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

[Pasha Korber-Gonzalez]

I have found with my own projects that even sometimes when the HVAC designer
has specified a specific capacity for htg water equipment that sometime in
my model file I still have unmet loads for htg.  I suggest at this point
specify additional htg capacity by either increasing the reheat delta-T from
say 30F to 50F and/or adding zone level baseboards.  By adding the
baseboards you are adding a component of the system that will supplement the
skin losses being experienced by the simulation model.

by adding baseboards for the additional requrired heat then you should be
able to meet your heating loads.

hope this helps,
pasha

On Thu, Jun 10, 2010 at 7:38 PM, Robert Des Rosiers <desrosiers at studioma.com
> wrote:

>  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
>
>
>
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