Air-conditioning myths exploded (Part 1)

Thursday 15 September 2011, 10.45am HKT

Updated 02 Aug 2013 with improved navigation links

>> To Part 2 >>

WE ARE MOSTLY MISLED about air conditioning.

I’m going to explode a few myths about ACs (air conditioners) because I’m angry and sick and tired of having to fix my two ACs year in, year out, every bloody summer.

At the time of this writing (12.55am), I’m drenched in sweat in a highly profuse way in 33°C (91°F) and 75% relative humidity in this toilet hellhole territory called Hong Kong (as if you didn’t know where I live already).

(By the way, don’t say “aircon” — it’s AC. Say it wrong and I’ll belt anyone around the mouth because I’m THAT upset from the heat.)

What happened?

Before my two present AC units, I’ve never had trouble with ACs. None ever needed anything more than general usual cleaning and usual upkeep.

Indeed, I’m generally very good with stuff. I used to have a Panasonic music centre (a ghetto blaster) from 1973 that was in daily use, and worked perfectly until it konked out in 1996 because of old age. Twenty-three years of service.

All my previous ACs worked and worked — until I bought those two Fortress brand ACs just 1½ years ago. Since then, they’ve broken down practically every bleeding quarter. Costing a cool HK$2,500 each (US$321 or £194), they ain’t exactly cheap either. So I’m namin’ names and kickin’ asses now.

One of the Fortress kicked the bucket in August (blown fan and compressor) — so that’s totalled. The other Fortress (still but barely functioning) probably has lost its refrigerant and is now spewing out more hot air than your favourite politician caught womanising. Fortress ACs are sodding hopeless machines.

Trust me, without the AC, life in Hong Kong in high summer just isn’t worth living. And to think that we’re officially in autumn (because of the Midautumn Festival).


More than 100 years of design and technology behind the AC — so how is it that the humble electric fan can work longer and more reliably than the AC?

Simply put, the AC is a more complicated piece of machinery. Complex engineering + bullshit propaganda = shite performance + needless expense.

Best AC that I ever bought was a Rasonic, made in Japan, and it worked and worked (just like Japanese cars tend to do) and gave out FREEZING air. I left the Rasonic at my old digs for the new tenants, and, sometimes, I have pangs of regret about that.

Back in the good ole’ days when my parents were still around, we had only “Made in USA” ACs. Dad preferred White-Westinghouse and Mum liked Polar — and they (parents and ACs) r-o-c-k-e-d, baby.

Trivia: Willis Haviland Carrier (1876-1950) invented modern air conditioning in 1902 one year after getting his engineering master’s degree from Cornell University. He’s the name behind the Carrier brand of ACs.

Off-topic: Mum and Dad also liked German TV sets (Saba, now Blaupunkt) and Grundig reel-to-reel tape recorders — but that’s another story.

Off-off-topic: Interestingly, Grandpa had the bizarre habit of using the long-defunct German words das Fernsehen or das Fernsehgerät for ‘television’ — that too is another story.

With over 100 years of history behind air conditioning, there’s really no reason for ACs to break down every bleeding quarter. Or ever.

So without further ado, let’s go straight to myth-busting.


Out there, there’s a lot of misconception, misinformation and plain old propaganda about air conditioning. Sniff around, and it really takes an effort of will to not see that most of the (mis)information and (mal)suggestions have been recycled around endlessly — particularly by those fine individuals with the words “sustainable living” hanging from the corners of their pursed lips.

I don’t claim my AC myth-debunking is any more complete than what you could find out there, but the myths that I recount are the main ones bandied about, at least here in Hong Kong.

* * *

Bullshit #1
Facts and figures speak for themselves.

We like to think of ourselves as reasonably scientific or logically minded. Truth is, we’re more into intuition — even that, our intuition mostly suck. The reason our intuition suck is precisely because we believe we’re reasonably logical.

Don’t be fooled by facts and figures. A lot of bullshit comes from burying things in a mass of numbers — supposed cost savings and general scientific-sounding lingo. Education have inured us to the idea that there is “austere beauty” in numbers — hogwash churned out by no less an idiot than Bertrand Russell.

We’re particularly (and peculiarly) fascinated with phrases like these:

“… reduce your energy use by 3% to 8% …”

“… save in the neighbourhood of $700/year …”

“… paying for itself in less than 6 years …”

Could be a lemon, though you wouldn’t think so from the way it looks

Facts and figures by themselves are fine. But it’s kind of silly too. Figures and stats used like that don’t necessarily tee in with your setup. It might not necessarily reduce your energy use by 3%, or save you $700 a year, or pay for itself in less than six years for you.

Of course, facts and figures put out by some organisation or whatnot are arguably just averages for general application.

But of course they are. We appreciate that, but please also explain the setup that the figures are derived from, or tell us how the averages were done — and that part is always conspicuously missing in any official recommendation.

I’m very sorry, but unless you do a better job at recommending, I just cannot take your word at face value. And that’s exactly what happened when I slipped up and bought those two lemons from Fortress.

* * *

Bullshit #2
Buying an energy-efficient AC will automatically reduce your electricity bills.

That will help, but even more important is buying a correctly sized AC. A small AC unit will struggle to keep your room cool. A big unit won’t cool your place down faster or remove moisture more thoroughly — it merely leaves your place cool but damp and clammy. Energy efficiency goes only so far.

Sizing an AC unit is using the correct capacity of AC for the size of the room.

Protip: To calculate the correct AC size to use, the professional rule of thumb is:

  • Temperate zone: 20 Btu’s per 1 sq. foot of living space (0.0063 kWh per 1 sq. metre)
  • Tropical zone: 25 Btu’s per 1 sq. foot  of living space (0.0072 kWh per 1 sq. metre)

Protip: Split the total Btu requirement over at least two AC units if over 10,000 Btu’s.

So, 500 square feet (46½ square metres) will require 500 × 25 = 12,500 Btu’s (2.93 kWh) of AC cooling capacity. That’s like two window ACs each of 6,000 Btu’s — because it’s better to have two or three AC units sharing the work than one gigantic AC handling it on its own. Remember Adam Smith, division of labour, no?

There is a more complicated way to size an AC unit [LINK].

Spit AC systems (a.k.a. central air conditioning) are measured by tonnage (not the same as weight tonnage). Splits provide overall climate control for the whole area. Very high initial installation cost if ductwork or electrical wiring are necessary. But splits have the highest savings potential compared with ductless or window units.

Protip: To convert Btu’s to tonnage, divide the total house Btu by 12,000.

So, 2,000 square feet (186 square metres) in the subtropics require 2,000 × 25 = 50,000 Btu ÷ 12000 = 4.1 tons. A 4½-ton AC unit would be the bare minimum size needed. That’s like eight or nine window AC units.

* * *

Bullshit #3
Your AC will perform the same no matter where you install it.

No, it does make a difference. A little planning goes a long way. Install in the right place and you’ll save energy and money.

The AC unit contains heat sensors. Install the unit at or near sources of heat, and you’ll make it work too hard. It’s common sense — you can’t expect the AC to cool if you put it in a hot place, right?

THINK! I used to know one idiot who installed the AC right next to the stoveworks and fridge, and then wondered why the AC kept breaking down. I wondered too, but more about why people like that idiot couldn’t spot the problem with that setup.

Protip: Install the AC unit in the shade because direct sunlight on the outdoor heat exchanger (backside) will reduce working efficiency. If no shaded area, then fix up a shade or canopy for it (especially important for window-type ACs).

Protip: Remove lamps, TV and any heat-emitting appliances near the AC thermostat — it senses their heat and can cause the AC to run too long or too much.

The truth is, optimal AC performance depends mostly on your geographical location and how you actually use the AC on a daily basis.

Some other factors:

  • engineering considerations
  • cost/efficiency considerations
  • effects of human metabolism
  • how your home as a whole uses energy
  • quality of your home insulation
  • prevailing weather conditions and general climate of your locale
  • your own perferred temperature range
* * *

Bullshit #4
Maintenance calls aren’t worth it.

O rly?

FACT: Preventative maintenance saves money.

Yearly maintenance agreements are more beneficial than most people think. Would you ignore changing the oil or filters in your car? Then why ignore maintenance on your AC?

  1. Failure to do something as easy as regular filter-changing can have drastic consequences. A dirty filter blocks proper airflow across the AC coils, making your unit less cooling, and eventually damages the coils and cost you hundreds or thousands of dollars to replace.
  2. Clogged drainlines cause mildew, mould and algal growth inside the unit. Water backs up inside and damages the unit. Excessive water buildup also causes safety switches to become activated (accordingly turning off the unit’s cooling parts) and requiring a thorough cleaning and draining of the system.

Repairs always cost more than preventative maintenance. Those two issues (and many others) can easily be avoided by proper and regular servicing.

* * *


Why the generally recommended AC thermostat setting for 25°C (77°F) is myth and propaganda all rolled into one.

>> To Part 2 >>

* * *

© The Naked Listener’s Weblog, 2011. Image of apple via Playerz Blog.

3 Responses to “Air-conditioning myths exploded (Part 1)”

  1. Hello, all is going sound here and of course everyone is sharing facts, that’s truly good, keep up writing.


  2. Kourtney said

    Oh my goodness! a fantastic post man. Thank you for
    sharing it.


Comments are closed.

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