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Aircon Inverter or not?

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  1. #1
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    Default Aircon Inverter or not?

    Would anyone here be involved in the (domestic) air-con industry ?
    We are getting a ducted air-con system but have some queries as to the best system and could do with some independant and knowledgable advice instead of some fresh faced salesman spin.
    Our main "dunno" is if to go inverter or non inverter system ?

  2. #2
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    I am not in the industry, my two cent worth, I don't understand with the invention of inverter technolgy why you would consider anything else they are more efficnt therefore less expensive to run etc.etc.

  3. #3
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    I'm not either but I too would not consider anything but an inverter - like variable speed in a drill, who on earth would want an old 2 speed only drill now??

    In fact, I believe there is now a new better version of an inverter called an electronically commutated motor - don't know exactly what it is but I believe it has something to do with missing out the inverter altogether and then using some smarts to vary the number of motor windings used to vary motor output I think.

  4. #4
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    If the heat load is accurately calculated, an inverter will save a little bit of money & may provide a less noticeable temperature variation of the air coming out of the evaporator.

    If the heat load is not accurately calculated, an 'old style' system will suffice.

  5. #5
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    Quote Originally Posted by gpkennedy View Post
    Would anyone here be involved in the (domestic) air-con industry ?
    We are getting a ducted air-con system but have some queries as to the best system and could do with some independant and knowledgable advice instead of some fresh faced salesman spin.
    Our main "dunno" is if to go inverter or non inverter system ?
    am not in the industry but did research these things when we bought ducted refrig A/C.

    old-style is a large AC compressor which can have two states -- "on" and "off".
    you often see lights dim/flicker when the compressor kicks in due to the large current inrush. that cycling of on/off may result in it overshooting/undershooting the temperature setpoint and may result in higher energy use as a result.
    may actually consume more power depending on how you are metered as power factor will not be close to 1.

    an inverter is basically where the compressor is DC powered rather than AC. as such there is no "current inrush" on startup but rather a gradual power 'ramp' and the system can run the compressor at different % power levels depending on requirements.
    e.g. turn system on and there is a large differential between temperature setpoint and ambient temperature and it can run the compressor at 110% for 5-10 minutes for rapid cool down, and as temperature gets closer to the setpoint ramps down the compressor to 80%, 66%, 50% etc. directly results in less power consumed.
    due to AC-DC conversion ("inverter"), PF remains close to unity.

    an alternative to an inverter is a digital 'scroll' compressor where the scroll is unloaded/loaded to achieve basically the same kind of thing as an inverter.
    i've heard they are good technology too.

    i agree with what elkangorito says, a correctly sized system should mean that either of the latter two are more efficient / cost less to run than a fixed speed compressor model.

    personally, i went with inverter by the people that created it. love it.
    i did spend a lot of time doing the calculations on system sizing though.
    plenty of tools on the net that show you how to do that - basically based on area and size of external walls, ceiling, floors, what they are, whether they are insulated and size of windows, type, shaded, etc.

  6. #6
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    Have a look at the Actron ESP as a good digital scroll compressor unit, there are many other advantages to Actron as well.

    I installed one 2 years ago as a replacement to an old Carrier Nova R22 system but I can't give an accurate comparison to running cost between the two because we increased the size of the house at about the same time and energy costs have significantly increased since we upgraded.

    That being said, it is quite expensive to run if it is used as we used the old one but we have adjusted how we use it and it's not too bad at all.

    If you search "Actron" on this forum you will find the stuff I wrote about it at the time and that may help you decide what brand and type to buy.

    For the record mine has been flawless in the 2 years it has been installed.
    Cheers

    Alan M

  7. #7
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    Go inverter. I would never consider anything else. Non inverters bang in and out of operation. Inverters slowly wind up and slowly wind down.

  8. #8
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    regardless of choice connect it to tariff 33. Half price electricty, for the inconveniece of a maximum 6 hours not available. 6-9 and 6-9.

  9. #9
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    Today I did a little observation and thought I'd share my findings with anyone who is interested.

    Today 26/1/11 was forecast as possibly the hottest day of this Sydney summer so I knew I would be using the AC.

    I know which phase the AC is on so I read the meter just after switching on at 10.45am and again just after switiching it off at 10.45pm. It used 56units (Kw/h) in the 12 hours of operation.

    The outside temperature at switch on was 32C and peaked at 37C, it stayed at 35 most of the day and I switched off at 27C outside.

    The inside temp was set to 25.5C and all zones were on, and we were all pretty comfortable (I was watching the cricket) The unit is a 18kw Actron ESP digital scroll type compressor.

    So by my calculations, 56kwh devided by 12 hours is 4.67kwh average.

    If the unit is running at 100% it would use 18kw per hour so if it only averaged 4.67kw
    I reckon it was operating at just under 26% of capacity on average.

    For such a hot day and for how well it kept the inside temperature so steady, I reckon that is pretty good.

    I intend doing some work to further reduce the heat load on the living space soon so I think it will only get better.
    Cheers

    Alan M

  10. #10
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    Quote Originally Posted by Make it work View Post
    The inside temp was set to 25.5C and all zones were on, and we were all pretty comfortable (I was watching the cricket) The unit is a 18kw Actron ESP digital scroll type compressor.

    So by my calculations, 56kwh devided by 12 hours is 4.67kwh average.

    If the unit is running at 100% it would use 18kw per hour so if it only averaged 4.67kw
    I reckon it was operating at just under 26% of capacity on average.
    nice analysis. but sadly, not correct.

    your Actron 18KW unit provides 18KW of COOLING CAPACITY. that does not mean it consumes 18KWh of power/hour to do so.
    somewhere it'll state what its "EER" is. typically this is better than 3.

    per http://www.actronair.com.au/UserFile...ies_16ppv2.pdf lets say you have an outdoor unit of SRD175C.
    that has an EER of 3.05. its stated maximum power consumption is 5.90KW.
    (5.9 x 3.05 = 17.99).

    what your tests have shown is that it was using 4.67/5.9 = ~91% of its rated capacity.

    i'd say that was probably closer to running at its real 100% as the 18KW cooling capacity probably relates to an inverter and its ability to run at "110% capacity".

    what the consumption number tells you is that the system worked hard ALL DAY to try to reach the setpoint of what you had set on the controller. and probably never got there. so never cycled down its power load.
    what did you set your setpoint to? on a warm day like that, i have found that its still comfortable in the house with setpoint set at 27C. i would have expected a correctly-sized unit to be capable of getting to that as its only a 10 degree delta. but a lot of that depends on your house itself...

    note that the EER numbers -- while helpful -- aren't the total picture.
    there are often refrigerant heaters (to stop the oil in the refrigerant line sitting in the compressor buggering it up), energy consumed by zone dampers, energy consumed by the indoor unit (which may be on a different phase power).
    then from an install, different R rating of ducts etc can influence efficiency. likewise how insulated or otherwise your house is, external blinds on windows, etc...

  11. #11
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    Quote Originally Posted by Make it work View Post
    The inside temp was set to 25.5C and all zones were on, .
    Quote Originally Posted by president_ltd View Post

    what the consumption number tells you is that the system worked hard ALL DAY to try to reach the setpoint of what you had set on the controller. and probably never got there. so never cycled down its power load.
    ...
    In a lot of situations A/C units are sized for either living zones or sleeping zones, not all at the same time.


    Guys can you expand a bit about being "on a different phase". I would expect any unit of this size to be 3 phase. Does your meter show energy per phase? or have you multiple meters?

  12. #12
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    Quote Originally Posted by Geoff2005 View Post
    In a lot of situations A/C units are sized for either living zones or sleeping zones, not all at the same time.
    yep. what i have (10KW Daikin inverter, 3.33 EER, 3KW max power consumption) is sized for one zone running (out of 3 total) for our house.
    certainly you can run all 3 zones at once but that may not be effective on a hot day.

    on a hot day with a single zone, its more than effective. we had a 40C day on new years' eve, system pretty much sat on 33% inverter speed (1KWh power consumption) keeping the zone we were in at 27C setpoint.

    Quote Originally Posted by Geoff2005 View Post
    Guys can you expand a bit about being "on a different phase". I would expect any unit of this size to be 3 phase. Does your meter show energy per phase? or have you multiple meters?
    i'm unfamiliar with the Actron system(s) but its forseeable that if the external/internal units are connected to power independently then its possible that the indoor condensor/fan unit is on a different phase to the outdoor compressor.

  13. #13
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    Default Install inverter split system air conditioner

    I am an installer and this is the basic advise I give to my customers.

    I recommend inverter to all my customers, especially for lounge room which are going to be used much more which will bring back the cost savings. Especially if they will be used for heat and cool. It will get used most nights in winter and days if people are home during the days. As for summer, bank on using around 20-40 days per year. In Melbourne, mainly in Feb and March but maybe a dozen other days.

    As for bedrooms, this depends on how much use you will get. ie: if you use for heat and cool and expect to use say 60-100 days in the year ie: Melbourne, then go for the inverter. Cost of inverter for bedroom is an extra $200, savngs in increasing elect bills will get good return on investement and a better machine.
    If you will use for cooling bedrooms in say Melbourne ie: 20 days per year, then inverter is not so important if budget does not permit.

    Note: If you ever have an inverter, you cannot go back to non inverter. The inverter is much more confortable, effortless, quieter, cheaper to run. It like a new car.
    Non inverter is like driving a GEMINI in comparison. People generally forget about the extra $200 or $300 after a couple of months.

    Jim Komps- Air con installer- 0417 209 552

  14. #14
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    If they were both going at 100% then not much difference, but that's not very often - and as said inverter is variable (as is your demand) so has a range of benefits because of that.
    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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