My daughter just moved into a small two bedroom home and she’ll be there for the next 12 months. She’s a college student and she’s majoring in Biology. She is a Senior.
The house is probably only about 600 or 700 sq feet and has two window Air Conditioning Units.
In the living room is a large 220 volt window a/c.
In the bedroom also has a large window a/c unit but it runs on 110 V.
She asked me if the electric bills will be high this summer and
I’m going to tell her to just run the 110 V AC unit and leave it running for long periods of time, or even just leave it running 24 hours a day, rather than turning it on and off.
I think I’ll tell her to just leave the 220 V A/C turned off and let the other one cool the house off.
Does anyone have any experience with this? I tried both a/c units and they both work pretty well.
^^^^^^
“The Older We Get, The Better We Were”
Replies
A large part of "cooling" cost is for moisture removal.
I am in the Kansas City area and typically don't turn on the air until the last week or two of June when the humidity levels go up. (I "ignored" the last couple of days as I knew that the weather would break).
When the ac is removing moisture the WORSE thing that you can do is to only run it part of the day and allow additional moisture to come the other part of the day.
So just turning them off is a no, no.
Now I have no way of knowing, but assuming that both units are of equal efficeny.
The main thing is what comfort level she can stand. For me I have more problems sleeping so I would keep that area the coolest. Not turn off the other one, but have it set higher.
Also comfort level depends on how easy the body can evaporate moisture. So a runing fans where you are helps.
mrfixitusa,
As you are aware most 220 volt units are more efficent than most 110 units (all things being equal) .. the question is is the 220 big enough to cool the whole area, does it need suplimental help from the 110 unit?
Is it too big? Will it be forced to constantly cycle on and off? If you can keep the room cool with just the 110 unit that's your best bet, if you need to supliment the 110 then try the 220 and on those scorcher days run both, heck better to pay a bit more to the electric company than suffer.
One bit of advice, open windows on cool days!
"As you are aware most 220 volt units are more efficent than most 110 units (all things being equal) "WRONG!Everything being equal means just that."One bit of advice, open windows on cool days! "ABSOLUTELY BAAAAD ADVICE.What is the summertime humidity levle in Wichita? How much energy is needed to remove moisture from the air?
Here in Kansas we have high humidity. It's 60 to 70 percent today.Humidity is high enough here that swamp coolers or water coolers do not work very well. It makes the homes too damp and humid.In Colorado the humidity is lower and they are able to use swamp coolers. I know of many homes with swamp coolers mounted permanently on the roof of the home.I may be wrong but my theory is she can leave the 110 AC unit running 24 hours per day and pay less than me with central air and the 220 V compressor kicking on and off all day long.Agree?^^^^^^
"The Older We Get, The Better We Were"
Well it really depends on the load and how air circulates in the house.But the small one running all the time will take out more moisture than a larger one that only runs short periods of time.One thing is that no one knows the history. It might be that someone AC'd the bedroom and that liked that, but it was not near enough so the larger one was added.And that the large one, by it'self, is right sized and air circulated enough to cool the whole house.
Well, if design/manufacturing is to the same level of quality on both units, the 240V unit will tend to be (somewhat) more efficient.The unit that is shaded the most during the day will get a slight performance boost.Keeping curtains closed to the sun can make a big difference.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
"Well, if design/manufacturing is to the same level of quality on both units, the 240V unit will tend to be (somewhat) more efficient."That is not what was stated. If they are Equal then that means that the efficiency rating is equal.Then the only difference would be the minor difference in loss in the power wiring.But we have no idea of the age, quality, or efficency of either unit.So any assumption based on 120/240 is meaningless.However, her is a good thing to look at. There is a good chance that the 120 unit is on an old shared circuit and thus over loaded.But 240 circuit would have to be run new for the AC (but that does not mean that it was done correctly and not also overloaded. it could well have been taped off an dryer circuit for example).
Bill,
220 A?C in Minnesota means hard wired.. It takes the cheap imported units out of the picture..
On a cool day open the windows is still good advice!
Air indoors can be dirtier than outside air..
Energy costs with open windows on a cool day, zip!
Though 120V window units are more common than 30 years ago, there are still plenty of 240V window units made. And as far as I know all window units plug in.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
The question is about WINDOW AC units.And yes there are a number of them that work on 240.http://www.fedders.com/catalog/appliances/roomac/All of these are 240http://www.sears.com/sr/javasr/subcat.do?vertical=APPL&cat=Air+Conditioners&subcat=Large+Capacity+Units&BV_UseBVCookie=YesAnd from other discussion it is clear that you have no concept of relative humidity or the energy needed to condense it. So I will not bother responding to your comments about turning off the AC.
And from other discussion it is clear that you have no concept of relative humidity or the energy needed to condense it.
Bill, at the risk of a hijacking a slowing thread (apologies to the op), do you have a good feel for the amount of energy required for dehumidification by ac?
I ask because we (PAHS) have no need for ac but, like any house, do deal with humidity. I've occasionally wondered which was cheaper to run, ac or dehumidifier. I've not seen dehumidification ratings on an ac. Obviously there are other issues, particularly air temp, that don't factor in here. In a separate thread we've been discussing PAHS in primarily cooling climates. PAHS Designer/Builder- Bury it!
A standard dehumidifier is basically a small window AC. It's just arranged so that the cold air from the evaporator (cooling) coil is fed directly to the condenser coil, so that no net heat is "pumped", aside from what is used to condense the moisture. The warm air coming out of a dehumidifier is a combination of the heat required to condense the moisture and the heat from friction/resistive losses in the system.In general, a larger AC unit will be more efficient than a smaller one, and a whole-house unit will be more efficient than a window unit. So based on economy of scale an AC is likely to be more efficient than a typical (relatively small) dehumidifier, at a purely mechanical level.However, having an efficient AC vs a (relatively) inefficient dehumidifier does you no good if you have no use for the cold air. With a dehumidifier the cold air is used to cool the condensor coil, improving the efficiency of the system (so, ignoring friction losses, you "pay" nothing to cool the air -- you just pay to condense the moisture). With an AC you're not only paying to cool the air, you'll eventually get things too cold (in a cool but humid environment), even though the humidity may not be where you want it.Big commercial systems can be arranged to work like a dehumidifier when needed (though even there many do that by simply heating the air with steam coils or whatever, vs recirculating the AC exhaust heat). Similarly, many car heating/cooling systems are now arranged to turn on the AC when defrosting, to dehumidify the air, even though this requires that the air be reheated after dehumidifying.But I'm not sure it would be practical to rig a home AC system to run in pure dehumidifier mode. And, when you're simply trying to remove moisture from a "tight" building, it could easily be more efficient to heat relatively dry outside air vs condense the moisture inside.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Wow, thanks.
I was aware of the similarity between dehumidifiers and small ac units. My use is drying incoming air, rather than fixing indoor air. Dry outside air we don't get this time of yr, the only time we have elevated indoor humidity. This is due to .5 ACH.
The dehumidifier lives outside, with the air stream separated from the hot parts to leave more of the heat outdoors. From there, the air stream goes through an air-to-air exchanger, then distribution. Works OK, always room for improvement. Which actually came in the form of a heat pump water heater a couple of yrs ago. Fantastic piece of machinery which does a great job of drying air (as a byproduct).
A much larger ac unit (or dehumidifier) would not be applicable, why I asked to compare window-sized and a dehumidifier. I'm using 50 pint.PAHS Designer/Builder- Bury it!
Not enough to try to do any calculations on it to compare different systems.I think that Dan has a good summary.
The operational cost is similar for dehumidification via direct expansion cooling only. The energy consumed is primarily to operate the compressor(s), and to a small extent the system blower and the condenser fan(s). The main difference between a dedicated dehumidification system and straight cooling system is the addition of a hot gas reheat coil downstream from the evaporator coil. The first cost is higher because of the additional controls, components and complexity.
In terms of the energy required on a pound by pound basis for changing the properties of air, the analysis goes as follows:
For sensible cooling only, the energy required (in BTU/HR or BTUH) is CFM X 1.085 X dT, where dT is the tempereature drop in degrees F. At 80 degF, water requires 989 btu/lb to condense or evaporate it. In terms of an air stream, air at 75 degF and 80% relative humidity (rh)contains 30.56 btu/lb and air at 75 degF and 40% rh contains 23.61 btu/lb. If you were to compare the energy required to cool 1600 cubic feet/min (cfm) from 80 to 55 (standard ARI conditions)vs taking 75 degree 80% rh to 40% rh, one is 1600x1.085x25=43,400 btuh. The other would be, 1600x30.56x60/13.8 - 1600x23.61x60/13.65 = 46,534 btuh, where 13.8 and 13.65 are the relative specific volumes of the air streams at conditions and 60 converts minutes to hours.
In reality, most dx systems provide a 0.75 to 0.8 s/t ratio, meaning that under standard entering air conditions, 75% of the energy transfered to to/from the air stream is sensible (i.e. lowers the temperature) and the remainder is latent (i.e. condenses water out of the air stream).
Edited 5/31/2006 10:34 am by Tim
Love this forum! Gotta study that later, professor. I've got a Cat waiting for attention. Thanks.PAHS Designer/Builder- Bury it!
Bill, could you explain about the energy needed to condense humidity, or more specifically how it relates to turning the a/c on and off. Here is why I ask: We normally run the a/c (new variable speed AH system installed in 2005) on humid summer days & nights. If it's a stretch of a few days, we leave it on the programed schedule. When it's cool/low humidity, we open windowsThe past few days have been upper 70s/low 80s, but the nights have been cool (in the low 60s). So, my wife has been turning the A/C on for a few hours in the evening to cool the house. By the time we go to bed, the temps outside are significantly lower, so we turn off the A/c, open windows, and leave the AH fan on to bring in the cool outdoor air. Are you saying it would be more energy efficient to leave it on all day/night, or is the scenario I've described an exception? It's still too early here in CT for round-the-clock high temps. In fact, if my wife weren't pregnant, we might not even feel the need for the AC until later in the summer.Thanks,Stace
I think that what Bill is refering to is the consequences you could experience at times of the year when the evening and night air outside is frequently cooler than the temperature that you would normally keep the inside of your house. I am experiencing conditions like that presently in Northern Illinois. For instance, right now it is 76 degrees outside, well withing the temperature range I would consider comfortable in the cooling season, although the rh is in the 80+% range, definitely NOT in the comfortable range for people, though fungi love it. It is expected to get down to 58 tonight, with a coincident 100% rh. My house will remain closed, because that is a huge amount of moisture to let in after paying to remove it. If, for instance you filled your house with 65 degF, 85 % rh air at night and then wanted to condition it to 75 degF and 50% with the outside air going up to 85, the amount of energy required to remove the moisture from conditions like this is equal to or very near so to the amoung of energy it would take to cool your house from 85 degrees to 75 degrees. So you have saved nothing. (See my previous post on a similar energy analysis of latent vs sensible cooling) Fresh air is good, and I like it, too. However, this is not only a matter of energy consumption, it is about humidity control and indoor air quality. Allowing a lot of very moist air in can create a poor and unhealthy environment. In times when opening up the house is only intermittant, and you plan to or expect run the AC again the next day, its best to keep everything closed up and maintain the good environment that AC system has hopefully created for you.
This approach obviously doesn't apply when the air outside gets cool and dry. I have some simple cheap electric thermometer/humidity meters that I got at the hardware store for about $12 a piece. I read them (one is inside, one is outside) all the time. These are not highly accurate scientific instuments but they give a good idea of whats going on. Now understand that I make my living as a mechanical engineer desiging and specifying HVAC systems and equipment, so this is something that I am interested in and pay a great deal of attention to, probably more so than the average person. When the relative humidity is much above 50% it is not comfortable to most people. When my house is 80 degrees and 45% rh its comfortable. If either of these parameters gets higher than that is not. When it is 75 degrees and 50% its also comfortable. When air drops in temperature only, the relative humidity goes up. When the air outside is cool and dry, or at leats as dry as you would want it inside the house, then opening up is a very good idea.
On the other hand, this is not rocket science, brain surgery or even finish carpentry. Do what you wish to and see what happens. Its your house and whatever makes (you and) your wife happy is what you should do.
Edited 5/31/2006 5:34 pm by Tim
When I walked up to my daughter's house for the first time my mouth dropped open when I saw the two large window a/c units. I saw dollar bills flying away from my billfold at the thought of both of these running at the same time.After further thought I have seen some homes with three, four, maybe even five window a/c units. I guess it's not the end of the world.I turned on the 110 v a/c unit and noticed it had cooled half the house in about 30 minutes. Again the a/c unit is a large unit that takes up most of the window opening.I'm going to tell her to turn on the 110 V unit during her lunch break and let it run all afternoon. She can shut it off at bedtime if it's cooling off outside.We'll see how this first month goes. The temp are getting into the 90's and most people have turned on their a/cI'll report back in a month and hope that her bill is lower than mine.Thanks again^^^^^^
"The Older We Get, The Better We Were"
"I have seen some homes with three, four, maybe even five window a/c units. I guess it's not the end of the world."
I bought one of those homes, built in the early seventies when nuclear power was going to make electricity "too cheap to meter". All electric baseborad heat, too. I have since removed and discarded all five of the "window units" (They had actually built them into the exterior walls, permanently in lieu of the in-the-window approach) and all electric baseboards.
Tim
Everything goes in cycles.. right now it's as cheap to run a home on electricity as to run it on gas.. In the near future I expect it to be cheaper!
Here's why.
In Minnesota we are near the western coal mines.. We also have two efficent large nuclear power plants that are paid for and Minnesota is becoming a hotbed of wind power.. (and we have several hydroelectric plants operating)
I know several farmers who have those big $700,000 wind generators up and running and they are sitting there without the network it takes to connect them.. It takes 3 months to get a generator built and in place and it takes the power company 4-5 years to get the power lines to connect them..
Luckily for the farmers they get paid as soon as the generator is up and working.. so the income stream starts at that point. since they are all profitable that means aside from the payments they have a positive cash flow from day one!
In addition many farmers have found that they can run their diesel generators just fine on waste cooking oil. it's becoming a minor little industry. medium to smaller sized towns have several guys going around with tanks in their pickups sucking up used cooking oil , filtering it, and pouring it into Generators, tractors and other diesel powered stuff.. .(if you are following a truck that smells like popcorn, it's using biofuel). Since electricity is nearly free that way, farmers {those notorius titewads} aren't buying as much power from the electric companies.. reducing the demand..
Hmmm, an increase in the amount of electricity available and a lessoning of demand due to alternatives.. while there is a finite amount of natural gas available.. Which would you bet on?
Regarding four window A/C units I expect to do just that! I run A/C less than three weeks out of the year. Not at all so far this year) Much prefer the windows open! Here in Minnesota the number of days where the temp is over 90 degrees is seldom over 15 or 20 for the year! Even then with a cool lake on our properties edge and large mature shade trees sheltering the house plus the super insulated properties of SIP's the house is always at least ten degrees cooler than the weather beareu reports. Add a slight cooling breeze and it's a rare day indeed where A/C is needed or called for.. On those rare occasions the window units I already have will do a nice job of cooling down the house! Central air would require me to put in the duct work to distribute A/C and duct work for heaters is wrong for A/C
Warm air rises cool air settles.. Duct work for a furnace comes out at your feet. Guess where the cool air from a central A/C unit would come out from? While room A/C will be installed near the top of the exterior walls..
"right now it's as cheap to run a home on electricity as to run it on gas"
This only true in some parts of the country. It is not true where I live
At my home, as of today, the price of electricity is $0.08/kW-hr and the price of liquefied petroleum gas is $1.50/gallon. Making the suitable conversions, the equivalents work out such that for each $ I spend for electricity, I get 42,500 btu. For each $ I spend on LP, I get 61,275 btu. Unless my overall efficiency is less than 69%, it costs me more to heat with electricity than it does with LP. My absorption chiller is down at the moment, so the only viable choice for air conditioning/dehumidification is to ustilize electric power. I spend 4 to 5 times on heating as I do cooling, so for me, your statement is not true.
"an increase in the amount of electricity available and a lessoning of demand due to alternatives"
This statement leads me to believe that you have very little direct contact with or knowledge the electricity production and distribution industry in this country. The "changes" you reference are insignificant (or nonexistant) in the present and foreseeable future. The demand on the power grid inceases daily and production has been falling behind for the last decade. I worked for the largest nuclear utility in the country for 7 years, and followed the industry quite closely.
Did you include the added efficiency of a heat pump in your calculations?
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
No, I was referering to resistance electrical heating. With the exception of the ground source tecnology, heat pumps are not very efficient at low temps like you in MN or I in N.IL will experience for more than a few days every heating season. In a milder climate, my analysis would need to include the performance of heat pumps, hence the qualifier "where I live".
Tim
Thank you for your input.. You are correct in that location will have a great deal of impact on that calculation.. Years ago I decided that there simply was no one size fit's all solution to energy needs..
I was impressed with the garbage gas burners that Cat markets. With the methane they gather from landfills they are able to generate electrical power.. Solar power while not yet really economically viable is a potential solution in some locations,,
Yes, I did greatly over simplify the equations.. I'm not doing an energy audit afterall, I'm simply pointing out facts.
I know of a few minihydro's in Western Wisconsin and have heard of some in south eastern Minnesota.. I don't expect that to be a major solution but it does all add up..
You comment about the increasing need for power is valid but perhaps not as critical as portrayed.. A small increase in efficency of peoples light bulbs adds up. Technology has increased the efficency of many things, with more on the way..
Do we need to build mega sized nuclear power plants? Perhaps not untill there developes the political will to solve the storage and disposal issue.. Is safety perfect? Nah! no system ever is but it can be adequite if the will and effort is spent..
Coal polutes but can be made cleaner if the will exisits. Sure there are losses in transmission, made worse by the concept of Mega anything! That's why Wind farms and aternative sources of energy are such a blessing.. We Not only decrease the demand for power in the more rural areas, we also don't suffer from transmission losses.
The Wind farms I know of still are able to grow crops on them so there isn't a tremendous reduction in food as there is with the production of Ethanol.
Out of couriosity, how many days a year do you use your A/C? (do they use degree days above say 70 degrees like they do for heating?)
"Is safety perfect?" The commercial nuclear industry in this country is extremely safe. From the time the first commercial unit came online to the present, two accidents of any consequence have occured, and only one one of those resulted in an uncontrolled realease of radiation, and that was far less severe than the press would have you believe.
"...if the will exisits.."
This applies to all changes required to reduce energy consumption, and IMHO, the US public are not interested in making those changes. A few are, but as the residents of Cape Cod are very prominent proof, it is a good idea for "people" to change for the sake of the environment, just not "me". The potential is there, but at the present the reality is not. I was in the equipment (HVAC) distribution business for a few years, and I can attest to the fact that most new homes are not built utilizing basic good efficiency that was available 10 years ago. Look at all the new houses in your local subdevelopments. See the b-vent stcking out of every roof and you will realize that that means low efficiency combustion (i.e. 84% AFUE or less, typically). Well of 90% of the equipment sold is to minimum standards. That means 80% AFUE furnaces, 60% efficienct gas water heaters and just as of January 2006, 13 SEER AC units.
"Out of couriosity, how many days a year do you use your A/C? (do they use degree days above say 70 degrees like they do for heating?) "
My AC gets turned on 15 to 20 days a year on an average, up to 30 on a very hot year. My house and my systems are not average. I rebuilt it from the ground up with double exterior walls, new efficient windows and fairly meticulous effort at sealing the "envelope".
There is what is called a Cooling Degree Day (CDD), which like the Heating Degree Day, is defined by when the mean daily temperature departs from 65degF.
It's that second accident that worries me. The circumstances around the Brown's Ferry incident indicated a total lack of understanding of the principles of redundancy, and illustrated how economic pressures to keep the system running can severely degrade human judgement.I'd like to believe that things have improved since then, but I've seen nothing to suggest this. Everything suggests that, had we continued on the arc of nuclear development we had in the 50s, by now we would have experienced at least one Chernobyl-class accident, just based on the laws of probability.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
"I'd like to believe that things have improved since then, but I've seen nothing to suggest this. "
I believe exactly the opposite, and have seen ample proof at many nuclear facilities across the country. The Brown's Ferry fire was the impetus for the physical separation and fire protection criteria that exists today (and subsequently the main reason that construction costs skyrocketed during the 70's, 80's and into the 90's). The fact that all commercial plants in operation at the time and those under construction at the time were required to begin implementing corrective actions immediately after the investigation and recommendations were complete, tells me that not only did the industry learn a great deal from the event, but they also acted upon in in a timely and well thought out manner. The nuclear power plants that I have personally seen the effects from "learning our lesson" from the BFNP are, Arkansas Nuclear One, Waterforford Steam Electric Station No.3, Sequouah Unit One and Unit Two, Commanche Peak, Watts Bar Unit One, Byron Units 1 & 2, and Palisades. At Sequoyah, I was part of a team than not only inspected, but cataloged and photographed every single fire barrier penetration/seal in the facility to verify the measures generated from BFNP were in place and effective (and also to create a comprehensive database from which future inspection lists could be derived). I worked on the completion and startup of many of the other plants listed above and have personally overseen the implmentation of the new separation criteria.
The other event , that occured at Three Mile Island Unit 2, also, as a matter of consequence brought about procedural and staffing changes implemented at all commercial nucear power plants in this country. The safety of these facilities has been greatly enhanced by "lessons learned".
BTW, the fire in the spreading room at Brown's Ferry occured 4 years before the loss of feedwater accident at Three Mile Island.
Right. I read the recommendations that came out of the Brown's Ferry investigation, and they totally missed the mark. Simply fire-sealing some wiring isn't the answer -- the designers totally missed the concept of redundancy:-- Both "redundant" sets of control wiring were routed within about 10 feet of each other.-- Both sets were routed through a high-power switch room, a place where an explosion could easily take out both sets in a single event.-- When control was lost through the first set of wiring, the reactor should have immediately been shut down. This is as critical a part of the redundancy concept as is the physical redundancy. Yet the reactor continued to operate until the second set of wiring was about 50% compromised. Only dumb luck prevented a TMI-like event or worse.The report of the investigation failed to suggest anything to fix these three serious problems, which were symptomatic of a failure to understand basic redundancy principles.Maybe some OTHER initiative fixed these problems, but the Brown's Ferry investigation did not.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
"I read the recommendations that came out of the Brown's Ferry investigation.."
I never read the report or any direct publication as a result of the incident. I was 9 at the time. Subsequently, I have seen many of the NRC directives based on the event. Whether the corrective actions that I have seen implemented were generated as a result of the actual event investigation report or subsequently, once the root causes and potential for disaster were fully realized, considered and discussed among the designers and engineers outside of, as well as inside of the NRC, is immaterial. The lessons were learned and actions taken. Your original statement implied that nothing of any real consequence has been done to prevent recurrence of a BFNP like event. I maintain that that is contrary to truth, that effective measures have been implemented throughout the industry and that redundency and separation are fully understood. 30 years of subsequent operations without a similar event does tend to bear that out.
The 30 years of subsequent operation has been largely without any new reactors. The system is "maze bright" with the old ones.Like I said, the recommendations in the report did not address the fundamental flaws in the design and operation of Brown's Ferry, but only the contributary details, like duct sealing. As a result, the recommendations were only worthwhile for existing reactors, and not for any new designs.Redundancy is, at its core, a very simple concept. Implementing redundancy properly, however, involves having the proper mindset and the political will to stick with it. NASA has struggled with this, in spite of having much more transparancy and more pressure for safety. Hard to see how the nuclear industry could do as well.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
A great many of the the reactors in service today came online in the 80's and 90's, and those were required to have made changes to incorporate the lessons learned from Brown's Ferry and TMI. Lots of engineers were gainfully employed for decades, including yours truly, updating/modifying existing designs to incorporate changes such that real redundancy and physical separation was built into the plants. Operators of reactors that were online at the time of the Brown's Ferry fire were eventually required to modify the plants to incorporate similar measures as well.
"As a result, the recommendations were only worthwhile for existing reactors, and not for any new designs."
This is contrary to reality. I cannot speak to the recommendations in "the report", (as if there is a single document that applies here; hundreds of documents, recommendations, mandates and directives exist on this subject alone) however the industry did address the "fundamental flaws in the design ". This is a physical, indisputable reality. It is a matter of public record, and is quite extensively documented. There is not, presently in the USA, a single operating nuclear power plant that does not have fully redundant, physically and electrically separated safety systems.
Edited 6/13/2006 8:55 am by Tim
>There is not, presently in the USA, a single operating nuclear power plant that does not have fully redundant, physically and electrically separated safety systems.Well, supposedly that was the case BEFORE Brown's Ferry incident, but clearly it wasn't. It's a "fool me once/fool me twice" situation -- my standard of proof is much higher now, and I'm not prepared to simply take the industry's word.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
I don't know how the industry represented itself prior to 3/75, but I suspect they thought they were providing the design features we're discussing, but obviously had not.
"I'm not prepared to simply take the industry's word.." Under the Freedom of Information Act, you can find all the supporting information required to meet your standard of proof. IF your prepared to look, the data is available.
(BTW, I was referring to "second" meaning "the one that wasn't TMI".)
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Tim,
Yes I've heard much of what you said, similar sort of information has been given to me by those in the nuclear industry.. I believe once we find someone with the poltical will to select a waste disposal site and live with it the nuclear industry can once again start to build power plants..
My comment on the safety of such plants remains.. While it is possible for events to happen which will cause damage and radiation release, as long as the industry is well regulated Nuclear can be a safe enough altenative.. (France for example uses a great deal of nuclear energy)...
As far as efficency, in this country people want bigger rooms and more closets more than they want low utilitiy bills.. Minnesota tends to be at the high end with the thousands of degree days we have. Thus often homeowners are forced to replace equipment simply to reduce their utility bills.
If all homeowners considered ICF's or SIP's in leu of a "great room" imagine how much the demand on utilities would lesson! Add HIgh efficency lighting, high efficency heating/cooling and other service..
Ahh well dreams,,.......
My particular situation calls for less than 10 days a year of cooling.. The window A/C units are paid for and have decent SEER numbers. I simply can't imagine replacing them with central A/C especially since I would need to add the required duct work!
I agree that it's stupid that we haven't created a nuclear waste repository yet. While I believe that current standards and practices (as I understand them) for reactors are insufficient for long-term safety, it's clear that nuclear waste can be safely transported and stored in an appropriate waste facility (and several viable such facilities have been proposed).What's lacking, as you say, is the "political will" to out-shout the anti-nuke folks who are playing on the public's emotions kind of like Bush played on nukes to justify invading Iraq. The opposition of these folks is illogical, but logic and politics are rarely even found in the same county.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
DanH
I believe we actually have created such a repository but cannot use it.. (I'm refering to Yucca mountain I believe)
Anti Nuc crowd can be pretty well silenced with a waste respository.. While a select fraction equate nuclear power with atom bombs and fail to see the usage France found ways to deal with those issues and we can as well..
Sure a whole lot of education will be required and maybe someone will have to change or modify processes and etc..
Yeah, I don't know how close to ready it is, but I know it's been in preparation.It's all a matter of spending political capital, and seems like the last several administrations have wanted to spend it elsewhere.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
DanH
Ever wonder why some stupid bills pass when anybody with a half a brain knows they are just stupid wasting of our tax dollars?
It's simple you get a senior politicain who doles out his support and votes on a bill in exchange for support on his favorite bill with out regard to the nations real interest..
There are two senators from every state.. little states can arm lock the rest of the country by carefull use of that ability.
I'm sorry I don't remember the exact details of the Yucca mountain project.. but yes it's mostly finished and then some "study" was created to delay once that "study" was finished more delays due to "budget priorities" were implimented.. tack it on this must have bill here, trade votes over there etc..
A carefull senator can create countless delays and cost over runs..
Then when everybody finally has it in their sights and decides enough is enough it passes only to be dismised in conferance committee.
As I understand it, most of the problem with Yucca mountain is that the legislature where it is (New Mexico?) must approve before it can go into active use, and they haven't/won't. Plus every state the radioactive materials must cross must approve, so shipping stuff from anywhere east of the Mississippi would be just about impossible.Given this is a federal project, and subject to "interstate commerce" regulation, these rules didn't have to be implemented, but they were added in Congress to hamstring the project.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Tim, That's a helpful explanation. In situqations of constant humidity, leaving the windows closed makes sense. Also, the humidity meter sounds like a good idea to set a baseline, but ultimately if someone (else) feels uncomfortable, the A/C is going on. Thanks,Stace
Since you work in the industry, I thought I might ask you a question that has bugged me for years.Is there any such thing as an absolute humidity measure? I understand that warm air can carry more moisture. As you noted, 75 degrees with 50% humidity can seem comfortable, as well as 80 degrees with 45% humidity.Our humidifiers have a sensor outside. As the temperature drops (in the winter) they increase the moisture in the system, though the humidistat stays constant (I set ours around 40 to 45%, a little bit higher than seems to be recommended, but that is where we are comfortable.)
Dew point.Re your humidifier, as the temperature drops the sensor DECREASES the humidity level inside, to prevent condensation.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Absolute measurement is really the 'wet bulb' temperature that is measured with a psychrometer. It has two thermometers one with a wetted bulb one without, and is slung around in a circle, as the water evaporates on the one thermometer it will measure the wet bulb temperature. Find out more here:
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/relhum.html
I work in the cooling tower industry which cools using latent heat evaporation.
Steve
Yeah, "wet bulb" and "dew point" are essentially the same. I think they generally differ by half a degree or so due to the differing standards for how they're measured, but this difference isn't significant for most purposes.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
"wet bulb" and "dew point" are essentially the same..."
Only for those who do not undestand psychrometrics, and some in the "cooling tower industry". The two properties are not the same and differ quite substantially for a sample of air containing the same amount of moisture at different dry bulb temperatures.
Yeah, minor brain fart there -- it's been about 35 years since I messed with this stuff. The wet bulb temp will always be higher than the dew point and below the dry bulb temp (which is "regular" temperature). It asymptotically approaches dew point under the right set of circumstances (which I can't remember right now).Wet bulb temp is a convenient measure for the chiller folks, though, since it roughly corresponds to the net cooling ability of the air.In any event, dew point or grams water per kg air (or ounces per pound or whatever) would be the two common "absolute" measures of water content in air, and converting between the two (assuming sea-level pressure) is easily done with a chart/equation. Either one is essentially independent of temp and will remain constant as a volume of air is heated/cooled.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Steve,
"Absolute measurement is really the 'wet bulb' temperature that is measured with a psychrometer"
See the previous post. Wetbulb is not an absolute measurement of moisture contained in air. The website you posted the link to is full of accurate information, you should check it out.
What is it that you do in the"cooling tower industry"?
The amount of moisture contained in air can be independently quantified by the Humidity Ratio, expressed in "grains of moisture per pound of dry air", also refered to as the Specific Humidity. Dewpoint (DP) is the same property expressed in terms of temperature, as DanH correctly pointed out. These numbers are really only of any use to those performing humidification and/or dehumidification calculations to size equipment or systems to control the air quality as desired.
However, "wet bulb" temperature is not an independent measure of moisture contained in air. It is dependent on moisture content and dry bulb temperature. For instance, if air is at 100 deg FDB (dry bulb) and a dewpoint of 35 degrees, is cooled to 70 deg FDB, with no moisture removed or added, the wet bulb changes from 63.6 to 52.2.
Humidity numbers expressed as percentages are "relative humidity" or rh. These are the most commonly discussed values and are the ones that affect appearant comfort. The rh is a ratio of the content of moisture in the air to the maximum moisture the same air could possibly hold, or the saturation moisture level (at the same temperature and pressure). In different terms, relative humidity is a measure of the air ability to dry things out.
"She asked me if the electric bills will be high this summer and
I'm going to tell her to just run the 110 V AC unit and leave it running for long periods of time, or even just leave it running 24 hours a day, rather than turning it on and off."
Doubt it matters much which unit is run in terms of energy used.
I do not understand the logic of keeping either unit on when not needed. The bedroom one in particular should probably be off except during the hours the room is actually used.
If she is out of the house all day, it makes little sense to keep either of them running, at least not at a normal temperature setting. Perhaps cap it at 80 degrees or somesuch on a really hot day to limit the discomfort of arriving home to intense heat.
Come home, crank them both up until comfort is achieved. Unless they are underpowered, the cool down time should be relatively quick.
Bill, not sure I understand your reply that says a large part of the cost of cooling is for moisture removal.
If you are saying that high humidity makes if feel warmer than low humidity (the weatherman's "heat index"), leading to running the AC more often, then I understand. In other words, 80 degrees at 80% relative humidity may send you running to turn on the AC, whereas 80 degrees at 25% humidity may feel fine.
But, if you are saying that it takes more energy to cool a given volume of air at high RH vs. low RH, then I'm not with you. Seems to me there is an equal amount of heat energy regardless of humidity. The fact that the moisture condenses out of the air when it drops below its dew point over the AC coils doesn't cause the AC to use more energy. Or does it?
It takes more energy to cool humid air vs dry air. The reason for this is that the AC must act as a dehumidifier as well as an air cooler, "pumping" the heat out of water vapor so it will condense. The "heat of evaporation" of water is relatively high (compared to the thermal mass of the air itself), so cooling air through the dew point (which almost inevitably happens anywhere other than in the desert) consumes a lot of energy.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
IF money is really all that tight the turn on only the one which is free to operate.
Otherwise, I would say air condition the room being used, when it being used. All of the discussion about humidity control in a two bedroom home with no central HVAC system is of no conseqence. (I would be that such a home is at least 50 years old, poorly insulated and poorly sealed, probably subject to less than diligent maintenance...)
If money is really tight, buy a window fan and leave the AC turned off. Builds character.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
"buy a window fan and leave the AC turned off. Builds character." Or in this case, spend a lot of time in the school library and let your tuition pay for your comfort while you spend the time earning your learning.