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  1. #1
    1K Club Member Gooner's Avatar
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    Default Evaporative Cooling in Melbourne

    I'm looking at getting evaporative cooling over the next couple of months in time for Summer and wanted some opinions on their effectiveness specifically in Melbourne.

    I've had a read through some threads on the forum and there seems to be some different opinions, but looking at historical weather data for Melbourne, it seems evaporative cooling is ideally suited. For the past few years, in most cases where the temperature exceeded 35+ degrees, humidity was very low. E.g between 5-30%.

    During the 40+ degree spell we had over several days last summer, relative humdity was around 6-10%. In these conditions, evaporative cooling should cool down to around 25 degrees, which would be great.

    I also noticed that the happiest people were the ones with "oversized" systems.

    Would be interested to hear opinions and recommendations regarding brands as well.

    Thanks
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    We have had ducted evap cooling for the last few years, more than happy with the system, doesn't cool down like a refrig system, but if it is 38 outside, it will be mid 20s' inside.
    Running costs are sweet bugger all
    Little to no noise
    The house here is about 14 squares, the cooler is good for 22 squares (if memory servers me)
    Bonair is the brand here

    There will be perhaps 2 or 3 days a year when the humidity is too high, but a soon to purchase inverter split system to replace the 2.5hp noise maker will take care of that

    Melbourne is well suited for Evap Cooling.

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    Default evaporative vs refrigerated

    i personally would not get an evap cooler around the melbourne area, they really only work around the northern end of the state. as you have said already, the lower the humidity the better it will work, and a lot of the time it will rain in the morning then get hot, which pushes the humidity up and stops the evap cooler from cooling. they will raise the humidity in the house which makes you sweat, and thats how it cools. i have a reverse cycle split system and recommend them to all my customers, because they will work under almost all normal conditions. hope this helps

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    Personally I can smell the difference inside a house that has evap. After years the plaster walls and carpet gets damp and develops a faint odour. That's my opinion and I don't want to start an argument about it. This is merely what I have observed.

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    1K Club Member Gooner's Avatar
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    Thought I would update this thread seeing as we have had a few consecutive days in 30+ degree heat. I installed a Breezair EXH190 evaporative cooler a few months back and its had its first trial over the past few days. Our house is around 140-150sqm so the EXH190 (being rated for a 190 sqm house) is bigger than what we require. However, the common thing I found is that those people who are happy with their evaporative cooling are those with oversized units so thats what I went for.

    Anyways, I am very happy with this unit. The house has been very comfortable over the past 3 days. It's 34 degrees (around 35% relative humidity) out now and the house is a pleasant 23 deg C and a nice breeze throughout the house with windows and doors open.

    Nice thing was that we were out most of the day yesterday and came back to a hot stuffy house. Within about 10 minutes of turning on the unit full blast, the house lost that stuffy heat. Within 30 minutes it cooled the place from 28 deg down to 23 deg and it was comfortable.

    Of course it doesn't make the house cool like a refrigerative system, but certainly makes it comfortable. A split system solution would have cost us around $12K. The evaporative $4.5K. So certainly bang for buck and not really worried about the amount of electricity it is using.

    As for Tricky's comment about the smell. Yes for the first few uses there was a smell in the house. It was because the filters were new. But now the smell has totally disappeared after a few uses. (And we don;t have carpet, so that isn't an issue).

    Our old box-in-the wall refrigerative unit uses 3.7Kw on full blast and only had the ability to cool down our main living area. (Barely). The evap unit consumes 1.5Kw (+ water) and cools the entire house. A couple of split systems to cool our house would have consumed about 9+Kw, so certainly an energy/$$ saver in this respect. I am convinced enough so far that I will be removing the box-in-the-wall unit over the coming months. I doubt it will be used again.

    So for those who are contemplating evaporative cooling I would say go for it unless you really want that extra cool feeling refrigerative provides. I would also recommend getting the biggest over-rated system feasible. The Breezair unit is quite nice and really quiet.

    There's my 2 cents for now.
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    Anyone know installers who are good value for money .Seems like prices vary big time!

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    1K Club Member Gooner's Avatar
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    Just another note on this... When I bought the unit I asked the dealer several times how much water the unit consumes. they never gave me an answer but instead dodged the question with "depends" and then went on to change the subject. I asked for "ball park" values which they never really gave me, instead telling me the capicity the unit holds, which does not answer my question.

    Yesterday I decided to measure it. On the 32-34 deg day with around 30% humidity I calculated that the unit used approximately 60 liters of water per hour when on full blast.

    It does seem like quite a lot, but if you look at the volume of air the thing displaces and the fact that the cooling does actually work on an evaporative principle, I guess 1 liter per minute does not seem that outrageous. Certainly not a water saver though!

    I also calculated that the water used equates to around 9 cents per hour. Electricity is around 15 cents per Kw so there is still a significant saving. I.e. 1.5Kw + 60 liters per hour = 22.5 cents (elec) + 9 cents (water) = 31.5 cents per hour.

    The Breezair brochure states "Cool your house for the price of running a light bulb". They must be talking about a pretty damn big light bulb.
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  8. #8
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    Cripes at that rate your water usage target is going to vanish with that thing on. Personally for me it doesnt do it. Moist warm air is worse than the heat. But thats just me. I have a split system, its quiet and efficient not like the old Westinghouse we used to have. Turn that on and the meter sounded like my DVD burner. Oh see you goading Rod on another thread, hope you got a wheel, Im plum out.

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    Quote Originally Posted by rrobor View Post
    Cripes at that rate your water usage target is going to vanish with that thing on. Personally for me it doesnt do it. Moist warm air is worse than the heat. But thats just me.
    It does seem high, but it's also use at the extreme.

    Gooner, it would be worth checking what the bleed rate is set to. If you are not aware, there is a water resevoir up in the unit that recirculates water through the pads - as some of it evaporates the remaining water concentrates and the % of salts and minerals increases in the remaining water. To compensate for this, there is a bleed to waste that basicly tips some of the concentrated water down the drain. You should be able to measure this at the end of the pipe coming from the cooler (usually just a bit of poly pipe) Adjustment is performed by a tap or swapping an orifice on the bleed, although things may have gotten more technical since the last time I had a play with one.

    rrobor, The coolers do moisten the air yes. At least half of the effect is performed by moving air across your skin, so for the system to work effectively the air must have somewhere to go, and there must be lots of it. So open all the windows and make sure you can feel a good breeze! I agree, if you don't have this, they can be quite unpleasant.

    Michael

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    1K Club Member Gooner's Avatar
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    Here (http://www.yvw.com.au/NR/rdonlyres/8.../EACReport.pdf) is a relatively good report on evaporative cooling and their water usage as compiled by Yarra Valley water and Water Association Victoria. If you look through it they state that the most efficent systems use around 1 lpm (60 liters per hour as mine does). As stated in the report, some use up to 10 liters per minute!!

    However, I assume this statistic may be skewed by the fact that the cooler needs to fill up with water before it is used and perhaps this initial fill up was used in the calculation, which doesn't really give a very good idea on water usage.

    However, certainly 60 liters per minute seemsw quite reasonable. The unit pushes something like 12,000 cubic meters of air every hour! So 60 liters per hour turns out to be 0.005 liters (5ml) of water per cubic meter of air. That doesn't sound outrageous once you do the math.

    No doubt a big water user and perhaps a future concern for our water resources if evaporative cooler installations continue increasing at the rate that they are. But cooling is a resource intensive affair. We are either consuming a s!^t load of electricity or a s!^t load of water.

    The bigger picture is that an evaporative cooler consistutes an average of 2% of your yearly household water usage.
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    Quote Originally Posted by Gooner View Post
    However, I assume this statistic may be skewed by the fact that the cooler needs to fill up with water before it is used and perhaps this initial fill up was used in the calculation, which doesn't really give a very good idea on water usage.

    However, certainly 60 liters per minute seemsw quite reasonable. The unit pushes something like 12,000 cubic meters of air every hour! So 60 liters per hour turns out to be 0.005 liters (5ml) of water per cubic meter of air. That doesn't sound outrageous once you do the math.
    Does the unit have an automatic dump valve? If not, it fills with water and tops up as the water is used or evaporates. I suspect that they would have tested the running usage rather than the season start usage.

    Is 12,000M/hr the max or the minimum flow?

    I still reckon it would be worth having a look at what the bleed arrangements are.

    In any case, you are right, they use water, and water is only going to get more expensive. I guess you could put in an extra rainwater tank for the cooler...

    woodbe.

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    well i would say if your in melbourne, at the moment for every person in your house you can run it for 2 1/2 hours and no showers or washing. Target 155

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    Quote Originally Posted by Gooner View Post
    Here (http://www.yvw.com.au/NR/rdonlyres/8.../EACReport.pdf) is a relatively good report on evaporative cooling and their water usage as compiled by Yarra Valley water and Water Association Victoria. If you look through it they state that the most efficent systems use around 1 lpm (60 liters per hour as mine does).

    However, I assume this statistic may be skewed by the fact that the cooler needs to fill up with water before it is used and perhaps this initial fill up was used in the calculation, which doesn't really give a very good idea on water usage.

    ...So 60 liters per hour turns out to be 0.005 liters (5ml) of water per cubic meter of air. That doesn't sound outrageous once you do the math.
    (disclaimer: I am huge advocate of evap coolers, so I'm biased, even though I have nothing to do with them business wise)

    I thought 1L/min sounded waaaay to high, so I had a read of the report. I can understand Yarra Water wanting to be able to model water usage on hot days. But I have to conclude the study is flawed.

    The main problem is they only measure gross water usage. (In fairness to Yarra water, this wasn't an efficiency study, it was a study of real-life gross water use, so maybe it isn't flawed at all).

    Firstly, they quite rightly correlate that the longer you use a unit, the more efficient it is (in terms of total water/total time).
    However, as Gooner has pointed out, nowhere in the study do they make the obvious connection that this is (most probably) due to filling of the sump.
    They say the "least efficient" units were used for less than half an hour, and in the lowest case, for 16 minutes! (Honestly, who on earth turns on their evaporative cooler, fills a 20 litre sump, and then turns it off after 16 minutes! No wonder the "efficiency" is crap.)
    Measured this way, it is also unsurprising the units that averaged 7 hours use a day used less than a litre per minute (as low as 0.3 Lpm).

    However, as far as water efficiency is concerned, there are other factors that weren't considered:
    - did any of the usage time include "fresh air" mode where the unit was running but the pump was turned off (so it only circulated air)?
    - did the units empty the sump each time the unit was turned off?

    The unit I have (I think a breezair) only empties the sump after 3 days. So if I continually turn it on and off it isn't wasting huge quantities of water.

    Gooner, glad you decided months ago to go evaporative. I think it is perfect for the dry Melbourne summers. Ok, so it doesn't work too well for maybe the 1 or 2 hot days we get which are very humid. But I would much rather that than sit in a hermetically sealed refrigerated house.

  14. #14
    1K Club Member Gooner's Avatar
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    Quote Originally Posted by John G View Post
    Gooner, glad you decided months ago to go evaporative. I think it is perfect for the dry Melbourne summers. Ok, so it doesn't work too well for maybe the 1 or 2 hot days we get which are very humid. But I would much rather that than sit in a hermetically sealed refrigerated house.

    So am I. With very young kids in the house it seems inpossible for them to close doors behind them. It's nice to keep doors and windows open on a hot day.

    The breezair unit I have has the same setting of 3 days dump. It also has the water monitor thingy-mijiggy that bleeds water as the salinity (I believe) gets too high. So its a "smart bleed" rather than a pre-set bleed.

    I have a EXH190 unit. John, I would be interested to know what unit you have and how much water it consumes on full setting. Just look at your water meter when on.

    Also, look at the graph below. 1 cubic meter of air = about 1.2Kg. Evaporative cooling raises humity in the house to about 80%. Therefore on a 30% RH day you are adding about 50% humidty. You can guesstimate from the graph below that on a 35 degree day (with 30% RH) this equates to about 10ml (or grams) of water per kg of air. I.e. about 8ml of water per cubic meters of air (considering 1 m^3 is approx 1.2kg).

    I initially made a mistake about my cooler. It actually displaces about 9500 cubic meters of air per hour, (not 12,000). Therefore 9500 cubic meters x 8ml of water per cubic meter = 76 liters of water per hour.

    This seems to correspond quite nicely with my approximate water usage when the unit is on full setting at these temperatures and humidity levels.

    Yeay for science.


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    Your numbers are pretty close, a 35 deg day at 30% RH will have 10.5g/kg moisture. Most evap cooler claim 90% saturation, so on that day the leaving air would have 15.6g/kg of moisture. Giving you a evaporation rate of 5.1 mls per Kg of air. At that temp one Kg of air is 858 litres. Therefore I work out the water consumption at around 56 litres an hour

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    Quote Originally Posted by AIRMAN View Post
    Your numbers are pretty close, a 35 deg day at 30% RH will have 10.5g/kg moisture. Most evap cooler claim 90% saturation, so on that day the leaving air would have 15.6g/kg of moisture. Giving you a evaporation rate of 5.1 mls per Kg of air. At that temp one Kg of air is 858 litres. Therefore I work out the water consumption at around 56 litres an hour
    its an interesting thing to compare total operating cost of evap (including water) with refrig approaches.

    lets say that the water consumption is 60L/hour and assuming one would run it for 8 hours/day in summer or say 80 days/year.

    that works out to: 60L x 8 hours/day x 80 days/year = 38400L of water.
    looking at a Yarra Valley water bill it says water on "block 1" is $1.2532 / KL.
    there is _also_ 'sewage disposal' charge tied to that "water consumption" value, it says on the bill its:
    (water_usage) x (seasonal_factor) x (discharge_factor) x $1.5126 / KL.
    (seasonal_factor) is currently 0.9698 and (discharge_factor) is 0.9.

    so taking that into account the cost of water would be:
    incremental water charge: 38.4 x $1.2532 = $48.12
    incremental sewer charge = 38.4 x 0.9698 x 0.9 x $1.5126 = $50.70

    overall incremental charge = $48.12 + $50.70 = $98.82

    turning those values back into cost/hour - above is based on 80 days x 8 hours/day, so that becomes $0.1544 / hour "water" costs.

    so .. overall cost is 1.5KW/hr @ $0.15 / KWH + $0.1544/hr

    I also calculated that the water used equates to around 9 cents per hour. Electricity is around 15 cents per Kw so there is still a significant saving. I.e. 1.5Kw + 60 liters per hour = 22.5 cents (elec) + 15.44 cents (water) = $0.3794 / hour.

    Melbourne Water charges are expected to increase around 62.4% courtesy of charges associated with new water pipeline + desalination, so assuming that doesn't also map to sewer chage means water charges will go to 20.13 cents, taking overall cost to:
    22.5 cents/hr (elec) + 20.13 cents (water) = $0.42632 / hour.

    that will still be significantly cheaper than refrig all-house ducted (both on installation cost and operating cost), but there may be some interesting comparisons with maybe some smaller only-selected-rooms-in-house split systems that have better R.O.P.

    based on the above, i take that cross

    its an interesting comparison to make perhaps versus some smaller split systems which have a R.O.P of around 4, the equivalent is: $0.42832/hr = 2.85KW @ $0.15 / KWh = ~11KW of cooling.

    some interesting comparisons.....

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    1K Club Member Gooner's Avatar
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    Quote Originally Posted by AIRMAN View Post
    Your numbers are pretty close, a 35 deg day at 30% RH will have 10.5g/kg moisture. Most evap cooler claim 90% saturation, so on that day the leaving air would have 15.6g/kg of moisture. Giving you a evaporation rate of 5.1 mls per Kg of air. At that temp one Kg of air is 858 litres. Therefore I work out the water consumption at around 56 litres an hour

    Yeah I made some coarse assumptions in my calculation but would need to get the old thermodynamics books out to calculate it properly. Stuff that. I was more interested in a ball-park figure and verify my water meter reading in case something was wrong and the unit using much more water than expected. Once again, I found the dealer very cagey when it came to the question of water consumption and I could not get any kind of answer out of him.
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    Quote Originally Posted by president_ltd View Post
    there is _also_ 'sewage disposal' charge tied to that "water consumption" value, .......
    You are absolutely right and I forgot about that even though I was examining my water bill the other night. Good pick up.

    In fact I have my water bills for the past several years, and I find it interesting how water charges have risen. you really have to compare bills, as over time they may change the block volume, or a seasonal factor, or block 1 price, or block 2 price, or both, or sewerage charge... etc etc.

    It really isn't anywhere near clear cut as, say, electricity, where you have a service and KW rate. With water you have to look at all the little factors and calculations.

    Looking at current and past water bills, I got an idea at how much exactly the price of water has gone up and how they have implemented it.
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    Quote Originally Posted by Gooner View Post
    It really isn't anywhere near clear cut as, say, electricity, where you have a service and KW rate. With water you have to look at all the little factors and calculations.
    ya, as part of looking at cooling for myself - and at the 'indirect' evap coolers also coming out ( i had a thread asking questions about that http://www.renovateforum.com/f78/tho...umidity-78209/ ).

    but basically i think many evap aircon companies aren't quite honest about real running costs, water consumption (typically never mentioned) or meaningful R.O.P comparisons.

    i was originally going to go with evap cooling in SE melb suburbs for our place.
    then discovered indirect evap units coming on to the market

    but have since done calculations like above - including cost of water (and what it does for the "155L target/day"), and i'm starting to lean more towards a few localized split system units, e.g. small unit in bedroom, small unit in study, maybe larger unit for living area.
    maybe not as nice as all-of-house ducted might be - have to close up the house to some extent - but even so ignoring up-front capital 11KW of split system refrig cooling (@ same running costs as evap) is still a fair bit of cooling nontheless.

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    just a follow-up too... out of interest how close do you think you'll be to moving into "block 2" or up a block in the water tariff charges?

    see Yarra Valley Water - Account charges explained

    gets more expensive...

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    Quote Originally Posted by president_ltd View Post
    i was originally going to go with evap cooling in SE melb suburbs for our place.
    then discovered indirect evap units coming on to the market

    but have since done calculations like above - including cost of water (and what it does for the "155L target/day"), and i'm starting to lean more towards a few localized split system units, e.g. small unit in bedroom, small unit in study, maybe larger unit for living area.
    maybe not as nice as all-of-house ducted might be - have to close up the house to some extent - but even so ignoring up-front capital 11KW of split system refrig cooling (@ same running costs as evap) is still a fair bit of cooling nontheless.
    Unfortunately, it's all a double-edged sword, isn't it? Do you go evap, and blow your 155 target? Or do you go refrig, and spew all that extra latrobe valley brown coal goodness into the air?

    Personally, I have chosen the first route. Although it uses water, at least evap doesn't actually destroy the water. It's free to go back into the air and make new clouds<sup>1</sup>. But once the coal is burned, it's burned. They're not making any new coal anywhere.

    <sup>1</sup>Ok, I'm not suggesting I make it rain more in victoria! But if we are comparing the environmental impact of evap vs refrig, for me, using water is a lesser evil than burning coal. Plus, with our water tank, we are well under 155 anyway.

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    I agree with John here. Although water has become an issue, it is still a renewable resource and there are solutions.

    Also, if you use, say, 200 liters a day on your evaporative cooler over, say, 30 days in the year, it averages out to about 16 liters per day in the year for the household. For a family of 4, thats 4 liters a day each to meet your all-year-round cooling needs.
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    Its really just a matter of putting in a water tank to overcome the argument.
    Here on the Central coast were we have had restrictions for years and anyone
    with a pool has to by law have a water tank to top the pool up instead of using town water.
    Saves the dam and saves your pocket. however we are lucky here with all the rebates
    on offer, we can have a 5000l watertank installed for free as long as you plumb it into
    your washing machine and toilet.

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    The irony is that the areas that are most suitable for evap cooling (hot and dry) are generally those that are short of water.

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    Quote Originally Posted by AIRMAN View Post
    The irony is that the areas that are most suitable for evap cooling (hot and dry) are generally those that are short of water.
    And the strange thing for me, always having lived where there's plenty, is that it's only in the past 2 or 3 years that I've realised that water is actually considered a valuable resource in many parts of this country. Prior to that, I'd just always taken it as plentiful and essentially worthless since, where I am, that's certainly the case.

    It's a real pity we can't have the water a bit more evenly distributed in this country. That would fix a lot of problems.

    All that said, I'd still argue that saving fossil fuels (non-renewable) is more important than saving water (renewable) in the vast majority of situations.

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    Quote Originally Posted by nww1969 View Post
    Its really just a matter of putting in a water tank to overcome the argument.
    ...we can have a 5000l watertank installed for free as long as you plumb it into your washing machine and toilet.
    The water tank definitely helps, but doesn't solve everything. Plumbed to toilets, washing machine and watering system, our 6500L tank will only last about 3 weeks without rain. Luckily, we've got about 20mm rain predicted for this weekend, which should about 80% refill it.

    Watching the level go down really makes you think about how much water you use. We just do the normal amount of laundry, so I reckon it must be the watering system that is killing us. Anyway... getting off the topic a bit...

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    Quote Originally Posted by John G View Post
    The water tank definitely helps, but doesn't solve everything. Plumbed to toilets, washing machine and watering system, our 6500L tank will only last about 3 weeks without rain. Luckily, we've got about 20mm rain predicted for this weekend, which should about 80% refill it.

    Watching the level go down really makes you think about how much water you use. We just do the normal amount of laundry, so I reckon it must be the watering system that is killing us. Anyway... getting off the topic a bit...
    Far out... you must have a water-hungry toilet/laundry/garden! Front loaders use about 50-60L per wash, and a good toilet is 3L/6L for half/full flush. Even with 5 washing loads a week and 15 toilet flushes a day for 3 weeks, that would equal 2790L.

    Good effort though connecting it up... mine was a bigger project than first imagined... you can always add another tank

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    Just moved into a new house, no cooling at all, not even a ceiling fan
    Curious to know how well evap cooling worked on a hot 40+ day like today?
    Anyone know where I can get a cheap Breezair system installed

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    FWIF, our unit dumps its water every 4 hours, approx 30lt, and refills, does not appear to top up in between times. It is fed from the water tanks, and the only time we hear the pump start is when the toilet is flushed or water is being used in the laundry.
    So 60lt a hour sounds like an heck of a of water usage to me.

  30. #30
    Diamond Member Terrian's Avatar
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    Quote Originally Posted by chris... View Post
    Just moved into a new house, no cooling at all, not even a ceiling fan
    Curious to know how well evap cooling worked on a hot 40+ day like today?
    Anyone know where I can get a cheap Breezair system installed
    our house has gotten up to approx 27c the last couple of 40c days, weatherboard house with tin roof.
    Bear in mind that we have batts in the ceiling, and all the exterior walls have 3.0+ batts as well.

  31. #31
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    Quote Originally Posted by Terrian View Post
    FWIF, our unit dumps its water every 4 hours, approx 30lt, and refills, does not appear to top up in between times. It is fed from the water tanks, and the only time we hear the pump start is when the toilet is flushed or water is being used in the laundry.
    just because you cannot hear it doesn't mean it isn't happening.

    is per chance your pump run off a Davey Rainbank?
    one can in fact 'trickle' water out of that without the pump running, as it 'primes' based on mains pressure and will in effect use some mains water.

    i have one of those and am quite disappointed in how a 'green' product is actually somewhat flawed in its design IMHO.

    Quote Originally Posted by Terrian View Post
    So 60lt a hour sounds like an heck of a of water usage to me.
    its relatively simple to calculate it out, Gooner has done so in post #14 above.

    for evap to work, you need to be replacing the air in your house X times an hour (X being between 30 to 60) otherwise you feel uncomfortable.

    you are therefore essentially continuously evaporating dry bumb -> wet bulb (getting to ~90+% R.H. saturation) on sufficient volume of air equal to the volume of space inside your house.

    i think you will find it to be SUBSTANCIALLY more.

  32. #32
    Old Chippy 6K
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    Advice from me on this forum is general and for guidance based on information given by the member posing the question. Not to be used in place of professional advice from people appropriately qualified in the relevant field. All structural work must be approved and constructed to the BCA or other relevant standards by suitably licensed persons. The person doing the work and reading my advice accepts responsibility for ensuring the work done accords with the applicable law.

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    Quote Originally Posted by president_ltd View Post
    just because you cannot hear it doesn't mean it isn't happening.

    is per chance your pump run off a Davey Rainbank?
    one can in fact 'trickle' water out of that without the pump running, as it 'primes' based on mains pressure and will in effect use some mains water.

    i have one of those and am quite disappointed in how a 'green' product is actually somewhat flawed in its design IMHO.
    Yeah, I think it uses the same concept as the instant hot water systems (flow detector needs min. of 1.5L/min to activate or you just get cold water!).

    Other problem with the Rainbank is it won't work in the case of mains failure, which is a shame.


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