Thread: Ducted whole house or wall splits ?

We have a long house with the boys down one end in an area containing two bedrooms, a TV room, bathroom and WC. We have a 5kW split in this TV room with an exhaust pulling air from the two bedrooms into the TV room. Without this flow the conditioned air cannot get into the bedrooms.

The rest of the house is served by one ducted AC with 3 zones.

The efficiency comes from the compressor type, being an inverter, scroll, whatever.

Splits are good for one room but you need something to pull air into the adjoining rooms.

If you don't have 3 phase power running to your house, then there's no point in going to the expense of doing so just to run an air con when there are plenty of perfectly good single phase units available.


Advice from air con specialist I know - brand wise - Daikin, closely followed by Mitsubishi Electric, followed by the also rans.....

Originally Posted by VladTepes

If you don't have 3 phase power running to your house, then there's no point in going to the expense of doing so just to run an air con when there are plenty of perfectly good single phase units available.


Advice from air con specialist I know - brand wise - Daikin, closely followed by Mitsubishi Electric, followed by the also rans.....

x2 For the brand list. Have 4 2.5kw splits and a 7kw split and a larger ducted 10kw system on my 2nd floor at work.

One thing you might like to consider is a 5.2kw solar system. I run the AC units during all day at work and 95% of my power bill is now covered by the PV system. I do not sell any back into the grid for the chicken feed rate they pay except on days I am closed .

I know that the solar will not be as helpful in winter as it is at the moment.

The evaporative system I had at home was the PITA. never worked when hot and humid like yours and was never needed the rest of the time

Insulation first is the key to not paying a truck load. Wish I owned the building at work as it had almost zero insulation in the roof.

Efficiency wise, small highwall splits would have the advantage over a split ducted. Some of the highwalls around 2-3kw are ridiculously efficient these days.

Split ducted units are a lot better for aesthetics though, inside and outside.

Never crossed my aging brain to draw air into the bedrooms with an exhaust fan back into the 'conditioned' room.

Luckily we have 3-phase power already connected. - SEC wanted to disconnect it when they installed the bi-directional meter.

We have 4.5kW of PV arrays up on the roof, in 3 'strings'. - Two facing NE and a recent, smaller set aimed for the afternoon sun.
Roof is about 17 degrees rake. - Not the most efficient angle but does OK.

Currently (sorry!) we're nearly $1k in credit, but then again, we're on the 40 cents per unit State Gov. bonus, plus 7 cents to SEC for exported power, which we buy back at 27 cents or thereabouts...

My medium term plan was to set up some more PVs, this time those 'in-built' inverters connected to the two phases not on the main, 4500W inverter. - But would still 'export' when the A/C was off.
This way, both styles of system would co-exist and at minimal co$t up-front.

Ideally, I'd like to keep the evap. unit, (IF we can rebalance the fan/motor) only because it's cheaper (?) to run and still handles over 50% of warm weather.

Plus, saves a long sheet of tin plus hassles of pulling it out !

I've hadn't heard that Mitsubishi have a reputation for quiet units... maybe that's why...

Yes, we do have R2 insulation throughout most of the house. Sheep-Wool over our main bedroom and poly-wool over most of the rest.

I've noticed that some brands are not terribly efficient on 'reverse', - their 'warming' kW are nearly the same as 'cooling'. Mitsi appear to be one of the more efficient ones...
Interesting comment on overall compressor and system efficiency ?

Originally Posted by Beery

Efficiency wise, small highwall splits would have the advantage over a split ducted. Some of the highwalls around 2-3kw are ridiculously efficient these days.

Split ducted units are a lot better for aesthetics though, inside and outside.

Another thought just appeared...
(Uncommon... so I tend to cherish the few that show up... )

Does anyone make a wall-split...where the main 'guts' is mounted OUTside the wall, with only intake/output grilles INside the house?
ie, from INside, you'd only see an intake grille (mounted at whatever the ideal height would be) and the cold grille mounted up higher, like a ventilation register...
That way, most of the circulatory fan noise/rattles/vibration is outside the house...
Agree. some bedroom-sized 1 to 3kW are ... very co$t-effective.

I can comment on longevity not the power consumption

your setup sounds great, Nice to be on that great grid price
The Power of my old Ducted heat/cooling is unknown as it is very old. Of all the Splits I installed 10 years ago the big one has failed once- Not a brand mentioned or will it be
I put a large Daikin inverter in 3 years ago. Unlike most home the work one is on 12 hours plus per day except sunday and a 1/2 day saturday.

If you had a two story place or a basement drawing cool are up or down (or warm air) makes a lot of sense. THe only risk I would see is if the unit is capable of a certain size and you tried to us it via moving the air from one room to another is overloading its capacity and reducing it effective life A bit like using a 2.5kw system in a house than needs 27kw of cooling

As I am renovating i had a energy rating done. It was very interesting as the 6 star plus build did not need what a few salesmen suggested I will need.

I looked at Tech Pack | ARVIO | The Home of Innovation Breath Fresh Air for Air Circulation and BIOPCM? to reduce heating cooling loads more. Still considering the Biopcm.

Originally Posted by VladTepes

Advice from air con specialist I know - brand wise - Daikin, closely followed by Mitsubishi Electric, followed by the also rans.....

Actually disagree.

Mitsubishi Heavy Industries and Daikin are the top of the tree IMO, and I lean heavily toward MHI as I've had less warranty problems with them. (two in eight years)

One of the blokes I'm currently working with confirmed that's his experience too, and he said the company he used to work for had heaps of Mitsubishi Electric and Fujitsu warranty issues.

Toshiba seem pretty good too, I started to trial them as a slightly cheaper/less bells and whistles option to MHI when I had my own business, and performance and efficiency wise they are very good.
I'm not fussed with the Korean stuff at all.

More important is the installation.

I've seen some shocking stuff done regardless of brand, and watched with amazement recently how an installer was piping up a commercial ducted system for a bar.
(We were installing the refrigeration, coolroom and beer systems)



Single phase up to 14kw nominal in a ducted system is easy, the modern inverters are incredibly efficient.
I've used 14kw ducted and 14kw commercial cassette systems in clubs and the quietness and efficiency is amazing, and as previously said, the 2.5kw and 3.5kw high wall splits are incredibly cheap to run these days, their COP is incredible.