AC myths 9: Protips and hacks

Thursday 15 September 2011, 4.50pm HKT


<< Part 8 << || >> Part 10 >>

(Continued from Part 8)

Almost at the end of the series. We roll with some low-cost and no-cost ways of running your AC properly for summertime.

* * *

First and foremost

Habits

1. Develop energy-saving habits. Savings come from little behaviour changes and habits. Strip down if you feel a bit warm, and put something on if a bit chilly. Stop running around the home in shirtsleeves in the middle of winter. Stop wearing dark suits and tie in the middle of summer unless at work.

Expensiveness

2. Realise that using an AC is a relatively expensive undertaking, and if you’re that worried about cost, maybe you shouldn’t have AC installed at all.

Costings

3. For all practical purposes, the modern AC is designed to run at its rated power consumption level, regardless of the thermostat setting. It also produces the same amount of pollution at whatever the temperature setting. (Details in Part 5.)

AC-related tips

Relative temperature

4. Rule of thumb is set the AC at 10 degrees below the outdoor temperature (using the Celsius scale). For instance, if outdoors is 30°C (86°F), set the AC to 20°C (68°F) indoors. Professionals in the HVAC (heating, ventilation and AC) business use this rule of thumb, and it’s no mistake why they use it. (Details in Part 2.)

Thermostat habits

5. Handle the AC thermostat properly. Cool to 20°C to 23° (68°F to 73°F) and switch off when you feel chilly (instead of messing with the AC thermostat). At 20°C to 23°C, the extra cost is only marginal, but your AC will work more efficiently than at higher thermostat settings. (This tip contradicts the convention advice often given elsewhere: details in Part 2).

Fans

6. Don’t run fans while the AC is on. This is not a hard-and-fast rule — sometimes you have to make an exception. Fans disrupt the AC airflow, causing the AC to work harder, and therefore shortening its lifespan. A running fan motor also generates heat, therefore counteracting the work of the AC. Try to cut down on the number of electrical appliances running while the AC is on. (Details in Part 3.)

‘Auto fan’

7. Always use the ‘Auto fan’ thermostat setting, never just ‘On.’ On Auto, humidity is kept lower, so AC costs are much lower and comfort is higher.

Registers

8. Keep open the AC air-supply registers at all times (relevant for some AC models). It doesn’t save money, but closing off the registers may lead to costly problems.

Steady as she goes

9. Don’t try to speed-cool at max-low thermostat settings when you return home. Instead, choose a normal evening setting (20°C to 23°C, or 68°F to 73°F). The AC cools just as fast at 20°C as it does at any lower temperature.

Sunlight

No canopy? Wait till you see the bills

10. Block sunlight streaming into the premises when the AC is on.  Shut curtains and blinds in the direction of incoming sunlight. Close windows. Shut room doors to bigger rooms. Seal airleaks around doors (use caulking and weatherstripping). Check for airduct leaks or disconnected ducts around the house. Duct leaks can double your cooling cost. Rig up a canopy around the AC unit itself so sunlight won’t shine on it.

Bath time

11. Shut the AC off when you take baths and have the bathroom ventilation fan switched on. What goes out, something must come in. Open a window to let air flow in to balance the air outflow — it’s not the job of the AC to do that.

Filters

12. Change or wash the AC air filter screen once a month. It feels like a hassle, but it really isn’t. If you leave things untouched, the filter cakes up even more badly — then it becomes a real hassle. Clogged air filters restrict airflow, ups running costs, and often lead to expensive-to-fix compressor damage. Cleaning the filter screen is highly important in a polluted, concrete jungle or dusty place (like Hong Kong, the Middle East or southern USA) — you may have to clean the air filter once a week.

Microwave ovens

13. Use a microwave instead of the range (gas) oven when the AC is on. A microwave doesn’t heat up the kitchen. Shut the kitchen door when you’re cooking. A microwave pollutes less than a gas oven.

Water mist

14. If the AC is starting to go on the fritz, spray a fine mist of water at the rear end of the AC unit to keep it on the cool. This is a only stopgap measure.

Not in use

15. Cover the roomside and exterior ends of the AC unit when not in regular use (as in winter) to protect it from sunshine, rain and general debris landing on it or clogging it up.

Factory presets

What’s correct humidity?

16. If you have a remote for the AC unit, removing and reinstalling the batteries should give you back the factory preset temperatures in each mode the product was manufactured for. For instance, the Mitsubishi preset is 21°C (71°F).

Measuring temperature

17. The correct way to measure AC air output temperature is to use a thermometer 1 metre (3 feet 3 inches) from the cold-air outlet. Don’t stick it right into the blowhole, as some Laurel and Hardy repairmen are apt to do. (Story in Part 2.)

Humidity

18. Set the indoor humidity level at 30% to 60% if your AC unit has humidity control settings. This is only a conventional wisdom, as there is no hard evidence to back up this recommendation. (Details in Part 7.)

‘Middle’

19. Set the AC to blow cool air towards the middle of the roomspace. That allows for a more even distribution of cool air.

Hands in pockets

20. Stop messing around with the AC thermostat. You’ll make it break down quicker. Shut it off or put something on if you’re feeling chilly. Strip down if it’s a bit warm.

* * *

NEXT IN PART 10

General tips for keeping cool and saving energy.

<< Part 8 << || >> Part 10 >>

* * *

© The Naked Listener’s Weblog, 2011.

Images: AC unit from author’s collection ♦ Thermostat setting by Tom Grundy via 123RF ♦ AC in the sunlight from author’s collection ♦ Sweaty Asian girls via c4c.

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