Question regarding DX-Cool-EIR-fPLR

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Everyone, has anyone ever modified the standard DX-Cool-EIR-fPLR curve
to fit a particular DX cooling system? If so, when you compared it to a
baseline DX cooling system, did you use the original eQuest
DX-Cool-EIR-fPLR?

I looked through ASHRAE 90.1 -2007 and although there is full load EER
data for air conditioners and heat pumps, there is no IEER data.

However, it occurs to me that if ASHRAE 90.1 starts including IEER data
(which shows up in ASHRAE 90.1 -2010 Section 6) how are we going to
modify the eQuest DX-Cool-EIR-fPLR to accommodate the IEER? The IEER is
a single number and we have no idea what the 25%, 50%, 75% cooling load
ratios look like.

Hmmm.

Kathryn Kerns

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Hi Kathryn,

On our projects where we take credit for part load efficiencies we use addendum s to 90.1-2007. This adds in IEER values for units so you're comparing apples to apples. The only projects we have modeled this on have had baseline systems that were 9.5 EER with an IEER of 9.6. With such a small difference between EER and IEER, the 25%, 50% and 75% values aren't that important. 9.5 EER at full load and 9.6 at the other values will get you the 9.6 required for baseline. For information on how to make curves I would look through the archives of this user group, there have been some great explanations.

Bobby Almeida, E.I.T.

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You would need to evaluate/modify two separate curves to match the IEER. IEER is a function of part load and condenser temperature, holding return air temperature (EAT) constant. The COOL-EIR-FPLR curve is a function of the part load ratio only, not temperature. The COOL-EIR-FT curve is a function of EAT and condenser temperature (OAT or EWT).

The IEER formula and methodology are described in section 6.2 of AHRI 340/360-2007 with Addenda 1 and 2.

Regards,
Bill

William Bishop, PE, BEMP, BEAP, LEED AP

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Remember a packaged cooling equipment EER is the ratio of cooling effect (Btu/hr) provided divided by the total (supply fan, compressor, condenser fans and controls) energy draw (W).
So to get from the packaged unit EER to DOE-2 cooling EIR value and the EIR curves you need to remove the fan energy at each point. That AHRI standard that Bill mentioned addresses what the fan volume and static pressure (but not explicitly fan power) has to be at each of the four part load points. Good luck.

Paul Riemer, PE, LEED AP BD+C
DUNHAM

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Thanks for the input. Yes I know we need to pull out the fan energy and yes I am familair with the AHRI 340/360-2007 methodology for creating an IEER value, and yes I concede that modifying the part load curve without modyfing the other curve is going to be an approximation. The point is - given a baseline IEER value can we create a baseline part load DX curve without the raw data? For that matter, given a proposed system IEER can we create a part load curve? I think the answer is, you can't. I can probably solve the proposed part load problem by asking a manufacturer for their IEER data, but what to do about the baseline?

I sense there is a way to gain energy savings here, but I am not sure how to go about proving it to the satisfaction of our unfortunately challenged LEED reviewers.

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ASHRAE 90.1-2010 Section G3.1.2.1 specifically requires that modelers reset the baseline equipment to match the IEER specified in the code.

I'm curious if the modeling research community (eg ASHRAE-funded, utility-funded, etc) have given any thought to an expected procedure to accomplish this.

One option would be for ASHRAE or another entity to produce peer-reviewed research developing specific baseline curves for specific pieces of equipment.

Until that time, the IEER rating conditions allow for a multitude of possible part load curves that would all comply with the minimum IEER.

Until that time, if any individual modeler creates a baseline curve that successfully calculates to the required baseline IEER, on what grounds could a reviewer or authority challenge that the modeler has violated the intent of G3.1.2.1?

Then,

Aaron Dahlstrom, PE, LEED(r) AP

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I don't know. I asked this question earlier because I sensed that there
was a way to show extra energy savings if we could define the baseline,
but I don't think anyone in the community has an answer. I am thinking
that unless someone gets an official ruling otherwise, I am going to
assume the DX baseline is single stage for smaller DX units, 2 stage for
larger (above 10 tons?) DX units, and 4 stage for really large (above 40
ton) DX units. It may not be right, but if people force you to use
things and not define them, you have to guess something.

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