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Re: 15 day heat wave and air conditioning

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The really hot days and nights in Adelaide are due to Northerly  Winds
off the desert in the centre of Australia.

By definition deserts are dry and hot and the air coming off them is
therefore dry and hot.

Any winds we get from the West and South are automatically cool
because they pass over the ocean.

It is just the way it is here. I've lived in Adelaide for 60 years and
as far as I know we have never had a 37C day with high humidity. It is
always low humidity when it is hot. We would all probably die if a
high humidity hot day ever happened. :)

You are welcome to look through previous Adelaide summers on the BOM
site and prove me wrong by finding a 37C day with 50% humidity in the
Adelaide records. Good luck. :)

Most Adelaide people would simply accept we have low humidity when it
is hot.

What Adelaide folk might call a "high humidity" day would have a
Queenslander splitting his sides with laughter.

For example,  _any_ 25C day in Adelaide is just a beautiful and very
pleasant and comfortable day.

A perfect day every time it is 25C.

People in Queensland couldn't ever say that.

Ross

Re: 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
.http://www.bom.gov.au/climate/averages/tables/cw_023000.shtml
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.









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Re: 15 day heat wave and air conditioning

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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.


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


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

 MrT.



Re: 15 day heat wave and air conditioning

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.
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



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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.



Re: 15 day heat wave and air conditioning

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much

But the coldest day probably is.

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

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Well he/she is wrong then.

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

MrT.



Re: 15 day heat wave and air conditioning

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See here for why Relative Humdity falls with temperature:

http://www.physicalgeography.net/fundamentals/8c.html

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

Re: 15 day heat wave and air conditioning
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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

Re: 15 day heat wave and air conditioning

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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


Re: 15 day heat wave and air conditioning
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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

Re: 15 day heat wave and air conditioning

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Hi Tony,

I found the following quote in a Braemar document at:

http://www.carraheatcool.com.au/brochures/paradigm.pdf

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

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


Re: 15 day heat wave and air conditioning

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Oops! Correction.

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

Ross



Re: 15 day heat wave and air conditioning

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

Bit of a dill today, it seems. :)

Ross

Re: 15 day heat wave and air conditioning
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the
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Evap.
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the
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or
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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)


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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%

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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


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Re: 15 day heat wave and air conditioning
Hi Tony,

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I'm told they need to be hosed off at the close of every season to get
rid of evaporated salts, mud etc.

However, after a few years (probably >5-8 years) they do need to be
replaced since a/c effectiveness drops off. They did initially claim
the celltek pads practically lasted forever, but that proved to be
optimistic.

If you are handy it is an easy job to do yourself. I haven't yet
priced replacement pads, but I'm told the celltek pads are not that
inexpensive.


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I wondered about that myself. At 22C here in Adelaide it is often 50%
humidity. And early this morning it was 14C and 65% humidity.

I'm unable to tell the difference between 22C at 50% humidity, or 22C
at 70% humidity. I thought I would easily know the difference but I
don't.

Without the a/c if the house got to 25C I felt like turning on a fan.
It was surprisingly consistent for me to do this.

I'm often seriously engrossed on my computer, and I was surprised to
find that dead on 25C with the evaporative a/c running I felt like
running a fan again.

Intuitively I'd have thought that the need to turn on a fan would
occur lower than 25C because of the higher humidity. But it didn'r. I
was a bit surprised at that.

Btw the Steadman Chart says 22C air at 50% humidity has an apparent
temperature of 22C, while 22C air at 70% humidity has an apparent
temperature of 24C. So my intuitive feeling is backed by scientific
fact.

However, for me I could tell no difference between  50% and 70%
humidity at 22C, despite the Steadman figures saying I should be able
to.

Ross



Re: 15 day heat wave and air conditioning

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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.

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



Re: 15 day heat wave and air conditioning

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

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occasions

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

MrT.



Re: 15 day heat wave and air conditioning

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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.



Re: 15 day heat wave and air conditioning
 As they DONT  work in the
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Works fine in Melbourne eastern states in my experience. Great cooling for
95% summer.

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Re: 15 day heat wave and air conditioning

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





Re: 15 day heat wave and air conditioning

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Let's put this thread to rest...can we all agree that...

Advantages of evaps. ACs...........................
Cheap to buy
Cheap to run
Useful most of the time in dry climates like Adelaide


Disadvantages of evap. ACs...................................
Marginal cooling effect, only 10degC or so under optimum conditions.
They increase humidity - which can make it more uncomfortable.
Useless most of the time for much of Australia, Sydney, Brisbane, Darwin etc.
Useless anywhere when ambient humidity is high.
Require a water supply

Advantages of refrigeration/heat pump ACs...........................
Maximum cooling effect - 20degC or more is easily achieved.
They decrease humidity - which makes it more comfortable.
They always cool effectively and always decrease humidity.
Usefull all of the time anywhere in OZ.
Reverse cycle units can heat efficiently in winter

Disadvantages of  refrigeration/heat pump ACs...................................
Higher initial cost.
Higher running costs - compressor, twin fans.
Require water drainage.








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