[Bldg-sim] simulation software

Bernard W. Nelson bnelson at mcw.com
Tue Dec 18 15:23:55 PST 2007


Hi All,

I agree with Mike Roberts.  I started my career 34 years ago as a sales
engineer for the Trane Company.  One of my responsibilities was to teach
consulting engineers how to use TRACE.  This was before the advent of time
sharing on mainframes when a completed input book was mailed to La Crosse,
Wisconsin for a two week turnaround.

I became an Energy Consultant in 1979 and used TRACE extensively for many
years in both new construction and the energy retrofit business. With the
migration of TRACE and DOE-2 from running on time shared mainframes to
running on the PC, the simulation world has really changed our business.
Some runs used to take 24 hours to process on the first PC versions.  I
incurred $20,000 in run time costs on a large project using time sharing on
a mainframe. Now, if software costs $1,700 to purchase with an annual $300
maintenance fee we think that it's cost prohibitive.  When a simulation
program takes three minutes to make a run we start looking at our watches.

In 1981 I learned how to read and write the Building Description Language
(BDL) and input DOE2.1E the hard way by coding everything by hand (sometimes
in Cartesian coordinates) and running it on a time shared mainframe.  I ran
many DOE2.1E simulations using time sharing and then using Micro-DOE2 on an
IBM 386 PC in the early 90's.  DOE-2 is a great program and provides the
knowledgeable user with just about any kind of hourly output you would like
to analyze.

In the last number of years I have used both TRACE 700 and eQUEST.  I like
using both programs depending on what I am trying to model.  If you are
going to run eQUEST you had better plan on experiencing a steep learning
curve so you can tweak the BDL as required instead of relying on the Wizards
for your input and output flexibility.  The CAD import feature of eQUEST is
a great tool.

I have received excellent technical support from TRACE CDS over the years
and very little technical support on DOE-2.  The quality of the technical
support received depends many times on how you phrase your questions and
whether or not you really understand what you are trying to accomplish.

For the last 17 years I have specialized in conducting facility assessments,
modeling new and existing building systems, preparing retrofit designs of
chiller plants, steam and hot water boiler plants, air systems, pumping
systems, direct digital controls systems and then providing "hands-on"
commissioning of the building's Direct Digital Control systems to ensure the
projects work.

Building system modeling is going to be "garbage in - garbage out" if you
expect pre-processing and post-processing software to do all the "heavy
lifting" for you. To be an effective modeler one has to develop a thorough
understanding of how HVAC systems work and how to design these systems that
are being modeled.    


Bernard W. Nelson P.Eng., PE 
Project Manager 

MCW Consultants Ltd. 
1400-1185 West Georgia St. 
Vancouver, BC V6E 4E6 
Phone 604-687-1821 Ext.126 
Fax 604-683-5681
E-Mail: bnelson at mcw.com 

 

-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Mike Roberts
Sent: Tuesday, December 18, 2007 12:15 PM
To: 'Karen Walkerman'; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] simulation software

Now this is the beginning of a very useful thread!

Steve Playo pointed out some important things to consider in choosing an
energy simulation program.  I also agree with Karen Walkerman in her defense
of eQUEST.  I, too, would use it in preference to TRACE in most cases.

What too many people do not realize is energy simulation is a very
complicated and detailed process.  Far too many assume the eQUEST wizard or
the TRACE entry method will allow them to simulate a building for LEED or
whatever without going through the agony of learning what the building is
doing or how the program models it.  It just isn't going to happen.

I have been doing energy simulation for 30 years.  I started with Cal-ERDA
1.3 (predecessor to DOE-2.2, the eQUEST calculation engine) on a time shared
main frame computer.  After a couple years of expensive time sharing, I
helped my employer install DOE-2.1 on a DEC System 10 main frame.  In 1986,
I left that employer to do energy simulation for my own company.  Over the
years, I have used DOE, TRACE, BLAST, and a number of other simulation
programs.  I have taken training courses in most of the ones I have used and
assisted in training courses for eQUEST.  The point is that even now, I
learn something new on every project.  I used to say that running DOE took
the equivalent of a five hour college course.  Now, I think it is the
equivalent of a college degree.

Don't worry about how cheap the program is to obtain.  Whatever it costs
will pale compared to the cost of learning how to use it.  Take the training
for whatever program you are going to use and then expect to spend a lot
more time on the learning curve.

This is not to discourage using energy simulation.  Energy simulation is a
wonderful tool.  It is easy to come up with more than enough energy and
dollar savings to offset the additional engineering hours.  And it will only
become more important in the future.  It's just not as easy as some people
would like to think.

Mike Roberts


-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Karen Walkerman
Sent: 12/18/2007 11:49 AM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] simulation software


Hi All,

I too have spent many frustrating nights trying to figure out what is wrong
with my eQuest models.  After all the brow-beating, I have always come to
the conclusion that something was wrong with my inputs, not with the
software, and been able to remedy the issue.  Not true for Trace700.  I
spent about a year with Trace, found a number of bugs (some of which the
company is now fixing), got frustrated with the long (hour-plus) simulation
times, and limitation to modeling 4 alternatives in one file.  Yes it's nice
that there's someone to call when you have questions, but they don't always
know the answer.  I had people telling me to check my fan energy inputs when
the odd data I was getting had nothing to do with fans.

In addition, I often have trouble with data corruption when editing
templates.  Granted, templates are a great idea and I wish eQuest had a
similar option, but when your inputs are corrupted and you have to go
through and check room by room to see what remains...  not a fun process.

Trace700 has no visual feedback for window, wall, room or roof geometry.
This can be a pain.

I also believe that their water source heat-pump system does not share
energy in the loop properly.  I created a test-file, consisting of two
10X10X10 rooms.  One room had a large cooling load, the other a large
heating mode.  Neither had any external surface areas.  The total energy
required to condition the spaces should have been much lower for heat pumps
than for fain coils... but, they were practically identical.  I sent the
model to Trace, and they argued that this was not a fair test of their
software????

So... though eQuest can be frustrating at times, I gladly use it over Trace.

~Karen~
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