[Equest-users] eQuest - outside air heating issues

[Nick Caton]

Scott,  

 

I want to say off the bat that you actually are asking a very good and
fundamental question:  What is a "best practice" for matching baseline
ventilation air rates to the proposed model? 

 

My general processes is:

1.       where I'll build a proposed model to match the
drawings/schedules, address anything that results in odd results/
warnings / unmet hours.

2.       Build the baseline - clear out any zone/system level OA inputs
to autosize, then 

3.       For each airside system, enter the 1.15/1.25 oversizing
parameters and a "MIN-OA-RATIO" at the system level to match the
corresponding proposed design model's system ratio

4.       Run both simulations and compare results for ventilation air to
determine if things are way off (and they have been) - I use the SV-A
reports and excel for this comparison

5.       Tweak baseline systems' OA-RATIOs as required up or down to
make the total ventilation air  sync with the proposed model's.  

 

Following this procedure, which I document for model review, the design
system OA sums between the baseline model, proposed model, and
construction documents are typically very close to each other, if not
perfectly in sync.

 

Is this a procedure others are following or is there a simpler way?

 

To the rest of your email... Different systems will use different
amounts/types of energy for the same amount of load (OA).  Your baseline
model's tripling of gas consumption isn't something  I'd immediately
discount as unreasonable, but worth reviewing to find something you may
have missed - perhaps lowering CFM's are the culprit?  In some cases,
the core "secret" to surprisingly outstanding proposed/baseline
performance is getting lucky with a terrible baseline...  the
prescriptive requirements, by their nature, can be close to or far from
"a good idea" for any given project/site.

 

~Nick

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of
Tomlinson, Scott
Sent: Wednesday, May 26, 2010 8:35 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] eQuest - outside air heating issues

 

Hello all,

 

I have a question regarding outside air input.  For my design building I
enter my outside air at the system level, as the minimum outside air
ratio, which I get from my equipment schedules.  90.1 requires that the
outside airflow be the same.  To do this I take my summary report from
my design building and enter the values from that report into the
baseline model zones.  When I run my baseline model the outside airflow
rates from the summary report match those of my design model, and my
unmet heating hours are good in both models, but the heating gas
consumption in my baseline building triples.  The result is I am getting
great, but unrealistic, energy savings.

 

Does anyone know why this is happening?  Why would entering the OA at
the zone level cause such increased heating for the save total CFM
entered at the system level?  How are you folks typically handling your
outside ventilation air.

 

Any help would be greatly appreciated, thank you.

 

__________________________________________

Scott Tomlinson, PE, LEED-AP

Mechanical

Symmes Maini & McKee Associates, Inc.

1000 Massachusetts Avenue, Cambridge, MA 02138

t: 617.520.9438

 

 

f: 617.354.5758

stomlinson at smma.com

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

 

 

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