System 4 Vs System 6

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I had used System 4 as a baseline for energy modeling and submitted the results for PEARL certification but later I was advised by my assessor that system 4(PSZ HP with CAV ) is not the correct baseline and i have to use system 6 ( packaged VAV with PFP Boxes ).

After revising the energy model with system 6.I notice that my fan energy as come down when compared to system 4 since system 6 being a VAV but my cooling energy as gone up when compared to system 4. This puzzles me.

The EER of system 4 was 9.3 and EER of system 6 was 9.5.. so technically the cooling energy should have come down... but my results is not like that..

Can anyone pls advise me whether my cocnept is correct.. or is it ok if the cooling energy is higher when using system 6.

Regards,

Jacquelin

Jacquelin
ESD Consultant

Jacquelin's picture
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Joined: 2013-10-22
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Have you broken out your fan power from your total unit EER?  If you have switched from System 4 to System 6 then you probably increased the fan power.  This should increase your cooling coil efficiency to maintain the same, or better, EER.  Also, it is possible that you are cooling multiple zones that might not be similar which would cause you to overcool supply air and reheat it whereas previously you just had unmet load hours.  Did the unmet load hours change significantly? 

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Joined: 2014-01-07
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