robbo mcs wrote: ↑Wed Jan 31, 2024 7:38 pm
Ducted systems are getting a bit of a bad rap on here, not all deserved.
The thing about then sucking warm air in the inlet is a bit of furphy. The air circulates from the high pressure area (rooms with outlet vents) to a central low pressure area with the inlet vent, usually in a hall. Normally the area where the vent is only 1-2C warmer than the rooms with outlet at the most, more often the same temperature. It is not like you are sucking it from 40C outside. So if you are just running a zone in one room, then it is only cooling that room and the hall.
Ducted generally is more efficient at keeping temperatures even within a room and across the house.
Also generally quieter than a split, talking about the air circulation, not the compressor which is the same.
The other thing about ducted systems is they are very efficient at equalising temps and spreading cool or warm air, even when not used in heating or cooling mode, just with the fan. So if you have a hot half of the house facing west, and a cool half facing east, you can run in low speed fan mode, and equalise the temps, even without running the compressor.
The modern ducted control systems are generally extremely flexible, and tend to offer a lot more fancy remote access options and smart control systems than splits
I have a house with ducted, and a holiday place with splits. I travel a lot, and stay in a lot of accomodation mostly with splits. I would rather have ducted any day for a house, unless it is tiny. A small apartment, then split is probably just as good
I absolutely agree about ducted being a less "obstrusive" system to use.
In my situation over the last few weeks in Brisbane, I have had temperatures inside the house of up to 32° and 70% humidity in the early evenings (the western side gets a bit hotter than the eastern side).
Typically I will turn on my 5kW split in my lounge room around 7pm, and run it until about 10pm. It is set for 25° (and gets there within about 30 minutes if it starts around 29°). The rest of the house is still at 29-30°.
Then around 8:30pm I will start my bedroom 3.5kW unit and set it to 20º (to drop the humidity as low as possible - it gets there from 30° in about 75 minutes). The rest of the house is still at 27-29°.
Then at around 10pm, the loungeroom unit goes off and the bedroom unit is set to 23° where it stays all night (it tends to "over-cool a touch and be around 21-22° at 6am the next morning).
Recently the temps in the rest of the house at 6am (when the bedroom unit is turned off) is between 25-28° and "sticky" with the outside humidity around 90-100%. For weeks now we have had "feels like" temps of over 30° at 7am due to high humidity & dew points. Also in times of sustained high temps (where it doesn't cool much overnight) the house insulation tends to get saturated after a few days, and if anything tends to trap heat inside overnight.
So, in my situation I can have 5°(or more - and that is after the initial cooldown which has closer to 10° difference) difference between our main bedroom & ensuite (under 40m²) and the rest of the house. If I had a ducted system the return vent would probably be in the main hallway and I would have to cool at least 120-140m² as (like most houses) it is fairly open plan and has a long U-shaped hallway that runs right around the house to the kitchen & family room. I would also have to close off the doors to the other bedrooms, study, laundry & longeroom which would get annoying doing that daily. Even though the area with the return vent wouldn't be set to cool to 23°, it would be seeing some cooling from the "high pressure" air being pushed back out under the bedroom door. What may, of course, be even more of a concern is the amount of that "high pressure" air that the ducted system is blowing into the bedroom is escaping through the ensuite extractor fan into the roof space (which I obviously don't want to pay to cool).
That is why I said above that choice between ducted & splits is a personal one that depends entirely on the design of the house and the needs / makeup of the people living there (and the location). If the house has good segregation (ie. doors that can be easily closed), and several rooms are being used simultaneously (like multiple bedrooms being used) and/or the house is in an area (perhaps like Perth) where things tend to cool down more obviously at night, or the humidity effect is less, then ducted may well be a better choice.
But if the cooling is for primarily people sleeping in one or two bedrooms (which is the impression I got from the poster who first mentioned getting AC, and I think he was in Brisbane, like me), and the location is in a high humidity area where the temperature doesn't drop much at night, then splits may be a better choice. In this situation I would wager that running 1-2 splits in bedrooms would consume a fraction of the electricity of running the ducted system all night.
Anyhoo, yes we have got off track a bit, so I will shut up now
