Ducted heating or heat/cooling

hi Willimstown,

I just purchased a single phase 14.5kW cooling/16kW heating Mitsubishi inverter ducted system. Its the largest of the single phase units. Cost me around the $10k mark and it runs beautifully. Very quiet and easy to use. I was actually talked out of purchasing Daikin. The installer told me they used to be good but turned bad a few years ago. Apparently most of the call outs he has with problems on newer systems (2 years or less) are mostly Daikin. They have dropped their quality. He recommended Mitsa by far.
If you're goint to stay in your place, it would pay to install gas heating also. Its a hell of a lot cheaper to run. Much cheaper!
I don't know why they've quoted you on a 20kW heating system. How big is your house? General rule from my research suggested 1kW for every square of your home...but there are many considerations to take into account of course. If you're interested in the mob I used, let me know. These blokes were really down to earth and actually went out of their way to help me save money on the installation, which is something you don't find much of anymore.

Dan.

Ken,
House is approx 130m2 and based on my calculations I would need between 15kw (fairair.com.au) and 18kw (Aircon direct), given I have 3.6mtr ceilings in most of the house. What is the size of the area your heating?


Do you have an idea how much cheaper the gas is to run then the inverter? I seem to be getting different advice based on the quote as only one person over the phone has told me that the gas is cheaper to run with most of them saying an inverter is similar price to run (however I’m pretty sure a 5* gas system with regulated gas flow will be cheaper). I just spoke to someone at Glo heating/cooling and they suggested def going gas for heating and bolt on the cooling later (price is similar) assuming correct ducting is used now..
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I assume you are happy with the unit then, I assume you haven’t received a electricity bill to give an indication of running cost? Is it a Mitsubishi Electric or Mitsubishi Heavy Industries unit?
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Do you have the system zoned and/or have you tried heating/cooling the whole house and if so how did it go?

Who did you have install the unit? I'd be interested talking to them.

Regards, Darren
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The 12kw is most prob zoned and the heating quote not hence why they have it big enough to do the whole house.

Zoning will add to both materials cost by about $120 a zone plus the installer mark up and install cost. But remember the benefit is that you are only paying to heat/cool the half of the house you are auctually in. There are many brand/s and types of zoning on the market, some bad and some good, alot of people pay attention to the brand of unit and forget about the zoning, thinking all are created equal. If you want any advise of zoning let me know.

Also if your wanting a top of the range unit that is better than a mitsubishi consider using a actron, their new esp units are very good and they can also supply intergrated zoning so that the zones work in conjuctiion with the unit and not independantly

Originally Posted by AIRMAN

Zoning will add to both materials cost by about $120 a zone plus the installer mark up and install cost. But remember the benefit is that you are only paying to heat/cool the half of the house you are auctually in. There are many brand/s and types of zoning on the market, some bad and some good, alot of people pay attention to the brand of unit and forget about the zoning, thinking all are created equal. If you want any advise of zoning let me know.

Airman,
Thanks for your comments, that makes sense. There is a minimum area that can be heated/cooled with an inverter system (flow and power), which for 12KW is approx 5kw and for 20kw is close to 8kw, so using a larger system may mean more zones need to be on at one time.
What I don't understand is that given my return will be in a common area (in the middle of the house) if I want to heat the bedrooms for example the return air still needs to flow via the common areas to get to the return vent. Doesn't zoning only make sense if the zone areas can be closed off, otherwise the return area is still being cooled/warmed running through the zones that are off.

Thanks for the tip abotu the actron, will check it out.

Your right about the return air as the unit will only cool/heat the return air by a certain amount of degrees, at myplace I have a a return and supply in every area, they are all zoned so when the zone turns on the return air also turns on. This is not very practicle for most people as it would be very expensive to do and install, it's like putting 2 set's of ducting, grilles and zoing in. I only did it as I got all the materials free and did the labour myself. Also by doing this I used a smaller unit as it doesn't have to work so hard, it also means that doors don't need to be undercut.

The actron units are more efficient than a inverter, the compressor can ramp all the way down to 10% as compared to a inverter that can only go, as you say down to about 40%.