Why are residential splits more efficient than commercial?

[jvithayapun]

Im looking at some Carrier condensers and the residential
(ex. model 24APA760---30, 5 ton) has a SEER=16, EER=13ish. Then if you look at the commercial models (while it is 1 ton more) a 6 ton unit has an EER=11.

I think I have seen this pretty common across the board from different manufacturers.

1) What difference is there b/w a residential unit vs commercial unit which causes a significant difference in EER/SEER rating?

2) What are the cons of using a multiple residential units (say 2 5-ton units) vs a single 10-ton commercial unit? It seems that the residential units would be more efficient.


thanks!

 

[TwinScrew]

1) Typically: Higher efficiency = larger condenser coils = additional material (namely, copper) = higher cost.

The commercial industry is, for the most part, cost-driven. You will notice that on most commercial jobs, 'minimum' efficiency equipment (as per ASHRAE 90.1) is specified/supplied. There are exceptions if the owner is willing to spend the money (ie. LEED Projects, institutions/hospitals, etc.).

2) Residential units are often more efficient, however, you will then be piping up 2 separate systems. This costs $ in labour, copper, etc. Again, most end users aren't as concerned with costs over the long term, as they are with short.

 

[Compositepro]

My guess is that residential units are made with lighter gauge closely spaced fins that give better initial thermal efficiency at a lower cost. This also results in a shorter service life due to fouling and corrosion.

 

[imok2]

Money = cost = efficiency

 

[EnergyProfessional]

EER does not equal SEER. SEER include some seasonal ("S" in SEER). Larger equipment often has IPLV (partial load ) rating that is higher than EER.

to actually judge efficiency you need unload curve and ambient relief and model it in Trane TRACE or similar software for your climate. EER, SEER, IPLV are just indicators based on some lab set points. Better than nothing, but not sufficient.