OT Home A/C

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There's another indicator that something's not quite right with that story. Automotive AC compressors eat up a lot more than 3HP when they're engaged - somewhere in the 10-15HP neighborhood. Now, you could spin one with a 3HP motor, but it would be at a much lower RPM. As the graph showed, the lower the compressor turns, the less cooling capacity it has.
Let's assume that it takes 12HP to turn this particular compressor at 3000RPM, where it's producing right around 2 tons of cooling (24,000 BTU). That means the torque component is 21ft.lbs (12HP000x/5252, x!). With a 3HP motor (that's actually capable of putting out 3HP - most electric motors are in the high-80's to low-90's efficiency rating), it would only be capable of turning that load at 750RPM (3HP!x/5252, xu0). At 750RPM, the compressor has about 8,000BTU's of cooling capacity (reference the chart previously posted).
So, 8000BTU's is your basic bedroom air conditioner. Looking up one of the popular models, an 8000BTU window AC unit draws 7.5 amps at 115VAC, or about 860 watts. That 3HP motor above is drawing over 2200 watts (1HPt6 watts), not even factoring in motor efficiency.
Given the cost per kilowatt hour, it's much better to comsume 860 watts per hour, than 2200 watts per hour.
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Tom Lawrence wrote:

Jesus, Tom. You crack me up. Have you ever thought about a "rewarding" career in chemistry? You'd be good at it.
:-) Craig C.
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That was chemistry?
beekeep
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beekeep wrote:

I was speaking of his thought process not the actual post.
Craig C.
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Great answer! :)
Thanks for the explanation, indeed.
I can picture myself in the past with a treble hook in my mouth listening to co-workers' stories..
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wrote:

I have no idea if the guy was telling a story or not. But, I do know when Dodge introduced the 1994 trucks with 134A systems they bragged that the A/C system was capable of cooling a 1500 square foot home, FWIW.
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While it may be possible, the compressor would require serious HP to spin it fast enough to accomplish it and even if you could find a motor strong enough to do it, the power bill would be astronomical.
--
If at first you don't succeed, you're not cut out for skydiving
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TBone wrote:

I just got my bill for last month's electricity... $7.85
All electric home, no gas. Got a well, no water bill either :)
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spin it

YOU SUCK!!! :-)
--
If at first you don't succeed, you're not cut out for skydiving



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In response to TBone 's post. I thought everyone should know:

i'll send ya some of mine beryl, just so you dont feel left out
--
Chris

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SnoMan wrote:

Wrong. EER is the efficiency rating of a unit operating at a specific or constant temperature and constant humidity.
EER = BTU per hour of cooling 95F / watts used at 95F
SEER is the efficiency rating of a unit (**A/C OR heat pump**) over the entire season.
SEER = BTU of seasonal cooling / seasonal watt hours used
SEER is a more useful measurement, because the temperature never stays constant. SEER also includes other factors that effect efficiency, like cycling and total energy used for indoor/outdoor blower motors, fans, etc.
There is a good explanation here:
http://www.hvacmechanic.com/energy/energy.htm
The closest analogy I can think of is mpg. If you measure the mpg of a vehicle in a controlled test, (no A/C, specific number of miles, flat terrain) you will get a number comparable to EER.
If you measure the mpg over the course of a tank of fuel or a few tanks of fuel, varied terrain, varied temps (A/C on/off) and varied driving conditions, you get a number comparable to SEER.
Obviously, the number most people would be interested in is SEER since none of us are in a constant/controlled temperature and humidity environment.
Craig C.
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We sure like our Trane mini-splits...
mac
Please remove splinters before emailing
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On Aug 25, 11:

Roy
6 years ago we had a Trane heat pump installed. 19 SEER. Twice a year maintenance from the installing contractor. No problems at all. Electric bill is $110.00 a month year round. 10 cents per kilowatt. Thermostat is set at 78 degrees in the summer and 68 degrees in the winter. House is more than well insulated. We don't have gas so everything is electric. 3 years from now, when the 10 years parts and labor and everything is up, I will renew the service contract again for 10 years.
Bob AZ
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Do what you want, but usually those service contracts are a rip off. You might be better just paying the HVAC company to stop by twice a year for service and pay what ever his rates are. It really depends on how the contract is written, and what is, or is not included. If the contract was written by the local company it is probably ok. If it is through some national warranty company, my bet is you are paying too much. I while back I had a customer ask me if they should renew their contract. They had spent $360 a year for ten years and got two quickie services a year out of the deal. If they had paid for the service calls they would have saved well over $2000 over the ten years. Then when the unit did die, the warranty company would not pay to get the equipment replaced with a comparable unit. they had one of Trane's best systems, and the company would only supply the cheapest equipment they could find! Greg
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Roy wrote:

Would you please stop "stirring the pot"? :-)
Craig C.
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You are correct, I apologize. When it comes to pot, it should be smoked not stirred. <VBG>

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Roy wrote:

Or shit in. That explains where Beryl originated.
:-) Craig C.
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yeah, tends to pull through when stirred..
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Unless you're making brownies...
mac
Please remove splinters before emailing
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Mmmmmmmmmmmmmmmmmmmm Brownies!
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