[Equest-users] 90.1 Supply Fan Energy

M. Shields mshields at fstrategies.com
Thu Apr 7 08:37:33 PDT 2011


The building is a residential high rise for seniors in climate zone 3B using
PTHP for heating and cooling.  For all of the residential spaces the fan
runs 24/7 as ASHRAE 90.1-2004 requires that the system run continuously
during occupied hours.  Cooling set point of 78, heating setpoint of 72.
Also the apartments are continuously ventilated through exhaust risers for
the bathrooms and kitchens of each area, so I suppose it should not be
surprising to have a high vent fan consumption, however, what surprised me
was how much it increased going from the eQUEST default values to my
calculated 90.1 values.  

 

From: Joe Fleming [mailto:joe at thespinnakergroupinc.com] 
Sent: Thursday, April 07, 2011 11:25 AM
To: 'M. Shields'; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] 90.1 Supply Fan Energy

 

I have personally never seen fan power equal the total of cooling and
heating power, except in certain climate zones where an economizer can run
often or when the exhaust/ventilation fan power, not associated with
cooling/heating, is high.

Not sure if you are stilling looking for help here.  

What does your fan schedule look like?  Is your fan set to run 24 hrs?

What climate zone are you in?  What are your space cooling and heating
temperature set-points?

 

-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of M. Shields
Sent: Wednesday, April 06, 2011 3:22 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] 90.1 Supply Fan Energy

 

Hi all,

 

I am in the process of breaking out the fan energy from my HVAC system per
ASHRAE 2004 G3.1.2.1, following G3.1.2.9.  The amount of energy coming from
my fans seems massive and I'm not sure if that is typical, or if I've messed
something up.  I started by setting the temperature difference of 20 degrees
between supply and desired temp (55/75 cooling and 90/70 for heating) and
specified 62.1-2004 ventilation for outside air.  I then ran equest and used
the SV-A reports to get supply CFM for each system.  From that number I then
used Table G3.1.2.9 to get BHP for each system, which I then converted to kW
using the formula in ASHRAE.  I then took that number and divided by CFM to
get kw/CFM and entered this number on the system->fan tab.  When I go to the
SV-A report the system kW is exactly what I calculated it to be, but the
energy required for my ventilation fans is about the same as my heating and
cooling load combined, which seems outrageous.  

 

Is this typical?  Have I entered it In the wrong way? I would think fan
consumption would typically be a fraction of the actually heating and
cooling energy.  Thanks for any thoughts.

 

____________________________
Michael Shields
Facility Strategies Group, LLC

1012 Market Street, Suite 307

Fort Mill, SC 29708

Phone: 803-493-4507

Fax: 803-548-2511
Email: mshields at fstrategies.com

 

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