The Home Air-Conditioner Thread

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Nereus
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Re: The Home Air-Conditioner Thread

Post by Nereus » Sun Oct 02, 2016 1:25 pm

My understanding is that "inverters" change your 220volt ac to dc. With dc you can slow the motor down when you need less cooling power.
Ah, not strictly true. The AC is indeed firstly changed to DC, but the DC is used by the inverter using a method called "pulse width modulation", to produce a variable frequency AC output to drive the AC motor. The speed of an AC motor is a function of the number of magnetic poles and the supply frequency. By varying the AC frequency supplied to the motor, and hence the compressor, it can be matched to the required load. It also has the advantage of starting the motor at a very low speed and then increasing it up to about 1.5 times the speed of a fixed drive, thus reducing the big inrush of current while starting.
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Re: The Home Air-Conditioner Thread

Post by BrianT » Tue Oct 25, 2016 6:52 pm

Hnlwayne wrote:There are several people on this thread that obviously know a lot more about air conditioning than I do but I can comment on running costs. In the past two years I replaced four ten year old Carrier split systems of various sizes with Panasonic inverter types. I got the deluxe ones that boast 60% energy savings compared to 50% for the standard inverter. This is supposed to be comparing new inverter vs. new non inverter. I am sure I am saving over 50% keeping mind I had old non inverters.

My understanding is that "inverters" change your 220volt ac to dc. With dc you can slow the motor down when you need less cooling power. It is also better for the compressor because starting and stopping is hard on them.

Keep in mind if you are going for Arctic conditions ( 23 Celsius) or less in a hot climate the inverter won't save you much because the compressor will be going full on all the time. We set ours at 26 or 27 and our savings will pay them off in less than two years. They would pay for themselves even sooner but two of them are not used much.
Thanks for this! Will refer back to this thread when I move in a few months:)

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Re: The Home Air-Conditioner Thread

Post by deepee » Mon Sep 18, 2017 6:53 pm

Been searching for info on correct sizing of air con units for specific situations for ages. When discussing sizes with Thai "experts" always seem to be recommended the biggest (and most costly of course)unit they could push onto me based on the most minimal of my details.
So managed to find an info source which might just be getting close to being helpful.

www.fairair.com.au/calculator.size.aspx

Obviously for Australian areas but if you input "Darwin" same latitude as a close equivalent to Prachuap Kiri Khan and reverse north with south and south with north in each field you can allow for local conditions. East and west remain the same of course.
finally you will need to convert the calculated unit size from kilowatts to BTU .
Would be interested to see if anyone can compare this chart with their current air con units sizing.
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Nereus
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Re: The Home Air-Conditioner Thread

Post by Nereus » Mon Sep 18, 2017 9:06 pm

Mostly you will be constricted by what size units are available. Here they range from 9,000 BTU, 12,000 BTU, 18,000 BTU, or if you really have a big area, 24,000 BTU which may be better served with 2 X 12,000 BTU units.

In the old money a rough rule of thumb was the area in sq feet x 25 = required BTU. Here you may want to X by 30 to cover the TIT.

1 Kw = 3412 BTU.

A lot of variables, even if you use the method that you posted. Unless you are doing a commercial installation you will probably not find any local installer that uses any type of formula. If you read through some of the previous posts most of it is good.(even that which I posted :rasta: )
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deepee
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Re: The Home Air-Conditioner Thread

Post by deepee » Tue Sep 19, 2017 7:08 am

Nereus
Based on this chart a unit around 12,000 btu would be adequate for our living space.
Last local installer was quoting 24,000btu for this same room based on floor area calculations only. Hell of a lot of difference
eh? Still be keen to hear of how this particular chart stacks up in comparison to what other folks have installed in their places.
The means may be likened to a seed ,the end to a tree;
And there is just the same inviolable connection between the means and the end
as there is between the seed and the tree.
............. Mohandas Karamchand GANDHI

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