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

[Li, Lan]

Pahsa,

 

Will you revise your design at this time?

 

Thanks!

 

Lan

 

Lan Li, PE

Mechanical Engineer

Scheeser Buckley Mayfield LLC                                     

1540 Corporate Woods Parkway

Uniontown, OH 44685

Phone: (330) 896-4664 ext. 123

Cell: (330) 904-6292

Fax: (330) 896-9180

lli at sbmce.com

www.sbmce.com <http://www.sbmce.com/> 

 

Columbus Branch Office (614) 448-1498

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Thank you

________________________________

From: Pasha Korber-Gonzalez [mailto:pasha.pkconsulting at gmail.com] 
Sent: Thursday, June 10, 2010 10:55 PM
To: Robert Des Rosiers
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Excessive Unmet Heating Load Hours with
anAuto-Sized HVAC System

 

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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