Aircons: To Invert Or Not, That Is The Question..

Air conditioning, fans, and anything related to keeping it cool, such as insulation. This would include any posts generally discussing how to keep it cool, such as which types of blocks are better insulators.... ideal wall thickness for keeping an A/C house cool, etc.

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Aircons: To Invert Or Not, That Is The Question..

Postby Greenside » Fri Jun 03, 2011 7:29 pm

I have decided to install aircon in two rooms: one bedroom of about 47cu m and one room, initially a bedroom but destined to be an office, of 40cu m. For reasons of economy, we use air at night as little as possible - probably a maximum of 35 nights a year and set to 22 degrees or so, although when the smaller room becomes an office the heat of the mainframe (kidding, but I do have a lot of hard drives) it will be needed for much of the hot season to make the room comfortable. The questions are:

    Is it worth the extra outlay for an inverter in terms of power savings - if you've switched to one did you see a noticeable drop in your bills? We can only expect electricity to keep rising and since Pork has gone up more than 20% since Songkran, who knows where we'll all be by this time next year?

    Are they proving at least as reliable as the older models?

    I read about multi units where one outside compressor runs several indoor fan units and as I understand that inverters are more effective when run for long periods of time it sounds like it makes sense to run one to feed two. Anyone researched or bought one?

    Finally - inverter or otherwise: any specific recommendations based on reliability, noise and cost in that order.


I'll post a picture of our project in Chiang Mai when it gets a bit further along.
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby geordie » Fri Jun 03, 2011 10:26 pm

Sounds intriguing but how does an inverter aircon work ??
The latest trend here is inverter generators inverter welders on pesonal experience both have died rapidly not fit for purpose although i have to admit i loved the ease of the welder compared to a normal ark/stick welder it lit up on contact even at low amps and was ok in continuous use WELL :lol: :lol: untill it burnt out the main circuit board :cry: :cry:
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby otis-a » Thu Jun 09, 2011 1:35 pm

mr green
appreciate u comments on paint for roof, seems u have some experience there or did lots o research, so i good to know such paints locally available.
A/C
4sure avoid samsu_k
one unit alreadry started surging type noises
what is that?
Unsteady air flow
without investigation i suspect it is caused by inverter malfunction on blower motor
when i get busy will slap amp meter across leads to see if current draw varies in sync to the air flow
inverter tech' ummm?
I suspect is to do things like soft start and varing motor speed to meet demand? Such programs are commonplace for inverter driven dc motors. Such dc fractional horsepower motors are common for conveyers, pumps, and manufacturing equipment to overcome inertia loads what would otherwise make for large current inrush and wasted energy. For large building ac units the trend is to use alternating current variable frequency drives to minimize power demand- in either case powering a centrifugal or axial gas machine requires adequate speed (rpm) to avoid the 'surge' effect.
For my samsung unit something is amiss but credit them with attempting to reduce power by providing variable air flow. Which for my units amounts to three modes:
turbo; cooling, drying, with dry being slowest speed. Also there is a fan only mode that cuts out compressor

hope this helps
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby John » Thu Dec 01, 2011 5:52 pm

A late reply but it might help someone.

Sellers of inverter AC units in Thailand make the most ridiculous claims for energy saving and are most of the time complete crap.
I advise anyone thinking of purchasing inverter AC units to do some research and then consider if they are right for your application.
Inverter AC units must be sized correctly or the compressor efficiency may fall below that of a conventional unit. The amount of time the AC unit is used and its location are also important factors.
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby otis-a » Thu Dec 01, 2011 6:21 pm

hi john
would it be an oversimplification to surmize than u consider soft start or inverter ac's to just save when compressor starts and if compressor runs most always there are little saving or worse if it runs ''off peak efficiency''?j
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby John » Sat Dec 03, 2011 5:37 am

otis-a wrote:hi john
would it be an oversimplification to surmize than u consider soft start or inverter ac's to just save when compressor starts and if compressor runs most always there are little saving or worse if it runs ''off peak efficiency''?j


Correct.

If a compressor is required to run almost constantly to meet demand then a conventional AC would be more efficient. AC compressors are most efficient when at full load. Inverter AC’s are effective when partial compressor load is frequent. This is why it’s important to size and consider the application carefully.
You could simplify this by saying, if your outside unit is constantly switching on and off to maintain your temperature setting then an inverter unit will be more efficient.
Inverter AC’s soft start (motor ramps up to speed slowly) which means less stress on mechanical components. They also control the running speed of the compressor depending on load required by a microprocessor inside the indoor unit.
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby geordie » Sat Dec 03, 2011 6:09 am

John wrote:
otis-a wrote:hi john
would it be an oversimplification to surmize than u consider soft start or inverter ac's to just save when compressor starts and if compressor runs most always there are little saving or worse if it runs ''off peak efficiency''?j


Correct.

If a compressor is required to run almost constantly to meet demand then a conventional AC would be more efficient. AC compressors are most efficient when at full load. Inverter AC’s are effective when partial compressor load is frequent. This is why it’s important to size and consider the application carefully.
You could simplify this by saying, if your outside unit is constantly switching on and off to maintain your temperature setting then an inverter unit will be more efficient.
Inverter AC’s soft start (motor ramps up to speed slowly) which means less stress on mechanical components. They also control the running speed of the compressor depending on load required by a microprocessor inside the indoor unit.


Sorry to quote the whole of this john but given that the difference seems to be a soft start compressor ?? is the extra electronincs worth the risk ;Are the savings over a conventional system going to show a return or is it another gadget to go wrong ? do the two different systems come out at about the same running costs ; and the benifit is that you are not giving the input (house supply) a high demand and volt drop problems IE: lights dipping when the compressor kicks in ! Would you achieve a cost saving by over specking the AC in the first place to reduce the running time/on of cycles
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby Roger Ramjet » Sat Dec 03, 2011 8:15 am

If you are running an air conditioner constantly for up to 8 hours a day and the compressor cuts in and out frequently there would be large savings in the long term if you used an inverter air conditioner. The saving would come from less maintenance, less wear and less power units consumed. If you were using a central air compressor and had it service the whole house, the savings would be slightly larger.
I think everyone is right about what they have posted, the question is will the savings be more than the initial large outlay for the inverter air conditioner? The answer would have to be, eventually yes, unless you were using the air conditioner constantly, then the savings would be seen quickly.
Here's an interesting article about both with a simple explanation; http://singapore-aircon-inverter.blogspot.com/
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby geordie » Sat Dec 03, 2011 10:07 am

Interesting article but all the indications are that the inverter compresor is going to be running longer hours ! all be it at a reduced speed , This being so how do the claims of less maintainance pan out We have soft start technology on angle grinders ect with no huge jump in price so getting a soft start compressor motor should not be that big a deal and should not involve a huge price hike ! given the technology is so widely available add to that switching off slightly later and on slightly later so more of a gap between cycles surely you could acheive the same savings or better still insulate the room to death so that when it is cooled it retains it (my intention is to do that)
Years ago you could buy a plug for the fridge to make it more economical to run all it did was time out the fridge allowing it to stay switched off longer taking the control away from the thermostat the damm thing actually worked it stopped the fridge switching itself on off evry few minuites at a cost of about £4 -200bht You could add a time clock to the compressor and acheive the same saving setting the pattern of the clock to suit your needs IE; on for an hour untill you fall asleep then off for half an hour at a time dependant on how well the room retains heat so your 8 hours becomes 4.5 being asleep you should hardly notice the difference :roll:
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby Roger Ramjet » Sat Dec 03, 2011 10:24 am

geordie,
Now if we were smart we would run tests on both types and not believe the pundits. Now I'm willing to be part of this experiment as I have two totally different types of air conditioners, one an Amena with no inverter and one a new Mitsubishi with inverter... the problem is the rooms are not the same size, and on top of that there is ceiling insulation in one room and not another. I do have a solution though. When I move to the new house I am willing to buy a new inverter type air conditioner and normal one for two rooms the same size, with the same insulation... but, and here's the catch I would need someone independent to record the data and check all the readings. So, when you sell your house and arrive in Bangkok I will arrange for you to do a flying visit to the house for a few hours, just so you don't become too complacent. How's that?
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby geordie » Sat Dec 03, 2011 10:45 am

Rodger i am up for it not only that i have a plug in bit of kit best described as a mini electric meter which you can set a rate and it will tell you how much=over a period of time and an infra red thermometer very acurate so you can base the fairness of the cooling on wall temperature rather than air temperature because as soon as you enter a room you change the air temperature so better to take ambient off a wall although i supose a couple of weather statuions would read remotely and cheap to buy here so you are on we will see if we can balance out the two for cost and comfort
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby John » Sat Dec 03, 2011 4:45 pm

otis-a
Sorry to quote the whole of this john but given that the difference seems to be a soft start compressor ?? is the extra electronincs worth the risk ;Are the savings over a conventional system going to show a return or is it another gadget to go wrong ?


Under the right conditions there is no doubt that inverter AC’s can save a considerable amount of energy. With this saving comes additional risk from increased purchase cost and higher repair bills. If nothing goes wrong out of the warranty period and during the cost recovery time then you win. Like my old boss used to say, if you want to keep your life simple and stress free avoid technology.

Geordie
you could acheive the same savings or better still insulate the room to death so that when it is cooled it retains it (my intention is to do that)


I could not agree more. What amazes me and especially in Thailand is how little time is spent on energy saving when a house is being constructed. The items that are going to dramatically effect energy bills only get attention after the walls have been painted. South facing bedrooms, huge leaky windows, thin cement block walls that act as storage heaters and roof spaces where temperatures reach 45 degC then radiate through the ceiling.

Geordie
We have soft start technology on angle grinders ect with no huge jump in price so getting a soft start compressor motor should not be that big a deal and should not involve a huge price hike


Personally I think inverter AC’s are going through that period where manufacturers can maximise profit from what the buyer sees as new technology. In the future all AC compressors will be inverter controlled and the price will drop. The soft start electronics of an A/C are a little more complicated than those used in electric drills which just use simple electronics to clip the ac supply. Inverters actually convert the ac supply to dc then back to ac with frequency control.

Geordie
Now if we were smart we would run tests on both types and not believe the pundits.


The simple test result below (from AC Company in Australia) will suggest what the result might be.


Inverter and non inverter units set at 26 deg C

Non Inverter
AC is started - compressor runs for 5 minutes then cuts off at 25.7 deg C
Temperature rises to 27.2 deg compressor cuts in
Temperature falls to 25.6 deg compressor cuts out
Temperature rises to 27.3 deg compressor cuts in

Inverter
AC is started - compressor runs full speed for 3 minutes then begins to modulate at 25.5 deg and continues to modulate holding a temperature between 25.9 and 26.2

The inverter controlled compressor is using less energy because its output matches demand and does not have to recover from a large temperature overshoot. A PID controller located in the inside unit is constantly updating its load demand by looking at the time it takes for temperature to rise fall and pass the set point.
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby geordie » Sat Dec 03, 2011 5:28 pm

so its set to recharge /cycle at a rise of 2 degrees in temperature but the pump if i understand is on? tickover between cycles?
It really does sound like they will all go down that road and i agree introducing more technology will probably result in more costs long term presumably the pump motor is about to!if not already getting smaller as its not required to deliver instantly and yet it will be expected to run longer working harder over it,s life the electronics side of it will be working harder the only thing you have saved really is the huge current demand of a normal compressor kicking in i will be taking the challenge Rodger has thrown down :roll: just to see if the same sort of saving can be reached i actually think i can do better But Rodger has built with aac blocks that will help one thing that gets missed regularly is the window so hopefully we will also rig a screen on one of the rooms to show how a simple thing like that can again show a saving especially on a bedroom i have roll out blinds that prevent sunlight coming in and that alone drops the temperature 3/4 degrees so with a bit of thought the old technology will win especially i think on reliability Only time will tell that one but the most dificult thing is beleiving the claims by the manufacturer And they are the people making the claims Try and get your well pump to produce the claimed output ? and if it don,t you will recieve the fob off= it will do that only under factory conditions same with a 6 kva generator
producing just under 5 kva because on paper the engine at 3500rpm will be able to turn the head fast enough to produce - 6kva Unfortunately as you all load/draw power the engine struggles so it will give you under 5kva Car manufacturers petrol consumption figures they never take them to spain and drive them up and down mountains with the aircon switched on and tell you the real damage ? they drive them straight and level with no trafic and then claim how fantastic they are Sorry i am a cynic but like most people have spent the money bought the product only to find out it will not do what it says on the box But i still have an open mind :lol: :lol:
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby otis-a » Sat Dec 03, 2011 8:56 pm

hi john,
thanks for the input but would it not present a clearer picture if the test also compared kwhr for the test cycles?
Am aware the inverter stuff is getting more popular. Seems many large buildings in usa have switch over to phase shifting aka vfd, in last 20yrs.
In a former life, the EE's refused to budge off conventional power. They replied that the additional cost for inverter coolers and rewire motors just could not close the savings gap- talking minimum of 5kw motors mind you.
The big boys could be real buggers to get going as were limits on starts allowed per hour. (winding cool down to protect winding insuation) Then there were issues on poor engineering. (all parties were found guilty- EE's were off in estimating grid dip & esp boys needed less dip than originally claimed to minimize burnouts) in some sectors, starting a big boy would trip out the esp's downhole pumps by sucking down line volts too much. Were plenty of issues, but the capx board always found better expendatures than going after vfd inverter technology. That is just my limited & sheltered industrial experience with the stuff.
So i still like to see some power measurement claims to verify, simular to Geo's idea. There are just too many times people make fine claims but when it gets applied all sorts of stuff comes out.
I totally agree, current inrush and voltage drop are really serious issues for any compressor motor.
What about using a smaller conventional baseload unit operating at max efficiency coupled with a phase shift unit to pull swings- is that a better alternative?
Also i wonder, have the helical screw compressors a flat efficieny curve vs rpm or do they act simular to a centifigual compressor with a narrow operating band for efficiency? What i recall is a vector diagram of gas velocity to machinery speed and as operation goes away from maximum momentum transfer, efficiency drops drastically as mentioned by another reader. The other alternative is the old piston/cylinder compressor who just has essentially valve losses to overcome. Is it correct most home vfd refer units use a helical compressor?
Thanks for the update.
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Re: Aircons: To Invert Or Not, That Is The Question..

Postby Roger Ramjet » Sat Dec 03, 2011 10:16 pm

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