[Bldg-sim] 90.1 Baseline Model for Proposed VRV Design Model

[Nick Caton]

The queries posed are of two sorts:  TRACE/HAP specific and 90.1/LEED
specific.  I can address the latter variety as I'm primarily an eQuest
user:

-          Combining similar zones/blocks may save some time in setting
up the model (for any software package), but you may find it causes more
work in the long run as you may be required to document/justify why your
modeled systems are of a larger capacity than the proposed/actual units
- food for thought.

-          Many tiny RTU's may seem unreasonable from an
equipment-selection perspective (and often is), but the goal 90.1 is
trying to establish is to set an efficiency standard for such equipment,
as Reba is alluding to.  Note that G.3.1.1 has provisions to define
additional (per floor) baseline system types where that may be
appropriate.  That said...

-          If your baseline model is outputting a significantly
different energy distribution (suggested by your concern about heating
becoming the primary consumption), that's a likely sign something else
is off in one or both models.  Make some QC checks to ensure the
loads/schedules/ventilation rates and other items that are supposed to
be identical between the baseline/proposed are as such.  A check of
unmet hours may lead you down the same path.

-          As to the PLANT/SYSTEM relationships - that sounds
TRACE-specific to me.  You might hold out for responses from others on
this list more familiar with TRACE, or perhaps post a specific question
to the TRACE-users list as well.  FYI: it's not entirely clear how/why
the results are unreasonable or whether you're talking about your
proposed or baseline results from the context ;).

-          It may be helpful to remember that terms like "zone" "space"
"plant" and "system" can have software-specific meanings/nuances, so
what may seem perfectly reasonable for HAP may not jive with TRACE and
vice versa.  

 

Hope this helps somewhat =),

 

~Nick

 

 

NICK CATON, P.E.

SENIOR ENGINEER

 

Smith & Boucher Engineers

25501 west valley parkway, suite 200

olathe, ks 66061

direct 913.344.0036

fax 913.345.0617

www.smithboucher.com 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Reba
Schaber
Sent: Tuesday, August 30, 2011 5:34 PM
To: Christian Kaltreider; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] 90.1 Baseline Model for Proposed VRV Design
Model

 

Christian,

I have not seen this with a VRV system, but I've had a similar
experience with a VAV system.  The LEED reviewer insisted thermal blocks
be modeled identically in Baseline and Proposed.  That meant a Proposed
bldg with 2 AHU's each with about 35 VAV terminal units became about 70
package units in the Baseline bldg.  Crazy, there is not enough roof
space for 70 units.

 

Even though the Baseline systems do not always make sense, Appendix G
attempts to make the energy models similar between everyone. It tries to
standardize things for equal comparison.  That's my understanding.

 

I do have a question.  I'm not familiar with Trace.  In HAP only systems
with heating or cooling coils can be added to a plant.  How is it that
Trace allows DX units be added to a plant?  Seems you have a choice of
multiple plants, one per system OR one plant for all systems.  I think
you should choose the model that most accurately represents a PSZ-HP.  

 

                 PH MECHANICAL ENGINEERING
         Reba Schaber      Mechanical Engineer, P.E.
                                     LEED Accredited Professional
1660 N. Alvernon Way                Voice: (520) 731-2060
Tucson, Arizona 85712                Fax: (520) 731-2061
                        rschaber at phmech.com

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Christian
Kaltreider
Sent: Tuesday, August 30, 2011 9:24 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] 90.1 Baseline Model for Proposed VRV Design Model

 

Hi All,

 

I am doing an Appendix G model for LEED.  The proposed building uses a
VRV system where each room has individual control over its own VRV unit.
All of the VRV units share 2 heat pumps.  My problem is this:  Since
each room has individual control, each room is a 'thermal block'.  I
have combined as many as I can according to the Appendix G rules.
However, I still have many thermal blocks.  For the baseline, I am
required to model a PSZ-HP (packaged roof top unit heat pump) for each
thermal block.  This is giving a bunch of tiny rooms their own
individual RTUs, which seems ridiculous and it is driving my baseline
energy use higher than reasonable (primarily in heating energy...not
sure why). 

 

I am modeling in TRACE, giving one SYSTEM per thermal block, and one
PLANT per SYSTEM.  If I am allowed to connect all of my systems to just
one plant, my energy use becomes more reasonable...but this seems to go
against Appendix G.

 

Has anyone come across this issue when modeling a baseline for a
proposed VRV system? 

 

Thanks,

Christian

 

 

Christian Kaltreider, LEED AP

Energy Engineer

Sud Associates, PA

20 Battery Park Ave

Flat Iron Building, Suite 706

Asheville, NC  28801

(828) 255-4691

ckaltreider at sudassociates.com

 

 

________________________________

No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1392 / Virus Database: 1520/3867 - Release Date: 08/30/11

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20110830/70b2ef51/attachment-0002.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 1459 bytes
Desc: image001.jpg
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20110830/70b2ef51/attachment-0002.jpeg>