SEER vs EER energy simulation 1

[DrRTU]

I am working on an energy simulation as per 90.1-2004 appendix G for a LEEDS project. I am having issues with SEER vs. ERR of unitary packages less than 65K btu/hr. 90.1 requires a SEER of 12.0 but the modeling software uses EER. Units larger then 65K are tested to a different ARI test standard and are rated in EER . Units less than 65K are tested at 85 degrees and larger units are tested at 95 degrees. What EER value have others used for the baseline EER on units less than 65K btu/hr?

 

[gepman]

You have hit on a problem for anyone using energy modeling. Energy efficiency organizations are pushing for the SEER (Seasonal Energy Efficiency Ratio) to go away since there is no direct correlation with EER (Energy Efficiency Ratio). Manufacturers of small unitary equipment don't want it to go away since the SEER numbers are so much higher than the EER numbers.

You have a couple of choices:

1)Contact the manufacturer for the EER rating which they probably know even if they do not publish it.

2) Estimate the EER using the compressor manufacturer's data (this is relatively easy if it is a Copeland compressor since they have all of their compressor data available in sizing software) and the existing SEER number. See the thread

http://www.eng-tips.com/viewthread.cfm?qid=201282&page=2

for information on the software.

Which simulation software are you using?

 

[DrRTU]

Gepman, I am using HAP. The equipment manufacture’s electronic catalog allows me to calculate an actual EER value for “proposed building” but as per table 6.8.1A units less than 65K shall be 12.00 SEER as tested to ARI 210/240. Upon reviewing the ARI standard, SEER is then calculated by three tests:

"B" test - cooling steady state - this is run at 80 db 67 wb and 82 db condenser air.

"C" test - steady state dry coil test - this is run at 80 db 57 wb and 82 db condenser air.

"D" test - Cycling dry coil test - this is run at 80 db 57 wb and 82 db condenser air - unit is cycled off and the degradation in cooling energy is measured.

SEER is then calculated as: SEER = PLF(0.5) * EER "B" test

PLF(0.5) = 1 - 0.5 * CD CD is derived from the "C" and "D" tests.

The default is a CD of 0.25

This results in an EER of 13.71 on a SEER 12. This seems wrong due to the EER exceeds the SEER

I find it very odd that we use EER at 95 degrees on larger unit and 82 degrees on small unit in the same model.

 

[gepman]

I never looked at ARI 210/240 before. The SEER number appears to be an attempt to balance sensible and latent heat removal capacities (based upon a dry coil and wet coil test) at an unrealistically low temperature. Therefore this number is afffected by the indoor coil design along with the compressor efficiency, condenser efficiency, and indoor and outdoor fan efficiency.

I think that there is some problem with the formula that you gave. Of the formula is PLF(0.5) = 1 - [0.5 * CD] then PLF(.5) would have to be greater than unity (one) for the SEER to be greater than the EER. This means that CD would have to be a negative number. Either that or the EER "B" is not the EER that is referred to in the modeling software (again very possible). Without spending a huge amount of time researching this I will direct you to a statement that I found at the following link:

http://www.aceee.org/pubs/a042_h2.pdf

"For baseline residential units we use a SEER12/EER 10 unit".

 

[DrRTU]

Gepman, you are correct on your assessment but formula is directly from the standard. I looked at a few catalog selections and ERR = approximately SEER * (.8 to .9) but they have a note stating EER is not as per ARI.

 

[gepman]

The EER is probably at a higher condensing air temperature which makes sense, probably at least 95 deg. F. I would use the EER that is approximately .8 or .9 of SEER because that is what I think that the modeling software would expect. I haven't done any energy analysis with HAP (my latest is 4.04) but I did a fair amount of design. I use eQUEST for my energy analysis which is a good energy analysis tool (but not as good a design tool, I feel, as HAP).

If you are interested in eQUEST you can download it for free at

http://www.doe2.com/equest/

courtesy of California electric utility ratepayers.