Variable Speed Screw Chiller Curves

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Well, I?m going over a year back into the archives, but hopefully someone can help. I?m modeling a project with 500 Ton Carrier Evergreen Water-Cooled Screw Chillers and would like to take advantage of the part-load efficiency benefits. It appears that Dan Nall posted custom efficiency curves for this specific equipment a while back, but when I use them in eQUEST my cooling energy gets tripled (from 800 MWh to 2450 MWh) as compared to the default eQUEST curves for Water-cooled Screw chillers. Does anyone have experience using these curves effectively? Am I misinterpreting the curve data? Are they intended for something other than eQUEST inputs? Or are the default eQUEST curves unrealistically efficient?

Thanks for any input,

Dan Russell

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Joined: 2011-09-30
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You may want to run an eQuest report on the chiller to see how the efficiency is varying throughout the year. Output the load and the power at each hour and you should get a better idea of whether the curves are working or not, or if the default curves are reasonable for your specific equipment.

David

David S Eldridge's picture
Joined: 2011-09-30
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If you want to take credit for a specific variable speed chiller I would
recommend working with the manufacturer to get you specific part-load data
and at varying LIFT DT?s. Anything simpler would be both inaccurate and
likely selling yourself short.

Robby Oylear, LEED? AP

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