Split system brands - any difference?

[Timmo]

Agreed they should be tested.

One problem with some inverters though is that the thermostats are outright dodgy.

Say you set it to 22 and it's in heating mode. Obviously if the temp drops to 21 then you want the unit to do whatever it takes to bring it back up to 22. If that's running at 100% constantly then so be it, you want 22 not 21.

But some cheat. They'll never run at 100% unless there's a big gap between the setting and actual room temperature. And so the only way for the consumer to get the unit to work properly is to set it warmer than they really want - with some you literally need to set it at 28 just to get full output in a 21 degree room and warm it to 22.

All split systems ought to be limited to a normal operation temperature variation of +/- 1.5 degrees otherwise they fail MEPS. That is, if it's set to 22 then at the very worst it ought to be at full output at anything below 20.5 and at full cooling output at or above 23.5

Ideally, a narrower range is desirable as this will reduce energy consumption - most people set thermostats to maintain comfort at the minimum point in the cycle (in heating mode) so the less accurate it is, the more over-heating takes place. Given that a simple bi-metal thermostat has a range of less than 1 degree for a quality unit it's not difficult to do. For that matter, a simple Dick Smith kit keeps my fish tank within 0.1 degrees. So a $2000 air-conditioner ought not have temperature variation of 6 or even 2 degrees from the set point.

3 degrees from hottest to coldest (that is, hottest point in cooling mode to coldest point in heating mode including the changeover) is pretty well accepted as being about the limit for comfort. Hence +/- 1.5 is the practical limit from the set point for a reverse cycle air-conditioner. And since most measure the temperature quite close (or in) the machine itself, that reduces the margin even further.

The shortfall of proportional only control loops. Inverters really need to be driven by P.I or P.I.D control to make the most out of their capability.

[Guvnaar]

.......at the total cost of purchase and operation. The cheaper ones might only cost $10 a month more to run , but over 10 years that more than makes up for price differences. BTW the cost of electricity is also only going to go up.

Installed a 4 1/2 star 7.1kW MHI unit in Jan, runs like a dream, very powerful and quiet - also got a great price on it so was very happy.

Until....... I copped the my first power bill of $550. Up from about $120. Now there were a few hot weeks in melbourne but most of the time I had the thing on economy mode and set the temp to 24C, only had it on once overnight.

Since the power fees are going up 17% I would advise people to rethink. Spend the money on isulation. Im thinking of replacing the doors with vaccum chambers and boxing in all my windows.

[Ashore]

From reading the posts it seams to come down to a decision of invertor or not
As an Engineer who has dealt with serviced and maintained ac units for over 30 years , (though much of that was before invertor systems) and having both a split system ( for the extensions) and a fully ducted system for the main house I am yet to be sold on the economic advantages of the inverter Ac units.
As for brand there is obviouslly little between the top brands so my advice would be to go with the best and easiest remote controle unit, Now this may sound silly but a remote that is easy and simple to use is proberly more important than a complex one when the output of the AC is close to the others