15 day heat wave and air conditioning

The issue here is not Adelaides climate. The issue is the limitations of evaporative coolers. Here are some other figures, for any where in the world, for the maximum cooling that can be achieved by one of these coolers .:- assuming that you can achieve 100% saturation (which I doubt)at 32degrees centigrade

70% rh down to 27deg 60% ...................26 deg 50%....................24 deg 40%....................22.7 deg 30.%...................21.6 And at these temps you would be near 100% humidity. (better not sweat cos it wont help you)

Incidentally the bom site .

has the mean adelaide 3pm temp max as 27 deg c at 40% humidity... so much for desert winds.

We have hot dry winds in Sydney too and these coolers would work then but that is only for part of the time.

The bottom line is that evap coolers have been around for many years. The technology has not changed. Things like the Coolgardie safe etc worked on the principle. They are coolers which are better than nothing for some of the time.

Architects and engineers choose refrigerated air and not evaporative coolers . You are not making any new revelations. If they were as good as you say they are why would any body bother with refrigerated air which is much more expensive,?

Why hasn't the refrigerated air industry gone bust? I have specified evap coolers on buildings myself where cost is a consideration. Only where it is nearly always hot and dry. Generally, they don't work on the coast. The clean up piles in Sydney were littered with evap coolers a few years ago when shops were cheeky enough to sell them. I have friends in Dubbo who threw out their evap cooler and replaced it with refrigerated air

I think you are suffering from the "I have got one therefore it is the best ". syndrome. You are prepared to ignore their limitations because they are cheap and it is obviously a hobby horse.

So you don't understand what "mean" is? If some days are cold and moist, and some are hot and dry, guess what the mean is.

Exactly, but more of the time in Melbourne and Adelaide.

Exactly, nobody said refridgerated AC wasn't better if running costs are not a consideration, and you don't care about environmental impacts.

MrT.

See here for why Relative Humdity falls with temperature:

If humidity is low when temperatures are high then evaporative coolers work well.

In many locations on this planet (including Adelaide) these conditions apply.

I've watched my local weather for many years.

37C days with 50% humidity just don't happen here, despite your pre-occupation with averages and your wish for it to be true.

I've been in locations where 33C is thoroughly unpleasant because of high relative humidity. It just doesn't happen in Adelaide.

In those unoleasant locations then evaporarive coopling wouldn't work very well. :)

Ross

I live in Perth and have had an Evap. A/C for 8 years. Apart from being handy to air the house (do you cook fish sometimes :-) it is a very workable compromise: Cheap to run, low maintenance but moderate or no cooling on certain days. In Perth a period of hot days usually ends with a HUMID CHANGE. In this case the land is still hot and we have a combination of high humidity and highish temperatures, at least for 1 day or a major part of it. That is when the Evap. A/C is rather useless. You run it and the condensation water might run down the walls but no cooling:-) (As we know, looking at the whet bulb temperature) These days don't happen too often and I can ($$$ will have to $$$) live with this drawback. Other humid days are by nature cooler anyway. If someone is very sensitive to heat an additional split system in a bedroom or living room may indeed be a workable compromise.

Tony

. That mean is for summer and the hottest day unlikely to be cold and moist.

Don't you ever have rain in summer, near %100 humidity and hot

Well one poster in this thread said exactly that it was better and even performed as well

There has been a lot of crap posted against refrigerated a/con in this thread more to do with political correctness than reality.

Don't teach your grandmother how to suck eggs

Do you know what a psychometric chart is? if you did maybe you would know what I am talking about. It is obviously above you so there is no point discussing it It is elementary thermodynamics.

Dont you ever have rain in summer. It can quite easily be 30 degrees and near 100% humidity on these occasions

the

Hi Tony,

Obviously I haven't had my evaporative a/c for 8 years so don't have your experience. :)

I did watch the local BOM weather station for quite a while prior to installation. The temperaure and humidity figures convinced me an evaporative a/c would work well in my location.

Our record 15 day heat wave ended with no particular humidity difficulty here.

And yes, I like the ventilation aspect myself too. Dries the floors quick if you mop too. :)

Frankly I was just totally impressed with the 15 day heat wave performance. I slept under a light quilt the whole heat wave, the house was so cool overnight. The house was 22C-25C throughout the heat wave. Without the a/c it might have reached 40C inside after 15 days.

My house is heavyweight brick, stone and concrete. If I had a humid day and the house was cool to begin with it would easily ride through a humid day without an a/c and be quite comfortable. Maybe use a fan on those days....

My brother has had an evaporative a/c for a considerable time, and he says if it ever seems like the unit is not quite working as well as normal a quick walk around outside soon changes his mind. :)

Ross

snip

Sounds good Ross. I hardly ever achieve more than 10 deg. temperature difference outside/inside. That's maybe because my house has lots of northern exposure (nice in winter). I have friends in Adelaide and I felt sorry for them when the heatwave didn't want to end. If you have no a/c and no pool a heatwave brings out the worst in you :-)

Tony

difference

Hi Tony,

I found the following quote in a Braemar document at:

"An evaporative cooler operates with its water temperature at close to wet-bulb temperature which is rarely higher than 24°C."

If the ouside temperature was 37C then maximum cooling possible with a wet bulb temperature of 24C would be:

90% of (37-24) = 11.7C and so evaporative a/c exit vent temperature would be about 25C under these circumstances.

Typically when it was 37C I was measuring 15C+ cooling so then the wet bulb temperature was probably near 20C.

Btw I was told by other people who had evaporative a/c it was important when buying a unit to at least 10% oversize the unit for best operation. Too small a unit resulted in quite poor performance.

Maybe that might be of significance for you?

Ross

Oops! Correction.

90% of (37-24) = 11.7C and so evaporative a/c exit vent temperature would be about 27C under these circumstances.

Ross

Cancel that. Had it right the first time. :)

Bit of a dill today, it seems. :)

Ross

much

But the coldest day probably is.

Sure, but not very often, that's the point. The rain usually comes with a cool change.

Well he/she is wrong then.

Or more to do with the rising cost of electricity. Lucky are those who do not need to consider it.

MrT.

Yes, but the southerly's usually bring a cool change.

occasions

In Adelaide? Not very often. Obviously if you live in Queensland or Darwin, evap is not a good choice!

MrT.

"Mr.T" wrote in message news:47f30dc4$0$18548$ snipped-for-privacy@news.optusnet.com.au...

God you are argumentative. My main objection in this thread was the misrepresentation by another poster that a refrigerated aircon was going to cost $300 per week to run and performed only marginally better than an evap cooler. I don't know why you are buying in. Just like to pick fights I guess. How you can compare a system which can easily say take a freezer room down to minus 15 deg c on a 40 degree ambient day (refrigeration) with something which is lucky to get 10 or 15 degrees under certain conditions and nothing under less favorable conditions. It is just rubbish and deserved to be corrected. I accept that evaporative coolers work most of the time in Adelaide especially when you have had a dry period as recently. This would not apply in the other states and was not mentioned in the general good rap these coolers were getting. As they DONT work in the coast of eastern states. Not just Queensland or Darwin I don't believe it will always be dry in Adelaide. It must get sea breezes some of the time. These occur near the coast on hot days when rising air over the land causes MOIST air to come in from the sea. The humidity will go up or at least remain stable when the temp goes up in these circumstances as moisture is being put into the system. Rain doesn't always come with a southerly change. Most of Australias rainfall comes from low pressure troughs inland anyway. A google search of aircon suppliers in adelaide showed that most providers supplied both evap coolers and refrigerated systems. The main advantage stated for the evap coolers was that they were cheap. One of the points for refrig coolers was they worked on humid days. According to you and your mates humidity doesn't occur in Adelaide. Obviously the aircon supplier doesn't agree with you and I know who I choose to believe. Finally by quoting temps, humidity and possible cooling taken from the psychometric chart I was just trying , in vain it seems, to quantify the cooling abilities of an evap cooler. This was in response to anecdotal evidence, such as my second cousin twice removed has one and thinks it is marvelous. Or it was so cool I had to sleep with a doona on. I picked a couple of figures which I supposed could apply to Adelaide and all I got was a diatribe from you and the other poster about adelaides weather. I supplied other figures which possibly would be more applicable but this was ignored. My main point in quoting the figures was to illustrate the relatively poor performance of these coolers compared to refrigeration units and NOT wether they would work most of the time in Adelaide or not . From a psychometric chart it is possible to calculate the possible cooling for any temperature and humidity combination so it would be possible to obtain figures on an hourly basis, of the maximum cooling available. Any one considering using one of these coolers would be well advised to do some of these calculations for their particular location. As for cost and enviromental concerns using refrigerated units. If they are used wisely the cost is not excessive and I haven't seen any great rises in electricity cost as yet. Refrigerated aircon is one of the whipping boys the greenies have decided to attack as part of the greenhouse gas thing due to energy requirements. (they can no longer attack the refrigerant as that has been cleared). They want us to revert to public transport and stop using water and drink sewage and other retrograde measures as well . As far as I am concerned refrig aircon is a valid energy use. When some of these greenies who spout this stuff start abandoning their overseas jet flights which put 50 tons of jet fuel and I don't know how many tons of CO2 in the atmosphere, then I might take notice. But then they like to jetset around don't they. About as hypocritical as turning the lights off for an hour once a year and pretending that has some affect.

"Bristan" wrote in news:47f35015$ snipped-for-privacy@dnews.tpgi.com.au: As they DONT work in the

Works fine in Melbourne eastern states in my experience. Great cooling for

95% summer.

Well I guess you are just easily pleased for 95% of summer.

choice!

You're the one ignoring the fact that Adelaide was specifically mentioned, just to make an argument.

MrT.

the

Evap.

the

or

Hi Ross, doesn't take long to work it out. Only the summers are a little different every year. And I suspect the pads lose efficiency over the years and I am thinking of replacing mine. Or has anyone ever managed to "revive" them? They clog up with calcium and dirt over time and I wondered if the same treatment you give pool filters would work with them? (acid bath)

snip stuff

They do work surprisingly well if the conditions are right. Yet I can't get myself putting up with a relative humidity higher than 60%

It should settle for the average day/night temperature with a little variation over time, like a large capacitor. Of course you adjust it by opening the windows at night. I used to live in an asbestos house with no a/c. It heats up and cools down much quicker,like a smaller capacitor:-) This is aus.electronics....:-) We had a water spray bottle (the one for the ironing) next to the bed to cool ourselves a little at night. The top maximum temperature in Perth in 1991 was

46.5... That's when you get desperate.

I don't have the patience to work out what's possible in theory. The bottom line for me is: Evap. a/c works in certain areas and with good insulated houses in general sufficiently well (the air can get little humid). It should be a standard in housing design; and solar water heaters of course. If I had the money and less consideration for the environment I would go for a refrigerated system, which has the great advantage of being a heater in reverse cycle mode. How about a ducted system where you can chose between either system depending on what's best for the day?

Tony

poster

So you should reply specifically to his posts and include HIS comments. But in fact some people would pay $300 per week to run their whole house ducted RAC during a 15 heat wave. If that was the only time it was needed though, I'd be more worried about the installation cost of either, than the running cost.

Pot, kettle, black mean anything to you?

That was his point as I read it.

Which usually brings cool relief from the hot North winds.

No, but air south of Adelalaide comes from cooler regions until global warming really destroys the Antarctic! Maybe you need to consult a map to get some idea?

for

Of course. So did you actually read the main argument that Evap was cheaper to run or not?

Please quote where I said that? The questin is how often does it happen and can everyone afford to worry about it.

choose

Please quote where I said air con was not superior for those who can afford to run it?

wether

So don't pretend you are refuting what was ACTUALLY said (rather than some specious claims)

are

in

Lucky you, mine just went up 20%. And I expect far greater rises in the years ahead. I guess it doesn't necessarily worry those with big incomes. It seems your whole point is YOU can afford it, so why should anyone else consider the cost?

to

Lucky you if you can afford not to care, your children will probably not be so lucky.

the

Many can't afford OS trips. Maybe Al Gore can, but they are not all like him you know!

Proof for this ridiculous assertion is where exactly?

MrT.