Zone Reheat Delta-T

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eQUEST users,

I am modeling a simple 9 story office building in v3.63. The system type is
VAV w/ HW Reheat. One Fan system per floor.

With a 20F Zone Reheat Delta-T the Annual Energy Consumption is 38% higher
than it is with a 30F Zone Reheat Delta-T.

This is not intuitive to me why the energy use greatly increases with a
lower zone reheat Delta-T.

Thanks for any help,

Dennis Hunt

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one think I can think of is - there might be more unmet heating hours
in the first case.

R B's picture
R B
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Dennis,

The first thing you should look at anytime you are analyzing the
difference in energy use is your BEPS/BEPU reports. Is the difference in
heating, cooling, fan energy, pumping? As R B said, is there a
difference in unmet hours?

For VAV-specific design/energy issues, check out this free resource:

http://www.energydesignresources.com/Technology/HVACDesign/tabid/97/arti
cleType/ArticleView/articleId/331/Default.aspx

Regards,

William Bishop, EIT, LEED(r) AP

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Thanks Bill, RB for your input,

I looked at the BEPS and found Heating, cooling, Vent Fans, Pump&Aux all
went up for the 20F Zone Reheat Delta-T.

Hours coincident Cool-Heat Load and Fan electric During Heat & Cool jumped
significantly. Any thoughts on this?

No unmet hours for either case

Thanks,

Dennis

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