Questions about getting ducted A/C

[Beachman]

Howdee,

We are considering getting ducted A/C for our house and just doing a bit of homework before I start discussing quotes with our local companies. Thanks to the Internet a lot of companies give rough prices on their web sites along with what size/brand machine is included in the price.

Our floor space is 165m2, but when working out A/C do you get a system that can do the whole house simultaneously or a system that can do say 75% of the house at any one time? How often do people have the A/C running simultaneously thought the whole house as I would have though you would run the living areas and maybe one bedroom during the day and then just the bedrooms at night??

Reason for my question is could I get anyway with a single phase system that can do 150m2? But if I needed the next sized system that can do 170m2, it means stepping up into the 3phase power category which also means extra money upgrading the meter box/new overhead power lines etc to accommodate the A/C. 

Thanks

[Goose]

I think to do it properly, you should be able to cool (given you're in QLD) 100% of the dry living areas of the house. This is bedrooms, lounge, kitchen, halls, study. Exclude laundry, bathrooms and garabe as you won't have outlets there, and they are easily closed off.

If you turn off a zone thats not in use and shut the doors, then the system will work quicker and use less energy as you're cooling a smaller volume of air.

Given its a capital investment in your property, i'd go with the best you can afford. There are a lot of people who have tried to cut corners with cheaper A/C systems and they only end up paying twice. Not sure if you're looking a cheaper system, but just saying.

I'm also interested in why you need to upgrade the overhead lines?? Are you on a farm or rurual property? You shouldn't need to pay for that unless maybe you have private polls?

[Pog]

Always go 25% bigger than any salesman recommends (then double it).

A ducted aircon is something you only want to buy once, and do it properly.

Where I am, Evaporatives work quite well due to our low humidty, and the salesman was trying to match one exactly to the size of our house. When he recommended the model, I went 2 x sizes up and told him that I would only consider a larger unit.

It was the best thing that we ever did, and on really hot dry days, it only just keeps up. I would hate to think what it would have been like withthe unit he recommeded.

[HKB Electronics]

I'd think about it carefully, everyone I know who has had whole home air conditioning
thought it was the bees knees still they got the next power bill, from then on they were
afraid to turn them on.

I'd only consider evaporative for whole home, and a few splits for others, I think from
memory the bigger the system the less efficient it is so a few splits will probably be
more economical anyway.

Leigh

[Wello-bob]

It also depends on the construction of your house,  is it well insulated,  do you have decent size eaves over your windows. This all helps in reducing the size of the system.  I have a brick veneer house with colour bond roof insulated with wool batts below and I have ducted Ac to 4 bedrooms,  kitchen, meals, family room and lounge,  all up about 150sq.m.

My Ac unit is 12.5kw of cooling and single phase. It is zoned so I can turn off the bedrooms during the day or turn off living areas at night when all are asleep.

I have never had a problem  with cooling capacity.

Cheers Bob

[Marschy]

I'd only consider evaporative for whole home, and a few splits for others, I think from
memory the bigger the system the less efficient it is so a few splits will probably be
more economical anyway.
Leigh

Evaporative doesn't work well in high humidity. All good for us southern folk, notsogood for our northern brethren.

[markg66]

In my humble experience conversing with the fridgies at my work they are all of the opinion not to go ducted but to get a few splits, one or two in the main room and then much smaller ones in the bedrooms. You'll save power at night by not running the big unit just to cool your bedroom.
Also if your aircon has a failure you've only lost one unit not the whole house full.

Which ever way you decide to go, If you are looking for a company to give you a quote, call Kim at Energy Air 1300656817 he's just a mate that manages that family business. (used to be my old boss)

[billnjim]

we have evaporative ducted throughout the house (excluding wet areas) and went bigger than was recommended. So long as its not humid it works a treat, however, for the days that it is humid it is pretty much useless. We ended up getting reverse cycle (split system) for the living rooms for those days............works a treat but hardly used - well used more as heater in winter then an aircon. Haven't noticed a huge difference in power bills/consumption with either system running but we have solar panels fitted & again went bigger than what was recommended.

[truckiejas]

check with your local sparkie because when i put 3phase on it had to go underground from the pole on the other side of the road, which was about 4 grands worth. personally id go with a couple splits in main living areas and master bedroom.

[JD-120]

Hey Beachman,

mate we have a 12kw Mitsubishi ducted unit, single phase. Cost us about 10k I think. Our house is of similar size. Cools the place down in about 5 minutes. fully zoned for 6 different rooms.  I will check the model for you if you are interested.

We usually have either the living rooms cooling, or the bedrooms, very rarely do we have all rooms cooling down at the same time as we do not occupy all rooms at the same time.

Justin

[Pete_R]

Whatever system you go with, make sure it is inverter as won't cost as much to run as a non-invertor system. We've got an ducted inverter system upstairs & a split system inverter downstairs & our power bill is still cheaper than quite a few households with no air-con at all.
Provided you are realistic about when you use it, you power bill should not go up too much

[D4D]

For those running spilts and evap, how well do they work together? If I look at the science, the split is trying to take moisture out of the air and the evap is putting it back in. Sounds counter productive to me...

[Pog]

For those running spilts and evap, how well do they work together? If I look at the science, the split is trying to take moisture out of the air and the evap is putting it back in. Sounds counter productive to me...

I have both, but am not that stupid that I would even think about running them together... That, as you say makes no sense!

You run either the evap, or the split, but never both at the same time.

I use my split only when it is humid, as the evap only makes things worse in humid conditions.

Evaps by their nature, only lower the temp by about 7 - 10 degrees, so on a 40+ degree day, the best you could expect an evap to do is 30+ degrees, which is still uncomfortable. That's when I would turn it off and run the split system.

The evap is great at night when I can close different windows in the house to direct more air flow through a few of the bedrooms to push a lot of cooler fresh air through on hot nights.

[Moggy]

I would agree with markg66. Just get splits. I had 14kw daikin inverter system in last house. Great system & fairly cheap to run, but its minimum usage was 6.3kw. Helluva lot of power for one room when kids left. Maybe even look at multi-head system. I recently had 6kw x 3 head inverter system installed for $4500. Probably dearer than single units, but not as messy outside

Sent from my XT905 using Tapatalk

[Beachman]

I'm also interested in why you need to upgrade the overhead lines?? Are you on a farm or rurual property? You shouldn't need to pay for that unless maybe you have private polls?

We live in a normal suburb with overhead power lines, but when ones of my mates upgraded to 3 phase last year he received a $3 500 bill. His power is underground, so not sure if that’s why he got charged.

[Beachman]

I was originally going to go down the split system path, but for the living room the only available free wall was at the front of the house and I didn’t want a system or pipework located there as would just look ugly.

[billnjim]

For those running spilts and evap, how well do they work together? If I look at the science, the split is trying to take moisture out of the air and the evap is putting it back in. Sounds counter productive to me...

bit pointless running both - we run one or the other; if i had my time over again I would of only got reverse cycle and not evaporative installed but funds at the time dictated evaporative was the way to go.

[Beatle]

I have ducted in my home (installed by previous owners).  But I'd go splits if I had a choice.

Not sure how modern zoned setups are rigged, but with ours we have outlets in every room, but only the one filtered inlet in the hall.  So that means you must leave an air path from the rooms you have selected to cool, back to the inlet, or else you'll starve the fan.  This means you'll shorten the fan life, get no cooling, and waste power.

For example, lets say the inlet is in the centre of a home, surrounded by kitchen (zone 1), surrounded by living rooms (zone 2) surrounded by bedrooms (zone 3).   In my case I can turn on only zone 3, but need to allow airflow back through zones 2 and 1, so I'm partially cooling them as well.

With a split system you can cool just the one bedroom (or one zone if you have more than one unit hooked to the outside pump) as the air stays in that room recirculated through the wall unti.  If the pump is running you may as well turn on all the connected interior units.

[Mikeb62]

you can get systems with multiple air returns, but of course costs add up. As Beatle says zoning only good if return air path is direct. There is a whole sub forum over at whirlpool on air conditioning   http://forums.whirlpool.net.au/forum/138?g=222