On 28.07.2014, at 01:22, "Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
Dear forum,
I and fellow forum member Francesco Passerini are working together to better represent the IPLV minimum required for DX coils (by ASHRAE 90.1 ? 2007).&nbssp; I have not paid close attention to this value in the past! My COP / EER values are â??perfectâ??, but my IPLV values have been much higher than are required by 90.1 This is primarily because I have used curve coefficients from example files for â??Baselineâ?? models. Those seemed reasonable and conservative?. But they alll result in improved EER at part loads, whereas the 90.1 IPLV values allow worse EER at part load.
Francesco pointed out that an undesirable result of this is that the Baseline energy model uses less energy than if the IPLV was â??perfectâ?? and may not gain as many LEED points for his clients. I believe that he is correct!
We think that we have created a reasonable solution, and would appreciate feedback from you regarding the calculation (which is attached).
Here is a summary of our observations so far:
· IPLV does not apply to equipment without capacity modulation (Larger DX equipment almost certainly has modulation, which is why 90.1 Table 6.8.1A. mentions IPLV only for capacities > 760 MBH / 220kW)
· IPLV assumes standard conditions for indoor (evaporator) and outdoor (condenser) coils
1. Coil entering condition: 80F/27C dry bulb & 67F/19C wet bulb
2. Outdoor part-load: 80F/27C dry bulb & 67F/19C wet bulb (coincidentally the same as indoor condition and applicable to ALL part-loads)
3. Outdoor full-load: 95F/35C dry bulb & 75F/24C wet bulb
· Two criteria must be met in an energy model regarding IPLV:
1. The Capacity and EIR curves must result in 1.00 at the â??rating conditionsâ?? of #1 & #3 above (so EER / COP is correct)
2. The part-load EIR must result in the proper IPLV. (I think it can remain constant.)
p.s., We have not yet tested this solution, but will do so shortly. Weâ??re hoping for constructive criticism about our methodology.
James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653
<IPLV Calcs 14-0727.xlsb>
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