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  1. #16
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    Quote Originally Posted by ian View Post
    the answer is simple.

    For almost all of Australia, it never gets cold enough for double glazing to make a difference. And besides, Australian houses are typically designed to "breathe" and to utilise cross flow vetillation which requires the windows to be open.

    Residential air con is something that has only become a "thing" in the past 20 or so years.
    Ian, Australian houses are for energy purposes leaky tents. We may not need better insulation for cold weather but we do for hot weather.
    CHRIS

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  3. #17
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    If you look at my energy use diagram you can see how much two splits, one is a 7.5kw unit uses up until the ducted was turned on at about 11:00am. As I write this we are producing 4.98, exporting 2kw and using the rest to run the house which includes both splits. There is no guesswork or calculations required as this is live monitoring. The two splits won't keep up if the temp goes north of the high twenties and the experts told me they would and when I questioned them I was basically told that the new inverters had changed things, yeah, right. I doubt they would keep the house temp under 30 degrees on days like we have just had. This house is fully insulated in all walls and ceilings and we have installed heavy rubber backed curtains to insulate the windows and anyone who has been in the house will tell you that the area we live in is not big by any means. With the ducted running it was 21 inside when it was 39 in my workshop yesterday. It might chew power but it works really well. We installed the splits to overcome another problem not to save power and that story is too long to tell here.
    CHRIS

  4. #18
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    Thank you for all the info.
    Good. I will save some money for the time being and just buy a fan for the living room.
    Our house is ducted for heating. The heating unit is 10 or more y.o. It is a good unit, but noisy.
    The AC would have been a ducted unit, not splits.
    We'll see when we decide to change the heating unit, maybe go with a heating/AC combo.

    As far as I remember, summertime, houses in the hot parts of Europe (Southern France, Italy, Spain...) are much more livable than houses here.

  5. #19
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    Quote Originally Posted by Chris Parks View Post
    Ian, Australian houses are for energy purposes leaky tents. We may not need better insulation for cold weather but we do for hot weather.
    funny

    our "planning betters" think that natural ventilation, especially cross flow ventilation is the way to go.
    https://www.planning.nsw.gov.au/-/me...-07.ashx?la=en
    "The area of unobstructed window openings should be equal to at least 5% of the floor area served.
    "Doors and openable windows maximise natural ventilation opportunities by using the following design solutions:

    • adjustable windows with large effective openable areas.
    • a variety of window types that provide safety and flexibility such as awnings and louvres
    • windows which the occupants can reconfigure to funnel breezes into the apartment such as vertical louvres, casement windows and externally opening doors."


    so even with double glazing, we're expected to keep the windows open most of the day.



    knowing who some of the "planning betters" are, I think very few of them live west of Bondi Junction.
    regards from Alberta, Canada

    ian

  6. #20
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    Our life has changed in the last few decades with regards to heating and cooling because before that it was a very expensive exercise to install AC in a family home but just like solar panels the cost has plummeted and a lot of the previous thinking is not valid. I saw an episode of This Old House showing air exchangers for sealed houses to admit air in the winter but I bet hardly anyone in Oz would know what it was if it bit them.
    CHRIS

  7. #21
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    Chris
    I don't want to appear to disagree with you.
    Almost 30 years ago, what was then Prospect Electricity, was subsidising the purchase of home air conditioners on the basis that it increased electricity consumption -- which is a good thing if you're an electricity retailer. And of course, homes in Western Sydney are prime candidates for air conditioning.

    More I was referencing current doctrine from the NSW bureaucracy that reinforces your "leaky tent" analogy.
    regards from Alberta, Canada

    ian

  8. #22
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    Quote Originally Posted by ian View Post
    Chris
    I don't want to appear to disagree with you.
    Almost 30 years ago, what was then Prospect Electricity, was subsidising the purchase of home air conditioners on the basis that it increased electricity consumption -- which is a good thing if you're an electricity retailer. And of course, homes in Western Sydney are prime candidates for air conditioning.

    More I was referencing current doctrine from the NSW bureaucracy that reinforces your "leaky tent" analogy.

    Agreed, it can be hard to say stuff in writing but I was agreeing with you about the out of date ideas that the govt still hold onto when things have changed. Energy usage can't be changed while we live in the same style of house we always have done.
    CHRIS

  9. #23
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    Quote Originally Posted by Chris Parks View Post
    Agreed, it can be hard to say stuff in writing but I was agreeing with you about the out of date ideas that the govt still hold onto when things have changed. Energy usage can't be changed while we live in the same style of house we always have done.
    it gets worse.
    Those "out of date ideas" were published less than 10 years ago (perhaps as few as 7) as representing the "desired future" for apartment design to obviate the need for air conditioning and thus represent "cutting edge" sustainability.

    I remember seeing them when they were first published -- given where I was working at the time it may have been a prepublication draft I was given to review.
    I remember at the time thinking that the people behind the "guidelines" were off the planet -- hence the comment that they must all live east of Bondi Junction.

    I think it's less a matter of being out of date, more one of ignorance.

    As a former work acquaintance put it -- "The [Sydney] Fish Markets is as far west as I want to go even on holidays. I'm sure that the people living in the Western [Sydney] Suburbs are nice people, I just don't want to go there."
    regards from Alberta, Canada

    ian

  10. #24
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    There is only one proper way to answer your question, calculate your needs then work backwards to discover what is required.

    You have given us temperature ranges and some other scope of use data. Unfortunately while that indicates what is required it doesn't give the whole picture. You would probably need to log temps in and outside over a period of time and decide just how many hours and how many degrees and the volume of the rooms to calculate air con requirements.

    21 in 40 degrees requires either tremendously efficient insulation, like a cool room, or a massively overspec'd system. I achieved this in my little teardrop camper and it was glorious, but it was the van park's power a tiny volume and massive styrofoam insulation.

    So from what you have told us lets assume you want to cool 100 sqm of well insulated house and knock 7C off temps. Most guides suggest 140 kW per sqm but I'd go up from that, maybe 200. That sounds like a lot but bigger units aren't that much dearer and given they are all inverters these days they won't use more power than they need.

    Incidentally I only ever buy panasonic. I know people who have had problems with every other brand, including daikin. I don't know anyone who has had an issue with a panasonic. The one running in my bedroom right now I installed in about 2000 and it has been saving my life every summer since. The only problem I have had was it stopped when a python climbed into it and inconsiderately died and got stuck in the fan.

    So you have 20kW of units. Their duty cycle is about 1/3 and power consumption is about 2/3 to 3/4 of rated power, so they will pull about 5kW/hr. You get about 4 hours effective production out of solar across most of australia so if you are using them for 8 hours 2 days a week (80kW/h) you will need about 3kW of panels assuming perfect storage (4*4*7. It's actually 2.8). I'd probably want 4kW but whatever. From there you have to size your batteries.

    Now you'd be crazy to size a solar system that way. What I'd be doing is sizing it to take the bulk of the load and adding an auto start generator. That would kick in when the load is high and the saving on the solar would pay to buy and run the genset for years and years. In fact if it was ONLY the air con I'd lose solar altogether and install a gas or diesel generator to do the whole shebang. Panels are cheap but the battery you'd need would be huge and expensive.

    Incidentally solar is not eco. Most enviro stuff isn't. Enviromentalism is a religion and only coopts science when it suits them. Photo voltaic panels need more energy to make them than they ever produce. You are exporting the pollution not negating it.

    Anyway hope that helps.
    I'm just a startled bunny in the headlights of life. L.J. Young.
    We live in a free country. We have freedom of choice. You can choose to agree with me, or you can choose to be wrong.
    Wait! No one told you your government was a sitcom?

  11. #25
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    Quote Originally Posted by damian View Post
    Incidentally solar is not eco. Most enviro stuff isn't. Enviromentalism is a religion and only coopts science when it suits them. Photo voltaic panels need more energy to make them than they ever produce. You are exporting the pollution not negating it.
    That was only correct up to about 2010. Since then photocells are making more than they use and by 2020 all the solar electricity production on the planet will have paid back all the non-renewable electricity that photo cells have ever used in their manufacture.

    See https://pubs.acs.org/doi/abs/10.1021/es3038824
    and
    https://phys.org/news/2016-12-solar-...ergy-debt.html

  12. #26
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    As someone else mentioned some caravan owners have done it:
    https://caravanersforum.com/viewtopic.php?t=79305
    but caravans are smaller. Interesting info anyway.

  13. #27
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    Tesla firewall wont work with a stand alone system. It's designed to work into the grid.

  14. #28
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    My understanding of the Tesla firewall battery was that it was an emergency back up system that is short term rated. The enigmatic Mr Musk just very slightly skipped over that when introducing the system. It is there to tide you over until normal supply can be restored. I don't know the details of how long it can last, but from time immemorial power stations have had a similar system in place, albeit with a different level of technology. Hospitals have an emergency back up sytem too: It's called a Diesel generator.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  15. #29
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    Quote Originally Posted by Bushmiller View Post
    My understanding of the Tesla firewall battery was that it was an emergency back up system that is short term rated. The enigmatic Mr Musk just very slightly skipped over that when introducing the system. It is there to tide you over until normal supply can be restored. I don't know the details of how long it can last, but from time immemorial power stations have had a similar system in place, albeit with a different level of technology. Hospitals have an emergency back up sytem too: It's called a Diesel generator.

    Regards
    Paul
    A Tesla battery has fairly low limits of discharge or current draw...

    Telsa's Powerwall 2, for example, has a continuous output capacity of 5kW (higher rates possible for short periods) and a storage capacity of 13.2kWh (at the beginning of its warrantied life). Tesla's Powerwall is a 'power battery', able to instantaneously release stored energy at a relatively high rate.Jun 15, 2018

    So run at maximum and allowing for the fact that it cannot be discharged entirely it will power a house for about two hours.

    CHRIS

  16. #30
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    Chris

    That is pretty much as I surmised, but thanks for supplying the detail.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

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