Evaporative cooling vs Split system

AJW · Oct 30, 2017 11:49 am

Well there you are, you are expecting miracles on a very hot humid day! They are the days that a refrigerative unit would be ideal, but for the other 350 days of the year, or 100days where one might need an a/c running evap is fine.

As to what many do wrong. Firstly not opening windows. Evap needs to replace the air regularly and in large volumes. Closing windows is what leads to it not being as effeicnt and the feeling of the house being too humid.

Secondly on those (few) days where it is hot AND humid turn off the water pump. The unit will still knock the edge off a hot humid day by replacing stale air and without extra water being introduced into the air the flow of air over human skin will for many, but not everyone lead to one feeling cooler. Against its about taking the edge off the heat not making you feel like you are at the snow in the middle of winter.

Which gets back to my original point don’t expect miricles.

Evap is a compromise solution. Refrigerative is clearly the best method but has its own issues, high capital cost and cost of running being two such issues. Evap is the compromise between capital cost and running cost that for many is good enough most of the time. The days it isn’t go to the movies!

Old Bloke · Oct 30, 2017 5:26 pm

Agree with you that refrigerated is clearly the best method and does have a high initial capital cost however not so sure about the running costs. Our electricity use last summer, which was a fairly hot summer in Melbourne, for a 21KW ducted refrigerated system in a 42 sq two storey house (with 2 teenagers) was sub $500 for the summer quarterly bill.

I know for a fact that friends who went for evaporative do keep windows open when using it and will ask them about turning off the water pump on humid days when we next see them all.

Not sure how many movie theatres are open between 10pm - 6am on those hot humid nights when you are trying to sleep.

JB1 · Oct 31, 2017 11:25 am

I'm not expecting miracles, but I would like to be comfortable enough not to toss and turn all night when it's humid

FYI, I do open window in the rooms where I want to cool.

I also use just the fan function when it's very humid, otherwise, it just adds to the humidity.

I will admit, evaporative is pleasant when it's a mild day/night and you can keep all the sliding doors open. Also when the house is hot and there is a cool change, I use the reverse fan function to suck in cool outside air into the house. Other than that, refrigerative all the way.

RC56 · Oct 31, 2017 3:35 pm

JB1

ilmessaggio

Type of house and geographical location usually determines the best approach
Melbourne generally fares better with evaporative
Both types have their advantage and disadvantages and asking one eyed individuals is not the best way to go

Melb has humid summers and evaporative is next to useless in the peak of summer, when you really need it.

One eyed? I have both evaporative and split air conds in the same house.

Is that expensive?? to have both evap and split?
how does the split work cost wise?

RC56 · Oct 31, 2017 3:47 pm

Thanks guys. For all your replies. It really helps.

Just a random question. Any idea how many split generally required for a family size- 4.83 x 7.00m

I am more worried because the split costs a lot with installation and the electricity consumption is high even.
Also, its hard for the cool air to be contained in such a large area and hence it uses more power

JB1 · Oct 31, 2017 6:05 pm

RC56

Thanks guys. For all your replies. It really helps.

Just a random question. Any idea how many split generally required for a family size- 4.83 x 7.00m

I am more worried because the split costs a lot with installation and the electricity consumption is high even.
Also, its hard for the cool air to be contained in such a large area and hence it uses more power

A single 5kw system will do it easily.

Electricity consumption isn't much from my experience.

RC56 · Nov 03, 2017 9:00 pm

So finally we had our electrical appointment yesterday. it went well and expensive too

With the confusion on evap vs split we landed up going for Refrigerated cooling. The price they quoted for the split was:

2.6kw for master bedroom- $2700
7kw for family dining kitchen- $3500

So this is basically the price for only 2 areas and not to forget the family kitchen and dining area is huge that there is chance of leakage of air and hence reducing the efficiency of the split. Therefore, we got inclined towards refrigerated cooling. the price quoted for it was:

Gas heating and electric cooling (Braemar)- $13000 (No zoning)
Electric heating and cooling (Actron air)- $13500 (includes 2 zones)

so this sounds like its a better option to get refrigerated ducted cooling rather than split because literally split costs half the price for only 2 areas of the house. Now the point is we were suggested to go for the Electric heating and cooling option by the sales guy as he says- the way things are going electricity prices are going to be cheaper than gas prices in future. This really turned our head upside down. Not sure if this is and old age thinking but isn't gas cheaper than electricity?

Any suggestions on this one? Gas heating/cooling vs Electric heating/cooling??

algernon · Nov 04, 2017 11:08 am

Gas is becoming more expensive as the gas companies make a greater profit from exporting it than selling domestically (there's a whole history of the government stuffing some key decisions that's lead to this - including the bizarre situation where the Japanese government earns more tax revenue from Australian gas exports than Australia does - but that's another story), which is driving up domestic prices significantly.

Add to this the declining domestic gas consumption in Australia and you have what energy experts call a 'death spiral' - fewer consumers means that the distributors have to charge each customer more in administration and servicing costs to cover their expenses, which leads to higher gas prices for the consumer, which leads to more consumers disconnecting gas entirely, which leads to higher network costs passed onto the remaining customers, which leads to more people leaving, and so on....

Conversely, the long-term projection for electricity costs are to reduce as renewable energy generation continues to become cheaper (already cheaper than coal, and falling further) and more people install rooftop solar. There's currently an artificial spike in Australian electricity costs, due to a combination of the government failing to commit to a coherent energy strategy, market gaming by electricity generators, and high peaking generation costs due to the high domestic price of gas - but all of these factors are ultimately transient.

Basically: the long-term trend is higher gas prices, lower electricity prices.

However, a key factor is that you're not comparing like-for-like with gas vs reverse-cycle heating: reverse cycle aircon is much more efficient than gas heating, so you use less electricity energy input that you would gas energy input. Research has shown that for most Australians, gas heating is more expensive to run than reverse cycle heating (e.g. google the University of Melbourne's "Switching off gas" report for one of the more prominent studies).

RC56 · Nov 04, 2017 4:56 pm

algernon

Gas is becoming more expensive as the gas companies make a greater profit from exporting it than selling domestically (there's a whole history of the government stuffing some key decisions that's lead to this - including the bizarre situation where the Japanese government earns more tax revenue from Australian gas exports than Australia does - but that's another story), which is driving up domestic prices significantly.

Add to this the declining domestic gas consumption in Australia and you have what energy experts call a 'death spiral' - fewer consumers means that the distributors have to charge each customer more in administration and servicing costs to cover their expenses, which leads to higher gas prices for the consumer, which leads to more consumers disconnecting gas entirely, which leads to higher network costs passed onto the remaining customers, which leads to more people leaving, and so on....

Conversely, the long-term projection for electricity costs are to reduce as renewable energy generation continues to become cheaper (already cheaper than coal, and falling further) and more people install rooftop solar. There's currently an artificial spike in Australian electricity costs, due to a combination of the government failing to commit to a coherent energy strategy, market gaming by electricity generators, and high peaking generation costs due to the high domestic price of gas - but all of these factors are ultimately transient.

Basically: the long-term trend is higher gas prices, lower electricity prices.

However, a key factor is that you're not comparing like-for-like with gas vs reverse-cycle heating: reverse cycle aircon is much more efficient than gas heating, so you use less electricity energy input that you would gas energy input. Research has shown that for most Australians, gas heating is more expensive to run than reverse cycle heating (e.g. google the University of Melbourne's "Switching off gas" report for one of the more prominent studies).

Very well explained.. Thanks. It was good to read a bit of the history to this ongoing issue.

Hfranco2018 · May 05, 2018 4:36 am

RC56

My husband and I are building Delta 25S with Metricon in Melbourne. We recently had our colors appointment and next week we have our electrical appointment.
We are stuck with the decision making for Evaporative cooling.

Many people suggest us its not worth it and people land up getting a split anyway. I have read reviews that it doesn't work above 30 degree temperature, there is always a wet feeling in the house and furniture.

Any suggestions anyone?? What is better- cost effective and usage wise?

Split Systems

Split systems will work in any climate and if you live in a humid climate they will be the best option
Buying a split system can be more affordable because you can add additional units to some systems or install additional units as your budget allows
In this case, repair costs can also potentially be lower. If one unit breaks down it can be repaired seperately and the others continue working
Replacement costs can be lower, although this is not always the case, this is very dependend on the individual installation

Evaporative Cooling

Increases humidity in the house
They are less effective when humidity is high outside
Generally require slightly more maintenance than air conditioning
Consider carefully before purchasing in water restricted areas or where dependant on limited water as water consumption can be up to 80 litres per hour.

If you made a decision enter here.

diggi · Jun 16, 2018 7:49 am

I have evaps in Brisbane and have been using them for 8 years.

we also ended up installing splits in every room for the really humid or cold days.
over time i have begun to realise that these systems are an advantage for your energy consumption if you learn when you can use them (using a humidity guage) as thety are much more effective than fans and use less energy than splits/ducted aircon.
if used correctly they can be very effective in keeping your running costs down for your house, although the install cost of both systems may put you off.

ddarroch · Jun 21, 2018 9:52 am

Joker

for melbourne generally, heating is more important, so as long as your ducts are the bigger type, you use your heating ducts for add on air con, we would use heating at least twice, maybe three times more in geelong, Melbourne areas, most here get gas central heating, and if you preplan and have the bigger ductwork needed for aircon, it is simple to add on air-conditioning, house is 48 square, garage not air conditioned, rest of house has 4 zones with actron add on air con,, 17 kW system, does house easily, never need more than 3 zones on at a time, our windows are thermally broken and double glazed, also have solar, which means when we are using our air conditioning, generally after work and on weekends, we are mainly using our own electricity, which makes air-conditioning really cost effective to run, and works really well, all the time

RC56

Therefore, we got inclined towards refrigerated cooling. the price quoted for it was:

Gas heating and electric cooling (Braemar)- $13000 (No zoning)
Electric heating and cooling (Actron air)- $13500 (includes 2 zones)

Now the point is we were suggested to go for the Electric heating and cooling option by the sales guy as he says- the way things are going electricity prices are going to be cheaper than gas prices in future. This really turned our head upside down. Not sure if this is and old age thinking but isn't gas cheaper than electricity?

Any suggestions on this one? Gas heating/cooling vs Electric heating/cooling??

I certainly wouldn't be installing gas heating. It's become more expensive to run than reverse cycle air conditioning, with costs only expected to climb higher. Unlike reverse cycle air con, these costs cannot be reduced with a solar PV system. Add to the fact that it's bad for the environment, & this won't improve. Currently electricity production is very bad for the environment, but this will improve as we move towards renewables.

As technology advances reverse cycle air cons are becoming extremely efficiently heat sources. Running costs will be lower than a gas heating, particularly if you have solar PV on the roof.

Personally, I'd forgo any gas in the house, & build an all-electric house. Removing the gas bill, & its daily service charges, will save money.

Instead of installing two separate, expensive systems for heating & cooling, I'd be installing a reverse cycle air conditioning system that does both. I'd be investing the savings in a roof top solar PV system, that will reduce the operating costs of both your heating & cooling needs.

ddarroch · Jun 21, 2018 10:13 am

AJW

Only issue with Canberra with reverse cycle is heating the heating effect is marginal on the very cold winter mornings. The units can spend more time defrosting than they do heating. Our struggles below about -5.

Great strides have been made in heat pump technology (of which reverse cycle air conditioning is a type) over recent years. Many highly energy efficient (Passive Haus) houses in North America, even in frigid Canada, use mini-splits as their only heat sources. These systems can operate efficiently far, far below zero C.

Yes, due to the way they work (extracting heat from the ambient air), heat pump efficiency will decrease as the ambient temperature decreases. But nowhere near as much as was the case only a few years ago. This is because older systems required an extremely energy inefficient electric element to defrost their coils, modern systems do not.

Though not all systems are created equal, only some are optimised for low temperature use (like Mitsubishi Hyper Heat). So it's worth doing your research before installing an AC system for heating in cold climates like Canberra or the alpine.

Bels · Jun 22, 2018 1:30 am

ddarroch

AJW

Only issue with Canberra with reverse cycle is heating the heating effect is marginal on the very cold winter mornings. The units can spend more time defrosting than they do heating. Our struggles below about -5.

Great strides have been made in heat pump technology (of which reverse cycle air conditioning is a type) over recent years. Many highly energy efficient (Passive Haus) houses in North America, even in frigid Canada, use mini-splits as their only heat sources. These systems can operate efficiently far, far below zero C.

Yes, due to the way they work (extracting heat from the ambient air), heat pump efficiency will decrease as the ambient temperature decreases. But nowhere near as much as was the case only a few years ago. This is because older systems required an extremely energy inefficient electric element to defrost their coils, modern systems do not.

Though not all systems are created equal, only some are optimised for low temperature use (like Mitsubishi Hyper Heat). So it's worth doing your research before installing an AC system for heating in cold climates like Canberra or the alpine.

The electric elements were used in the discharge air stream when the system cycled into defrost to defrost the coil so as to not blow cold air into the conditioned space as defrost mode essentially switches to cooling.

You're confusing air conditioning with low temp refrigeration which uses electric elements for periodic defrost cycles.