Installing central air costs a lot of money. Once it's installed, the cost of running it is less than the cost of what you have now. However, it would take more than 30 years to make up the cost. It could even take more than 100 years. In other words, if it costs you $1000 a year to run window units and $800 a year to run central air that's a savings of $200. However, if central air costs $6,000 to install, it will take 30 years times $200 a year for you to get your money back. So if you are comfortable now, don't change. If you are hot now, consider the money.
We can't *see* it from here. Call your local, *competent*, licensed, insured, professionally trained, HVAC technician to do a complete assesment of what your home requires so that it can be fitted with a complete comfort system and what the cost vs payback is for you home. In this neck of the woods, the payoff is pretty quick (roughly 5 years) for a complete high efficiency comfort system.
If you're shopping for a central AC unit, do not ask for a rotary compressor. You'll get a curious look from the salesman. Most geo units and most window units come with rotary compressors, central units no. Did you mean *scroll*?
If a house currently has multiple window air-conditioners, are these significantly less efficient than central air, if the house were retrofitted with it?
I realize the comparison is complicated, so assume all other factors equal, and assume: the vents and their position for central air would be adequate; about half the rooms are normally in use; nobody's concerned about the window-view obstruction, etc.; Chicago climate; poorly insulated house.
A companion question is, does the efficiency of air conditioners increase significantly with size?
Generally whole house will be more efficient and more trouble free as well as quieter.
Windows units can be more efficient as you can zone each room, so while the individual unit may be less efficient, you may use less overall energy because it is easier to turn them off in one room.
If Chicago is as warm as I think it is, I'd go with central if possible. More efficient, quieter, more even temperatures in the house.
Where I live, it becomes marginal most years. Normal summer we need AC maybe five to 8 days and maybe an additional 10 nights in just the bedroom. That makes window units far more economical compared to running a big system.
In warmer climates I'd never consider window units..
"Are you still in the business Turtle? 6K is a normal median price. Some are less, some more. You can't touch an Infinity system for 6K, nor even just a 13SEER 410-A over 3.5 tons. "
And of course it all depends on where you're starting from. If the house has a modern forced air heating system, it;s one thing. If it has hot water heat, then it's a different story.
Are you still in the business Turtle? 6K is a normal median price. Some are less, some more. You can't touch an Infinity system for 6K, nor even just a 13SEER 410-A over 3.5 tons.
Window AC's typically 10 to 12 SEER (Seasonal Energy Efficiency).. 12 is not bad... 10 is not so hot.
You can buy central AC's at 14 Seer thats hot.
However there are losses with duct work in a central AC that you dont have in window AC. (depending on duct leaks etc etc. in the 5 to 10% range...not so good actually)
Window AC's are dirt cheap to install compared to central AC's and provide good 'zone control' so can be a lot less expensive to operate than central AC
Home resale will be better with central AC of course.
No..efficiency goes down with size because its running partially loaded most of the time. The window AC's will be most cost effective across the boards especially if you buy the high efficiency models (and go to heat pump window AC's)... zone control is a major advantage with multiple window AC's
I don't know of any single hvac system that cost $6K as of now or in history of Oakdale.
There is 3 -- 410-A systems in oakdale and all 3 of them are not working. We had a local install them and they don't work right. He has not got paid for them yet and is being sued.
The highest bid i know of was $5,300.00 for a 5 ton 13 seer rheem heat pump for a small Church and plenty of ductwork.
now if you get commercially the money goes up and $6K is nothing for a job. Now all residentiually job are poor boy stuff and is low ball, city. We have one hvac fellow who trys to get $250.00 off a complete system change out of 4 or 5 tons.
"PrecisionMachinisT" wrote in message news: snipped-for-privacy@scnresearch.com...
Satire. Willis Carrier didn't come up with refrigerated AC until the 1905's or something like that.. Earlier we had steam jet refrigeration (a high pressure steam venturi side port, at approx 28" water column (vacuum) was connected to a large evaporating tank, water evaporate and cooled to 40F or so and that was pumped around to air coils... prior that that goes back to BC egypt, importing ice from Mt Kilimanjaro, into deep caves the cool air circulated through the palace.
The Montgomery Ward Store in Sacramento Calif though had an ammonia chilled water system as late as 1967 that I am aware of, it was still operating the last time I worked on it. It dated from the turn of the century 1915 as a guess.. Two 50 ton baker 200 rpm reciprocating compressors driven by synchronous DC motors..(multple coils around a rotor, looks like an old radial airplane motor.)
The Budweiser micro breweries built in the 70's used similar machines, approx 4,000 tons total of horizontal Baker reciprocating compressors, 200 RPM DC sychronous motors.. ammonia.
Why you might ask? Ammonia is the most efficient refrigerant bar none in those temp ranges. by a very wide margin. and because... volumetric efficiency goes way up with the ultra long stroke and proportionately reduced head space volume of those huge slow long stroke compressors. The suction lines on those plants were 24" main header... 10" to each of the Baker recips.
Latest addition though were 1000 hp Frick screws (made in Germany).
These are 3 stage cascade/ compound systems.. two compound ammonia stages, the lowest stage ammonia evaporator acting as the condenser for a CO2 system to minus 110F...(200 hp of Vilter reciprocating compressors, 1750 rpm, 480volt conventional squirel cage motors... all built nicely into one large machine building ( 300' square approx) with natural gas fired boilers...so that if there is a suitably sized ammonia leak, to the explosive limit ranges, the boiler pilots lite off the vapor cloud and make for interesting times in the vicinity..releasing about 8,000 lbs of ammonia to the atmosphere.
The CO2 as liquified at -110F under pressure for use in carbonating the beer..(not 100% naturally carbonated that stuff)
With large scale ammonia systems there are issues of liquid slugs in long suction lines, with pressure behind them and suction pressures approaching zero psig ahead of them.. slug velocity can reach over 700 mph. Such a 'slug' of liquid hits an elbow or end cap and blows it off ... releasing the entire charge of ammonia to the atmosphere. clearing the sinuses of a few thousand people it doesnt kill and pissing off the local authorities entirely...most older systems were not built with the super sonic slug scenario in mind.
Now a question? What do you think happens to an all steel ship, with frozen storage holds 6 decks deep, below the water level, with only the outside of envelope of the holds insulated, not the steel plates between the holds...those welded solid of course across the hull.
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