Evaporative Vs Refrigerated Air Conditioning?

Hi all,

Looking at getting ducted air conditioning installed.

Living in Adelaide in an old bungalow house with double brick walls.

Mostly want it for heating as the house is freezing in the cooler months. It also does get hot after a few consecutive days of heat, so cooling is important too, but main priority is heating the house.

Any tips, recommendations etc are appreciated :)

Comments

  •  

    how much space under your flooring?

    We had enough to fit ducted gas heating, it was very good. Mid 60's housing trust built house (brick veneer).

    We already had an evaporative system installed a few years earlier so it made sense to install separate heat only as oppose to heat/cool.

    it would likely be cheaper to install ducted reverse cycle as opposed to two separate systems though. running costs are another thing though???

    Adelaide also seems to be getting more humidity in summer which sucks for evap.

    •  

      I have no idea haha! But yes it would be cheaper and more straightforward to just get the one system installed

    •  

      Evaporative cooling is just useless. Either get proper air con/split cycle or don’t bother.

      Do you not have existing heating ?

      • +2 votes

        It isn't useless, it's ineffective if RH is above 50.

        RH is usaully below 50 in Adelaide.

  • +2 votes

    Refrigerated Air Conditioning (reverse cycle)! all the way!
    If don't want to take my word for it, just google it https://www.google.com.au/search?q=issues+with+Evaporative

  • +3 votes

    Mostly want it for heating as the house is freezing in the cooler months

    Then Evaporative cooling won't help you with that.

  • +3 votes

    RC, and install solar panels to help keep running costs in hand.

    •  

      Thanks. Isn't a RC just a single unit to heat/cool a single room?

      •  

        Yes

      •  

        You can have a whole house ducted system, running reverse cycle.
        But I would recommend getting two or three single room devices in preference. Usually cheaper to buy and install, and if something breaks, cheaper to repair/replace. And easy to just use the one(s) you need at any time, and have them set to individual preference.

        The way airconditioners work is to use a compressor to change the state of a refrigerant liquid between gas and liquid.
        When the liquid evaporates to gas, it gets cold (like the outside of a BBQ cylinder running flat out), and vice versa.
        This pumps the warmth out of the air to the cooling fins outside. Run it in reverse and it pumps the warmth into the house.

        Most importantly, if you use it for heating, is that we can make compressors so efficient that they can pump more warmth per kilowatt hour of energy than you would get if you just used the power for heating directly (in a bar or column heater, say). This is the coefficient of performance, and some can produce 5 times or more heat from each kilowatt hour. It is this that makes them the cheapest heating to use if you can get reasonably priced electricity (hence my suggestion to install solar too, as SA power prices are high).

  •  

    Another vote for RC, ducted is expensive to run since you're heating a large area. If you already had evaporative cooling installed then I'd say an individual gas heater but if you don't then it is probably too expensive to install. Evaporative cooling is really inexpensive to run.

    •  

      I'm a little confused haha!

      So RC is a single unit in a single room?

      •  

        Refrigerated cooling is ducted with zones. Zones will mean you might not be able to let it operate in one room only (i.e. has to be all bedrooms or first floor only or ground floor only, etc.)

        Single unit in a single room sounds like split system for me though that's not what you want.

        •  

          What makes you think it isn't what he wants? It's cooling and heating in one.

        •  

          @Quantumcat: OP mentioned ducted airconditioning that's why. But then open to suggestions so why not?

      •  

        Yes. It isn't too expensive to install, mildly expensive on the electricity to run (not as much as ducted gas). As a poster above said, if you also get solar panels then the expensiveness of the electricity won't be a problem. Unless you have a large house or have two floors a single unit is fine. You can always have a column heater for example in the bedroom that's the furthest away.

        •  

          Ok thanks I hadn't really though of this as an option as I just assumed it wouldn't be adequate

  •  

    Have you seen the price of electricity in Adelaide. I would only consider gas central heating.

    Make sure you've at the very least got some ceiling fans and consider installing at least one split system unit for cooling. It can also heat but as it uses electricity can be quite expensive compared to gas which is much cheaper.

    • +1 vote

      Gas is still cheaper per heat unit, but if you get an RC system with a coefficient of performance over 3 or so (and 5 or even 7 is achievable) then RC AC is cheaper , even considering SA 35c/kWh power prices.

      •  

        Gas costs about 1.75c/MJ. A kWh is equivalent to 3.6MJ which makes gas about 6.3c/kWh.

        At a COP of 3.5 that would make electricity costing 35c/kWh about 10c/kWh of useful heat output.

        So…in my opinion gas is much cheaper.

        • +1 vote

          Where are you getting gas for 1.75c/Mj these days? Sign me up!
          A quick look at AGL in postcode 5000 shows 3.85c/MJ. (ouch!)
          Also painful is the electricity prices at 41c/kWh. Both prices are inc GST so might look a little higher than what is on a bill. Note also there can be discounts for on time payment, but these tend to favour electricity a bit too.

          As you point out, a kilowatt/hour is 3.6Mj. Or 13.86c per kWh per kWh for gas. So a 3.5 coefficient of power RC AC system will be cheaper up to 48.51c/kWh. If you can get a better COP, it is imporved.

          A $1000 Fujitsu like this model FUJITSU - astg12kmca / aotg12kmca (4.56 COP):
          https://www.harveynorman.com.au/fujitsu-3-5kw-reverse-cycle-...

          Uses 0.81kW to produce 3.7kW of heating (source http://www.energyrating.gov.au/calculator)
          Or 33.21c per hour to run. Equivalent heat from gas would cost (3.73.63.85) = 51.28c.

          So the difference is quite substantially in favour of heating with RC AC.
          You get the cooling in summer too.

          And if you can avoid gas altogether, you can save the standing charge of $277p.a.

        •  

          @mskeggs:

          Origin Energy. I'm not using the first more expensive rate which would just cover hot water and cooking. I'm using the second rate over winter.

        •  

          @mysterytal:
          That sure shows the benefits of shopping around. My rate in NSW on Origin has a lowest point of 2.1c, with most of my usage falling into 2.4c.
          I just changed gas suppliers because of this thread, and I reckon I will save about 10%, win!

          As for electricity vs gas, calculating it backwards, with the example aircon and 41c/kWh electricity, the aircon is cheaper if gas costs more than 2.5c/MJ.

          So for OP, if they have other gas appliances and go on the Origin rate you have and have no solar panels, gas would be cheaper. If they have no other gas appliances, RC aircon would probably be cheaper (unless they run it flat out).

      •  

        Maybe I can get ducted gas heating and just forget cooling for now

  •  

    I'm building a new home and after researching extensively I have decided that RC is the way to go. Evaporative cooling can actually be harmful for your house.

    I live in Melbourne and I have been in homes with Evaporative cooling and I find it almost useless. In summers, you have to have it running all the time and leave the windows/doors open for it to have any kind of effect and it leaves a kind of damp and icky feeling if the house is not properly ventilated when it is running (and Melbourne is already quite humid as it is). Expect an increase in your water bill. I find it provides minor relief when temperatures are around 28-34 degrees but anything higher and its completely useless.

    RC can handle both heating and cooling. It consumes a lot more power when compared to Evap but at least it serves its intended purpose and it does it well. I plan to offset the running costs by having solar panels installed.

    •  

      Thanks!
      How many separate RC units will you be getting?

      •  

        Just the one Reverse Cycle ducted system for the whole house (Actron or maybe Mitsubishi) with about 4 zones.

        •  

          Also, I'm more biased towards Reverse cycle systems because there is no dependency on Gas. I hate the idea of using gas for anything in the house and my new home wont be having it for any purpose. Makes more sense for me since I plan on installing a solar panel system anyways.

  •  

    I was on the 'evaporative is garbage' bandwagon, but after trying it at a friends, its a godsend overnight. You can set to low, and actually get to sleep, while with AC units they suck moisture out of the air so you wake up with a dry throat.