Validity of SEER ratings on AC units (moved from Thermodynamics)

[wfowfo]

I posted this in thermodynamics section by mistake, so my apologies.

The electric Coop I work for spends a lot of time and effort promoting high efficiency AC units (SEER 14 or better).
On the other hand, my brother-in-law sells AC units for a living and has the opinion that, once you get above a certain SEER rating (ie-12), the SEER values become more a matter of the manufacturers ability to manipulate the criteria involved in establishing the values.

His example: The poverty level of <$8,000/yr. hits 10%. So you re-define the poverty level to <$10,000/yr. Fewer people qualify, therefore the poverty level drops to 8%, and it looks like everything is getting better for everyone.

His point being that the criteria used to develope high SEER values becomes more of a marketing game than pure engineering.

What little I can find on the subject indicates that SEER values are established at some arbitrary temperature difference (a 2 degree differential) and not particularly representative of the units efficiency at more realistic temperature extremes.

Any comments? If the above is true, is there a better method of evaluation? We don't want to promote something at our Coop that costs our members more money, but isn't founded in anything more than a marketing ploy.

 

[tombmech]

COP is the proven theoretical method for judging A/C and refrigerant cycle performance. Other quantities are politically motivated and can be manipulated or optimized with little effective improvement to the equipment - as you and your brother-in-law have noted.

My pet peeve with big systems is the infamous "KW/ton" efficiency rating for centrifugal chillers. Very few quantities are manipulated as much and are as misleading - when applied in the field in an overall system.

Unfortunately, whether your brother-in-law is really correct doesn't mean anything, either. Establishing a minimum SEER standard is also a political decision. If a unit doesn't have it, it doesn't have it - period.

 

[wfowfo]

"COP" would be what and where can I research it?

 

[TBP]

COP is coefficient of performance.

It's interesting to note that heating equipment suffers from the same "numbers game" as AC. I particularly dislike the "AFUE" ratings. It seems to me to be the marketing department, rather than engineering, doing efficiency calculations. It's a complex process of trying to get a large number of accurate readings, then apply that data to an equally complex set of calculations. The chances for errors - accidental or otherwise - is very large. It's like the old saying "Figures can't lie, but liars can figure." But manufacturers are required to comply with this process.

All the while the boring old (but dead accurate and easy to calculate from a few pieces of data) "boiler efficiency" calc of "net heat out, divided by heat input times 100" is just left sitting there. It won't tell you where the losses are, but it will capture ALL of the losses. And it can be applied to steam & hot water boilers, forced air furnaces, unit heaters, etc. It would provide an apples to apples comparison allowing the average purchaser to make an informed choice. Oh, wait - making the whole process so overly complex that it can't be verified in field installations may be the point...