Inverter types try to accomplish the constant temp (constant in a range of a few degrees), that’s why they have an operating range, as some were pointed out in an earlier post of mine. It is important to get the right range for the room eg a 5 kW would be cycling like an older compressor type as it would be just too much. I definitely think that a recommendation will be between the 2.5 kW and a 3.5 kW unit. Both have a low roughly 1 kW lower output so both will drop to that level as the room cools to the set temp. It will be what is the upper part of the range needed that will determine the unit capacity and this is what an assessment will be determining.
2 Likes
I can attest to the fact that the 3.5 in my bedroom does not and is incapable of ‘changing the temp quickly’ if the room is warm. When the room is at temp it is a nice low power consumption idle or just above on cooling on a 28~30 day, and it runs moderately hard from the mid-30s. I do not routinely use it for heat since we have a hydronic system, so won’t comment on that aspect.
IMO a 2.5 would for the OPs need would be marginal although probably could do the job. If the 2.5 could not, there is no way to recover. When one has a situation on the balance between two sizes it is usually best to go one up.
3 Likes
We have the SRK25ZSA-w for our two bedrooms. Approx 15sq m each. SE Qld timber house with basic ceiling insulation. They are quiet. Handle our 35C summers and higher peaks really well. Once the rooms are cooled in summer they draw very little power, as recorded by our solar smart meter over night.
The difference with the ‘X’ (Avanti vs Avanti Plus for the -X) is approx 10% in efficiency. There are some other minor differences. You might like to look to the MHI web site here for access to the main brochure and basic specs. It’s worth half a Star better on GEMs 2019 labelling.
https://mhiaa.com.au/document/split-systems-brochure/
These particular models do not cycle the room temperature. The inverter drive and control system provide a very even temperature and well regulated almost silent airflow.
We have two larger 7.1kW units in our kitchen and living areas. Also excellent. One manages 50sq m mid summer with insulated ceiling and verandahs to shade the windows/walls. The other a slightly smaller area including the kitchen. So both are about twice the size of your 23sqm bedroom, one having all the stray heat loads from the kitchen.
The MHI approximate sizing chart might guide your sizing if you choose to go with MHI.
https://mhiaa.com.au/document/srkdxk-room-sizing-chart/
P.S.
As a guide to pricing Bunnings have the Avanti (not the plus model) listed at $799 2.5kW SRK25ZSA and larger 3.5kW SRK35ZSA for $959. No need to buy at Bunnings. Just be careful not to pay more.
I’ve seen the SRK25ZSXA listed at $1050. Note there may currently be a manufacturers/brand cash back offer on selected or all models in the MHI range. Applicable where ever you purchase from.
Edit note:
I’m inclined the same as @PhilT for sizing if the call is marginal go up one. A 3.5kW high efficiency inverter unit will draw very little extra power (running cost) compared to a 2.5kW for the same cooling load, on average loads. Some users might accept setting the temperature a little higher on really hot days 27C or 28C rather than the recommended 25-26C. Each degree warmer supposedly saves 10% on the power bill. There are ways to get away with a unit that is ok most days, but smaller than you might like, at the cost of not staying cool. If as you suggest keeping the temperature consistent is critical a 3.5kW unit is available in the Avanti-Plus (-X) models. It’s what we would need for a 25-30 sq m room with shaded walls and insulated ceiling.
2 Likes
Depending on the severity of your daughter’s sensitivity, it may be worth considering additional measures because no matter the size of the unit as discussed above, there will be variations in temperature around the room.
Your primary consideration needs to be how to equalize the temperature around the room so it is not hotter or colder near the head unit compared to other parts of the room.
Perhaps you could add a reversable ceiling fan as well to increase the air circulation, thereby better equalizing the temperature?
1 Like
Postscript: installer recommended 3.5 kW. So, we have installed that and all seems fine.
3 Likes
