[Bldg-sim] Load Calcs with Energy Simulation Software

[Michael Haughey]

Hi Jonathan,

 

I also recommend using a good load calculation program for calculating the
loads.  Elite CHVAC seems to meet the criteria well and not be so
complicated that errors get introduced merely from confusion.  Load
calculation programs are designed for a different purpose than energy
modeling programs.  The design intent is to estimate the load on the
building at specific weather and internal conditions and be reasonably close
to the worst case load at those given conditions for the purpose of
selecting equipment.  An energy modeling program is designed to give results
that match the energy consumption of the building and thus is more focused
on a dynamic situation.  They might use TMY weather data that doesn't match
the % load exceedance that would be the goal of a load calculation (the
ASHRAE 97-1/2% and 2-1/2% conditions for example).  Often the program is
tweaked to get the result to match existing utility bills, or to model a
system that it was not programmed to handle.  There are a lot of dynamic
variables that cannot be precisely defined, such as occupancy patterns, mass
influence, lighting and equipment loads and schedules, and so on.  The
energy modeling programs thus need to be more complicated, and therefore are
more susceptible to errors from confusion, lack of systems understanding and
experience regarding inputs, or programming errors not yet fixed.  When
drawings are imported from a CAD program, there is even more potential for
input error as the black box tries to put that into the appropriate format
for a load calculation.

 

I would certainly be great to have programs that we have more confidence in
to perform both energy and load calculations.  I'm hopeful that soon that
will happen.  We sure could make good use of tools like that.

 

Michael Haughey, P.E., LEED AP

Silvertip Integrated Engineering Consultants

303-650-1080

mhaughey at earthlink.net

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From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of W. Peter
Anderson
Sent: Friday, January 25, 2008 2:52 PM
To: Jonathan Curtin; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Load Calcs with Energy Simulation Software

 

Jonathan-

Greetings.  I have a little experience in CHVAC and slightly more in eQuest,
and here is my $0.02 worth.

 

If your objective is sizing equipment, developing detailed zone loads for
system and equipment sizing, CHVAC is, in my opion the much better way to
go.  I found it easy to set up zones, create systems, and the output is very
well oraganized in terms of providing the design engineer with the
information they need.

 

To try and do the same thing in eQuest is much more difficult and time
consuming than CHAVC.  Furthermore, the program inputs outputs are focused
on energy use.  The system sizing information is not as easy to locate and
discern as in CHVAC.

 

Again, bare in mind I am new to both these programs.

This forum (Bldg-sim) will get you many other worthy opinions, I hope mine
helps.

 

Regards and good luck.

W. Peter Anderson, P.E
JP Engineering
41 Mechanic Street
Windsor, CT 06095
Ph: 860/688-5223
Fax: 860/688-5269

----- Original Message ----- 

From: Jonathan <mailto:jcurtin at WylieAssociates.com>  Curtin 

To: bldg-sim at lists.onebuilding.org 

Sent: Friday, January 25, 2008 4:24 PM

Subject: [Bldg-sim] Load Calcs with Energy Simulation Software

 

Hello All,

Would anyone out there like to share experiences or precautions in using
simulation models (particularly eQuest, DOE2.1e, EnergyPlus) for load
calculations? Any advantages/disadvantages, tricks, or warnings in using
these simulation models as opposed to dedicated load calculation software
like Elite's CHVAC? Any studies comparing the two?

 

Thanks,

 

Jonathan Curtin EIT, LEED AP

 

W  Y  L  I  E 
C O N S U L T I  N G
E  N G  I  N  E  E R S

6161 Savoy, Suite 700   Houston, Texas 77036
713.781.2526     713.781.2536 fax

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


  _____  


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