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Air Conditioner/Tasmanian "Heat Pump"

As you would probably know, it gets a little colder here in Tasmania than it generally does on the north island. We also do not have mains gas in most places (although it is being introduced gradually at mains electricity prices). Being adaptable creatures with only very occasional use for an air conditioner, Tasmanians have made the appliance their own by calling it a heat pump and using it predominantly for heating.
It would be interesting to know:
•how this effects its performance and longevity
•Whether this should be considered when calculating reqired capacity
•Whether we should be using an alternative appliance (bearing in mind the gas situation).

I have heard that mainly using your air conditioner as a heating unit is detrimental to its health.

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Hi @Pierissima, welcome to the community.

If you have a particular reference/s to your enquires it sometimes helps to provide a reference or link so the community can check them out.

Choice has some great advice on air conditioners including the benefits of using them for heating.

There are limitations to reverse cycle air conditioners in extreme cold. Each manufacturer provides advice on the operating conditions their systems are designed to operate within. Temperatures to less than 0C are not necessarily a limitation.

how this effects its performance and longevity
It is not a restriction, noting for cold climates the right split system air conditioners will be supplied with heaters that ensure the compressors and lubricating oil is are kept above a minimum.

Whether this should be considered when calculating reqired capacity
RC aircons actual work better in heating than in cooling by a small margin. The COP can be as high as 4.0 IE for every one kilowatt of power the aircon draws from the grid you get 4kW of heat into the room. Typically aircon capacity is rated by it’s cooling capacity in kW. The heating capacity will be slightly more. A 4-5 star rated air con that has an 8kW heat output to suit a large living space will use less electrical power than a common 2.4kW electric column oil heater.

Whether we should be using an alternative appliance (bearing in mind the gas situation).
Gas heating delivers most of the heat energy into the room or house or through alternate systems such as hydronic heating panels or under floor. I won’t comment on the economics, but if it is Tassie which has a low carbon electrical grid, gas is a poor solution compared to electrical. If the drying effect of air cons is an issue a new build can use an electrical powered heat pump for hydronic heating systems, or as a retro fit.

Fujitsu says


Never come across that before. Do you have any reference that says it is so?

It is no more detrimental to your health than living in a low humidity environment, eg Inland or high altitude.Cooling by A/Con.also produces a low humidity environment.

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Cold climates (snow and ice outside) are also low humidity. A common solution is to have a room humidifier, water top up required, fragrant infusions optional.

It is possibly better to use the term relative humidity rather than humidity per say.

An air conditioner reduces the relative humidity within a room as the evaporator coil/heat exchange is much colder than the ambient air temperature causing condensation on the coil/exchange and this reducing the moisture content of the air. This process reduced the humidity of the air at the coil/exchange. At this point, the relative humidity could be 100%…that being the air can’t hold any more water vapour.

As this air passes back into the room, it is warmed by the air within the room. This warming reduces the relative humidity of the air making it feel drier. The process continues as the room is cooled.

When our son and his family were living in Queenstown in Tassie in the 1990’s in an old weatherboard low set house, he researched their options and settled on having several “heat pumps” installed which they were very happy with.

And as a “heat pump” is simply an electrical device, it does not produce any of the toxic gases or particles that gas heaters and wood heaters do.

I believe there should be no health issues and that it is a far safer option.

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That is obviously if you choose to increase the humidity, however most dwellings in a cold climate are fairly well sealed, and natural human activity increases the humidity.

I don’t get technical as it tends to loose meaning and confuse people who are not technically able.I am a Refrigeration and Aircon engineer.

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As pointed out, it may not be a problem maintaining a comfortable level of humidity acceptable to the occupiers of some homes using RC Air Cons for winter heating.

Without a hygrometer and a study of individual properties?

How well sealed is the house?
What sort of activities might assist to increase the humidity?
How many air changes per hour are required to meet national building design codes?

There seems to be a variety of advice on line re the impacts of low moisture content of cold air, and consequences of heating rooms causing low relative humidity.

If it is a concern, there are simple solutions. Humidifiers, keep the kitchen on the boil, spouted kettle on a simmer on the end of the stove, drop in gym in the lounge room.

The last may add more than exhaled water vapour?

It was not clear that there was an inference that using the reverse cycle is hazardous to the human’s health, or if the statement implied running an A/C in reverse cycle was detrimental to the A/C (eg its health).

If the latter is correct, the reverse cycle units are designed to heat and cool, and there should be no adverse effect which mode reflects the primary use (I was unable to find any evidence nor even a statement suggesting that may be the case, from a brief search).


When we replaced the old box aircon with a Fujitsu inverter in our bedroom at our previous residence over a decade ago, the reverse cycle model had a higher EER rating than the cooling only model.

I called Fujitsu and I was put throught to an engineer who explained that it was because they used a higher efficiency motor in the reverse cycle model.

We bought the reverse cycle model even though we would hardly need heating in Cairns, but we would save much more than the small difference in the prices with lower power bills.

So Fujitsu had definitely designed this unit to cope with heating.

After working for many years in the Ski Field and Lodges during the Ski season,low Humidity was never a problem, and I never once saw a Humidifier.

This is 2 years old but might be interesting.


Yes,I believe atmospheric moisture (humidity)is associated with more health problems than low humidity.

Why is that, do you have some reason to say so? The linked article above tells us that for influenza at least low humidity is worse.

It is generally accepted that high humidity allows the proliferation of moulds and fungus which are real issues as far as health is concerned. The above article only mentions the contagion of the flue,not the cause.

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The core question at the first post in the topic.

The simple answer is reverse cycle air conditioners are widely used for heating in colder climates. And without concerns for longevity of the units. It’s important to purchase units intended for operation in colder environments. Tropical RC Air Cons may lack the additional heaters required to keep the compressor lubricating oil above a minimum temperature for safe starting. Perhaps there are anecdotal histories of failures of units in Tassie not so equiped, or from poor performing defrosting protection.

There are limitations, although outside temperatures of below -10C to -15C would suggest it’s not an issue for most of Tasmania?


Isn’t there a consensus indoor relative humidity (RH) should be kept below 50%?
While, informed comment includes for personal comfort to also aim to stay above 40%. The recommendations seem to vary a little based on temperature.

The issues of excess moisture and too little appear often in topics concerning household comfort in places with similar Winter weather to Tasmania. Hobart is approx 43degrees South. Similar to Christchurch in NZ (South Island). Tokyo Japan is closer to the equator at approx 37North. The latter nationals go to some effort to manage indoor comfort. Humidifiers are a common winter accessory, used as needed.

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It is the true that moulds in the house are detrimental to health. To avoid this prevent damp inside the house and very high humidity. You do not need to have low humidity.

Influenza is endemic to society worldwide, it does not disappear and reappear, there are accounts of the flu going back hundreds even thousands of years. It mutates into new strains constantly and several strains can be going around at once. The spread and severity can be reduced with vaccines but these cannot wipe it out (like some other endemic diseases) because they are not given universally, they are not 100% effective and because of the constant mutation. Therefore managing contagion as best we can is also important. The low humidity of winter is a major reason for flu running in waves every winter in both northern and southern hemispheres.

I do not follow your comment on the source of flu, would you care to explain a bit?

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The source of Influenza must come from a carrier, no carrier, no Influenza.Influenza can be spread in many ways, to isolate one (Low Humidity) bellies many other forms of transfer.