat a parking lot in the winter and air condition a green house in the summer. I've done a lot with sealing things up and adding insulation over the years but it just doesn't seem to make all that much difference from one year to the next with this old house.

I dont see a problem

Actually I've had the system going for about three weeks now and my local power company has an online system where I can check my power usage at any time. So far they show no change in my overall power usage.

A 4 ton system running 75 % of the time Vs the 3 ton of window AC units running all day seems to be balancing out on their readings. The last power bill was ~$135 which is right in the normal range for this time of year.

You just have a training problem.

Who pays the cooling bill?

Fortunately I have the daughter trained to get after mom now. If she doesnt everyone goes without AC.

I have 5 tons and my home is approx 1500 Sq. Ft. you should be fine on the cooling. You have to work on the wife!

Right now I'm using an evaporative cooler below.

Champion Cooler Model # MCP44 4000 CFM Slim Profile Window Evaporative Cooler for 1600 sq. ft.

It works well up to about 108 degrees F. outside temp. or if the humidity rises too high, all I do is kick on the A/C and shut the windows for a few hours or days.

It saves me a ton of money on electric!!!

Right now I'm using an evaporative cooler
Those are great for low humidity climates. Here in Florida they aren't so helpful. Relative humidity on non-rainy days is 60+%.

It could be worse. Houston, for instance.

You're right. According to this site, Houston at 75% is only 1% worse than Tampa (74%).

The major cities in FL have an average annual humidity of:

• Jacksonville - 76
• Miami - 73
• Orlando - 74
• Tampa - 74

Design WB in Dhahran is 86dF (30dC). I think that's the worst place.

Works best in Arizona and New Mexico.

I was told by my HVAC guy that the new "scroll compressors" did a lot to increase the efficiency of AC units along with the variable speed fans. I took several courses inn HVAC and back then they preached 77 degree F with a 40% RH as being optimal to shoot for. I agree with Solar Eagle about the size being somewhat large for that square footage but then insulation, infiltration and construction could be the saving grace there. Had a neighbor tell me how he was going to install 5 tons and I advised him against it since 3 1/2 to 4 tons was appropriate for our size houses. He did it and guess what..cool and damp as expected. But it cooled down fast and that was his aim.

30 years ago I hooked up a water hose to spray over the heat exchanger to gain greater efficiency from my central unit because it was under sized for my home here on the gulf coast. This is common in industrial cooling towers where the "wet bulb" temperature allows the evaporator to increase performance of refrigeration.

In dry climates it is particularly effective.

I noted a few days ago where some outfit reinvented my idea by selling a misting device to spray over air conditioners to improve their efficiency..

Don't know of any trick that will overcome the law of energy conservation. Maybe Al Gore can come up with some way. He has a way with BS.

These have been around since I was a kid....the problem was the water spray nozzles would eventually clog up and the charge, set to run with the extra cooling effect of the water, would then run high head pressure leading to all sorts of problems and reduced cooling....Had a friend that worked on this for his buddy for years, the water would only come on when the head pressure hit 275 or somethin.. nobody else could work on the unit...lol

this stuff has been around for yearshttps://www.youtube.com/watch?v=lflKBkJwRtM

I'm sure you've seen mist systems on golf carts , patios etc. this low tech works well if you can spare the water, and no they don't clog up all the time

Why wouldn't a NC solenoid valve wired into the AC contactor circuit, filter and a small line to the roof spray tree work just as well as these complicated $300-400 dollar units?

not really. they work best to control head pressure. if they came on with the contactor the coil would chill during light loads and the evap would freeze overnight.

We don't have light loads here in Phoenix, and

if freezing is a problem.

That's OK, I'm too old to be going up on roofs and working anyway.

is that from the smithsonian?? actually Vegas and PHX are loaded with commercial machines that incorporate waterspray.

My pool pump timer.

I've installed 100's of these just for head pres control and prevention of freeze ups but you need additional water to pull it down further

Efficiency is you gotta run the new airconditioning unit and your wife pays the purchase and might as well the electricity bill later on hihihi. ;)

I agree with the electronics control and high efficiency motors being able to squeeze a bit more motor efficiency out of things but I don't have the ability to do so with a 30+ year old single phase compressor unit and its not really worth my time and money to refit it with a variable speed unit for what little I would gain in the long run.

Exspecially so for an old trailer house that's likely going to be come a low usage guest house in a year or two.

Mostly with this thread I was wondering how the new high efficiency units made gains over the old style systems.

Speaking of electronics control, After 33 posts, I haven't seen any mention of thermostats. A good programmable thermostat that changes the temperature setting according to time of day, day of week, and even such things as the number of occupants and amount of activity can save considerable energy.

Unfortunately, the user interfaces on most of them leave much to be desired, so they tend not to be as efficient as they could be, if they were more intuitive. I have not yet tried the Nest or any of it's competitors, but the ability to turn the temperature up when not at home, and turn it back down remotely when coming home could potentially save energy for homes where everyone is away during the day.

I have digital thermostats for both the house furnace/AC systems and the boiler system.

They work great for the heating side of things but unfortunately the wife has figured out that she can adjust the cooling side of things as she wants based on her whims of perceived temperature not actual temperature which pretty much overrides any energy savings by keeping it at specific temps during the day.

I have five digital thermometers throughout the house and from highest to lowest there is usually a less than 2 degree F variance but that mean nothing to a woman I guess. One minute 75F is too cold and the next it's too warm and back again a few minutes later and all those thermometers are obviously wrong all at once.

You are facing the greatest challenge of a married man and a thermostat.

Female hormonal HOT FLASHES!!!!

Good luck!

Yea I am aware. Last week she was telling me about how much physical labor is involved with vacuuming the house and how it gets her all tired and sweaty.

THis was about the same time I had just gotten home from my dads from a 4 day job of moving a 24' x 32' pole barn in form ~70 miles away all in several days of 90 - 94 degree heat with little wind.

Yea I can relate to how much worse the work that friggin vacuum cleaner takes to move around compared to loading and unloading ~80 concrete blocks a dozen or so 6" x 6" x 4' wood beams and three 6" x 6" x 23' steel beams mostly by hand plus had a ~3 hour drive in a my flatbed truck with no AC bringing the building home.

But you know it's worse for her because her back/neck/head hurts a bit (mostly from being lazy and out of shape).

tcmtech,

You're fighting a losing battle. I have no ideas for you in that field.

I had to divorce the woman that was doing exactly what yours is doing to you. That was the only resolution available. She wouldn't even discuss anything!

Other than digging a hole in the vast Las Vegas desert, but I wasn't up for that amount of digging in the middle of the night!

Good luck!

<...actual physics tricks...>

Apart from at singularities in Black Holes, the laws of Physics are the same all over the Universe.