[Equest-users] Excessive Unmet Heating Load Hours with an Auto-Sized HVAC System

[Robert Des Rosiers]

All:

I have completed an energy model for a baseline scenario from which to
compare my proposed design.  The baseline HVAC system is a constant volume
single zone AHU w/ no reheat; the AHU is served by HW and CHW loop from a
central plant.  I have set this up in eQuest as a "Variable Air Volume"
system type with the AHU fan control set to "Constant Volume"; my thought
here is that each zone fed by the AHU will control temperature using a VAV
box w/ no local reheat or cooling.  Flow and temperature from the AHU will
be delivered based on the coolest or warmest zone it serves.

 

All seems fine with the design flows, ventilation flows and cooling
capacities.  My problem is with the heating capacity as I have excessive
unmet heating hours (50,000).  I have allowed eQuest to size the heating
capacity of the preheat and heating coil as well as the minimum flow ratios.
Does anyone have any thoughts as to what is causing these unmet heating load
hours?  Is the way I have set-up the desired baseline HVAC system incorrect?

 

Any guidance is greatly appreciated.  Thanks -

 

Robert Des Rosiers, LEED-AP

STUDIO MA

130 N Central Avenue, No.300 Phoenix, Arizona 85004

Telephone 602 251 3800

Fax 602 251 3100

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20100610/340fa0fa/attachment.htm>