Are these Air-Con units adequate or too much?

Hi,

I'm getting to the time of selecting AC for my new build. Downstairs all internal living area is about 160 squares, upstairs is 80 squares.

I got an initial quote of 1 unit Daikon ducted 16kw to run the entire house. Later they reckon this will be a struggle and not efficient.

Now a new quote of two Daikon units, one 16kw to run downstairs and one 14kw to run upstairs.

Is it better to have two units for a better efficiency?

your installer should be able to explain this in greater detail for you and provide the calculations for the size of your home and usage of the system. But to put it in perspective i have a 24kw actron for a 32sq single level home.

I'm sure the installer/seller will have good reasons to sell me these two units. I just want an idea of what size unit is capable of what size room. I've only used split systems in the past. For ducted AC, they said the ducts would be too long to run off 1 unit to reach each room.

Thank you, you've always been helpful.

I think youre missing what im saying - the sizing has to be calculated by the installer, not to sell you two systems, but to ensure they meet your cooling needs. Those calculations can be provided to you to show how they came to the conclusion you need this size system.

Part of the calculations considers your usual living arrangements - i.e. how many rooms will be occupied at a time, whole house cooling only half at a time or mixed. All of this needs to be factored in.

The calcs will show how many KW is required for each area, then its added up to work out total KW required for whole house cooling - then depending on how you want to split your cooling needs, youll be able to work out if you need 16 or 30kw.

WHo is your installer?

I have 240sqm living areas and a daikin 16kw 3phase ducted system is plenty big enough for cooling in Brisbane summers. The worst part is its too big to run just the bedrooms at night during sleeping hours so its running some living as well which is a waste of power.

Have you checked your nathers certificate? It usually have the heating and cooling cooling on per square meter. Its also climate dependent. My internal space is 241 square meters. My daytime area is 120 square meters which is the ground floor area. My 14kw ducted aircon is quite big already. My climate is zone 65 cold temperate.

By the way upgrading your insulation, minimizing windows facing east and west if possible is better option.

I'm in 62 climate zone in VIC. Just checked the report, it says 98.6MJ/m2 for heating and 24MJ/m2 for cooling.

I have minimum west facing windows, only splashback, laundry and ensuites windows. East facing only has living rooms downstairs. All bedroom windows face north or south.

Someone my builder uses regularly I think.

So it seems that the installer hasn't spoken with you then? Id suggest a call with the installer to discuss your cooling needs and calcs to get comfort your system is sized for you needs correctly.

Alternitively there calcs publishe don line on how to calculate the system size you could do on a whole home basis to get a ball park figure, but youll need to speak with the instalelr for a more detailed break down

What

Yourr r 16kw is more than enough. Its heating rating is 18kw. Zone your house. For daytime and nightime areas

Really? The reply from the guy in Brisbane says it's big enough too.

There are probably only 2 people in the house most of the time anyway.

The house is built on stumps and bearers. Ducts will run under floor for downstairs, and run in ceiling for upstairs. My builder was saying either the ducts would be too long or too difficult to reach everywhere from just one unit.

your assumption is that their cooling needs are neatly split between day time living and night time bedrooms and doesn't require whole home cooling (or a variation of) As does the calc you send me in PM.

Where this falls over is if for example is if you have kids who utilise the upstairs bedrooms/rumpus while adults are downstairs during the day. A very common scenario. You cant cool both zones effectively or efficiently on 16KW.

Hence the system needs to be sized to your needs.

If your needs are neatly split in day/night time, great. That doesn't mean everyone else's is.

I see.

There are probably only 2 people in this house for most of the time. No kids, and there is no activity/rumpus upstairs. So unlikely to spend any time upstairs other than sleeping.

In saying that, I probably do want to switch on the AC before I go to bed in summer, while I'm still downstairs.

you do lose efficiency the longer the ducts are. Worth noting. That's why i keep saying speak to the installer (or even an installer youre not using to keep it unbiased)

You wouldn't ask your dentist to give you advice for a skin disorder.

To solve for the aircon size use the data from nathers multiply it by the area you want to condition then convert mj to kw and divide the overall result to 365

if there are only two people, you may considder ducted downstairs, and splits up top. Because 14kw seperate system for upstairs with only two people will be expensive to run.. You wont be able to just run it for one bedroom and will likley be a waste of energy.

but yeah have a think about your usage patterns and where you will be in the house. You always with your partner?

I'll try to get another opinion from a different installer.

I do have a second quote of one Bravis 15kw unit, but the cost is almost the same as two Daikon units.

There is one guest bed downstairs and 3 beds upstairs only. The guest bed might get turned into exercise room or something. I'd assume we will have either downstairs turned on or upstairs all 3 rooms turned on if family/friends are staying.

I can cool the whole house (all zones on) in a 35+ degree Brisbane summers day no issue with a 16kw, with the house including some huge single glazed western windows and large void. Just standard roof and wall insulation too - nothing special.

Of course you should do your own research but I reckon you'd be fine with 16kw.

As stated above i'd consider ducted down and some splits for upstairs for optimal efficiency. Ducted isnt most efficient but certainly looks best, easy to control, quiet etc.