VAV System Energy Consumption

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My "Energy Consumption Summary" report numbers were wacky. I modelled a VAV with gas heating and electric reheat at the boxes and got a huge number for gas consumption and zero for electric consumption. Does anybody know what goes on in the background of this software? How does Trane know when electric reheat will be used? From my results, it looks like I do not need reheat.

Then I modelled a changover-bypass VAV with gas heating and no electric reheat. The results were shocking to me. With the same room and vent  loads, the gas consumption was a lot lower than the VAV w/reheat system. Even the primary cooling was results were lower too.

 Can anybody shed some light on this topic? Thanks.

karlsbad's picture
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A few thoughts:

1) Make sure the preheat coil is set to the gas heating coil. This is a common confusion point, but the gas coil at the AHU is NOT the "main heating coil". In your case, the gas coil is the Reheat coil, and the main/reheat coil is electric (the coil at the box). 

2) Check your minimum flows and outdoor air in your checksums, especially if modeling standard 62.

Joe's picture
Joe
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Are you setting discharge air temps in the Systems? Should leave blank.

Are you over writing the SACFM's for cooling & heating?

Be Sustainable -- Never let today use up tomorrow!.

Bobba_Fett's picture
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