Roopftop Evaporative Cooling Upgrade - What Should I Do?

• 

  [Deactivated] on 01/03/2019 - 22:23

  +3

  Evaporative cooling is a joke. When you really need it, when its really hot, it doesn't work. Replace it with ducted reverse cycle, you wont regret it.

• 

  cyvirus on 01/03/2019 - 22:32

  +3

  Had one for 4years now. No complaints. 23 deg inside while 38deg outside. don't think 23 deg with evap is not cool..coz it sure is Test it for yourself if you know someone with evap cooler. Will cost peanuts to run.
  Where are you located (Melbourne /Sydney/Adelaide)?

  • 

    [Deactivated] on 01/03/2019 - 22:54

    Melbourne. It's particularly painful when 35+ degrees.

    • 

      cyvirus on 01/03/2019 - 23:06

      +2

      Should work fine in Melbourne. All those houses with evap can't be all wrong as some of the refrig advocate says here.
      As I say don't take my word for it, try to test it in a hot day if you have a friend or know anyone that has evap. This topic has been done to death in Whirlpool forum.

• 

  wordplay on 01/03/2019 - 22:34

  +1

  they never feel cold, cool yes, but not cold. weigh up the price of comfort. I'm quite frugal so restrict air conditioning to 6 days per month.

  • 

    Quantumcat on 02/03/2019 - 10:54

    Evaporative cooling costs very little to run, no need to be frugal

  • 

    Euphemistic on 02/03/2019 - 13:06

    +1

    Why do you want to feel cold in the middle of summer. Cool should be enough.

• 

  lgacb08 on 01/03/2019 - 22:39

  +2

  8kwh in the common area is more than enough to blast your common area cool, I got my 7kw burning 2.5kwh each hour in 40deg+ to blast cool air from living room down to kitchen and dining areas, my house is even bigger than yours (but need to close off the bedrooms and bathroom/laundry to avoid heat loss). But if you want to keep the electricity bill down at night, get one or two more smaller dedicated units for the bedroom.

• 

  horsome on 01/03/2019 - 22:49

  +1

  We shut ours off and put a split where the air flow would be best through the house. It does your heating too.

  Our evap was a shocker of a setup and I don’t recommend them to anyone.

• 

  cyvirus on 01/03/2019 - 23:04

  +4

  Depends how the evap was designed. I stand by my opinion that evap works. When it was mid 30s the other night we were sleeping under the doona. Plus knowing that I'm paying less than a dollar to run it makes for a more comfy sleep. But hey, to each his/her own.
  I don't need it to be 16-18 degrees inside the house when it is 30-40 deg outside. Im comfy at 22-23 deg.

• 

  [Deactivated] on 01/03/2019 - 23:15

  +4

  Where do you live? (I live in Perth) If you live somewhere humid then Evap is not good. If you change to refrig then you will probably also need to move the outlets. We had a similar dilema last year and replaced the Evap for $3k, But we would have had to spend $10k on a fully ducted refrig system as there is 4 people in the house a couple of splits wouldn't have cut it. I am pretty happy with the evap, it doesn't get over 25 in the house. You just need to have it running all day on hot days.

• 

  coin saver on 02/03/2019 - 06:08

  +1

  A lot of my mates here in Adelaide have ducted evap thru the house and a split in the living area for humid days i personally have no problem with just evap.

• 

  Ocker on 02/03/2019 - 09:18

  +1

  (In Melbourne) we have both evap. for the whole house of about 270 sqmt, and a 8kw slpit system in the kitchen/meals/living area of approx 70 sqmt.
  On days like we have recently had we run the evap. overnight to cool the whole house, and then the split system during the day.
  Last night, with the evap. running at 1/3 power the inside temperature was down to 21 degrees. Outside temperature was about 25d
  Split systems are not particularly cheap to run as apart from electricity. using about 0.5kw per hour at 1/3 power, there is also the water usage to consider.
  As mentioned earlier, evap. is not effective on a very humid day.

• 

  JimmyF on 02/03/2019 - 09:36

  +1

  Since this summer was particularly hot, it wasn't working nicely either anyway.

  Was it humid outside? They really only work best in dry heat.

  • 

    [Deactivated] on 02/03/2019 - 11:13

    That and I found it only knocks off about 10 degrees from the outside temp. So if it's 40 out there then 30 inside, which is not quite working.

    Could be the old unit tho.

• 

  Quantumcat on 02/03/2019 - 11:04

  +1

  Something I like about evaporative over split cycle is you need to have the doors/windows open, and you get a lovely breeze going all through your house, which makes it feel cooler than it actually is. With split cycle you would want to keep everything shut and then the stuffiness makes it feel hotter than it actually is.

• 

  rompastompa on 02/03/2019 - 11:10

  +2

  Evaporative = water running down some bats, and a fan pulling air through it. You need to have your windows open for the cool air to come in through the bats, and out through your windows. Evaporative doesn't work when it's super humid, as you're just adding more water in the air. I reiterate, it doesn't work if you close the house up. Cheap to run, as you're just trickling water (and recycling it with a pump) and a large fan.

  Refrigerative has a condenser the same as your fridge. It'll cool the air using electricity. You need to keep the house closed up for it to work properly and will cost you significant amount if you're running it all the time.

  Hope technology advanced much in year 2019?

  There's not much technology in evaporative.. Fans will be optimized for flow and power reduction and bats will likely hold more water and allow more airflow, but in the end, it's akin to holding up a wet towel covering your car window while driving on a hot day (how our car 'air conditioners' worked 30 years ago).

• 

  savage bargain on 02/03/2019 - 13:03

  +8

  The other reason you can't swap the unit out with refrigerated is because for evap, you want the vents far away from windows so the cooled air goes across the room to the exit. Whereas refrigerated, you want the vents as far away from the intake so the air goes across the room back into the system - if you keep the evap vent set-ups, the refrigerated won't work properly.

  Evaps are pretty energy efficient (fans + water) vs refrigerated, so if you're in an area where evap does work, it's probably better to keep evap and pop some splits in. The only reason people complain about evaps is no one is taught how they work so they don't know when to turn them off and close up the house to keep heap out so that it doesn't cook the house during heat waves.

  So as someone who's done some HVAC engineering, here's some tips:

  • Evaps work by adding water into the air to get the air temperature closer to the dew point temperature you see on the weather websites. The bigger the difference between the current air temperature and dew point, the lower the humidity is and the more cooling it will do. A crude way to see if it's worth having the evap on is to average the current temp & dew point, and you want the result to be under 24 deg, and it's getting borderline as that gets towards 26. E.g. 1: current temp 34, dew point 14, average is 24. Hence evap can go on - the air coming out will be very roughly 24 deg C. E.g. 2: current temp 38, dew point 28, average is 33. Don't turn on (otherwise you'll be pumping 30+ deg air into the house) - close up the house and do whatever you can to keep heat out.
  • If the average comes out over 26 deg C, you will feel very uncomfortable. Don't turn it on - try to keep the heat out of the house through closing blinds/doors/etc. or if you have a split, this is the time to use it.
  • Buy vent covers for the evap vents to both stop heat coming in when the average ends up over 26 and to keep heat in during winter.
  • Even if you've had a hot day and haven't used the evap/only used your split, your house will have absorbed that heat and will "release it" into your house overnight/next few days until it gets back to normal. To help get rid of the heat stored in this thermal mass of your house, as soon as that average drops under 26 (or ideally under 24), open up the house/turn off the split and turn on the evap. Evaps get rid of heat faster due to the constant air pumping out. So even in heat waves in a house with no split, the house will be better off using the evap overnight until the 24 average is hit, then closing up until the 24 average comes back. Because by using that evap when it was cooler, the heat has been "flushed out" so the house can a absorb more heat again before you feel the temperature rise.
  • If that average ends up under 18, you'll feel cold. And chances are the outside air temp is under 24. So either put it on fan or turn it off.
  • Use lower fan speeds when the average is closer to 18 and higher fan speeds when the average is closer to 24.
  • Windows/doors needs to be open for the evap to work properly. About 1/4-1/3 open is good - more open for higher fan speeds.
  • Windows/doors need to be closed for refrigerated/split to work properly.

  If you use the evap as much as possible how I've described above and vent covers, you'll end up with lower power bills as you won't need your split to keep "catching up". As the more heat the split needs to remove from the air, more power is required. Oh and see if you can get away using 25 or 26 as the temp on your split - that also saves money as it doesn't need to remove as much heat.

  • 

    [Deactivated] on 02/03/2019 - 15:10

    Thanks for good write up. Sounds like I need a backup split system installed somewhere, on top of evaps.

    • 

      savage bargain on 03/03/2019 - 03:20

      No problem!

      It definitely does help for the heat waves so it's a bit more comfortable. Plus you can also use it as a heater in winter - reverse cycle is pretty efficient. But you'll want to get the vent covers as when the evap is off, it's literally just holes to your roof. I glued a bit of foam into mine too for extra insulation. (Just polystyrene - it's good enough for that purpose).

    • 

      Darkscythe on 04/03/2019 - 11:31

      +1

      That's the same setup we have. New evap for the entire house which is fine for 95% of the time in Melbourne, plus a split system in the lounge for humid days (probably turned on 4-5 times a year).

• 

  Chris Topher on 02/03/2019 - 18:03

  I saw a Melbourne house burn down from a nearby bushfire.

  The 'straw' in the rooftop evaporative cooler caught fire from the super heated air and from there into the roof space…

  It was the only house in the area that suffered this fate. If the 'straw' hadn't ignited all would have been well.

  Evaporative coolers simply don't work in high humidity, refrig coolers work in all conditions especially reverse cycle models. They are very efficient

  'nuff said? O^O

  • 

    cyvirus on 02/03/2019 - 21:47

    +1

    Lol.. whatever you say,mate 🤣

    • 

      Chris Topher on 03/03/2019 - 21:02

      And what part of it is so funny?

      1)I saw a Melbourne house burn down from a nearby bushfire.

      2) The 'straw' in the rooftop evaporative cooler caught fire from the super heated air

      3) the only house in the area that suffered this fate. If the 'straw' hadn't ignited

      4) The efficiency of reverse cycle refrigerated against ineffective evaporative cooler.

  • 

    Quantumcat on 02/03/2019 - 23:39

    +1

    However efficient split cycles are they're going to cost way more to run than evaporative

    • 

      Chris Topher on 03/03/2019 - 21:03

      -1

      which proves beyond doubt that you get what you pay for.

      • 

        Quantumcat on 03/03/2019 - 21:14

        +1

        Yes, that it is worth spending a little more on a good evaporative system to reap the benefits long into the future.

        How can you call split cycles more efficient when they use way more electricity and therefore cost way more to run? By definition that's way less efficient

        • 

          Chris Topher on 04/03/2019 - 14:21

          -1

          @Quantumcat: In your opinion. Mine differs

          • 

            Quantumcat on 04/03/2019 - 14:46

            +1

            @Chris Topher: Maths isn't a matter of opinion

            Unless you have a different definition of efficiency besides cost or kilowatts…. I would grant it if it were amount of time taken to lower the temperature by a degree, then split cycle will probably win

• 

  Masterpupil on 04/03/2019 - 09:19

  +1

  We are going to put solar on the house and switch to ducted refrigerated. The weather in Victoria has become increasingly humid and very hot, and the evap just does not deal with it.

  I think it depends on your body type, in the sense that my wife is not bothered by the evap just being cool, whereas I am one of those people that is always warm and sweats.

  The evap is super cheap to run, but a our relatives have refrigerated and their homes a just so comfortable during summer.

  • 

    [Deactivated] on 04/03/2019 - 10:25

    Have you got any quotes? We do have solar but it's only 5kwh system whereas ducted refrigerator cooler is like 10kwh for starter. Then There's cost of replacing all the joints for smaller and insulated one as it has much lower airflow.
    So wonder what's the quote people gets for this sort of things.

    The other thing you might wanna know is the grid operator put us on TOU metre for solar connection so that it costs a lot for using grid supplied power during the peak hour.

    • 

      Masterpupil on 04/03/2019 - 22:32

      No we haven't sought quotes yet. No hurry at this point as summer is behind us.
      I'm considering a full system or possibly a number of splits in key rooms depending on cost.
      I'm not sure about the solar but we can always add panels later.