extrapolating performance curves for VRF systems

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For the boundary curve, you should predict ODB given IWB, as I show in the spreadsheet. To plot these points on the same graph as CapFT vs ODB, you need to convert the IWB used to regress the boundary curve to a CapFT value at the intersection of the low and high curves. This is simple since the low curves are flat vs ODB for each IWB. So for each IWB, swap out the low CapFT value and then plot the boundary curve using the "IWB converted to CapFT" vs ODB (or CAPFTiwb vs ODB).

Don't forget you can use table objects to describe performance.

http://www.fsec.ucf.edu/en/publicatio... If anyone is interested in doing this, Figure 6 shows how and you would only need the one table and NOT need the boundary curve or the high ODB curve (if I remember correctly).

Waseem, I missed this post originally, but have been making VRF performance curves in a similar manner to you. It' s not clear if your problem has been resolved, so I'll add a couple of thoughts. I have good agreement for my boundary curves when using either quadratic or cubic curves (but cubic seems slightly better). The only way that I can imagine for your boundary curve to vary so greatly from the actual data, which has a distinct and simple shape, is that you have calculated the curve using some incorrect values. As Richard says, the boundary curve data values should be Toa for each WB, in your case only 10 data pairs. This is the chart Richard showed. Did you find the problem? p.s., The chart below shows a composite view of low and high cooling capacity with the boundary condition incorporated. Solid lines are actual data; dashed lines are the curve-predicted values. p.p.s., High quality modeling requires the attention to detail that you have shown by checking the curve's actual performance Good work!