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Air conditioner efficiency: what do they change other than using more materials? (aussie.zone)

submitted 6 days ago* (last edited 6 days ago) by [email protected] to c/askscience

13 comments fedilink hide all child comments

Context: I am not a fridgy, I work with electronics. I would love to answer my question by tearing open a dozen different aircon units, but I'm sorely lacking in that department.

Question: Are there some optional components or fancier materials that are simply too expensive to use in the lower end aircons; but are used in the higher efficiency expensive units? The range of COP/EER I see advertised is wild, from 2 to 6 or so.

I already vaguely understand that these things help efficiency:

Bigger indoor & outdoor coils with more metal in them (working fluids get returned hotter/colder gives better carnot efficiency)
Operating compressor at its optimal power level (I believe they have an efficiency vs power curve with a single peak, so it's better to use a bigger compressor if you need more power output)
Inverter control instead of on/off control (most situations, but technically some use cases will have them on par)
Choice of refrigerant (but that seems to be controlled in my market, I have not seen many options)

Is there anything else they change? Or is that most of the difference?

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[–] [email protected] 13 points 6 days ago* (last edited 6 days ago) (1 children)

Micro channel vs tube and fin coils is another area for you to look into in terms of build differences.

Then you get your indoor coil shapes, A coil vs N coil. You got your pistons vs thermo static valve (txv)

there is a lot of areas in the equipment and accompanying equipment that will throw those efficiencies out the window..

[–] [email protected] 5 points 6 days ago (1 children)

Microchannel coils: Wow. I assumed the pressures were too high for such construction to succeed. Thankyou :)

Fluid metering: I was aware of TXVs and capillary tubes, but not reverse bypass piston inserts. Would these options only be a few dollars difference in BOM price between each other? I guess the extra labour from soldering more pipes and connections for a TXV might be more costly than the extra materials themselves.

A vs N folded coils: interesting. I have mostly seen split systems and their unfolded coils, not central AC units with these A & N folded coils.

[–] [email protected] 1 points 5 days ago

Cars have micro channel evap coils, central does as well. Not sure about ductless however, probably not unless it's outdoor

Reversing valve is typically in heat pump applications, allows the refrigerant to flow in reverse effectively supplying heat to the space instead of extracting it.

I'm used to central AC mostly, but I have worked with and used ductless, I'm not overly a fan myself. Controls are too much. I like simple relays and switches, less logic on the board. I want to be able to repair failures easily should they arise.